HSE
Health & Safety
Executive
Whole-body vibration on agricultural vehicles:
evaluation of emission and estimated
exposure levels
Prepared by Silsoe Research Institute and
RMS Vibration Test Laboratory for the
Health and Safety Executive 2005
RESEARCH REPORT 321
HSE
Health & Safety
Executive
Whole-body vibration on agricultural vehicles:
evaluation of emission and estimated
exposure levels
A J Scarlett, J S Price, D A Semple
Silsoe Research Institute
Wrest Park, Silsoe
Bedford, MK45 4HS
R M Stayner
RMS Vibration Test Laboratory
26 Coder Road
Ludlow Business Park
Ludlow, Shropshire
SY8 1XE
A study was conducted to quantify whole-body vibration (WBV) emission and estimated exposure levels found upon a
range of modern, state-of-the-art agricultural vehicles (tractors, self-propelled sprayers and all-terrain vehicles
(ATVs)), when operated in controlled conditions (traversing ISO ride vibration test tracks & performing a range of
agricultural operations) and whilst under normal ‘on-farm’ use. The potential consequences of WBV operator
exposure level limitations, prescribed by the European Physical Agents (Vibration) Directive:2002 (PA(V)D), upon
agricultural vehicle usage patterns in the UK were also considered.
Agricultural tractor WBV emission levels were found to be very dependent upon the nature of field operation
performed, but less dependent upon vehicle suspension system capability (due to horizontal axis vibration levels).
However, this trend was reversed during on-road transport. Virtually all ‘on-farm’ tractors (~95%) exceeded the
Exposure Action Value (EAV) during an 8-hour working day, requiring implementation of measures to reduce &
manage worker vibration exposure. Few (~9%) ‘on-farm’ operations (cultivating & trailer transport) approached or
exceeded the PA(V)D WBV Exposure Limit Value (ELV) during 8 hours operation, although this would have increased
(to 27%) during longer, more typical working days.
The PA(V)D is unlikely to restrict the operation of large, modern tractors during an 8-hour day, but will become a
limitation during certain operations if the working day lengthens significantly. Selfpropelled sprayers exhibited a
similar trend, with the EAV being exceeded in most cases; although working day length would have to reach
unsustainable levels (~22 hours) for the ELV to be exceeded. Whilst ATVs exhibited high levels of both WBV and
hand-arm vibration (HAV) on occasion, limited daily usage (generally less than 11/2 hours) prevented the (WBV or
HAV) ELV being exceeded. Further ‘on-farm’ WBV data collection is required to enable creation of a robust, generic
WBV emission database for agricultural vehicle operations. Standardised (ISO) methods of agricultural vehicle WBV
measurement require further development to permit quantification of the likely effectiveness of tractor WBV-reducing
design features during in-field operation(s).
This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including
any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
HSE BOOKS
© Crown copyright 2005
First published 2005
ISBN 0 7176 2970 8
All rights reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted in
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photocopying, recording or otherwise) without the prior
written permission of the copyright owner.
Applications for reproduction should be made in writing to:
Licensing Division, Her Majesty's Stationery Office,
St Clements House, 2-16 Colegate, Norwich NR3 1BQ
or by e-mail to [email protected]
ii
ACKNOWLEDGEMENTS
Silsoe Research Institute & the RMS Vibration Test Laboratory gratefully acknowledge the
assistance provided by the Agricultural Engineers Association, CNH (UK) Ltd, JCB
Landpower Ltd, John Deere (UK) Ltd, Renault Agriculture Ltd, Househam Sprayers Ltd,
Fieldens plc, Honda UK Ltd, Kawasaki Motors UK Ltd, Suzuki GB plc and Yamaha Motor
UK Ltd, for the provision of test vehicles. We are also indebted to the large number of
farmers who willingly participated in the study: without their assistance and patience this
investigation would not have been possible.
iii
iv
CONTENTS
Page No.
Acknowledgements
iii
Contents
v
Executive Summary
ix
1. INTRODUCTION
1
2. AGRICULTURAL VEHICLE REVIEW
3
2.1
Agricultural Vehicle Design Features
3
2.1.1
Operator seat suspension
3
2.1.2
Vehicle cab suspension
4
2.1.3
Vehicle axle suspension
5
2.1.4
3-point linkage dynamic ride control
9
2.2
Agricultural Vehicle Fleet Composition and Usage Patterns
9
2.3
Target Vehicle Identification
14
3. WHOLE-BODY VIBRATION (WBV) MEASUREMENT
3.1
3.2
3.3
15
European Union Physical Agents (Vibration) Directive
15
3.1.1
Introduction
15
3.1.2
Terminology and implementation
15
3.1.3
Practical implications
20
Instrumentation
24
3.2.1
Measured parameters
24
3.2.2
PC-based data acquisition
24
3.2.3
PC card recorder data acquisition
28
Data Analysis
28
3.3.1
ISO test track data
28
3.3.2
SRI ’in-field’ data
29
3.3.3
‘On-farm’ data
29
3.3.4
Hand-arm vibration (HAV) data
29
4. SELF-PROPELLED SPRAYERS
31
4.1
Test Vehicles
31
4.2
ISO Test Track WBV Emission Measurement
34
4.2.1
Procedure
34
4.2.2
Results
35
4.2.3
Summary
37
v
4.3
4.4
SRI ‘In-Field’ WBV Emission Measurement
42
4.3.1
Procedure
42
4.3.2
Results
42
4.3.3
Summary
49
‘On-Farm’ WBV Exposure Measurement
50
4.4.1
Introduction
50
4.4.2
Procedure
50
4.4.3
Results
51
4.4.4
Summary
57
5. AGRICULTURAL TRACTORS
59
5.1
Test Vehicles
59
5.2
ISO Test Track WBV Emission Measurement
60
5.2.1
Procedure
60
5.2.2
Results
62
5.3
5.4
SRI ‘In-Field’ WBV Emission Measurement
68
5.3.1
Introduction
68
5.3.2
Spraying
68
5.3.3
Ploughing
71
5.3.4
Plough transport
73
5.3.5
Cultivating
74
5.3.6
Trailer transport
77
5.3.7
Summary
81
‘On-Farm’ WBV Exposure Measurement
83
5.4.1
Introduction
83
5.4.2
Procedure
83
5.4.3
Results
84
5.4.4
Summary
103
6. ALL-TERRAIN VEHICLES (ATVs)
105
6.1
Test Vehicles
105
6.2
ISO Test Track Vibration Emission Measurement
107
6.2.1
Procedure
107
6.2.2
Results
107
6.2.3
Summary
112
6.3
SRI ‘In-Field’ Vibration Emission Measurement
115
6.3.1
Procedure
115
6.3.2
Results
115
6.3.3
‘In-field’ and ISO test track performance comparison
116
vi
6.4
6.3.4
Comments regarding standardised tests
119
6.3.5
Summary
119
‘On-Farm’ Vibration Exposure Measurement
121
6.4.1
Farm description and ATV utilisation
121
6.4.2
Procedure
121
6.4.3
Results
122
6.4.4
Summary
130
7. DISCUSSION
133
7.1
Self-Propelled Sprayers
133
7.2
Agricultural Tractors
136
7.3
All-Terrain Vehicles (ATVs)
141
7.4
Overall
142
8. CONCLUSIONS & RECOMMENDATIONS
149
9. REFERENCES
153
APPENDICES
Appendix 1.1
155
Self-Propelled Sprayer Specifications:– ISO Test
Track Programme
Appendix 1.2
155
Self-Propelled Sprayer WBV Emission Data:- ISO Test
Track Programme
157
1.2.1
Unladen
157
1.2.2
Laden
161
Appendix 1.3
Self-Propelled Sprayer WBV Emission Data:- SRI ‘In-Field’
Programme
165
Appendix 1.4
Self-Propelled Sprayer ‘On-Farm’ WBV Exposure Data:Synopsis of Results
Appendix 2.1
167
Agricultural Tractor Specifications:– ISO Test Track
Programme
171
Appendix 2.2
Tractor Suspension Seat Specifications
173
Appendix 2.3
Agricultural Tractor WBV Emission Data:- ISO Test
Track Programme
Appendix 2.4
Appendix 2.5
Appendix 2.6
175
Agricultural Test Tractor Set-up:- SRI ‘In-Field’
Programme
179
Agricultural Tractor WBV Emission Data:- SRI ‘In-Field’
Programme
183
Agricultural Tractor WBV Emission Data:- SRI ‘In-Field’
- Trailer Transport
184
vii
Appendix 2.7
‘On-Farm’ Agricultural Tractor Cab Floor WBV
Emission Data
Appendix 2.8
185
Agricultural Tractor ‘On-Farm’ WBV Exposure Data:Synopsis of Results
186
2.8.1
Suspended Cab & Front Axle Tractor
186
2.8.2
Fully Suspended (Front & Rear Axle) Tractor
197
Appendix 3.1
ATV WBV & HAV Emission Data:ISO Test Track Programme
Appendix 3.2
ATV WBV & HAV Emission Data:SRI ‘In-Field’ Programme
Appendix 3.3
215
ATV ‘On-Farm’ WBV Programme:Forward Speed & Operator Seat Presence Details
Appendix 4.
213
ATV ‘On-Farm’ WBV & HAV Exposure Data:Synopsis of Results
Appendix 3.4
209
219
Estimating WBV Exposure from Measured Data:Particular Issues
225
viii
EXECUTIVE SUMMARY
The overall objective of this investigation was to determine currently achievable Whole-Body
Vibration (WBV) emission and exposure levels associated with representative ‘state-of-the-art’
agricultural vehicles. For each of the test vehicles WBV levels have been measured in three
generic test situations; namely whilst:•
•
•
traversing standard ISO 5008:2002 ride vibration test tracks;
performing typical agricultural field operations in representative, controlled
field conditions (‘in-field’);
performing the same range of field tasks during normal operation on working
farms (‘on-farm’).
Additionally, the investigation has considered the consequences, for agricultural vehicle usage
patterns in the UK, of prescribing limits for operator daily exposure to WBV, as specified by
the European Union Physical Agents (Vibration) Directive (PA(V)D). The investigation has
targeted three generic types of agricultural vehicle: self-propelled sprayers; all-terrain vehicles
(ATVs); and agricultural tractors, the latter whilst performing typical agricultural tasks (‘infield’ and ‘on-farm’) with a range of attached implements (spraying / fertiliser spreading,
cultivating, ploughing, plough transport, and tractor-trailer transport).
Two comparable 2500 litre-capacity, self-propelled sprayers have been investigated, one
embodying an advanced design of (self-levelling, air spring) axle suspension system. The
vehicles were compared in terms of WBV emission levels, measured both upon the cab floor
and the operator’s (suspension) seat, whilst performing a range of ‘back-to-back’ tests, both
upon the ISO track and in controlled ‘in-field’ conditions. WBV emission and operator
exposure levels were then recorded upon three ‘on-farm’ examples of the advanced machine
during typical usage over ½ day (~4-hour) periods.
A similar procedure was followed during assessment of the agricultural tractors, with the
exception that four state-of-the-art 4-wheel-drive vehicles in the 90-130 kW engine power
range were considered, each embodying a different level of (cab and/or axle) suspension
system complexity (each incorporated an operator’s suspension seat). The tractor suspension
systems included:•
unsuspended;
•
suspended cab;
•
suspended front axle & cab;
•
fully suspended (front & rear axle).
Cab floor and operator’s seat WBV emission levels were recorded upon each vehicle whilst
traversing both (‘smoother’ and ‘rougher’) ISO 5008 ride vibration test tracks, at a range of
forward speeds. WBV levels were subsequently measured upon each machine in turn, whilst
performing the abovementioned range of operations in controlled ‘in-field’ operating
conditions. Finally, cab floor and operator’s seat WBV emission levels, and operator ~4-hour
WBV exposure levels were determined upon 11 ‘on-farm’ examples of the suspended front
axle & cab tractor, and a corresponding number of the fully suspended (front & rear axle)
tractor. These vehicle variants being selected as being representative of the current leading
edge of popular agricultural tractor suspension system design, and having demonstrated
marginally superior ride comfort to that of the other test tractors during the majority of ‘infield’ test operations.
ix
ATVs (quad bikes) were evaluated in a similar manner, whilst traversing the ISO track (100 m
‘smoother’ track only), in controlled ‘in-field’ conditions, and ‘on-farm’. However a marked
difference was that vibration levels were measured upon the operator’s seat (saddle), one of the
footrests (having first established its representative nature), and upon both handlebars (to assess
hand-arm vibration emission levels). Four vehicles in the popular 300-400 cc engine capacity
range were selected, each embodying a different degree of axle suspension system complexity,
each being subjected in turn to ISO track and ‘in-field’ test programmes. Three examples of
one machine variant were subsequently targeted during subsequent ‘on-farm’ emission /
exposure measurements.
The PA(V)D stipulates daily vibration exposure criteria in the form of an employee daily
Exposure Action Value (EAV), above which actions for reduction of vibration exposure must
be taken, and an Exposure Limit Value (ELV) which must not be exceeded. Daily exposure in
excess of the EAV requires the implementation of measures to reduce and manage worker
vibration exposure, as proposed by the Directive (see Section 3.1.3). It should be stressed that
the WBV Exposure Limit Value (ELV) should not be considered a ‘safe’ level of vibration
exposure in the workplace, but rather as a high, undesirable level of vibration exposure (and a
legal threshold) to be avoided at all costs. It is for this reason the Directive requires action to
be taken, so far as is reasonably practicable, to minimise vibration exposure once levels exceed
the Exposure Action Value (EAV);
Virtually all the agricultural vehicle operations investigated, involving modern, state-of-the-art
tractors, self-propelled sprayers or ATVs, will result in operator WBV daily exposure
exceeding the PA(V)D Exposure Action Value (EAV) during a normal working day (see
Table ES.2), thereby requiring the implementation of vibration reduction / management
measures. Following the stipulations of the Directive, the daily WBV exposure levels
encountered upon the agricultural vehicles targeted by the investigation, and the extent to
which they may affect typical daily usage, sub-divide into three broad categories (see also
Tables ES.1 & ES.2 attached):•
Vehicle-operations that generate sufficiently low WBV levels, such that the ELV is
unlikely to be exceeded even if the working day length exceeds 8 hours. This scenario
applies to self-propelled sprayers, and tractors whilst spraying / fertiliser spreading,
whilst transporting ploughs (on farm tracks & roads), and ploughing conducted in
favourable operating conditions;
•
Vehicle-operations, whose (moderate - high) WBV levels may cause operator daily
exposure to approach or reach the ELV during 8 hours operation, but will cause the
ELV to be reached and/or exceeded if the working day lengthens significantly (~12 –
14 hours). This scenario was found to apply to agricultural tractors whilst cultivating
medium to rough stubble ground, whilst performing tractor-trailer transport operations,
and possibly (on occasion) whilst ploughing;
•
Vehicle-operations that generate high WBV levels, but the (apparently typical) short
duration of daily use (less than 2 hours per day) ensures that operator daily exposure
does not exceed the ELV. However, this would not be the case if daily operating
duration were to increase. This scenario applied to the ATVs investigated, but in these
particular instances hand-arm vibration exposure could on occasion become a limiting
factor.
x
Table ES.1 Relative WBV magnitudes arising from agricultural tractor operations
performed during the SRI ‘in-field’ investigation
WBV Emission Level (energy-equivalent continuous (overall average) r.m.s. acceleration)
Low
Moderate
High
Spraying / Fertiliser Spreading
Ploughing
Cultivating (rough ground)
Plough Transport
Trailer Transport
Table ES.2 Summary of ‘on-farm’ agricultural vehicle operations investigated
Vehicle / Activity
S.P. Sprayer
Tractor – Spraying
Seat overall
average r.m.s.
(Aeq) WBV
level (m/s2)
Time to EAV
(A(8))
(hrs:mins)
0.53 – 0.69
4:12 – 7:7
22 - >24
0.36 – 0.78
3:17 – 15:26
17:23 - >24
2:19 – 8:20
12:14 - >24
1:36 – 9:3
8:26 - >24
1:2 – 7:7
1:2 – 2:46
Time to ELV
(A(8))
(hrs:mins)
Average
Working
Day
(hrs)
Likelihood of Exceeding
Value in a Normal
Working Day:EAV
ELV
10.1
Yes
No
8.9
Probably
No
8.9
Yes
Unlikely
8.9
Yes
Possibly
5:29 - >24
8.9
Yes
Possibly
5:29 – 14:39
1-2
Possibly
V.unlikely
(0.5 – 0.74)
Tractor - Ploughing
0.49 – 0.93
(0.73 – 0.89)
Tractor – Trailer
Transport
Tractor – Cultivating
0.47 – 1.12
(1.05 – 1.32)
0.53 – 1.39
(1.2 – 1.49)
ATV
NB:-
0.85 – 1.39
Tractor WBV data in parentheses originates from SRI ‘in-field’ measurements (performed in controlled field
conditions) and encompasses all tractor suspension system designs investigated;
All other WBV data above relates to ‘on-farm’ measurements and, in the case of tractors, only includes
suspended front axle & cab, and fully suspended (front & rear axle) tractor models.
The requirements of the Directive, as expressed via the ELV can potentially restrict agricultural
vehicle daily operating durations in instances of potentially high daily vibration exposure. In
the majority of instances it appears unlikely that it will have significant impact upon current
usage patterns of modern, state-of-the-art agricultural vehicles in the UK. Over 50% of the ‘onfarm’ tractors / operations surveyed would have to work for approaching 24 hours per day to
xi
exceed the ELV. However, longer shifts, extending to 12 – 14 hours per day, which are
common at peak times in agriculture, would result in over 25% of the large, modern ‘on-farm’
tractor-operations surveyed causing the ELV to be exceeded. Also, it is possible that WBV
emission levels upon older and/or smaller vehicles may be greater than those reported here,
requiring careful selection of appropriate machines for given tasks. However, perhaps such
machines will not be subjected to daily operational periods of the magnitudes expected of
newer vehicles.
Differences between overall average (Aeq) WBV emission levels generated by individual
tractor (axle and cab) suspension designs, operating in controlled ‘in-field’ conditions, were
generally found to be less than those evident between the different agricultural operations
performed (spraying / fertiliser spreading, ploughing, plough transport, cultivating, trailer
transport), particularly when evaluated by the ‘largest single weighted axis’ (ISO 2631-1:1997
‘Effect of Vibration on Health’) methodology favoured by the Directive. However, WBV
exposure levels evident during ‘on-farm’ agricultural vehicle operations were found to vary by
as much as ±50% or more for the same task (see Table ES.2) depending upon ground
conditions, driving technique and operational requirements (‘the need for speed’). This is much
greater than the likely differences in WBV levels generated by alternative types (capabilities) of
tractor cab and/or axle suspension system, whilst operating in similar conditions.
Developments in suspension system design were shown to reduce the WBV emission levels of
self-propelled sprayers. Developments in tractor (cab and axle) suspension systems appear to
yield improvements in subjective ride comfort: a fact confirmed by evaluation of cab floor and
operator seat WBV levels by the vector sum (RSS) method. The latter suggested the ride
comfort of the fully suspended (front & rear axle) tractor and the suspended front axle & cab
tractor to be marginally superior to that of the other test vehicles in the majority of instances.
Cab floor WBV levels derived by the largest single axis method displayed a similar trend
between tractor designs, but this was not so apparent amongst operator seat WBV values
derived by the technique: and the latter are, of course, the WBV emission levels from which
operator daily exposure would be derived.
The Directive requires WBV levels in each axial direction to be assessed separately, and the
axis with greatest (overall average) magnitude be identified. However, action is required to
reduce exposure to vibration in all axial directions in which the EAV is exceeded (see
Section 7.4). A given vehicle / application may exhibit high overall average longitudinal (X) or
transverse (Y) axis WBV levels, whilst significant peak acceleration events (shocks and jolts)
are generated in one or more of the other axial directions, and are possibly not well represented
by the r.m.s. (A(8)) evaluation method. During the majority of self-propelled sprayer and
tractor-implement operations, largest (overall average, axis weighted) WBV magnitudes were
generated in the transverse (Y) axis: during tractor-trailer transport the longitudinal (X) axis
WBV took precedence. However, maximum peak acceleration levels frequently occurred in
the vertical (Z) axis, and vertical (Z) axis WBV levels dominated ATV operation.
Certain methodologies employed by the Directive give rise to debate. The apparent importance
of horizontal (X & Y) axes WBV levels reported in this investigation is undoubtedly
accentuated (and arguably distorted) by use of the ‘largest single weighted axis’ (ISO 26311:1997 ‘Effect of Vibration on Health’) methodology, arguably employed without adequate
justification. Were 1.4x multiplying factors not applied to horizontal vibration components,
vertical (Z) axis WBV levels would be the largest for a greater number of the vehicles /
operations surveyed.
For agricultural operating conditions, there is little equivalence between the 8-hour energyequivalent, frequency-weighted r.m.s. acceleration (A(8)) and vibration dose value (VDV)
xii
methods of WBV exposure assessment, as specified by the Directive. This is because the
equivalence is based upon the estimated vibration dose value (eVDV), and the requirements for
using eVDV are not met by the WBV encountered in real agricultural conditions. In
agricultural operating conditions the A(8) EAV and ELV appear to be less stringent (equate to
longer operating durations) than their VDV-specified equivalents.
If a comprehensive, generic database of agricultural vehicle WBV emission levels is deemed
desirable, to provide farmers with adequately robust data to enable estimation / calculation of
likely WBV daily exposure levels (as required by the Directive), and/or to identify the possible
need for workplace measurement of WBV exposure levels, where these may approach the ELV
(see Table 7.3), then a more comprehensive WBV exposure data gathering exercise will be
required, embodying a greater number of measurement replications. This issue is particularly
pertinent to tractor-implement operations, which typically generate WBV daily exposure levels
between the EAV and ELV (see Table ES.2). Such a database would be of considerable value,
enabling an employer to target specific operations of concern in greater detail (workplace
exposure measurement), whilst permitting recommended WBV estimation / calculation
techniques to be used for other (lower exposure level) operations, with confidence.
Use of ISO 5008 ride vibration track tests provide a reasonable basis for comparison of selfpropelled sprayer WBV emission levels, but for agricultural tractors the resulting data bears
little resemblance to WBV levels measured under ‘in-field’ or ‘on-farm’ conditions. This is
largely because of the lack of attached implements or trailers and consequent differences in
vehicle mass, weight distribution, tyre inflation pressures and external force systems acting
upon the vehicle. Consequently, current test track techniques require development / adaptation
to improve their suitability for tractor-implement combination WBV emission assessment.
Such developments would ideally deliver standardised testing methodologies, capable of
quantifying the likely effectiveness of tractor WBV-reducing design features when operating in
typical agricultural conditions (discussed further in Section 7.2).
Finally, in the case of ATVs, hand-arm vibration exposure is more likely to restrict vehicle
daily operating duration (due to exposure in excess of the ELV), rather than exposure to wholebody vibration. The slatted construction form of the ISO 5008 test track is inappropriate for
ATVs, because of vibration generated by the inter-slat spacing. The suitability of the
alternative moulded concrete type of track has not as yet been evaluated.
xiii
xiv
1.
INTRODUCTION
It has been widely recognised for a number of decades, that whole-body vibration (WBV) is a
major source of discomfort for agricultural tractor operators during typical farm operations
(Matthews, 1966; Stayner & Bean, 1975; Bovenzi & Betta, 1994; Lines et al., 1995).
Engineering solutions to reduce WBV levels experienced by agricultural vehicle operators are
commonplace, historically in the guise of spring suspension seats (see Section 2.1.1), but
more recently in the form of cab and/or axle suspension systems (see Section 2.1.2 & 2.1.3).
Whilst these measures have undoubtedly reduced vehicle WBV emission levels, increased
annual utilisation of fewer, larger vehicles in UK agriculture has conspired to increase likely
exposure durations for many operators. The situation is further complicated by the absence of
a detailed and reliable quantitative dose-response relationship between WBV exposure and
the development of lower-back disorders. Nonetheless, strong evidence exists linking both
WBV exposure to ill health, and increasing levels of exposure to an increased risk to health.
Minimising WBV exposure is therefore highly desirable, although until recently legislation
has not existed to attempt to limit the daily exposure of workers to WBV in the workplace,
thereby protecting against the possibility of vibration-induced spinal injury. The European
Union Physical Agents (Vibration) Directive (EU PA(V)D, 2002) (see Section 3.1) attempts
to address this shortfall by specifying both practical limits for daily personal vibration
exposure, and (lower) levels above which employers should take steps to reduce exposure.
However, there are widespread concerns within the UK that the Directive will limit WBV
daily exposure levels for operators of agricultural and other off-road vehicles, thereby
potentially requiring alterations in vehicle usage patterns at a time when the farming industry
is under severe economic pressure. It was therefore in the interest of employers, vehicle
manufacturers and the Health and Safety Executive (HSE) to ensure that the proposed
legislation was both adequate (in terms of operator protection) and realistic (in terms of
practical implementation) prior to its introduction in the Member States (proposed 2007 for
new agricultural & forestry vehicles; 2005 for all other new vehicles).
Consequently, the overall objective of this investigation was to determine currentlyachievable Whole-Body Vibration (WBV) emission and exposure levels associated with
representative ‘state-of-the-art’ agricultural vehicles, both whilst traversing standard ISO ride
vibration test tracks and whilst performing typical agricultural operations, the latter in both
representative controlled field conditions and during normal operation on working farms.
Additionally, the investigation proposed to consider the consequences of prescribing limits
for operator WBV daily exposure, upon agricultural vehicle usage patterns in the UK. The
investigation targeted three generic types of agricultural vehicle (self-propelled sprayers, allterrain vehicles (ATVs), and agricultural tractors), the latter whilst operating (‘in-field’ and
‘on-farm’) with a range of attached agricultural implements. Details regarding the design,
selection and evaluation of these vehicles are given in the following Sections.
It is to be expected that agricultural vehicle operators will be exposed to WBV levels above
the (PA(V)D-specified) Exposure Action Value in almost all tasks during typical working
days. The work presented here indicates the extent to which the Directive may impinge on
modern farming operations, by possibly restricting the working day length of certain
machines / tasks, unless daily vibration exposure levels can be reduced even more than at
present. The latter possibly being achievable by further developments in machine design (for
enhanced operator comfort) and/or by informed changes in vehicle driving or operating
practice / techniques on farms.
1
2
2.
2.1
AGRICULTURAL VEHICLE REVIEW
AGRICULTURAL VEHICLE DESIGN FEATURES
As previously stated, it is widely recognised that agricultural tractor operators are exposed to
high levels of whole-body vibration (WBV) during typical farm operations. Low-frequency
tractor ride vibration, the resultant problem of driver discomfort and the possibility of spinal
injury, first became recognised issues during the 1960’s. Since that time the majority of
agricultural tractors have incorporated one or more design features that attempt to reduce the
levels of WBV experienced by the operator. This vibration reduction ‘technology’ has
subsequently been transferred to other self-propelled agricultural machines as the latter
became commonplace during the 1970’s and 1980’s. The following sections review these
features found on current, state-of-the-art tractors and other agricultural vehicles.
2.1.1
Operator seat suspension
Suspension seats have been an almost universal feature of agricultural tractors throughout the
last 30 years, being a mandatory requirement upon wheeled agricultural and forestry tractors
in Europe since 1978 (EEC, 1978). Primarily introduced to improve driver comfort, thereby
reducing fatigue and improving productivity (e.g. higher vehicle forward speeds on rough
ground; preparedness of operators to work longer daily periods at peak times), suspension
seats were rapidly recognised by employers and workers alike as being a worthwhile
investment, especially coupled with the introduction of other driver comfort-enhancing
features, such as low-noise level tractor cabs, during the mid-1970’s. The effectiveness of
some early suspension seat designs may have left something to be desired, but their ability to
attenuate the extreme peak accelerations so common in tractor ride, was indisputable. Early
suspension seats of the late 1960’s and early 1970’s, which provided suspension solely in the
vertical (Z) axis, mainly utilised adjustable rubber-in-torsion or tension coil spring suspension
elements, together with telescopic hydraulic dampers, giving simple vertical movement.
Later designs, some utilising adjustable mechanical torsion springs, incorporated low-friction
‘scissor’-type suspension linkages, giving true vertical (Z) axis movement and adjustable ride
height. Many modern tractor seats still utilise this basic design, albeit higher specification
models use air springs which are readily adjustable to the operator’s weight, in place of the
earlier mechanical suspension elements.
Current off-road vehicle seats are produced almost exclusively by specialist ‘Original
Equipment Manufacturers’ (OEMs). The majority of modern seats commonly fitted to
medium – high-powered tractors incorporate (adjustable) air spring & (adjustable) damper
suspension systems in the vertical (Z) axis, and (fixed) mechanical spring & (fixed) damper
systems in the longitudinal (X) axis (see Table 5.2), the latter in an attempt to attenuate
vehicle pitch acceleration. Certain manufacturers also offer similar (fixed) mechanical spring
& (fixed) damper suspension systems in the transverse (Y) axis, vehicle lateral ‘roll’ being a
major source of WBV as tractors become larger and seat positions become higher relative to
the vehicle roll centre. However, limited cab internal width and seat proximity to sidemounted controls, restrict available suspension system movement in this direction, thereby
limiting the scope of this albeit desirable feature. One of the most recent developments in
agricultural tractor seating was introduced by John Deere in 2002. The John Deere ‘Active
Seat’ utilises combined (parallel) electro-hydraulic and air suspension systems, featuring
electronic sensing and electro-hydraulic control of ride height, plus automatic sensing of seat
top (vertical) acceleration (via an integral accelerometer), effecting dynamic adjustment of
seat suspension system stiffness in response to the accelerometer output. In combination,
3
these features are designed to reduce driver WBV still further, reductions in Z-axis weighted
r.m.s. acceleration (in comparison with a typical air suspension seat) of over 65% being
claimed by the manufacturers (Dufner & Schick, 2002).
Tractor suspension seat technology has been progressively transferred to other self-propelled
agricultural machines (e.g. sprayers, forage harvesters, combines), although many of these
machines do not experience the same rough operating conditions / ride vibration levels as
agricultural tractors in the majority of applications. Smaller vehicles (e.g. garden tractors,
ride-on lawn mowers, all-terrain vehicles (ATVs)) typically do not incorporate suspension
seats, either due to seat (relative to vehicle) cost or incompatible vehicle design (lack of space
for installation).
2.1.2
Vehicle cab suspension
The logical method of reducing ride vibration levels upon any vehicle is to introduce one or
more suspension systems between the vehicle vibration source and the operator. The majority
of whole-body vibration present upon tractors is ground-induced. The basic requirements of a
tractor, namely to pull draught (soil-engaging) implements, to provide a stable mounting
platform for carried implements, and to provide high levels of traction in adverse, off-road
conditions (i.e. incorporate large diameter tyres), together with the historic ‘unitary’ structural
engine-transmission-rear axle construction method, makes the incorporation of an effective
axle suspension system a significant (and costly) design challenge. Consequently, many
tractor manufacturers, having embraced the ride vibration reduction benefits of suspension
seats, regarded incorporation of vehicle cab suspension as the logical (and potentially most
economic) next step.
Experimental tractor cab suspension systems were developed by a number of research
institutes / universities during the 1970’s, initially as proof-of-concept systems (Stayner et
al., 1975). Having achieved worthwhile reductions in operator WBV levels, subsequent
systems were developed to facilitate simple, economic incorporation into tractor designs of
the period (Lines et al., 1989). Regrettably, at that time (late-1980’s), few tractor
manufacturers considered provision of tractor cab suspension systems, however effective, to
be justified by European market demand. Consequently no ‘global’ tractor manufacturers
(e.g. Ford, John Deere, Massey Ferguson, International Harvester) offered this feature during
the next 10 years, the only exception being Renault. Today (2003) every ‘mainstream’ tractor
manufacturer either offers some form of cab suspension system, or is rapidly in the process of
developing a system to meet perceived market demand!
The Renault ‘Hydrostable’ cab suspension system (see Figure 2.1) was the first, massproduced tractor cab suspension system and is the most numerous in use, having been
available on many tractor models since 1987. A true ‘full’ suspension system, combined coil
spring & telescopic damper units (4) support the cab upon each corner (3); cab lateral location
is provided by transverse Panhard rods front and rear (5), and twin longitudinal struts (7)
provide longitudinal location. A rear-mounted anti-roll bar (6) limits cab (Y-axis) roll. The
majority of other European tractor manufacturers have opted for simpler cab suspension
systems in which the rear of the cab is suspended from the tractor rear axle, but the front
pivots on anti-vibration rubber mountings; lateral location at the rear being provided by a
Panhard rod(s). This approach is typified by the New Holland ‘Comfort Ride’ cab suspension
system, as fitted to the New Holland Series TM tractors (see Figures 2.2 & 2.3). Some
manufacturers utilise air-over-oil suspension elements in these systems, thereby permitting
control of cab ride height with operators of different mass. However, the majority of
4
manufacturers choose the simpler combined mechanical spring-hydraulic damper solution, as
used by New Holland (see Figure 2.3).
Figure 2.1 Renault ‘Hydrostable RZ’ cab suspension system (courtesy Renault)
2.1.3
Vehicle axle suspension
As previously discussed, during the 1980’s many tractor manufacturers viewed tractor axle
suspension as a complex design challenge of dubious economic benefit. Experimental, proofof-concept tractor front axle suspension systems were developed by a number of research
institutes and universities during the 1970’s and 1980’s, frequently in conjunction with
‘global’ tractor manufacturers. These experimental systems, as typified by Peachey et
al. (1989), met with considerable success, the Silsoe Research Institute (then NIAE) example
undergoing extended practical evaluation on working farms. The majority of systems
provided suspension of the tractor front axle only, this being a simpler and cheaper
modification of the two-wheel-drive tractors which comprised the majority of 1970’s sales.
Provision of rear axle suspension was a considerably more complex task, given variable
weight transfer onto the rear axle from mounted implements and the characteristic unitary
construction of tractors of that period.
The Trantor vehicle, developed and marketed in the 1970’s, proved that a fully suspended
(front & rear axle) tractor was feasible. However, the vehicle suffered from a number of
design and component availability restrictions, and arguably preceded market demand: it
consequently failed to become a commercial success. Other fully suspended vehicles, such as
the Unimog, were marketed in agriculture, but failed to satisfy all requirements placed upon
the typical agricultural tractor.
(continued)
5
Figure 2.2 New Holland Series TM tractor ‘Comfort Ride’ cab suspension system
(courtesy CNH)
Figure 2.3 New Holland ‘Comfort Ride’ cab suspension system (detail) (courtesy CNH)
6
Figure 2.4 JCB Fastrac chassis and suspension system (courtesy JCB)
2.1.3
Vehicle axle suspension (continued)
JCB took up the challenge in the late 1980’s, culminating in the launch of the ‘Fastrac’; a
fully suspended, four-wheel-drive (4wd) vehicle capable of performing all tractor-type
draught operations and travelling legally (and safely) at up to 65 km/h (40 mph) on the road.
Unhindered by previous construction practices, JCB designed a fully suspended vehicle first
(arguably drawing much upon commercial vehicle design principles), and subsequently made
it perform adequately as an agricultural tractor. Departing from the unitary method of
construction, driven axles were attached, via suspension components, to a ‘ladder’-type
chassis (see Figure 2.4). Radius arms, coil springs, telescopic dampers and a Panhard rod (not
shown) provide front axle location / suspension. A self-levelling hydro-pneumatic suspension
system supports the rear axle, upper and lower radius arms providing axle location. Anti-roll
bars (not shown) are fitted to both front and rear axles to provide lateral roll stability. The
rear 3-point linkage system and trailer hitch attach directly to the rear axle. Over a decade on,
with an unchanged basic design and a range comprising six models, JCB can justly claim the
Fastrac to be the most successful fully suspended agricultural tractor produced to date.
Whilst no other major tractor manufacturers have yet launched a fully suspended vehicle in
Europe in direct competition with the Fastrac, during the last 4 years there has been a
widespread introduction of ‘optional’ front axle suspension systems on 4wd tractors of
otherwise ‘conventional’ design, especially above ~70 kW engine power. Indeed, market
demand for this feature is such that front axle suspension and cab suspension systems may
almost be regarded as standard product offering on frontline (high utilisation) arable farm
tractors in Europe today.
‘Conventional’ 4wd tractor front axle suspension systems are typified by those offered by
New Holland and John Deere (see Figures 2.5 & 2.6 respectively). Both utilise self-levelling
air-over-oil (hydro-pneumatic) suspension elements, powered by the tractor hydraulic system
and providing both springing and damping functions. Longitudinal axle location is provided
7
by a pivoting, tubular radius arm that encases the front axle driveshaft, its rear end being
attached to the centre of the tractor chassis via a spherical bearing. A Panhard rod effects axle
lateral location, but the axle is free to oscillate in a similar manner to an unsuspended design,
no anti-roll functionality being provided. Certain manufacturers (Steyr, Massey Ferguson,
McCormick, John Deere (8020 Series)) utilise independent ‘wishbone’-type front axle
suspension systems, dispensing with the conventional ‘live’ front axle and embodying
universal-jointed driveshafts to the front wheels. Whilst an interesting solution to the
problem, it is not known whether this approach delivers any benefits over other ‘live’ front
axle suspension designs. It is debatable whether the recent introduction of ride-comfort
enhancing features, such as front axle and cab suspension systems, would have been quite so
widespread had it not been for the commercial competition provided by the JCB Fastrac. In
any case, the vehicle operator can only benefit from the greater availability of this technology
Figure 2.5 New Holland ‘Terraglide’ front axle suspension system (courtesy CNH)
Figure 2.6 John Deere ‘Triple Link Suspension’ (TLS) front axle suspension system
(courtesy John Deere)
8
2.1.4
3-point linkage dynamic ride control
This feature is almost exclusive to agricultural tractors, as indeed is the 3-point (3pt.)
implement attachment linkage system of which it is a feature. Harry Ferguson developed the
3pt. hydraulic linkage, as a means of attaching or ‘mounting’ soil-engaging implements onto
tractors, in 1925. Since then it has become a universal feature of agricultural tractors
throughout the World. During the late-1980’s the implement (draught force and position)
sensing and hydraulic control components of many 3pt. linkage systems were upgraded by the
incorporation of microprocessor-based electronics (e.g. Bosch EHR-D system). This
revolution permitted the subsequent development of other 3pt. linkage features, amongst them
dynamic ride control.
The basic principle of dynamic ride control is that during road/track transport with mounted
implements, particularly long, heavy equipment such as fully-mounted ploughs, a substantial
proportion of tractor pitch (X-axis) acceleration results from the dynamic movement of the
implement in the vertical (Z) axis. These forces are transferred from the implement to the
tractor chassis via the 3pt. linkage, which (fortuitously) incorporates electronic force sensors
as part of the draught control system. Dynamic ride control systems sense the magnitude of
these dynamic forces and dynamically modulate the hydraulic pressure in the 3pt. linkage lift
cylinder(s), thereby permitting the implement to lower/raise slightly relative to the tractor at
critical moments in the combination’s (relatively slow) pitching cycle, effectively operating
as an active suspension system between the tractor and mounted implement. An effective
dynamic ride control system can substantially reduce the ride vibration of a tractor-implement
combination during transport. Unfortunately, current systems are unable to determine the
position of the implement’s centre of gravity: an important factor in the performance of the
system. Consequently, the majority of systems are optimised for long, heavy mounted
implements, for which they are indeed most needed, but they perform less effectively with
shorter/wider implements. However in the latter instances, vehicle pitching during transport
is a lesser problem. 3pt. linkage dynamic ride control is a standard feature on the majority of
European tractors over 75 kW engine power and was present upon all the tractor models
evaluated during this investigation.
2.2
AGRICULTURAL VEHICLE FLEET COMPOSITION AND USAGE
PATTERNS
Agricultural vehicle usage patterns, in general, reflect changes in both the nature and
prosperity of agriculture as a business. To that end the following comments are, admittedly,
based purely upon an interpretation of available facts, to enable derivation of the desired
information: they also relate solely to the UK.
Reductions in the value of most arable commodities (e.g. wheat, oilseed rape) during the last
3 years have significantly reduced UK arable farm profitability, many enterprises reaching the
verge of commercial viability. Figure 2.7 illustrates that during the 1987 – 2000 period, the
number of UK agricultural holdings diminished significantly across both arable and livestock
sectors: however, those remaining increased in both size (see Figure 2.8) and productivity.
Farm enterprise structure has also changed, with moves towards operational amalgamation of
enterprises, as typified by corporate / contract farming arrangements in the arable sector, in
order to optimise utilisation of larger, more productive machinery and spread labour costs
over larger cropped areas, thereby reducing Fixed Costs. However, during the period in
question, farm labour force reductions have not been restricted to the arable sector; the
number of workers employed in the industry having reduced by 35% (DEFRA, 2001).
9
10
0
% Change: 1987 - 2000
-10
-20
-30
-40
-50
-60
-70
Crops &
Grass
Cereals
Oilseed
Rape
Potatoes
Sugar Beet Dairy Cows
Beef
Breeding
Sheep
Breeding
Pigs
Broilers
Figure 2.7 Change in number of UK agricultural holdings: 1987-2000
130
120
110
% Change: 1987 - 2000
100
90
80
70
60
50
40
30
20
10
0
Crops &
Grass
Cereals
Oilseed
Rape
Potatoes Sugar Beet Dairy Cows
Beef
Breeding
Sheep
Breeding
Pigs
Broilers
Figure 2.8 Change in UK holding average cropped area / herd size: 1987-2000
These changes have, to an extent, been offset by corresponding changes in agricultural
machinery and associated working practices. Agricultural tractor sales are recognised by the
industry as an accurate indicator of mechanisation trends, particularly in the arable sector.
The 1987 – 2001 period witnessed a substantial reduction in tractor unit sales (see Figure 2.9),
but this was largely offset by significant rise in the average size (engine power) of vehicles
sold (see Figure 2.10). Although this trend may have stabilised in recent years (2000 – 2002),
numbers of medium / large (100 – 160 hp) four-wheel-drive tractors sold has continued to
increase (see Figure 2.11), indicating that today’s agricultural industry uses fewer, larger,
more productive machines, frequently selected to enable labour force reductions. Whilst such
equipment generally embodies higher technological content and improved levels of operator
comfort (see Section 2.1), its higher purchase price necessitates greater annual usage in order
to offset cost of ownership.
10
25
Tractors sales> 40 hp (thousands)
20
15
10
5
0
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
Year of manufacture
Figure 2.9 UK sales of agricultural tractors (above 40 hp)
130
Average horsepower of tractors > 40 hp
120
110
100
90
80
70
60
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
Year of manufacture
Figure 2.10 Average engine power of tractors (above 40 hp) sold in the UK
Although independent data is not available to support the view, it is widely recognised within
the agricultural engineering industry that annual, and particularly daily, usage levels of higher
capacity / higher cost machines has increased significantly, especially given that many
customers are large farming enterprises and/or agricultural contractors. Today many front
line agricultural tractors complete 2000 hours work per year, whereas two decades ago usage
11
exceeding 1,000 hours per year was considered intense. For example a typical contractor
would now wish to operate a self-propelled sugar beet harvester (and associated tractors /
trailers) for at least 70 hours per week during the October – February period.
Consequently, more acres (hectares) are being farmed by fewer enterprises, using fewer men.
Whilst the proportion of farm work performed by contractors has undoubtedly increased, the
fact remains that tractor drivers, be they farmers, farm workers or contractor’s employees,
spend more hours each year in the driving seat: tractor annual utilisation is increasing.
Farm restructuring and greater use of contractors has led to increased use of self-propelled
sprayers, although this is not immediately evident from recent vehicle sales statistics (see
Figure 2.12). Nonetheless, the fact that machine sales levels have been maintained, despite
reductions in arable farm profitability, indicates the importance of this machine type in
modern UK agriculture. Need to reduce both the initial purchase and operating costs of
machines has also led to a significant increase in (non-recreational) sales of All-Terrain
Vehicles (ATVs) (‘Quad Bikes’) (see Figure 2.13), these machines frequently supplementing
or replacing expensive four-wheel-drive utility vehicles on livestock farms.
Agricultural tractors currentlly licenced (estimated)
(with respect to hp class)
7000
6000
5000
4000
3000
2000
1000
0
1997
1998
1999
2000
2001
2002
Year of manufacture
41 - 60
61 - 80
81 - 100
101 - 130
131 - 160
161 - 200
201+ (hp)
Figure 2.11 Engine power distribution of UK agricultural tractor sales (above 40 hp)
12
UK sales of large Self-Propelled Sprayers
250
200
150
100
50
0
1998
1999
2000
2001
2002
Year of manufacture
Figure 2.12 UK sales of self-propelled sprayers
10000
9000
ATV's sold for non-recreational use
8000
7000
6000
5000
4000
3000
2000
1000
0
1998
1999
2000
2001
2002
Year of manufacture
Figure 2.13 UK sales of ATVs (for non-recreational use)
13
2.3
TARGET VEHICLE IDENTIFICATION
Given the trends in UK agricultural vehicle fleet composition and usage discussed above, it
appeared appropriate for this investigation to target vehicles which were likely to be subject
to high annual usage, the operators of which therefore receiving longer exposure to wholebody vibration (WBV). Additionally, it also seemed correct to target vehicles which
potentially subject their operators to high WBV levels and/or are increasing in popularity
within UK agriculture. To this end the following vehicles were selected as targets for this
investigation:-
Agricultural tractors
The primary agricultural power unit and therefore a must for inclusion in the investigation,
four state-of-the-art 4wd tractors were selected from the very popular 120 – 170 hp (90 –
125 kW) engine power range, these representing front-line tractors from medium-large UK
farms and farm contractors. The vehicles were selected to encompass the entire range of
WBV reduction features currently available on the UK tractor market, these being:•
•
•
•
Unsuspended
Suspended cab
Suspended front axle & cab
Fully suspended (front and rear axle).
Self-propelled sprayers
These machines were selected due to their increasing market popularity and high utilisation
by agricultural contractors. Self-propelled sprayers have historically embodied some form of
axle suspension, but system complexity / capability is increasing due to market demand for
greater operator comfort / productivity. To this end two typical (largely identical) machines
were selected, albeit differing in design of suspension system used, one being the ‘new,
improved’ replacement of the other.
All terrain vehicles (ATVs or ‘Quad Bikes’)
Selected due to increasing popularity within UK agriculture and typical use at medium-high
speeds across rough terrain, which could potentially lead to high WBV emission levels.
However, daily usage periods are likely to be relatively short and so operator WBV exposure
may be acceptable. Very little data is currently available to confirm this. Four competitive
machines in the popular (within UK agriculture) 300 – 400cc engine size range were selected
for investigation.
14
3.
WHOLE-BODY VIBRATION (WBV) MEASUREMENT
3.1
EUROPEAN UNION PHYSICAL AGENTS (VIBRATION) DIRECTIVE
3.1.1
Introduction
The European Physical Agents (Vibration) Directive (EU PA(V)D – EEC:2002) was issued
by the European Parliament and the Council for the European Union in July 2002, after
undergoing lengthy debate over a period of years. The overall purpose of the Directive is to
encourage improvements, particularly in the working environment, to effect an improved
level of worker health and safety protection. The PA(V)D attempts to achieve this by
protecting workers from the risks resulting from exposure to vibration, whole-body vibration
(WBV) and/or hand-arm vibration (HAV), whereas other EU Directives consider noise and
other so-called physical agents. The justification for the PA(V)D is “to introduce measures to
protect workers from the risks arising from vibrations, owing to their effects on the health and
safety of workers, in particular muscular / bone structure, neurological and vascular
disorders.”
The Directive defines whole-body vibration as “the mechanical vibration that, when
transmitted to the whole body, entails risks to the health and safety of workers, in particular
lower-back morbidity and trauma of the spine.” Strong evidence exists linking regular, longterm WBV exposure to the development of lower back pain and related disorders although,
given the absence of a detailed and reliable quantitative dose-response relationship, the
precise risks are not well-defined. Nonetheless, higher levels of exposure have been shown to
increase the risk to health. Also, other workplace factors, such as manual materials handling
and poor or constrained driving posture, are recognised as contributory factors, and should
therefore be considered and addressed wherever possible. However, returning to WBV, the
main sources are considered to be the seats of industrial and/or agricultural vehicles, and the
platforms of heavy machinery. Hand-arm vibration is defined as “the mechanical vibration
that, when transmitted to the human hand-arm system, entails risks to the health and safety of
workers, in particular bone or joint, neurological or muscular disorders.” HAV is deemed to
result from use of powered, hand-held tools; powered, hand-guided machinery, and from
holding work pieces being processed by machine.
This investigation concerns itself primarily with emission of whole-body-vibration (WBV)
from agricultural vehicles, and the subsequent exposure of the vehicle operators to this
vibration. Hand-arm vibration is measured and commented upon within the All-Terrain
Vehicle (ATV or Quad Bike) investigation programme (see Section 6), but WBV remains the
main target of the study.
3.1.2
Terminology and implementation
The PA(V)D stipulates vibration exposure criteria for WBV and HAV, in the form of
employee daily vibration exposure levels which must not be exceeded (limit values), and
(lower) exposure levels (action values), above which actions for reduction of employee
vibration exposure must be taken. These specific Exposure Action Values (EAV) and
Exposure Limit Values (ELV) are stated in Table 3.1.
With particular regard to WBV, it should be stressed that the Exposure Limit Value (ELV)
stated by the PA(V)D should not be considered a ‘safe’ level of vibration exposure in the
workplace, but rather as a high, undesirable level of vibration exposure (and a legal threshold)
to be avoided at all costs. It is for this reason the Directive requires action to be taken, so far
15
as is reasonably practicable, to minimise vibration exposure once levels exceed the Exposure
Action Value (EAV). As mentioned above, although risks are not well-defined, there is a
lack of strong evidence of health risk from daily exposure to WBV levels at or below the
EAV. However, if daily exposure levels exceed the EAV and approach the ELV, it is likely
the level of risk to health will increase. Hence justification for requiring actions, on the part
of the employer, to reduce risks / vibration exposure wherever practicable (see later).
Whilst the Directive refers to vibration in terms of daily exposure, it will be noted that the
majority of vibration measurements made upon vehicles within this investigation relate to
vibration emissions or emission levels. The situation may be further confused by the fact that
the units of measurement of both parameters can be the same, namely metres-per-secondsquared (m/s2). To clarify the situation (in admittedly simplistic terms), vibration emissions
are a quality of a product or machine, i.e. the vibration levels which come out of a machine, in
the form of an acceleration level with varies (very rapidly) with time (an acceleration time
history). As a first stage of analysis, WBV acceleration time histories are frequency-weighted
to reflect the sensitivity of the human body to vibrations in certain frequency ranges (see
ISO 2631:1997). Vibration exposure, on the other hand, is the level of vibration received by a
person (from a machine / source) over a period of time. It is therefore a function of the
magnitude of vibration emissions received during that period and the length of the (exposure)
period.
WBV emission levels are evaluated in terms of frequency-weighted root-mean-square (r.m.s.)
acceleration (aw) (units: m/s2). This technique generates a single value to represent a period
of vibration measurement:-
1T
aw = ⎡⎢ ∫ a 2w (t ) dt ⎤⎥
⎣T o
⎦
1
2
(1)
where:aw(t) = frequency-weighted acceleration time history (m/s2)
T
= duration of measurement (seconds)
Where vibration exposure consists of two or more periods of exposure to different magnitudes
and durations, the (frequency-weighted) energy-equivalent acceleration (Aeq) corresponding
to the total duration of exposure may be derived. This is effectively an overall average r.m.s.
acceleration value for the total period in question (∑Ti):-
Aeq
⎡ ∑ a 2wi .T i ⎤
= k⎢
⎥
⎣ ∑T i ⎦
1
2
(2)
where:Aeq =
axis-weighted energy-equivalent
acceleration (m/s2))
continuous
acceleration
(r.m.s.
awi =
vibration magnitude (r.m.s. acceleration (m/s2)) for exposure period Ti
∑Ti = total duration of exposure / measurement
k
=
orthogonal (measurement) axis multiplying factor specified by ISO 26311:1997 (see Table 3.2)
16
For whole-body vibration (WBV), as opposed to hand-arm vibration (HAV), the PA(V)D has
proposed two alternative methods of vibration exposure assessment and European Member
States have the option to implement the Directive using either technique. The Exposure
Action Value (EAV) and/or the Exposure Limit Value (ELV) may be defined either as a daily
vibration exposure, expressed as frequency weighted, energy-equivalent continuous r.m.s.
acceleration over an eight-hour period (A(8)), or as a vibration dose value (VDV) of the
frequency-weighted acceleration (see Table 3.1).
In either case, the vibration exposure levels are evaluated individually from the acceleration
time histories recorded in each of three orthogonal axes (X-longitudinal, Y-transverse & Zvertical), following application of the frequency-weightings (Wd or Wk) and axis weighting
factors (k), as stated in ISO 2631-1:1997 regarding “Effect of Vibration on Health” (see
Table 3.2 and Paddan et al., 1999). The resulting A(8) or VDV values for each (X, Y & Z)
axis are then compared individually with the EAV and ELV. The axis-weighting (or
multiplying) factor (k) effectively increases the magnitudes of the horizontal (X & Y) axes
WBV values (see Equation 2).
The daily vibration exposure level (A(8)) (units: m/s2), expressed as eight-hour energyequivalent continuous, frequency-weighted r.m.s. acceleration (A(8)) may be derived from
the equivalent continuous r.m.s. acceleration (Aeq) via Equation 3, below:-
A(8)
=
Aeq
t
8
(3)
where:t
= daily exposure period (hours)
Aeq = the energy-equivalent continuous r.m.s. acceleration which is
representative of the exposure period (m/s2)
Alternatively, if the equivalent continuous r.m.s. acceleration (Aeq) value (effectively the
overall average r.m.s. value) for a period of vibration exposure has not previously been
derived (thereby permitting the use of Equation 3 above), the daily vibration exposure A(8)
value may be derived directly from the frequency-weighted acceleration time history using
the formula:-
⎤
⎡1 T
A(8) = k ⎢ ∫ a 2w(t ) dt ⎥
⎦
⎣ To 0
1
2
(4)
where:aw(t) = frequency-weighted acceleration time history at the supporting
surface (m/s2)
T
= total duration of exposure within any period of 24 hours
To
= reference duration of 8 hours (28,800 seconds)
k
= orthogonal (measurement) axis multiplying factor specified by
ISO 2631-1:1997 (see Table 3.2)
17
Table 3.1 Vibration exposure values specified by the EU PA(V)D
8-hour energy-equivalent
Vibration Dose Value
r.m.s. acceleration – A(8)
(m/s1.75)
(m/s2)
Exposure Action
Value (EAV)
0.5
9.1
Exposure Limit
Value (ELV)
1.15
21
Exposure Action
Value (EAV)
2.5
-
Exposure Limit
Value (ELV)
5.0
-
Whole-Body Vibration
Hand-Arm Vibration
Table 3.2 Frequency weightings and multiplying factors for health aspects of wholebody vibration (WBV) as specified by ISO 2631-1:1997 for seated persons
Measurement axis
Frequency weighting
Multiplying factor (k)
Longitudinal (X) axis
Wd
1.4
Transverse (Y) axis
Wd
1.4
Vertical (Z) axis
Wk
1
For comfort evaluation ISO 2631-1:1997 recommends multiplying factors of 1 in all axes.
The daily vibration dose value (VDV) (units: m/s1.75) of a person may be derived from the
formula:-
⎡T
⎤
VDV = k ⎢ ∫ a 4w (t ) dt ⎥
⎣o
⎦
1
4
(5)
where:aw(t) = frequency-weighted acceleration time history at the supporting
surface (m/s2)
T
= total duration of exposure (seconds) within any period of 24 hours
k
= orthogonal (measurement) axis multiplying factor specified by
ISO 2631-1:1997 (see Table 3.2)
18
The relative advantages and disadvantages of the alternative A(8) and VDV approaches are
discussed by Coles (2002). However, one point to highlight relates to the equivalence of the
A(8) and VDV techniques. The A(8) and VDV EAV and ELV values specified by the
Directive (see Table 3.1) are intended to be equivalent for exposure to vibration over an
8 hour period (see Figure 3.1). However, this equivalence is based upon the calculation of an
estimated VDV (eVDV) from the r.m.s. acceleration value (as proposed by ISO 2631-1:1997
and Equation 6). Regrettably the eVDV only provides an accurate estimate of the actual
VDV if the prevailing vibration is more or less continuous and devoid of transient high
acceleration events and/or shocks: otherwise an underestimate is likely to result (Coles,
2002). Most conditions in which WBV exposure is of concern do not conform to these
limitations. Thus a vibration exposure that yields an r.m.s. (A(8)) of 1.15 m/s2 is likely to
result in a true VDV very different from the (supposedly equivalent) 21 m/s1.75. At the time
of writing the HSE is undertaking a public consultation exercise regarding implementation of
the PA(V)D in the UK. Whilst it is highly likely that the ELV will be specified by the A(8)
technique, debate is currently ongoing as to whether the EAV will be implemented in VDV or
A(8) terms. Irrespective of this, all VDV values reported in this study are based upon actual
measurement of the parameter, as opposed to its estimation from r.m.s. acceleration values.
Estimated vibration dose value (eVDV) = 1.4 a w t
1
4
(6)
where:aw =
frequency-weighted r.m.s. acceleration (m/s2)
t
exposure duration (seconds)
=
Issues concerning the use of the eVDV with regard to agricultural vehicles, and derivation of
the A(8) and VDV from WBV field data, are discussed further in Section 7.4 and Appendix 4
respectively.
The Directive provides a derogation permitting weekly averaging of daily personal vibration
exposures, but this is intended for use in circumstances where occasional high vibration
exposure levels (greater than the ELV) are likely to be encountered during the working week,
but otherwise levels are usually low (below the EAV). In such circumstances, which may
well be rare in agriculture, the weekly average personal vibration exposure (A(8)week)
(units: m/s2), i.e. the total exposure occurring within a period of seven consecutive days,
normalised to a reference duration of 40 hours, may be derived from Equation 7:
A(8)week
=
1 7
2
∑ A (8) j
5 j =1
(7)
where:A(8)j = the daily vibration exposure for day j (m/s2)
Unlike WBV, exposure to hand-arm vibration (HAV) is quantified by calculation of the eighthour energy-equivalent, root-sum-of-squares (RSS) frequency-weighted total r.m.s.
acceleration value (A(8)), derived from three orthogonal measurement axes (X-longitudinal,
Y-transverse & Z-vertical) (see ISO 5349-1:2001 and Equations 8 & 9). The vector-sum
vibration value (ahv), which represents vibration magnitudes in all three axial directions, is
19
used to calculate a single A(8) value for the exposure duration in question: this A(8) value
may then be compared with the HAV EAV and ELVs specified in Table 3.1.
A(8)
= a hv
T
(8)
T0
where:-
ahv = the vector-sum vibration magnitude (m/s2)
T
= duration of exposure to the vibration magnitude ahv
To = reference duration of 8 hours (28,800 seconds)
The vector-sum (root-sum-of-squares) vibration magnitude (ahv) is derived by use of the
formula:-
ahv
=
a hwx + a hwy + a hwz
2
2
2
(9)
where, ahwx ahwy and ahwz are the r.m.s. acceleration values (m/s2) measured in three orthogonal
directions (X, Y & Z), at the vibrating surface in contact with the hand and frequencyweighted using the function Wh (see ISO 5349-1:2001).
3.1.3
Practical implications
As previously stated, at the time of writing the HSE is undertaking a public consultation
exercise regarding implementation of the PA(V)D in the UK, so it is not currently possible to
give a definitive review of all the practical implications of the Directive. Indeed, one of the
main justifications for this investigation was to identify and explore the extent of these
implications regarding the use of agricultural vehicles. Nonetheless, it is possible to highlight
the main practical requirements of the Directive and consider how these may translate into
practical actions required in the workplace.
The current form of the PA(V)D (EEC, 2002) requires employers, where there is likely to be
a risk from exposure to vibration, to:Reduce vibration exposure to a minimum (an overall requirement)
Assess the particular risks
Implement a programme of measures to reduce those risks
Keep worker daily exposure below the Exposure Limit Value (ELV)
Provide information & training to workers, on the risks of vibration exposure &
means of their control
Provide appropriate health surveillance when daily exposure levels reach / exceed
the Exposure Action Value (EAV)
20
Given that agricultural vehicles are a known source of WBV, a vibration risk must be
assumed to be present during their operation, requiring an employer to perform a “suitable
and sufficient assessment of risk”. A key purpose of the assessment is to determine whether
the daily vibration exposure level of an employee performing a given operation, is likely to
exceed the EAV or the ELV. In certain instances, it may be possible to perform a vibration
exposure assessment by combining vibration emission data published for the machine /
operation and knowledge of the likely period of operation (see Equation 3). However, in the
absence of suitable published data, or in situations where exposure levels may approach the
ELV, an employer may consider it necessary to actually measure the levels of vibration to
which workers are exposed.
If a worker’s daily vibration exposure level should exceed the (WBV or HAV) Exposure
Action Value, the Directive requires an employer to implement a programme of technical
and/or organisational measures intended to reduce vibration exposure in the workplace to a
minimum. Whilst admittedly revisiting many of the points already highlighted, it is
interesting to note that the Directive actually states that such measures would include:•
Limitation of the duration and intensity of exposure
Choice of appropriate work equipment of appropriate ergonomic design,
producing the least possible vibration
Selection / implementation of alternative working methods which incur less
worker exposure to mechanical vibration
Implementation of appropriate work schedules with adequate rest periods
Provision of auxiliary equipment that reduces the risk of vibration-related
injuries, e.g. seats which effectively reduce WBV or vibration-isolated handles
which reduce the transmission of HAV
Provision of clothing to protect exposed workers from cold and damp
•
Consideration of the design and layout of workplaces and work stations
•
Provision of adequate information / training / instruction to workers to ensure work
equipment is used correctly and safely, to reduce vibration exposure to a minimum
•
Implementation of appropriate maintenance programmes for work equipment, the
workplace and workplace systems
As previously stated, on no account should workers be exposed to vibration above the
Exposure Limit Value (ELV). If the ELV is exceeded, immediate action must be taken to
reduce vibration exposure below the ELV and measures be implemented to prevent it being
exceeded again. As discussed earlier, the Directive does provide a derogation permitting
weekly averaging of daily personal vibration exposure levels, but this is intended for use in
circumstances where occasional high vibration exposure levels (greater than the ELV) are
likely to be encountered during the working week, but otherwise levels are usually low
(below the EAV). Current evidence strongly suggests that the majority of agricultural vehicle
operators will exceed the EAV during most normal (full) days, thereby preventing the use of
this derogation.
It is likely that workers who are subject to high levels of mechanical vibration in the
workplace (daily exposure exceeding the EAV) will be entitled to appropriate health
monitoring. However the method(s) of implementation of this requirement in the UK are
currently the subject of a consultation exercise between the HSE and relevant industries. A
21
major difficulty is the non-specific nature of the ill effects of WBV (primarily lower back
pain), unlike the well-documented ill effects of HAV. As previously discussed, these (back
pain) symptoms may also result from a range of causations, such as manual handling and poor
posture, acting in addition or in place of WBV exposure, any of which may be encountered
both within or outside the workplace.
One important practical issue to note is that (as stated previously) the EAV and ELV values
stated by the Directive refer to either exposure to equivalent continuous r.m.s. vibration over
an eight-hour (daily) reference period (A(8)) or, alternatively, a daily vibration dose
value (VDV). The issue is the time dependency of vibration exposure. The period of time
over which an individual must be exposed to WBV in order to reach the PA(V)D-specified
EAV or ELV depends upon the magnitude of the prevailing WBV emissions level (see
Equations 3 & 5 and Figure 3.1). In simple terms, exposure to higher vibration (acceleration)
levels will cause the EAV and ELV to be reached in less time, and vice versa. This directly
affects the maximum operating durations for particular machines and/or operating conditions.
3.5
Weighted r.m.s. Acceleration (m/s2)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
2
4
6
8
10
12
14
16
18
20
Time (hours)
Exposure Action Value (A(8))
Exposure Action Value (eVDV)
Exposure Limit Value (A(8))
Figure 3.1 Effect of WBV emission magnitude upon exposure duration required to
reach the PA(V)D EAV and ELV
As indicated by Figure 3.1, if a worker’s period of exposure is likely exceed 8 hours/day, the
maximum average r.m.s. WBV magnitude is in fact lower than the stated (A(8)) ELV of
(1.15 m/s2). For example, an operator receiving an overall average r.m.s. acceleration (Aeq)
level of, say, 1 m/s2, in the vertical (Z) axis, would receive a daily vibration exposure (A(8))
of 1 m/s2 after 8 hours operation (see Equation 3). However, if the operating period extended
to 12 hours, the daily vibration exposure (A(8)) value would increase to 1.22 m/s2, exceeding
the ELV. The operating duration would in fact be restricted to approx. 10½ hours by the
Directive (see Figure 3.1). This is a potentially important fact for industries such as
agriculture, where working day lengths frequently exceed 8 hours. Conversely, it may be
legally acceptable (but arguably not best practice) for an individual to be exposed to WBV
22
emission levels (overall average frequency-weighted r.m.s. acceleration (Aeq) magnitudes)
above the nominal, numerical A(8) EAV and ELV levels IF the period of exposure is less
than 8 hours. Figure 3.1 indicates the extent to which this is the case.
ISO 2631-1:1997 suggests approximate indications of public perception to a range of overall
total (RSS – r.m.s.) vibration emission values (see Table 3.3). These are admittedly
approximations, but nonetheless they provide some indication to the layman of levels of
perceived discomfort that may be associated with broad r.m.s. WBV levels, in an otherwise
complex world of vibration evaluation.
This information also serves to reinforce an important message concerning WBV: specifically
that the Exposure Limit Value (ELV) stated by the PA(V)D should not be considered a ‘safe’
level of vibration exposure in the workplace, but rather as a high, undesirable (and
uncomfortable) level of vibration exposure (and a legal threshold) to be avoided at all costs.
It is for this reason the Directive requires action to be taken, so far as is reasonably
practicable, to minimise vibration exposure once levels exceed the Exposure Action
Value (EAV) (0.5 m/s2 A(8)). Also, it is important to highlight that whilst the Directive
requires WBV exposure levels to be assessed separately in each axial direction, and the
measurement axis with the greatest (overall average) magnitude is identified, action is
required to reduce WBV exposure in all axial directions where the EAV is exceeded. In
practical terms whilst, for a given vehicle / application, the longitudinal (X) or transverse (Y)
measurement axes may exhibit the highest axis-weighted overall-average acceleration levels,
marginally lower Aeq levels in the remaining axial directions may still require vibrationreducing actions on the part of the employer if above the EAV, especially if significant peak
acceleration events (shocks and jolts) are present (see Section 5.4).
Table 3.3 Likely perception of discomfort resulting from WBV (as suggested by
ISO 2631-1:1997)
Vibration total value (m/s2)
Perceived comfort level
Less than 0.315
Not uncomfortable
0.315 – 0.63
A little uncomfortable
0.5 – 1.0
Fairly uncomfortable
0.8 – 1.6
Uncomfortable
1.25 – 2.5
Very uncomfortable
Greater than 2.0
Extremely uncomfortable
Finally, whilst the precise methods of implementation of the Directive in the UK are, as yet,
subject to the outcome of a consultation exercise, it is likely that practical guidance will be
provided to employers where necessary. This may include guidance to assist employers to
make simple vibration exposure assessments, to plan control measures, to source appropriate
training and, to identify instances where additional (expert) help may be needed.
23
3.2
INSTRUMENTATION
3.2.1
Measured parameters
Throughout the self-propelled sprayer and agricultural tractor programmes, acceleration
levels were measured simultaneously in three mutually - perpendicular directions
(X - longitudinal, Y - transverse, Z - vertical), at two locations on each machine. Tri-axial
vibration present on the cab floor, close to the seat mounting point (see Figure 3.2) was
measured using an array of three mutually-perpendicular piezo-resistive accelerometers with
integral signal conditioning (IC Sensors type 3140-005, Serial Nos. 0673 005, 0673-007 and 0673042). Vibration on the driver’s seat was measured by placing a semi-rigid mounting disc,
incorporating a tri-axial 100mV/g ICP accelerometer (PCB model 356B40, serial no 18201), on
the seat cushion, approximately between the driver's ischial tuberosities (vertically below the
Seat Index Point) (see Figure 3.3). In addition to these six vibration signals, a seventh
channel was used to record either marker pulses, for the beginning and end of the ISO 5008
test track sections, or forward speed from a Doppler radar speed meter during the ‘in-field’
and ‘on-farm’ measurement programmes.
For tests involving all-terrain vehicles (ATVs) (see Section 6), an eighth channel was used to
record the signal from an operator presence switch attached to the seat pad, so that later data
processing could eliminate periods when the driver was not in contact with the seat. The
ATV tests were also repeated when acquiring data from tri-axial accelerometers attached to
the handlebars (see Figure 3.4), in place of the usual signals from the seat (see Figure 3.5) and
footrest (see Figure 3.6). These were, for the right hand a PCB tri-axial unit type 356A24
(s/n 14583), and for the left hand a composite unit comprising two PCB model 352C22 (s/n 23863,
23865) and one PCB model 353B16 (s/n 64999).
Two data acquisition arrangements were used to record the above signals. The first was a PCbased system, which was used upon the tractors during the ISO test track and SRI ‘in-field’
programmes. For the ‘on-farm’ tractor investigation this was replaced by a PC-card recorder,
which was more suitable for longer recording durations and was easier to package within the
cabs of everyday working vehicles. This system was subsequently used for all measurements
on both self-propelled sprayers and ATVs, whether ISO track, ‘in-field’ or ‘on-farm’.
3.2.2
PC-based data acquisition
During the agricultural tractor ISO test track and SRI ‘in-field’ test programmes,
accelerometer outputs were acquired by a ruggedised laptop-Personal Computer-based signal
conditioning, data acquisition and analysis system (HVLab version 3.81) (see Figure 3.7). This
system was developed by the Institute of Sound and Vibration Research, University of
Southampton, for acquisition and analysis of time-varying signals. Silsoe Research Institute’s
HVLab system incorporates signal-conditioning circuitry to enable direct interface with piezoresistive or strain gauge-based transducers. A Larson Davis Human Vibration Meter type
HVM100 (serial No 272) was used to condition the seat accelerometers’ output, prior to data
acquisition. The acceleration waveforms were low-pass filtered at 100 Hz, via integral antialiasing filters in the HVLab system, and then digitised at 300 samples/second. An additional
data acquisition channel was used to record either marker pulses, for the beginning and end of
the ISO 5008 test track sections, or vehicle forward speed during the ‘in-field’ and ‘on-farm’
measurement programmes. The forward speed signal was derived from either the test
tractor’s own Doppler radar speed meter, or from a separately attached unit (Vansco Model
33800 s/n M0115AP-0067), depending on the availability.
24
Figure 3.2 Cab floor accelerometer system
Figure 3.3 Tractor WBV measurement instrumentation showing seat pad
accelerometer unit
25
Figure 3.4 ATV handlebar accelerometers (for HAV measurement)
Figure 3.5 ATV seat pad accelerometer unit
26
Figure 3.6 ATV footrest accelerometer installation
Figure 3.7 PC-based signal conditioning, data acquisition and analysis system
27
3.2.3
PC card recorder data acquisition
During the investigation a miniature, 8-channel digital data recorder, using PCMCIA-sized
flash data storage cards (TEAC model DR-C2 PC-card recorder serial no 751160 with 128Mb data
card), replaced the PC-based data acquisition system. This produced a more compact data
acquisition system, which could be housed in a standard tractor toolbox, thereby greatly
assisting rapid ‘on-farm’ installation. The process of importing the data into the HvLab
system (for subsequent analysis) was transferred to the laboratory, where analysis could be
performed more rapidly upon a desktop PC. Digitising rates used upon the PC card recorder
were either 200 Hz for whole-body vibration or 2 kHz for hand-arm vibration.
In a further adaptation, the signals from the floor accelerometers were passed through a
second Human Vibration Meter (Larson Davis type HVM100 serial No 215) before acquisition.
The Human Vibration Meters (HVMs) provided the equivalent of anti-aliasing filters for the
PC card recorder and also an alternative acquisition system for acceleration time histories, but
not for the seventh and eighth data channels. For data acquisition purposes, the memories of
the HVMs were set to hold r.m.s. averages of the weighted acceleration signals, together with
the peak acceleration, for each minute of work, and Vibration Dose Values (VDV) for each
15-minute period. For the ‘on-farm’ measurements, the HVM memories were downloaded to
a desktop PC for post-processing, as described below, while the digitised recording provided
vehicle forward speed histories and a backup record of the vibration data. For the selfpropelled sprayer and ATV ISO test track and SRI ‘in-field’ programmes, this digitised data
provided the main source of vibration information, as provided previously by the laptop PCbased acquisition system (see Figure 3.7).
3.3
DATA ANALYSIS
The analysis procedures for the three types of data (ISO test track, SRI ‘in-field’ and ‘onfarm’) differed slightly because of differences in the acquisition methods or in the parameter
values. However, all sets of acceleration histories were examined visually for abnormalities
before processing.
3.3.1
ISO test track data
ISO test track data was derived from the digitised acceleration histories recorded either by the
PC-based (HVLab) acquisition system (tractors) or the PC card recorder (self-propelled
sprayers and ATVs).
During the process of data analysis, it was initially necessary to extract the sections of the
acceleration time-histories which corresponded solely to travel upon the ISO tracks; i.e. to
eliminate the run-up and run-off periods. These sections were extracted from the
acceleration-time data by use of the driver-instigated start and stop marker pulses acquired
during each test. The acceleration records were then normalized (to remove any remaining
zero offsets) and frequency-weighted, using the weighting factors wd and wk specified in
ISO 2631-1:1997 for the horizontal and vertical axes respectively, before calculation of rootmean-square (r.m.s.) acceleration values. The horizontal (X and Y-axis) components were
multiplied by a factor of 1.4, as also specified in ISO 2631-1:1997. Combined (vector-sum)
three-axis acceleration values were obtained for both the cab floor and driver’s seat, by
calculating the root-sum-of-squares (RSS) of the combined orthogonal axes components (see
ISO 2631-1:1997).
28
The frequency-weighted r.m.s. acceleration values were entered into spreadsheets for plotting
against vehicle forward speed and for comparison with r.m.s. acceleration values obtained
from the SRI ‘in-field’ measurement programme.
3.3.2
SRI ‘in-field’ data
SRI ‘in-field’ ride vibration data was derived from the digitised acceleration time histories
recorded either by the PC-based (HVLab) acquisition system (tractors) or the PC card recorder
(self-propelled sprayers and ATVs).
In these applications there was generally only one section of data to “extract” and analyse,
namely that corresponding to the duration of the ‘in-field’ activity (usually 25 – 30 minutes).
There were some exceptions where it was of interest to obtain values for separate parts of the
road / field transport records, or to distinguish between values in work and those travelling to
/ from the field. The boundaries of the complete records, or of the specific sections, were
identified from vehicle speed vs time data. Otherwise, the same data analysis procedure as
that described for the ISO test track data was used.
3.3.3
‘On-farm’ data
‘On-farm’ vibration data were mainly calculated from the acceleration - time histories
acquired by the HVMs. These histories were stored as frequency-weighted values, whether
r.m.s. or VDV. However, although the 1.4 multiplying factor had been used in generating the
stored RSS values, it was not applied to the individual horizontal axes values as stored.
Consequently, after downloading to a desktop PC as text files, the HVM-stored data was
imported into spreadsheets for calculation of cumulative r.m.s. values (Aeq) and Vibration
Dose Values (with 1.4 multiplier where necessary) for the measurement period in question.
These spreadsheets were also used to calculate, for each ‘on-farm’ ‘seat’ acceleration record,
estimates of VDV’s for an 8-hour exposure period and the operating time to reach the
Exposure Action and Limit Values, as defined in the Physical Agents (Vibration) Directive.
They were also used for presentation of acceleration history curves. As in all cases, it was
necessary to derive vehicle forward speed histories from the digitised PC card recorder data.
In the case of the ATVs, the ‘on-farm’ data were calculated from the digitised histories, by
use of HVLab software, as well as by the method described above. This was done in order to
set to zero the seat acceleration values during those periods when the driver was not in contact
(standing or dismounted).
3.3.4
Hand-arm vibration (HAV) data (ATVs)
The hand-arm (handlebar) data from the ATVs was processed in a similar way to the wholebody data, with the differences that the frequency weighting for all three axes was the same
(wh); no 1.4 multiplying factors were applied and Vibration Dose Value was not relevant.
There was no method for identifying any periods when the driver may have taken his hand off
either grip.
29
30
4.
4.1
SELF- PROPELLED SPRAYERS
TEST VEHICLES
As previously discussed in Section 2.4, self-propelled sprayers were included within this
investigation because they are vehicles which typically have high annual usage and which
perform considerable amounts of road and farm track travel; activities which previous studies
Lines et al. (1995) have associated with moderate to high WBV levels. Two very similar selfpropelled sprayers were kindly loaned by their manufacturer for the purposes of the
investigation. Both were state-of-the-art, fully (front and rear axle) suspended, hydrostatic
transmission, four-wheel drive and steer machines, incorporating forward control cabs, 24 m
booms and 2500 litre capacity spray tanks. The major constructional difference between the
vehicles concerned their respective suspension systems; one utilising a mechanical coil spring
and hydraulic damper system (see Figure 4.1), the other being fitted with a self-levelling air
spring and hydraulic damper system (see Figure 4.2): the air spring machine representing the
latest evolutionary development of the base vehicle. Each machine was operated in turn fitted
with standard (12.4 R32) and flotation (600/55 R26.5) tyres. Test vehicle specifications are
provided in Table 4.1. Both machines were fitted vertical (Z) axis ‘scissor’ linkage
suspension seats, one of which also incorporated limited longitudinal (X) axis suspension
capability (see Table 4.2). The vehicles were subjected to identical test programmes,
including both a modified ISO 5008:2002 test track methodology and SRI ‘in-field’ operation
(see Figure 4.3).
Table 4.1 Self-propelled sprayers used in the investigation
Vehicle
Tank
capacity
(litres)
Operating mass
(kg)
Unladen
Laden
(80%)
Househam
Super Sprint
2500
5340
7340
3.10
Househam
Super Sprint
2500
5825
7848
3.10
Suspension
features
Tyre fitment
Wheelbase
(m)
(front & rear)
‘Standard’:12.4 R32
‘Flotation’:600/55 R26.5
‘Standard’:12.4 R32
‘Flotation’:600/55 R26.5
(in addition to seat)
Coil springs &
hydraulic dampers
(front & rear axles)
Air springs &
hydraulic dampers
(front & rear axles)
Complete sprayer test specifications may be found in Appendix 1.1
Table 4.2 Sprayer suspension seat details
Sprayer
(suspension
type)
Seat
manufacturer
/ model
Coil spring
Air spring
Suspension type
Z-axis (vertical)
X-axis (longitudinal)
Isringhausen
Mech. spring (adj.)
+ damper (fixed)
None
KAB 856
Air spring (adj.)
+ damper (fixed)
Mech. spring (fixed)
+ damper (fixed)
“adj.” = adjustable rate or pre-load: “fixed” = fixed rate: “Mech.” = mechanical
31
Figure 4.1 Househam coil spring suspension, 2500 litre, 24 m boom, self-propelled
sprayer fitted with ‘standard’ (12.4 R32) tyres: details of suspension system (inset)
Figure 4.2 Househam air spring suspension, 2500 litre, 24 m boom, self-propelled
sprayer fitted with ‘flotation’ tyres: details of suspension system (inset)
32
Figure 4.3 Self-propelled sprayer experimental test programmes
33
4.2
ISO TEST TRACK WBV EMISSION MEASUREMENT
4.2.1
Procedure
Whole-body vibration (WBV) emission levels were recorded upon each sprayer in accordance
with a modified version of the test methodology described in ISO 5008:2002. Each vehicle
was driven over the SRI ISO 100 m (smoother) ride vibration test track (see Figure 5.2) at a
range of appropriate forward speeds (see Table 4.3), fitted with either standard or flotation
tyres, with booms stowed (for travel) or extended (working position), in both unladen and
laden (2000 litre (80%) tank fill) condition. The latter was chosen to represent the sprayer
with a partial tank load during typical field operation and between field travel. Additionally,
this condition encouraged any dynamic surging of the spray tank contents during travel. Full
details of the ISO track test permutations are given in Figure 4.3. Wherever possible, tyre
inflation pressures were adjusted to manufacturer’s recommended levels for the resulting
(laden and unladen) axle loads (see Appendix 1.1). Tyre pressures were re-checked / adjusted
following initial vehicle ‘warm-up’ travel, immediately prior to WBV emission measurement.
Vehicle suspension seats were adjusted in accordance with operator instruction book
recommendations: where seat designs embodied selectable longitudinal (X) suspension
facilities (see Table 4.2), these features were enabled / utilised.
During each pass across the tracks, acceleration time histories were recorded in three
mutually-perpendicular directions (X-longitudinal, Y-transverse, Z-vertical), both upon the
surface of the operator’s seat and the cab floor, close to the seat mounting (see Figures 3.3 &
3.2 respectively). Acceleration data was acquired and analysed by the methods previously
described in Section 3.2 & 3.3, in accordance with the recommendations of ISO 2631-1:1997.
The resultant frequency-weighted r.m.s. acceleration values are depicted in the line graph
sections of Figures 4.4 to 4.11 inclusive.
The ISO 5008:2002 test methodology was extended for the purposes of this investigation, in
terms of the range and increments of vehicle forward speed used upon the ISO 100 m test
track with the spray booms either extended or stowed (see Table 4.3). Whilst the ISO 35 m
(rougher) track was considered to be unrepresentative of typical sprayer operational
conditions (excessively severe), the speeds currently recommended by ISO 5008 for use upon
the ISO 100 m (smoother) track were considered likely to be too low to adequately stress
modern, state-of-the-art self-propelled sprayers embodying suspension features, particularly
in relation to farm track travel with the booms stowed. Additionally, it was deemed prudent
to incorporate sufficiently small speed increments to enable identification of points at which
the test vehicles’ ride vibration behaviour may exhibit non-linear characteristics. To address
these issues, the modified forward speeds ranges depicted in Table 4.3 were used for the
investigation, solely upon the 100 m (smoother) track. Three test replicates were performed
at each (original) ISO 5008 forward speed and one replicate at all others, in order to maintain
the test programme within reasonable limits.
34
Table 4.3 Sprayer forward speeds used upon the ISO 100 m (smoother) ride
vibration test track
4.2.2
Boom position
Sprayer forward speed (km/h)
Extended (open)
10, 12, 14
Stowed (closed)
10, 12, 13, 14, 15, 16, 18, 20
Results
The results of WBV emission measurement upon the ISO 100 m (smoother) test track are
presented graphically within the line graph sections of Figures 4.4 – 4.11 inclusive, and
numerically within Appendix 1.2. The data falls into four basic categories: the nature of the
test vehicle’s suspension system (coil or air spring) and the tyre equipment fitted (‘standard’
or ‘flotation’). Within each of these categories the influence of the vibration measurement
location upon the vehicle (‘floor’ or ‘seat’) and its loading condition (laden or unladen) may
be considered. Primarily the semi- (80%) laden condition is considered in the following
discussion of results, because it is deemed to represent a larger proportion of typical vehicle
operation. Also, cab floor vibration levels provide a more reliable basis for comparison
between given vehicle suspension system / tyre fitment configurations, given that they are
independent of operator suspension seat performance. This is important given that the seats
fitted to the vehicles were not of similar design or condition.
Coil spring suspension – standard tyres
Considering initially WBV measurement upon the cab floor of a semi- (80%) laden sprayer,
with the spray booms in stowed position (see line graph section of Figure 4.4), the highest
acceleration levels were recorded in the vertical (Z) axis, making this the ‘major’ axis in
relation to the other (Y and X) axes. Transverse (Y) and longitudinal (X) axis levels were,
respectively, of lower magnitudes. Z-axis WBV emission levels were found to increase
significantly (~1.1 - 2.2 m/s2) with vehicle forward speed: X-axis levels exhibited a lesser
trend (~0.4 - 0.6 m/s2), whereas Y-axis emissions were independent of vehicle speed.
Operator seat WBV levels differed to those recorded on the cab floor in that the
transverse (Y) and vertical (Z) axis emissions were of similar magnitude and significantly
higher than those of the longitudinal (X) axis (see Figure 4.5). Whilst the seat Z-axis
acceleration levels were similar to those recorded upon the cab floor, the seat X-axis levels
were slightly higher than their cab floor equivalents and the Y-axis seat levels were
significantly greater those of the cab floor (see Figures 4.4 & 4.5). The unladen vehicle
exhibited similar WBV emission trends, with respect to the laden machine, upon both the cab
floor and operator’s seat, with the exception that all recorded levels were of slightly reduced
magnitude (see Appendix 1.2).
35
Air spring suspension – standard tyres
This vehicle exhibited similar cab floor WBV trends to the coil spring suspension machine, in
that acceleration levels were highest in the Z-axis followed, in reducing magnitude, by the Y
and X-axes (see Figure 4.6). However, Z-axis emission levels were significantly lower than
those of the coil spring suspension machine, being in the range ~0.8 - 1.28 m/s2. Both Z and
X-axis emission levels increased with vehicle speed but, once more, transverse (Y) axis
acceleration was independent of this parameter.
Vertical (Z) axis acceleration levels measured upon the operator’s seat were also largest,
followed, in reducing magnitude, by Y and X-axis emissions respectively (see Figure 4.7). X
and Y-axis seat acceleration levels were marginally higher than their respective cab floor
values, but Z-axis seat levels were lower than the floor values, probably indicating the
effectiveness of the operator’s seat suspension system. Both Y and Z-axis seat acceleration
levels were significantly lower than those recorded upon the coil spring suspension machine:
longitudinal (X) axis levels were also lower, but to a lesser extent (see Figure 4.5). The
unladen vehicle exhibited similar WBV emission trends, in comparison with the laden
machine, upon both the cab floor and operator’s seat but, in this instance, acceleration
magnitudes were of similar levels (see Appendix 1.2).
Coil spring suspension – flotation tyres
Cab floor WBV recorded upon this sprayer variant in laden condition, exhibited similar trends
to those of the coil spring suspension machine fitted with ‘standard’ tyres. Z-axis acceleration
levels were largest followed, in reducing magnitude, by those of the Y and X-axes (see
Figure 4.8). However, whilst longitudinal (X) and vertical (Z) axis acceleration levels were
similar to those experienced with ‘standard’ tyres fitted, transverse (Y) axis levels were
significantly higher (~1.15 compared with ~0.75 m/s2)(see Figures 4.4 & 4.8). Whilst Z-axis
floor vibration was found to increase significantly with vehicle speed, X-axis emission levels
exhibited a similar but less substantial trend: transverse (Y) axis acceleration was independent
of this parameter (see Figure 4.8).
A similar trend of Z-axis dominance was recorded upon the operator’s seat: however, in this
instance, both X and Z-axis emission levels increased significantly with vehicle speed. Once
more Y-axis values were independent of speed (see Figure 4.9). Z and Y-axis acceleration
levels were similar to those recorded upon the cab floor (see Figure 4.8), but X-axis levels
were higher. Once more the unladen vehicle exhibited similar WBV emission trends, both
upon the cab floor and seat but, as in the case of the coil spring suspension vehicle when fitted
with ‘standard’ tyres, vibration levels were slightly lower in all measurement axes.
Air spring suspension – flotation tyres
As in all other self-propelled sprayer tests upon the ISO 100 m track, cab floor Z-axis
acceleration levels were typically the largest, equalled, at lower test speeds, by Y-axis
magnitudes; X-axis levels being the lowest recorded at all test speeds (see Figure 4.10). Once
again X and Z-axis vibration increased with respect to forward speed, but Y-axis acceleration
remained relatively constant. X and Z-axis WBV emission levels were similar to those
recorded upon the air spring suspension machine fitted with ‘standard’ tyres, but
transverse (Y) axis levels were significantly higher (~1.0 compared with ~0.75 m/s2)(see
Figures 4.6 & 4.10). However, whilst cab floor X and Y-axis WBV levels were similar to
36
those recorded upon the coil spring suspension machine fitted with ‘flotation’ tyres, Z-axis
acceleration levels were significantly lower.
Operator seat measurements demonstrated similar Y and Z-axis WBV levels at given forward
speeds, these both being higher than the X-axis emission levels. Once more, whilst Y-axis
seat WBV emissions were independent of forward speed, both X-and Z-axis vibration levels
increased with vehicle speed (see Figure 4.11). As in the case of the coil spring suspension
sprayer fitted with ‘flotation’ tyres, Y and Z-axis seat acceleration levels were similar to those
recorded upon the cab floor (see Figure 4.10), but X-axis levels were marginally higher.
However, Z-axis seat acceleration levels were significantly lower than those recorded upon
the coil spring suspension machine. When compared with the air spring suspension sprayer
fitted with ‘standard’ tyres (see Figure 4.7), seat X and Y-axis WBV levels were higher but Zaxis levels were of similar magnitude. Additionally, in comparison with the laden machine,
the unladen vehicle exhibited similar WBV emission trends and magnitudes, upon both the
cab floor and operator’s seat (see Appendix 1.2).
4.2.3
ISO Test track WBV Emission Measurement - Summary
An overall summary of the self-propelled sprayer ISO test track programme is as follows:•
•
•
•
•
•
•
Vertical (Z) axis WBV emission levels were consistently higher than longitudinal (X)
and transverse (Y) axis levels, irrespective of vehicle forward speed. However, in
many instances, Y-axis WBV levels approached those recorded upon the Z-axis;
Cab floor transverse (Y) axis WBV levels are independent of vehicle forward speed;
Cab floor vertical (Z) axis WBV levels recorded on the air spring suspension vehicle
are significantly lower than those of the coil spring suspension machine. However,
longitudinal (X) and transverse (Y) axis acceleration levels are comparable between
the vehicles;
Cab floor transverse (Y) axis WBV levels are significantly higher when the vehicles
are fitted with ‘flotation’ rather than ‘standard’ tyres. This is to be expected because
the lower inflation pressures of the flotation tyres gives lower stiffness and hence
greater low-frequency roll motion;
The air spring suspension seat fitted to the air spring suspension vehicle was more
effective in reducing vertical (Z) axis vibration than the (rather ‘tired’) mechanical
suspension seat fitted to the coil spring suspension machine;
WBV emission levels upon the coil spring suspension vehicle were found to be lower
in the ‘unladen’ rather than the ‘laden’ condition;
Extending (unfolding) the sprayer booms (24 m), rather than operating with them in
‘stowed’ position, consistently caused an increase in longitudinal (X) axis WBV
levels and, less frequently, increased vertical (Z) axis acceleration levels.
Transverse (Y) axis levels decreased slightly or remained the same. Coil spring
suspension machines demonstrated these trends more consistently than air spring
suspension vehicles. Vehicle loading condition (laden or unladen) had no effect upon
these trends, which are probably a result of the sprayer weight distribution and pitch
centre moving rearwards when the booms are unfolded, their stowed position being
forwards alongside the operator’s cab (see Figure 4.1).
37
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Task Longitudinal (X)
Track Longitudinal (X)
Track
Spraying
Overall
Task Segments
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 4.4 Coil spring suspension sprayer: Floor acceleration (1.4 multiplier):
Standard tyres; Laden (full tank)
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
2.0
2
Weighted r.m.s. Acceleration (m/s )
2.2
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Track
Spraying
Overall
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 4.5 Coil spring suspension sprayer: Seat acceleration (1.4 multiplier):
Standard tyres; Laden (full tank)
38
30
Spee d (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
2.0
Weighted r.m.s. Acceleration (m/s2)
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Task Longitudinal (X)
Track Longitudinal (X)
Spraying
Track
Overall
Task Segments
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 4.6 Air spring suspension sprayer: Floor acceleration (1.4 multiplier):
Standard tyres; Laden (full tank)
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
1.8
2
Weighted r.m.s. Acceleration (m/s )
2.0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Track
Spraying
Overall
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 4.7 Air spring suspension sprayer: Seat acceleration (1.4 multiplier):
Standard tyres; Laden (full tank)
39
30
S peed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
2.0
Weighted r.m.s. Acceleration (m/s2)
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Task Longitudinal (X)
Track Longitudinal (X)
Track
Spraying
Overall
Task Segments
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 4.8 Coil spring suspension sprayer: Floor acceleration (1.4 multiplier):
Flotation tyres; Laden (full tank)
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
1.8
2
Weighted r.m.s. Acceleration (m/s )
2.0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Task Longitudinal (X)
Track Longitudinal (X)
Track
Spraying
Overall
Task Segments
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 4.9 Coil spring suspension sprayer: Seat acceleration (1.4 multiplier):
Flotation tyres; Laden (full tank)
40
30
S peed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Track
Spraying
Overall
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 4.10 Air spring suspension sprayer: Floor acceleration (1.4 multiplier):
Flotation tyres; Laden (full tank)
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
1.8
2
Weighted r.m.s. Acceleration (m/s )
2.0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Task Longitudinal (X)
Track Longitudinal (X)
Track
Spraying
Overall
Task Segments
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 4.11 Air spring suspension sprayer: Seat acceleration (1.4 multiplier):
Flotation tyres; Laden (full tank)
41
30
4.3
SRI ‘IN-FIELD’ WBV EMISSION MEASUREMENT
4.3.1
Procedure
Following the self-propelled sprayers ISO test track investigation (Section 4.2), a detailed
programme of sprayer ‘in-field’ WBV emission measurement was performed upon the Silsoe
Research Institute (SRI) estate, using the same test vehicles. The objectives of this work
were:• To quantify each sprayer’s ‘in-field’ WBV emission levels whilst performing a range
of typical operations, in known / controlled conditions;
• To investigate the similarity (if any) between WBV emission levels encountered
during these operations and those generated during ISO 5008 ride vibration track
testing (Section 4.2).
Each self-propelled sprayer (coil spring suspension and air spring suspension – see
Figures 4.1 & 4.2) was operated in (semi) laden condition (~80% spray tank load), whilst
fitted with either ‘standard’ or ‘flotation’ tyres, along a composite test circuit comprising
smooth road travel, farm track travel and field (spraying) (see Figures 4.3, 4.12 & 4.13). The
test circuit composition was selected to represent typical operations which a self-propelled
sprayer would be subjected to during ‘on-farm’ use. Accordingly, the sprayer booms were
stowed (closed) for ‘road’ and ‘track’ travel and extended (open) for field ‘spraying’. During
performance of the test circuit, which occupied approx. 25 minutes, acceleration time
histories were recorded simultaneously upon the operator’s seat and the sprayer cab floor, by
use of the vehicle-mounted instrumentation described in Section 3.2. Additionally, vehicle
forward speed was derived from a Doppler radar sensor mounted upon each test vehicle (see
Figure 4.13). The test circuit duration was chosen to encompass and minimise variations
relating to operating conditions. Each machine permutation (suspension type / tyre fitment)
performed two replicates of the test circuit. To minimise variations attributable to personal
operating technique, the same individual operated each test vehicle in turn.
4.3.2
Results
Detailed results of the self-propelled sprayer SRI ‘in-field’ test programme are depicted
graphically in the bar graph sections of Figures 4.4 to 4.11 inclusive, and in tabular form
within Appendix 1.3. Figures 4.4 - 4.11 indicate weighted acceleration magnitudes recorded
in the X (longitudinal), Y (transverse) and Z (vertical) axes, upon the seat and floor of each
sprayer ‘permutation’, during the ‘road’, farm ‘track’ and field ‘spraying’ sections of the
composite test circuit, plus an overall average of the three test conditions. Typical sprayer
forward speeds used in each test circuit section are indicated in Figure 4.13. Sprayer axle
loadings and tyre inflation pressures used the SRI ‘in-field’ test programme are detailed in
Appendix 1.1
Standard tyres
Considering primarily the floor acceleration levels, thereby removing the influence of the
operator’s seat suspension system, it is evident that when fitted with ‘standard’ tyres,
vertical (Z) axis acceleration was consistently the largeset during both road travel and field
spraying operations, both for the coil and air spring suspension machines (see Figures 4.4 &
4.6). Z-axis WBV emission levels were followed (in reducing magnitude) by those upon the
transverse (Y) and longitudinal (X) axes, respectively.
42
:
Figure 4.12 Househam 2500 litre, 24 m boom, self-propelled sprayer fitted with
‘standard’ (12.4 R32) tyres, performing ‘field’ section of composite test
circuit
50
45
40
Speed (km/h)
35
30
25
20
15
10
5
0
0
200
400
600
800
1000
1200
1400
1600
1800
Time (seconds)
Figure 4.13 Typical sprayer forward speed history during SRI ‘in-field’ test circuit
Indicates:- Initial and final calibration checks
Short farmyard travel before High-speed ‘road’ travel (~35 km/h)
Slower travel on rough farm ‘track’ (~12-14 km/h)
Pause for extending booms (~420 – 450 seconds)
Sequence of simulated ‘field’ spraying bouts (~14 km/h
spraying speed but lower speeds during headland turns)
43
‘In-field’ spraying generated higher WBV acceleration levels than high-speed road travel.
However, floor acceleration magnitudes upon the air spring suspension machine were typically
~30% lower than those of the coil spring suspension vehicle in these particular test conditions.
Travel upon a rough farm ‘track’ generated the highest WBV levels of the test conditions, but
in this case acceleration levels in the transverse (Y) axis were the largest, followed, in reducing
magnitude, by those in the Z and X axes respectively. The air spring suspension sprayer
produced similar X-axis floor acceleration levels to those of the coil spring suspension
machine, but its Y and Z-axis emission levels were lower (see Figure 4.6 & 4.4).
Overall (average of all ‘in-field’ test conditions), in the case of the coil spring suspension
sprayer, vertical (Z) axis floor acceleration was the largest by a substantial margin, followed, in
reducing magnitude, by levels in the Y and X axes (see Figure 4.4). The air spring suspension
machine demonstrated a different pattern in which Z and Y-axis acceleration levels were of
similar magnitude, but those of the X-axis were approx 35% lower (see Figure 4.6).
Comparing the performance of the two machines, they produced identical transverse (Y-axis)
WBV emission levels, but the air spring suspension sprayer generated marginally lower levels
in the longitudinal (X) axis and substantially (~30%) lower levels in the vertical (Z) axis.
In terms of seat acceleration levels, upon the coil spring suspension sprayer, overall these were
approx. 20-25% higher than the floor levels in each respective measurement axis; those in the
vertical (Z) axis being the largest (see Figure 4.5). Seat acceleration levels upon the air spring
suspension machine were similar to the floor levels in the X-axis, but seat Z-axis levels were
approx. 9% higher than the corresponding floor levels and Y-axis seat values were approx. 15%
higher than those recorded upon the floor. Y-axis WBV emission levels were larger than those
in the Z-axis by a small margin upon this vehicle (see Figure 4.7).
Flotation tyres
Once more considering cab floor acceleration levels, both coil and air suspension sprayers
exhibited similar behaviour during ‘road’ and farm ‘track’ travel. For both vehicles Y-axis
WBV emission levels were the largest (by a substantial margin) during ‘track’ travel, followed
in reducing magnitude by Z and X-axis levels respectively. During farm ‘track’ travel the X
and Y-axis floor acceleration levels of the air spring suspension sprayer were similar to those
generated by the coil spring suspension machine. However the air suspension machine
returned lower Z-axis levels than the coil spring suspension vehicle in this test condition, and
also lower levels in the Y and Z axes during ‘road’ travel (see Figures 4.8 & 4.10).
‘In-field’ spraying with the coil spring suspension machine generated largest average WBV
emission levels in the Z-axis, the Y and X axes following in reducing magnitude (see
Figure 4.8). The air spring suspension machine exhibited slightly different behaviour: Y-axis
emission levels being the largest, followed by the Z-axis and then the X-axis (see Figure 4.10).
Comparing the performance of the two vehicles during field ‘spraying’, the air spring
suspension machine generated Y-axis WBV levels similar to those of the coil spring suspension
vehicle, but lower comparative levels in the X and Z axes.
Overall, averaging the results of each ‘in-field’ test condition and considering WBV emission
levels in individual measurement axes, the coil spring suspension sprayer produced its highest
(average) acceleration levels in the Y-axis, closely followed by those in the Z-axis and
thereafter by X-axis levels. The air spring suspension machine also generated its highest
(average) acceleration levels in the Y-axis, but the Z-axis acceleration magnitude was approx.
30% lower than that of the Y-axis: levels in the X-axis were lower still. Comparing the air and
44
coil spring suspension machines, similar WBV levels were recorded in the X and Y axes, but
the former vehicle returned 25% lower levels in the vertical (Z) axis (see Figures 4.8 & 4.10).
Comparing operator seat and cab floor acceleration levels when the sprayers were fitted with
flotation tyres, upon the coil spring suspension machine, seat acceleration levels were higher
than floor levels by approx. 19%, 27% and 14% in the X, Y and Z axes respectively: Y-axis
WBV levels being largest (see Figures 4.8 & 4.9). The air spring suspension machine
demonstrated a similar trend of Y-axis dominance and higher seat acceleration levels, but in
this instance seat WBV levels were larger than cab floor levels by approx. 15% and 9% in the
Y and Z axes respectively, whereas those in the X-axis were similar (see Figures 4.10 & 4.11).
Y-axis seat acceleration levels would be expected to be higher than those recorded upon the cab
floor, due to the greater relative distance of the seat surface from the vehicle roll centre.
‘In-field’ overall performance
A summary of self-propelled sprayer ‘in-field’ WBV emission performance is presented in
Figures 4.14 and 4.15 for ‘standard’ and ‘flotation’ tyre fitment respectively. These Figures
depict both cab floor and operator seat weighted acceleration levels of the air and coil spring
suspension machines, for each ‘in-field’ test condition, in ‘largest-single-axis’ terms, as
required by the Physical Agents (Vibration) Directive (see Section 3.1). The identity of the
measurement axis in which largest average r.m.s. acceleration level was encountered during
each test condition, is also indicated. It is advisable to base comparisons between vehicle ride
performance primarily upon cab floor acceleration values, thereby removing the effects of
different suspension seats (design and condition) fitted to the machines. However suspension
seat performance will mainly affect seat vertical (Z) axis acceleration levels and, to a lesser
extent, those in the longitudinal (X) axis, given that the seat upon the air spring suspension
sprayer embodied a degree of X-axis suspension (see Table 4.2). In cases where transverse (Y)
axis acceleration levels were the largest (e.g. ‘standard’ tyres – ‘track’ and virtually all
‘flotation’ tyre instances), a direct comparison may be drawn between vehicle seat WBV levels.
Considering initially sprayer performance when fitted with standard tyres (see Figure 4.14) the
dominance of operator seat acceleration levels over those recorded upon the cab floor is
immediately evident, as are the lower WBV levels achieved by the air spring suspension
machine in comparison with the coil spring suspension vehicle, in virtually all test conditions.
The largest WBV levels were encountered in the transverse (Y) axis during farm ‘track’ travel.
However, in virtually all other test conditions (with standard tyres), highest WBV emission
levels were found in the vertical (Z) axis. Nonetheless, although the WBV emission levels of
the coil spring suspension machine exceeded the r.m.s.-specified Exposure Action
Value (EAV) (A(8) - 0.5 m/s2), even these did not reach the PA(V)D-prescribed Exposure
Action Value (ELV) (A(8) - 1.15 m/s2).
As noted before during the ISO test track programme, sprayer performance when fitted with
flotation tyres appears to be worse in terms of ride vibration (see Figure 4.15). Once more, seat
acceleration levels were higher than those recorded upon the cab floor, in all operational
conditions, and once again the air spring suspension machine achieved lower WBV emission
levels than the coil spring suspension vehicle in virtually all test conditions. Transverse (Y)
axis average r.m.s. acceleration levels were larger than those of the X or Z axes in virtually all
test conditions, the highest levels being encountered during farm ‘track’ travel. However,
whilst the WBV levels generated by the flotation-tyred sprayers during field ‘spraying’ were
marginally lower than the machines when equipped with standard tyres, farm ‘track WBV
emission levels were substantially higher: the air spring suspension sprayer ‘seat’ values
approached the ELV, whilst those of the coil spring suspension machine exceeded it.
45
1.2
Weighted r.m.s. Acceleration (m/s2)
1.0
0.8
0.6
0.4
0.2
0.0
Road
(Z-axis)
Track
(Y-axis)
Spraying
Road
(Z-axis) (Z-axis)
Coil (seat)
Track
(Y-axis)
Spraying
(Z-axis)
Road
(Y-axis)
Coil (floor)
Track
(Y-axis)
Spraying
Road
(Z-axis) (Z-axis)
Air (seat)
Track
(Y-axis)
Spraying
(Z-axis)
Air (floor)
Fig 4.14 Sprayer ‘in-field’ average weighted floor & seat acceleration levels:- coil
spring & air spring suspension vehicles:- ‘standard’ tyres
(largest axis indicated)
1.4
Weighted r.m.s. Acceleration (m/s2)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
(Y-axis)
Track
(Y-axis)
Spraying
Road
(Y-axis) (Y-axis)
Coil (seat)
Track
(Y-axis)
Spraying
(Z-axis)
Road
(Y-axis)
Coil (floor)
Track
(Y-axis)
Spraying
Road
(Y-axis) (Y-axis)
Air (seat)
Track
(Y-axis)
Spraying
(Y-axis)
Air (floor)
Fig 4.15 Sprayer ‘in-field’ average weighted floor & seat acceleration levels:- coil
spring & air spring suspension vehicles:- ‘flotation’ tyres
(largest axis indicated)
46
Average Weighted r.m.s. Acceleration (m/s2)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
SRI Field (flotation tyres)
SRI Field (standard tyres)
Longitudinal (X)
Figure 4.16
ISO 100m Track
(flotation tyres)
Transverse (Y)
ISO 100m Track
(standard tyres)
Vertical (Z)
Coil spring suspension sprayer average weighted floor acceleration
levels (incl. 1.4 multiplier):- SRI ‘in-field’ (‘track’) and ISO test
track (12 km/h)
Average Weighted r.m.s. Acceleration (m/s2)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
SRI Field (flotation tyres)
SRI Field (standard tyres)
Longitudinal (X)
Figure 4.17
ISO 100m Track
(flotation tyres)
Transverse (Y)
ISO 100m Track
(standard tyres)
Vertical (Z)
Air spring suspension sprayer average weighted floor acceleration levels
(incl. 1.4 multiplier):- SRI ‘in-field’ (‘track’) and ISO test track (12 km/h)
47
Self-propelled sprayer ‘in-field’ and ISO test track performance
The comparison of ‘in-field’ and ISO test track data is frequently an unrewarding activity,
primarily because the vehicle state (axle loadings / weight distribution, tyre pressures and
forward speeds) is often different between the test conditions under consideration. Also it is
only possible to draw valid comparisons between similar operating surfaces and measurement
locations upon the vehicles. Fortunately, in the case of the self-propelled sprayers, it was
possible to select particular test conditions between which ride vibration performance
comparisons could be drawn.
The ISO 100 m ‘smoother’ test track was originally devised to represent a farm track surface.
‘In-field’ farm ‘track’ travel was performed in (80%) ‘laden’ condition with the spray booms
stowed, at ~12 km/h forward speed (see Figure 4.13). Consequently it was possible to
compare these results to those derived from the vehicles when operated upon the ISO test
track in a similar loading condition at 12 km/h. The respective cab floor weighted
acceleration levels are depicted in Figures 4.16 and 4.17 for the coil spring suspension and air
spring suspension vehicles respectively.
Considering the coil spring suspension vehicle (see Figure 4.16), longitudinal (X) axis
acceleration levels recorded upon the ISO test track were similar, regardless of the tyre
equipment fitted. However, the ‘in-field’ WBV levels were approx. 30% lower than ISO test
track values. Much greater similarity existed between transverse (Y) axis ‘in-field’ and ISO
track acceleration levels, those for ‘standard’ tyres being almost identical. However, in the
case of ‘flotation’ tyres, ISO track Y-axis levels were marginally higher than the ‘in-field’
values. The greatest disparity existed between vertical (Z) axis acceleration levels, those
recorded upon the farm ‘track’ being more than 50% lower than the ISO track values.
Therefore, in summary, good comparability existed between Y-axis values, but this
deteriorated in the X-axis and became very poor in the Z-axis. Tyre equipment, whilst
affecting the particular WBV levels recorded, had no effect upon the nature or degree of
agreement.
A similar pattern was evident in the case of the air spring suspension sprayer. X-axis ‘infield’ ‘track’ levels were approx. 23% lower than comparative ISO test track values (see
Figure 4.17), regardless of tyre equipment. Y-axis acceleration levels were identical when the
vehicle was fitted with ‘flotation’ tyres, but a slight difference was apparent between
‘standard’ tyre ISO test and ‘in-field’ values. Z-axis ‘in-field’ ‘track’ levels were once more
approx 50% lower than comparative values recorded upon the ISO test track. Consequently,
once more very good agreement was found between transverse (Y) axis acceleration levels;
this relationship deteriorated in the longitudinal (X) axis and became very poor in the
vertical (Z) axis. Once again, tyre equipment had little effect upon the quality of relationships
demonstrated.
It was regrettably beyond the financial and logistical constraints of this investigation to
explore the relationships between ISO test track and ‘in-field’ vehicle ride vibration
behaviour in greater detail. However, this approach is considered to be beneficial if an
improved understanding of the factors contributing to these differences is to be gained. This
is surely a requirement if vehicle test track WBV emission assessment procedures are to be
improved in the future.
48
4.3.3
‘In-Field’ WBV Emission Measurement – Summary
The objectives of the ‘in-field’ self-propelled sprayer WBV investigation were:•
•
To quantify each sprayer’s “in-field” WBV emission levels whilst performing a range
of typical operations, in known / controlled conditions;
To investigate the similarity (if any) between WBV emission levels encountered
during these operations and those generated during ISO 5008 ride vibration track
testing.
The results of the SRI ‘in-field’ self-propelled sprayer WBV measurement programme may
be summarised as follows:•
•
•
•
•
•
•
•
•
Air spring suspension sprayer cab floor WBV emission levels were generally lower
than those generated by the coil spring suspension machine in the longitudinal (X)
and vertical (Z) axes, but the transverse (Y) axis levels of both machine were similar;
Tyre equipment (and associated inflation pressures and carcass stiffness) has a
substantial effect upon vehicle WBV emission levels, especially in the transverse (Y)
axis, ‘standard’ tyres being deemed to be dynamically stiffer than ‘flotation’ tyres;
Farm ‘track’ travel generated the highest WBV emission levels of all ‘in-field’ test
operations; these levels always occurring in the Y (transverse) axis;
Operator seat WBV emission levels were always higher than those measured upon
the cab floor, but this trend was less pronounced upon the air suspension machine.
The latter is almost certainly due to the disparate suspension seats (of both different
design and age) fitted to the test machines;
When fitted with ‘standard’ tyres, vertical (Z) axis WBV emission levels were found
to be the largest during ‘road’ travel and field ‘spraying’, whereas transverse (Y) axis
emissions were the largest during farm ‘track’ travel, once again irrespective of the
vehicle suspension system or the measurement location (see Figure 4.14);
Transverse (Y) axis WBV emission levels were almost always the largest of any axis
during the ‘in-field’ test programme, when machines were fitted with ‘flotation’ tyres
(see Figure 4.15);
‘In-field’ and ISO test track transverse (Y) axis WBV emission levels exhibited very
good agreement, but the degree of agreement was less good in the longitudinal (X)
axis and very poor in the vertical (Z) axis. Vehicle tyre equipment was found to have
no effect upon the degree of agreement observed;
When attempting to compare WBV emission levels recorded ‘in-field’ and upon the
ISO test tracks, it is important to select appropriate track and field test conditions for
comparison;
Differences between ISO test track and ‘in-field’ data require closer investigation if
improved test track WBV assessment methodologies are to be developed (see
Section 7.4).
49
4.4
‘ON-FARM’ WBV EXPOSURE MEASUREMENT
4.4.1
Introduction
A programme of ‘on-farm’ WBV exposure level measurement was performed upon a number
of self-propelled sprayers across East Anglia. The objectives of this part of the investigation
were:• To verify the practical applicability of the detailed self-propelled sprayer WBV
emission data derived from the SRI ‘in-field’ and (possibly) ISO Test Track
measurement programmes;
• To explore the variation in (and magnitudes of) WBV emission and resultant
exposure levels encountered upon ‘on-farm’ self-propelled sprayers during typical
half-day (4 hour) work periods;
• To enable limited investigation of typical usage patterns of ‘on-farm’ examples of
one self-propelled sprayer design included in the overall investigation.
4.4.2
Procedure
The principle objective of the overall investigation was “to determine WBV emission and
exposure levels associated with representative ‘state-of-the-art’ agricultural vehicles
performing agricultural operations….”. Consequently the ‘on-farm’ WBV study was
intentionally restricted to one of the self-propelled sprayers previously tested, i.e. the vehicle
design considered to embody the greatest proportion of WBV-reducing features. Therefore
‘on-farm’ examples of the Househam Super Sprint sprayer fitted with ‘Air Ride’ selflevelling suspension system and ‘standard’ tyres were targeted.
As the previously completed SRI ‘in-field’ WBV emission measurement programme had
embodied all aspects of typical sprayer operation (road & farm track travel, in-field spraying
plus optional tyre equipment), it was not difficult to locate ‘on-farm’ machines performing
similar tasks during day-to-day operation. During May-June 2002, WBV acceleration time
histories were recorded upon 3 separate examples of the chosen sprayer model, thereby
providing 3 test replications and permitting derivation of WBV emission and exposure levels.
Suitable ‘on-farm’ test vehicles (i.e. correct physical specification and less than 2 years old)
were identified with the assistance of the sprayer manufacturer. Indeed, one ‘on-farm’
machine was actually the air suspension machine evaluated at SRI, having subsequently been
delivered to customer. Given each owner’s preparedness to participate in the study, ‘on-farm’
WBV measurements were made during a nominal ‘half-day’ (4-hour) period (in one instance
comprising 2 x 2-hour periods due to prevailing weather conditions), during typical sprayer
operation. This was considerably simpler than the comparable tractor ‘on-farm’ WBV
measurement programme (see Section 5.4), given that the additional factor of attached
implement / operation selection was not present.
Acceleration time histories were recorded simultaneously upon the operator’s seat and the cab
floor of each sprayer, by use of the vehicle-mounted instrumentation described in Section 3.2,
but in this application individual Larson Davis Human Vibration meters (type HVM100) were
also used to reduce the acceleration data in real-time, to record peak values and to derive
vibration dose values (VDV) for each 15-minute section of the total operating period. As
before, vehicle forward speed was recorded (derived from a Doppler radar sensor mounted
upon each vehicle), to enable quantification of this important operational parameter and
identification of any stationary / inactive periods during the measurement periods.
50
4.4.3
Results
As discussed previously (Section 3.1), the European Union Physical Agents (Vibration)
Directive (PA(V)D) defines the WBV Exposure Action Value (EAV) and Exposure Limit
Value (ELV) in two alternative ways. Either as an 8-hour energy-equivalent frequency
weighted r.m.s. acceleration value (A(8)), or as a vibration dose value (VDV). Member
States are given the option of implementing the Directive using either method, using the
values stated below (see Table 4.4). Specific details are discussed in Section 3.1, but an
important difference between the methods is as follows. The root-mean-square (r.m.s.) or
A(8) method produces a value which is an average vibration level adjusted to represent an 8hour working day, whereas the vibration dose value represents cumulative exposure to
vibration over the working day. The practical significance of this is clearly depicted by
Figure 4.20. If, over a given working period, frequency-weighted r.m.s. acceleration levels
recorded upon the operator’s seat are relatively consistent, the resultant equivalent continuous
acceleration (Aeq) value (only A(8) if exposure period = 8 hours) changes little, having once
reached an average ‘plateau’ value. However, in the same circumstances, the VDV increases
throughout the work period in a cumulative manner. Additionally, the A(8) method
represents steady levels of vibration with reasonable accuracy but gives poor representation of
shocks and jolts, whereas the VDV method performs well in both instances (Griffin, 1998;
Coles, 2002). These issues, together with those of sampling duration, are discussed in greater
detail in Appendix 4.
Throughout this investigation we have primarily utilised the A(8) method but, during ‘onfarm’ exposure measurement, vibration dose values have also been derived (see Figure 4.20
and Appendix 1.4). At the time of writing the HSE is undertaking a public consultation
exercise regarding implementation of the PA(V)D in the UK. Whilst it is highly likely that
the ELV will be specified by the A(8) technique, debate is currently ongoing as to whether the
EAV will be implemented in VDV or A(8) terms: the implications of this stance are discussed
in Sections 3.1 & 7.4.
An important aspect of interpretation of results concerns how estimates for a whole day’s
vibration exposure can be made from values measured over a shorter period (see also
Appendix 4). Nominal half-day (approx. 4-hour) measurement periods were used ‘on-farm’
to ensure the data acquired were characteristic of the operation. If using the r.m.s. A(8)
approach, the resultant overall average frequency-weighted r.m.s. acceleration (Aeq) value
measured for the shorter (~4-hour) period can be considered to extend throughout the entire
day’s use of the machine. The Aeq value becomes equivalent to the daily occupational
vibration exposure (A(8)) value for that operation, if the vehicle in question were to be
operated for 8 hours. Consequently the Aeq values generated by this investigation may be
compared directly with the A(8) EAV and ELV values stipulated by the PA(V)D whenever
the working day length approximates to 8 hours. For shorter or longer working days the
respective A(8) value for the daily exposure period in question may be calculated from the
Aeq value, prior to comparison with the EAV or ELV (see Section 3.1, Equation 3). A
similar approach is necessary for the VDV: its cumulative nature requires a value for a shorter
period be re-calculated to estimate the VDV after the full day’s exposure. This is performed
by assuming subsequent WBV emission levels are similar to those recorded during the
(~4 hour) measurement period (see Appendix 4). Examples of estimated 8-hour VDV’s
appear in Table 4.5, Figure 4.20 and Appendix 1.4.
Seat WBV data arising from the ‘on-farm’ self-propelled sprayer investigation are
summarised in Table 4.5 and Figure 4.19. Corresponding cab floor data appear in Table 4.6
& Figure 4.18. Generally the individual ‘on-farm’ operations reflect similar WBV emission
51
levels to those obtained from SRI ‘in-field’ measurements, with one possible exception. (see
Figures 4.18 & 4.19). Seat acceleration levels were in all instances higher than those
recorded upon the cab floor. The major axis (the generating the largest overall average r.m.s.
acceleration (Aeq) values) was primarily the transverse (Y) axis for seat WBV emissions, but
for measurements made upon the cab floor, the vertical (Z) axis took precedence (see
Tables 4.5 & 4.6). This would seem to suggest that Z-axis acceleration levels were the largest
in the forward-mounted sprayer cab, but the operator’s suspension seat, if not particularly
effective in attenuating vibration in this axis, at least caused little amplification of Z-axis
acceleration. However, the suspension seat was unable to effect any attenuation whatsoever
in the transverse (Y) axis, the greater relative distance of the seat surface from the vehicle roll
centre resulting in significantly higher Y-axis seat acceleration levels when compared with
those recorded upon the cab floor (see Tables 4.5 & 4.6).
Table 4.4 WBV exposure values specified by the EU PA(V)D
8-hour energy-equivalent
Vibration Dose Value
r.m.s. acceleration – A(8)
(m/s1.75)
(m/s2)
Exposure Action Value (EAV)
0.5
9.1
Exposure Limit Value (ELV)
1.15
21
Table 4.5 ‘On-farm’ WBV seat data: self-propelled sprayer with air spring suspension
Sprayer
Duration
(hr)
2
Average r.m.s. acceleration (m/s )
X
Y
Z
Major axis
Aeq
RSS
2
2
(m/s ) (m/s )
Est. 8 hr
VDV
1.75
(m/s
)
Time to
EAV
(hr)
(VDV)
Time to
Time to
EAV
ELV (hr)
(hr)
(A(8))
(A(8))
1
3.50
0.28
0.52
0.53
Z/Y
0.79
0.53
13.8
1.52
7.12
>24
2
4.50
0.38
0.59
0.37
Y
0.80
0.59
15.8
0.88
5.73
>24
3(a)
1.75
0.94
1.27
0.88
Y
1.81
1.27
33.3
0.04
1.23
6.52
3(b)
2.00
0.69
0.68
0.68
X/Y/Z
1.18
0.69
18.6
0.46
4.23
22.39
3 (ave.)
3.15
0.82
1.00
0.78
Y
1.51
-
-
-
-
Table 4.6 ‘On-farm’ WBV floor data: self-propelled sprayer with air spring suspension
Sprayer
Average r.m.s. acceleration (m/s 2 )
Duration
(hr)
RSS
(m/s 2 )
X
Y
Z
Major axis
1
3.50
0.26
0.39
0.39
Y/Z
0.61
2
4.50
0.31
0.36
0.37
Z/Y
0.61
3(a)
1.75
0.57
0.59
0.78
Z
1.13
3(b)
2.00
0.44
0.54
0.65
Z
0.95
3 (average)
3.75
0.50
0.56
0.71
Z
1.04
52
Average Weighted r.m.s. Acceleration (m/s2)
1.20
1.00
0.80
0.60
0.40
0.20
0.00
Longitudinal (X)
Transverse (Y)
SRI (field, standard tyres)
Figure 4.18
Farm 1
Vertical (Z)
Farm 2
Farm 3
Air spring suspension sprayer average weighted floor acceleration
levels (incl. 1.4 multiplier):- SRI ‘in-field’ (‘overall’) and ‘on-farm’ use
Average Weighted r.m.s. Acceleration (m/s2)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Longitudinal (X)
Transverse (Y)
SRI (field, standard tyres)
Figure 4.19
Farm 1
Vertical (Z)
Farm 2
Farm 3
Air spring suspension sprayer average weighted seat acceleration
levels (incl. 1.4 multiplier):- SRI ‘in-field’ (‘overall’) and ‘on-farm’ use
(plus PA(V)D Exposure Limit Value)
53
15.00
2
12.00
1.5
9.00
1
6.00
0.5
3.00
0
0:00
VDV (m/s1.75)
2
Weighted r.m.s. Acceleration (m/s )
2.5
0.00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y)
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: Househam Air Suspended
Reg No: FY02GRU
Spraying
Task:
Bush & Sons (Farmers)
Place:
VDV
Day
29
1.75
Month
May
Year
2
Start time:
08:50
Z
0.37
Sum
0.80
Z
17.20
Sum
17.10
2
Total VDV (m/s
)
Time
X
8.6
04:30
8-hr est tot
9.9
Y
13.7
15.8
Z
8.8
10.2
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.88
>24
r.m.s./A(8)
5.73
>24
Figure 4.20
Aeq
Average r.m.s. (Aeq) (m/s )
X
Y
0.38
0.59
Sum
17.7
20.5
2
Maximum peak value (m/s )
X
Y
5.12
9.44
Typical time history of weighted 1-minute r.m.s. accelerations (seat, Yaxis, Air Spring Suspension Sprayer) plus development of equivalent
continuous r.m.s. acceleration (Aeq) & 15-minute record of Vibration
Dose Value (VDV) and table of seat WBV parameters
Comments
•
•
•
•
•
•
•
An extremely variable vibration record (Y-axis largest) reflecting cyclical nature of activity
(refilling, travel to field, spraying, travel to base, refilling);
Whilst overall average r.m.s acceleration (Aeq) value identifies Y-axis as largest, greatest
peaks actually occur in the Z-axis;
The overall average (Aeq) acceleration level is moderate: this calculation method smoothes
the time history to a degree and does not respond to the peak events as significantly as the
VDV method (see trace and also Appendix 4);
The Aeq reduces during refilling periods, but remains relatively constant (0.5 – 0.6 m/s2)
throughout the survey period, any significant increases being due to uncharacteristic peaks
(~ 3 & 3¼ hrs);
The VDV Exposure Action Value (EAV) is exceeded in less than 1-hour operation;
The A(8) Exposure Action Value (EAV) is exceeded in approx. 5¾ hours operation
The (A(8)) Exposure Limit Value (ELV) will not be exceeded in a 24-hour period;
54
Figure 4.20 depicts the parameters arising from the ‘on-farm’ sprayer WBV measurement
programme in a generic presentation format. Tabular data specifies the measurement location
(seat or floor), sprayer model, geographical location, date and measurement duration. The
corresponding graph depicts a time history of frequency-weighted 1-minute average r.m.s.
acceleration values, as recorded in the orthogonal axis which consistently generated the
largest overall average values throughout the operating period. This is supplemented by
traces depicting 15-minute vibration dose values (VDV) and development of equivalent
continuous frequency-weighted r.m.s. acceleration (Aeq) which, as previously discussed, may
be related to the A(8) value. Tabular WBV data are presented in terms of overall average
frequency-weighted r.m.s. acceleration (Aeq) and peak values for each measurement axis,
together with corresponding root-sum-of-squares (RSS) values. Individual axis and RSS
VDV values for the measurement duration, and estimated (VDV) values for an 8-hour period,
are also included. Finally, estimated operating periods until the EAV and ELV are reached,
are shown, both in relation to the A(8) and VDV calculation methods. Comments relating
specifically to the measurement example appear at the base of the Figure. A summary of cab
floor and seat WBV data from the entire ‘on-farm’ measurement programme is presented in
this tabular / graphical format in Appendix 1.4.
As previously stated (see Section 3.1), the Directive specifies action and limit values for
operator daily exposure to WBV and requires actions on the part of the employer, to reduce
worker daily exposure should the EAV be exceeded. In simplistic terms, vibration exposure
is a function of the intensity of vibration to which an operator is exposed and the period of
exposure to it. A seated vehicle operator (as in this case) primarily receives WBV through the
vehicle seat (can be via the feet for a standing operator): it is therefore the equivalent
continuous (Aeq) WBV levels recorded upon the operator’s seat which are of importance.
The range of seat WBV emission levels (0.53 – 1.27 m/s2) encountered during the ‘on-farm’
spraying operations are shown in greater detail by the equivalent continuous r.m.s. (Aeq)
acceleration traces depicted in Figure 4.21. These traces indicate the degree of (Y-axis) WBV
magnitude variation between the measurement replicates performed, the Aeq value at the end
of each measurement period (end of trace) being the (overall average) Aeq value stated in
Table 4.5.
It would appear that considerable similarity exists between the Aeq levels of three replicates
(0.53 – 0.69 m/s2), with only one test replicate exhibiting a significantly higher WBV
magnitude (1.27 m/s2), apparently as a result of uncharacteristically rough local operating
conditions. Despite the limited size of the ‘on-farm’ sprayer WBV survey, it would appear
reasonable to propose ‘generic’ WBV emission levels for self-propelled sprayer operation.
This being the case, the data given in Table 4.5 suggests that the operator of a state-of-the-art
self-propelled sprayer would receive sufficient exposure to vibration to exceed the Exposure
Action Value (EAV) in 2-3 hours operation – if specified in VDV terms (see Table 4.4).
However, if specified in A(8) terms, the EAV would only be exceeded after approximately
4 – 7 hours operation. Irrespective of the specification method used, it is very likely that the
EAV would be exceeded during typical sprayer operating days (see below), thereby requiring
employers to implement a range of measures to reduce vibration exposure, as discussed in
Section 3.1. However, the data also suggests it is extremely unlikely that the A(8) Exposure
Limit Value (ELV) would be exceeded during the longest working day. Operating periods in
excess of 22 hours being necessary in all but the most extreme operating conditions.
As part of the ‘on-farm’ investigation, the sprayer operators recorded their driving hours
during the (5-day) ‘week’ encompassing the target WBV measurement day. This effectively
produced a survey of 15 ‘sprayer-days’ of which 14 days (93%) were operational. The results
obtained are summarised in Table 4.7 and Figure 4.22. Whilst 57% of ‘sprayer-days’
exceeded 8 hours operation, a significant proportion reached 12 or 14 hours per day.
55
1.6
Weighted r.m.s. Acceleration (m/s2)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Sprayer 1
Figure 4.21
Sprayer 2
Sprayer 3(a)
Sprayer 3(b)
Equivalent continuous r.m.s. seat acceleration (Aeq, Y-axis) traces for
‘on-farm’ self-propelled sprayers
5
Number of working days
4
3
2
1
0
4
6
8
10
12
14
Period of daily operation (hrs)
Figure 4.22
‘On-farm’ daily usage of self-propelled sprayers surveyed
56
16
Table 4.7 ‘On-farm’ daily usage of self-propelled sprayers surveyed
Number of days
surveyed
Number of
operational days
Number of
operational days
<= 8 hrs
Number of
operational days
> 8 hrs
Average
operational day
length (hours)
15
14
6
8
10.1
However, despite the fact that self-propelled sprayers are (theoretically) expensive, highly
utilised machines, especially during the seasonal period studied, average weekly usage for the
three machines studied was a very consistent 45 hours over a 7-day week. Whilst the survey
performed was admittedly of restricted scope and a survey encompassing a greater number of
machines and other seasonal periods would be advisable, the consistency exhibited and data
generated is somewhat of a revelation.
Consequently, given the evidence provided by this investigation, it seems unlikely that the
PA(V)D Exposure Limit Value (ELV) will be exceeded during typical machine operation,
and therefore the requirements of the Directive will not restrict the daily or weekly usage of
self-propelled agricultural sprayers of this generic design / construction, in the UK. However,
the Exposure Action Value (EAV) will very probably be exceeded during typical working
days, requiring employers to implement measures to reduce and manage operator exposure to
WBV (see Section 3.1) and advise potential operators of the WBV risk.
4.4.4
‘On-Farm WBV Exposure Measurement - Summary
The findings of the ‘on-farm’ self-propelled sprayer WBV exposure measurement programme
may be summarised as follows:•
•
•
•
•
•
•
The majority of ‘on-farm’ self-propelled sprayers generated WBV emission levels
similar to those experienced during the SRI ‘in-field’ measurement programme (see
Figures 4.18 & 4.19);
Only during one instance did an ‘on-farm’ sprayer generate WBV magnitudes which
were significantly different to those encountered during the SRI ‘in-field’ operations.
This was deemed a result of disparate (unusually rough) ‘on-farm’ operating
conditions (see Figures 4.18, 4.19 & 4.21);
In all instances, seat acceleration levels were higher than those recorded upon the
sprayer cab floor (see Tables 4.5 & 4.6 and Figures 4.18 & 4.19);
Whilst the largest overall average r.m.s acceleration (Aeq) levels recorded upon the
vehicle seats, were primarily in the transverse (Y) axis, the greatest peak values
actually occurred in the vertical (Z) axis (see Table 4.5, Figure 4.20 & Appendix 1.4);
Vertical (Z) axis overall average r.m.s WBV emissions were consistently largest
amongst measurements made upon the vehicle cab floor (see Table 4.6 &
Figure 4.18);
A majority (57%) of the sprayers surveyed were operated for more than 8-hours per
day. A number of machines were operated for up to 14-hours per day (see
Figure 4.22), but total weekly operation was a remarkably consistent average of
45 hours;
All of the ‘on-farm’ sprayers surveyed exceeded the PA(V)D 8-hour Exposure Action
Value (EAV), whether specified in vibration dose value (VDV) or equivalent
continuous r.m.s. acceleration (A(8)) terms.
57
•
•
•
•
•
Only one ‘on-farm’ sprayer exceeded the Exposure Limit Value (ELV) within
8 hours operation, in an uncommonly rough application (see above). Working day
length would have to increase to unsustainable levels (> 22 hours) for the other
sprayers surveyed to exceed the A(8) ELV;
During a typical working day, it is very likely that the operator of an ‘on-farm’ selfpropelled sprayer would receive WBV exposure in excess of the Exposure Action
Value (EAV), but below the Exposure Limit Value (ELV). In these circumstances
the PA(V)D would require employers to implement measures to reduce and manage
the operator’s exposure, but daily operation of large, modern, ‘state-of-the-art’ selfpropelled sprayers is unlikely to be restricted by the requirements of the Directive,
even if the working day were to lengthen significantly beyond 8 hours(see Table 4.5);
Daily working patterns, including rest breaks, machine maintenance and periods of
general inactivity, can all contribute to a reduction in the Aeq WBV exposure value;
Variation in WBV exposure levels was found to be present between certain example
sprayers. This was not assisted by the relatively small number of individual machines
investigated; the 3 replicates performed being adequate to indicate ‘on-farm’ WBV
levels, but insufficient to determine the degree of WBV emission variability between
supposedly identical vehicles / operations;
Whilst the consistency between WBV emissions encountered during ‘on-farm’
sprayer operation is encouraging, a more detailed investigation of similar format, but
comprising a larger number of measurement replications, is advisable in order to
enable creation of a robust database of generic WBV emission data for modern selfpropelled agricultural sprayers.
58
5.
5.1
AGRICULTURAL TRACTORS
TEST VEHICLES
As previously discussed (Section 2.4), a range of modern, state-of-the-art tractors deemed
suitable for the investigation were identified and kindly loaned by their respective
manufacturers (see Table 5.1 and Figure 5.1).
Table 5.1 Tractors used in the investigation
Tractor
Engine
power
(kW)
Unballasted
mass (kg)
Suspension
features
Wheelbase
(m)
Tyre fitment
None
Fully-suspended cab
(in addition to seat)
John Deere
7810
129
7036
2.800
Front:- 16.9 R28
Rear:- 20.8 R38
Renault Ares
630 RZ
88
5537
2.750
Front:- 14.9 R28
Rear:- 18.4 R38
New Holland
TM165
120
6502
2.787
JCB Fastrac
3185
127
Front:- 540/65 R28
Rear:- 650/65 R38
Suspended front axle
– Cab suspended at
rear only
Front:- 540/65 R30
7245
3.050
Rear:- 540/65 R30
Complete test tractor specifications may be found in Appendix 2.1
Figure 5.1 Tractors used in the investigation at SRI
59
Suspended front &
rear axles
All test tractors were four-wheel drive models: all were fitted with ‘scissor’ linkage-type
suspension seats embodying air spring / hydraulic damper vertical (Z) axis suspension
systems, with the exception of the Renault Ares 630 RZ, whose seat incorporated an
adjustable mechanical spring / hydraulic damper system. All seats embodied limited
longitudinal (X) axis mechanical spring and hydraulic damper suspensions: the John Deere
7810 also incorporated this feature in the transverse (Y) axis. In certain cases the seat
suspension damping was also adjustable. A summary of test tractor suspension seat
specifications is given in Table 5.2: full details are provided in Appendix 2.2.
Table 5.2 Tractor suspension seat details
Tractor
Seat
manufacturer
/ model
John Deere
7810
Suspension type
Z-axis (vertical)
X-axis
(longitudinal)
Y-axis
(transverse)
Sears FS 92/01
Air spring (adj.)
+ damper (adj.)
Mech. spring (fixed)
+ damper (fixed)
Mech. spring
(fixed)
+ damper (fixed)
Renault Ares
630 RZ
Grammer
MSG 85/731
Mech. spring (adj.)
+ damper (fixed)
Mech. spring (fixed)
+ damper (fixed)
None
New Holland
TM165
Sears
SA15748
Air spring (adj.)
+ damper (adj.)
Mech. spring (fixed)
+ damper (adj.)
None
JCB Fastrac
3185
Grammer
MSG95A/721
Air spring (adj.)
+ damper (fixed)
Mech. spring (fixed)
+ damper (adj.)
None
“adj.” = adjustable rate or pre-load: “fixed” = fixed rate: “Mech.” = mechanical
5.2
ISO TEST TRACK WBV EMISSION MEASUREMENT
5.2.1
Procedure
Following a similar test procedure to that employed for the self-propelled sprayers (see
Section 4.2), whole-body vibration emission levels were recorded upon each tractor in
accordance with an extended version of the test methodology described in ISO 5008:2002.
Each vehicle was driven over the SRI ISO 100 m (smoother) and ISO 35 m (rougher) ride
vibration test tracks (see Figure 5.2), at a range of appropriate forward speeds (see Table 5.3).
During each pass across the tracks, acceleration time histories were recorded in three
mutually-perpendicular directions (X-longitudinal, Y-transverse, Z-vertical), both upon the
surface of the operator’s seat and the cab floor, close to the seat mounting (see Figures 3.3 &
3.2 respectively). Acceleration data was acquired and analysed by the methods previously
described in Section 3.2 & 3.3, in accordance with the recommendations of ISO 2631-1:1997:
the resultant frequency-weighted r.m.s. acceleration values are depicted in the line graph
sections of Figures 5.3 to 5.10 inclusive.
The ISO 5008:2002 test methodology was extended for the purposes of this investigation, in
terms of the range and increments of vehicle forward speed used upon each test track (see
Table 5.3). Whilst the speeds currently recommended by ISO 5008 for use upon the
ISO 35 m (rougher) track were considered adequate, those proposed for the ISO 100 m
(smoother) track were considered likely to be too low to adequately stress modern, state-of-
60
the-art tractors embodying axle and/or cab suspension features. Additionally, it was deemed
prudent to incorporate sufficiently small speed increments to enable identification of point(s)
at which the test vehicles’ ride vibration behaviour may exhibit non-linear characteristics
(usually 12-16 km/h for conventional tractors). To address these issues, the modified forward
speed ranges depicted in Table 5.3 were used for the investigation. Three test replicates were
performed at each (original) ISO 5008 forward speed and one replicate at all others, in order
to maintain the test programme within reasonable limits.
ISO 35 m (rougher) track
ISO 100 m (smoother) track
Figure 5.2 ISO 35 m and 100 m ride vibration test tracks
All additional ballast weights were removed from the tractors prior to testing (as required by
ISO 5008). Wherever possible, tyre inflation pressures were adjusted to manufacturer’s
recommended levels for the resulting unladen axle loads, but frequently a combination of
generous tyre sizes and low axle loads made this impossible. In such instances inflation
pressures were reduced to the lowest levels recommended for 30 km/h operation of the tyres
in question. Tyre pressures were re-checked / adjusted following initial vehicle ‘warm-up’
travel, immediately prior to WBV emission measurement. Tractor suspension seats were
adjusted in accordance with operator instruction book recommendations: any adjustable
damper features were adjusted to mid-range settings and where seat designs embodied
selectable longitudinal (X) and transverse (Y) axis suspension facilities (see Table 5.2), these
features were enabled / utilised. Full details of test tractor specifications and set-ups are
provided in Appendix 2.1.
61
Table 5.3 Tractor forward speeds used upon the ISO ride vibration test tracks
Tractor forward speed (km/h)
Test track
Current ISO 5008
‘Extended’ ISO 5008
ISO 35 m
(rougher)
4, 5, 7
4, 5, 6, 7
ISO 100 m
(smoother)
10, 12, 14
10, 12, 13, 14, 15, 16, 18, 20, 24, 30
5.2.2
Results
The results of WBV emission measurement upon the ISO test tracks are presented graphically
within the line graph sections of Figures 5.3 – 5.10 inclusive, and numerically within
Appendix 2.3. The data falls into four basic categories: the test track used (35 m ‘rougher’ or
100 m ‘smoother’) and measurement location upon the vehicle (‘floor’ or ‘seat’). Within
each of these categories the behaviour of the (four) test tractors may be considered. An
immediate overall conclusion is that in all instances, measured WBV emission levels
increased in proportion with forward speed, irrespective of the suspension systems present
upon the test vehicles.
Cab floor – ISO 35 m ‘rougher’ track
Consideration of vibration levels measured upon the cab floor (see line graph sections of
Figures 5.3, 5.5, 5.7 & 5.9) enables the (potentially variable) influence of the vehicle
suspension seats to be minimised. The 35 m track generated the highest WBV levels
recorded, equalled only (occasionally) by the conventional tractors (i.e. unsuspended,
suspended cab, suspended front axle & cab) when operating at high speeds (24-30 km/h) on
the 100 m ‘smoother’ track. All vehicles generated highest acceleration levels in the
transverse (Y) axis: followed (in reducing magnitude) by the longitudinal (X) and vertical
(Z) axes. A degree of Y-axis dominance is to be expected, given the nature of the test surface
and its tendency to encourage lateral roll of the vehicle. All the test vehicles performed
similarly, irrespective of their different suspension system designs / capabilities.
Cab floor – ISO 100 m ‘smoother’ track
Once more WBV levels were found to increase with forward speed, but at a lesser rate than
had been encountered upon the 35 m track (see Figures 5.3, 5.5, 5.7 & 5.9). However, in this
case, slight differences were found between the test vehicles. The conventional tractors (i.e.
unsuspended, suspended cab, suspended front axle & cab) all exhibited very similar
behaviour. Up to forward speeds of approx. 20 km/h, transverse (Y) axis weighted r.m.s.
acceleration levels were generally highest, followed (in reducing magnitude) by those in the
vertical (Z) and longitudinal (X) axes respectively. At speeds above 20 km/h, vertical (Z)
axis acceleration levels exceeded those of the transverse (Y) axis and continued to increase at
higher speeds. This behaviour was not, however, exhibited by the fully (front & rear axle)
suspended tractor, whose overall WBV levels demonstrated a much smoother and more
predictable increase with forward speed, and lower overall levels than the other test tractors
(see Figure 5.9).
62
Operator’s seat – ISO 35 m ‘rougher’ and ISO 100 m ’smoother’ tracks
What effect do the suspension seats have? Initial observation of the test results (see linegraph sections of Figures 5.4, 5.6, 5.8 & 5.10) would appear to question their effectiveness
upon any of the test tractors in these conditions, given that longitudinal (X) and transverse (Y)
axis ‘seat’ acceleration levels appear to increase relative to those recorded upon the cab floor
at identical forward speeds (seat & floor WBV was measured simultaneously). This trend is
particularly apparent within the 35 m ‘rougher’ track data where, additionally, vertical
(Z) axis acceleration levels, if not amplified by the same degree as the X & Y-axes, were not
attenuated. However, these characteristics are not as surprising or devastating, as one might
first believe. The 35 m ‘rougher’ test track tends to generate high acceleration levels in the
transverse (Y) and longitudinal (X) axes. The operator’s seat surface is further (higher) from
the tractor’s lateral (roll) and longitudinal (pitch) centres than the cab floor: consequently,
acceleration levels measured in those axes at that point will be greater than those recorded on
the cab floor. Allied to this is the difficulty of incorporating effective horizontal (X or Yaxis) suspension systems into agricultural vehicle seats. Several of the tractors tested were
fitted with seats incorporating X-axis suspension, and one included both X and Y-axis
suspension (see Table 5.2). However, the low vibration frequencies involved, together with
practical restrictions upon seat horizontal travel due to in-cab space, combine to greatly limit
the effectiveness of horizontal axis seat suspension systems.
Suspension seat development has, to date, concentrated upon vertical (Z) axis performance.
Modern suspension seats undoubtedly do serve to improve operator ride comfort, but are most
likely to attenuate Z-axis vibrations. Even then their effectiveness is limited to circumstances
when the input acceleration (cab floor) frequency is greater than the natural frequency of the
seat suspension system. This point is demonstrated by WBV data presented in Figures 5.7 &
5.8. Whilst the seat achieves little (if any) attenuation of Z-axis acceleration upon the 35 m
track, significant reductions in Z-axis r.m.s. acceleration are achieved at higher forward
speeds (above 20 km/h) upon the 100 m track. This is primarily due to the increasing
importance of the vertical axis component of the seat input acceleration as forward speed on
the 100 m track increases (see Figure 5.7).
63
Speed (km/h)
0
5
10
15
20
25
30
35
40
45
50
2
Weighted r.m.s. Acceleration (m/s )
2.5
2.0
1.5
1.0
0.5
0.0
Ploughing
ISO 35m Test Track
ISO 100m Test Track
Plough Cultivating Spraying Trailer
transport
transport
Field Task
Task Longitudinal (X)
Track Longitudinal
Task Transverse (Y)
Track Transverse
Task Vertical (Z)
Track Vertical
Figure 5.3 Unsuspended tractor: Floor acceleration (1.4 multiplier)
Speed (km/h)
0
5
10
15
20
25
30
35
40
45
50
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
ISO 35m Test Track
ISO 100m Test Track
Ploughing Plough Cultivating Spraying Trailer
transport
transport
Field Task
Task Longitudinal (X)
Track Longitudinal
Task Transverse (Y)
Track Transverse
Task Vertical (Z)
Track Vertical
Figure 5.4 Unsuspended tractor: Seat acceleration (1.4 multiplier)
64
Speed (km/h)
0
5
10
15
20
25
30
35
40
45
50
2
Weighted r.m.s. Acceleration (m/s )
2.5
2.0
1.5
1.0
0.5
0.0
ISO 35m Test Track
Ploughing Plough Cultivating Spraying Trailer
transport
transport
ISO 100m Test Track
Field Task
Task Longitudinal (X)
Track Longitudinal
Task Transverse (Y)
Track Transverse
Task Vertical (Z)
Track Vertical
Figure 5.5 Suspended cab tractor: Floor acceleration (1.4 multiplier)
Speed (km/h)
0
5
10
15
20
25
30
35
40
45
50
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
ISO 35m Test Track
ISO 100m Test Track
Ploughing Plough Cultivating Spraying Trailer
transport
transport
Field Task
Task Longitudinal (X)
Track Longitudinal
Task Transverse (Y)
Track Transverse
Task Vertical (Z)
Track Vertical
Figure 5.6 Suspended cab tractor: Seat acceleration (1.4 multiplier)
65
Speed (km/h)
0
5
10
15
20
25
30
35
40
45
50
2
Weighted r.m.s. Acceleration (m/s )
2.5
2.0
1.5
1.0
0.5
0.0
Ploughing
ISO 35m Test Track
ISO 100m Test Track
Plough Cultivating Spraying Trailer
transport
transport
Field Task
Task Longitudinal (X)
Track Longitudinal
Task Transverse (Y)
Track Transverse
Task Vertical (Z)
Track Vertical
Figure 5.7 Suspended front axle & cab tractor: Floor acceleration (1.4 multiplier)
Speed (km/h)
0
5
10
15
20
25
30
35
40
45
50
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
ISO 35m Test Track
ISO 100m Test Track
Ploughing Plough Cultivating Spraying Trailer
transport
transport
Field Task
Task Longitudinal (X)
Track Longitudinal
Task Transverse (Y)
Track Transverse
Task Vertical (Z)
Track Vertical
Figure 5.8 Suspended front axle & cab tractor: Seat acceleration (1.4 multiplier)
66
Speed (km/h)
0
5
10
15
20
25
30
35
40
45
50
2
Weighted r.m.s. Acceleration (m/s )
2.5
2.0
1.5
1.0
0.5
0.0
ISO 35m Test Track
Ploughing Plough Cultivating Spraying Trailer
transport
transport
ISO 100m Test Track
Field Task
Task Longitudinal (X)
Track Longitudinal
Task Transverse (Y)
Track Transverse
Task Vertical (Z)
Track Vertical
Figure 5.9 Fully suspended (front & rear axle) tractor: Floor acceleration
(1.4 multiplier)
Speed (km/h)
0
5
10
15
20
25
30
35
40
45
50
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
ISO 35m Test Track
ISO 100m Test Track
Ploughing Plough Cultivating Spraying Trailer
transport
transport
Field Task
Task Longitudinal (X)
Track Longitudinal
Task Transverse (Y)
Track Transverse
Task Vertical (Z)
Track Vertical
Figure 5.10 Fully suspended (front & rear axle) tractor: Seat acceleration
(1.4 multiplier)
67
5.3
SRI ‘IN-FIELD’ WBV EMISSION MEASUREMENT
5.3.1
Introduction
Following a similar test methodology to that employed for the self-propelled
sprayers (Section 4.3), a detailed programme of agricultural tractor ‘in-field’ WBV emission
measurement was performed upon the Silsoe Research Institute (SRI) estate, using the same
test tractors as used within the ISO test track experimental programme (Section 5.2). The
objectives of this work were:• To quantify each tractor’s ‘in-field’ WBV emission levels whilst performing a
selected range of identical agricultural operations, in known / controlled conditions;
• To investigate the similarity (if any) between WBV emission levels encountered
during these operations and those generated during ISO 5008 ride vibration track
testing (Section 5.2).
A range of target ‘field tasks’ was selected to reflect typical agricultural usage of modern
four-wheel-drive tractors in the chosen (88-127 kW) engine power range; these being
ploughing, plough transport, cultivating, spraying/top dressing and trailer transport.
Acceleration time histories were recorded simultaneously upon the operator’s seat and the
tractor cab floor, by use of the vehicle-mounted instrumentation described in Section 3.2.
Additionally, vehicle forward speed was recorded (derived from a Doppler radar sensor
mounted upon each vehicle), to enable quantification of this important operational parameter.
Each vehicle performed each field operation for a sampling period of 25-30 minutes, to
encompass and minimise task or operating condition-related variations. Two replicates of
each task were performed. Additionally, to minimise variations attributable to personal
operating technique, the same individual operated each test vehicle in turn.
5.3.2
Spraying
A three-point (3pt.) linkage-mounted, 1000 litre capacity, air-assisted sprayer (Figure 5.11)
was selected for this operation, this being a typical UK mounted sprayer and also,
fortuitously, of similar mass and weight distribution to many linkage-mounted twin-disc
granular fertiliser distributors. The target implement was therefore representative of both
chemical application and fertiliser spreading equipment. (Test tractor axle loadings and tyre
inflation pressures selected for this field task are detailed in Appendix 2.4). Each tractor
performed a ‘mock’ spraying operation in turn, upon a damp, clay field, following existing
post-harvest tramlines at a target forward speed of 10 km/h. The sprayer was operated with
booms unfolded; headland turns were performed as per usual spraying practice: however, no
water was actually discharged during the operation, so the tractor-implement combination’s
mass and weight distribution remained unchanged throughout.
The WBV emission levels recorded during this task were the lowest of any selected field
operations (see Figure 5.13). This is not particularly surprising, given that tractor forward
speed was not excessive and the only sources of ride vibration were due to crossing tramlines
(at headlands) and occasional changes in direction (headland turns). As previously discussed
(Section 3.1), the PA(V)D follows the ISO 2631-1:1997 WBV data analysis practice for
‘Operator Health’ as opposed to ‘Operator Comfort’, in that it considers only the frequencyweighted r.m.s. acceleration magnitude of the largest single orthogonal axis, rather than
combining the magnitudes of all (X, Y & Z) axes into a vibration total value of weighted
r.m.s. acceleration, via the vector sum or root-sum-of-squares (RSS) method. Also the largest
single axis is chosen following application of an axis-specific multiplying factor.
68
Figure 5.11 Suspended cab tractor, spraying
Figure 5.12 Suspended front axle & cab tractor, ploughing
69
1.20
Y-axis
2
Weighted r.m.s. acceleration (m/s )
1.10
1.00
X-axis
0.90
0.80
Y-axis
0.70
0.60
Y-axis
Y-axis
0.50
0.40
Spraying
Plough in transport
Ploughing
Trailer transport
Cultivating
Tasks
Range of average WBV emission levels recorded upon tractor cab floors
during SRI ‘in-field’ investigation (largest axis denoted upon each bar)
1.4
28
1.2
24
1.0
20
0.8
16
0.6
12
0.4
8
0.2
4
0.0
Speed (km/h)
2
Weighted r.m.s. Acceleration (m/s )
Figure 5.13
0
Unsuspended
Cab suspension
Front axle & cab
suspension
Front & rear axle
suspension
Tractor
Longitudinal (X)
Figure 5.14
Transverse (Y)
Vertical (Z)
Speed
Cab floor WBV emission levels recorded during (tractor-based) spraying
operations at SRI
70
Consequently, following PA(V)D methodology, the highest axis-weighted overall average
r.m.s. acceleration (Aeq) levels recorded on the cab floor during spraying were consistently in
the transverse (Y) axis, irrespective of the tractor in question. Acceleration magnitudes were
also very similar between vehicles (see Figure 5.14), cab floor average weighted r.m.s.
acceleration levels being in the range 0.41 - 0.48 m/s2 (see Figure 5.13 and Appendix 2.5).
Operator seat WBV levels displayed less marked differences between the measurement axes
but, as previously discussed (Section 5.2.2), differences in suspension seat performance and
vehicle / seat matching can introduce considerable uncertainties / variability.
Comparing cab floor field spraying weighted r.m.s. acceleration levels with those recorded
upon the ISO test tracks (see Figures 5.3, 5.5, 5.7 & 5.9) immediately indicates little
similarity. Transverse (Y) axis acceleration magnitudes obtained upon the test tracks were
much greater, particularly in the case of the conventional (unsuspended, suspended cab,
suspended front axle & cab) tractors. The ISO 100 m track is probably the closest
representation of the field surface conditions encountered during spraying, but even this is
likely to be too severe, given that the 100 m track was designed to represent an un-metalled
farm road. Also, it is appropriate to consider only the 10 km/h travel speed upon this surface,
this being that used for the field task. Given this difference in operating surfaces and also the
(unavoidably) different tractor weight distributions and tyre inflation pressures used for the
field and ISO track tests (see Appendix 2.4 & 2.1 respectively), the lack of similarity between
the ‘field’ and ‘track’ results is not surprising. However, greater similarity exists between the
performance of the fully suspended (front & rear axle) tractor in these respective conditions
(see Figure 5.9), but this may solely be a consequence of its relatively good ‘track’
performance and indifferent ‘field’ performance during the task in question.
5.3.3
Ploughing
A fully-mounted 5-furrow reversible plough was chosen for both this and the subsequent
‘plough transport’ operation. The plough selected (see Figure 5.12) was typical of those
likely to be used with the tractors under investigation, especially in the heavy, damp clay
stubble field conditions encountered during the test period (mid-September). WBV data was
acquired for a period of 30 minutes whilst ploughing at a 6.5 km/h target forward speed
(typical for the field conditions), during which time the test vehicles managed to complete
approx. 9 passes along the test field and 8 corresponding headland turns. Two replicates of
this field test sequence were performed, the graphical results presented in this report being the
means of parameter values acquired. Tractor average forward speed may appear to be
somewhat lower than the intended target (see Figure 5.15 and Appendix 2.5), but this is a
consequence of averaging data throughout the test period, including the deceleration and
reversing cycles of headland turns.
Cab floor weighted r.m.s. acceleration levels recorded during ploughing were of moderate
magnitude in relation to other ‘field’ tasks, being in the range 0.60 – 0.70 m/s2 (see
Figure 5.13 and Appendix 2.5). In all instances the greatest acceleration was recorded in the
transverse (Y) axis, followed (in decreasing magnitude) by the longitudinal (X) and
vertical (Z) axes respectively. Little significant difference was evident between the test
tractors (see Figure 5.15), unless the vector sum (RSS) acceleration is considered, in which
case the (fully) suspended front & rear axle tractor delivered a slightly lower vibration total
values, when measured either upon the cab floor or the operator’s seat (see Appendix 2.5).
71
14
1.2
12
1.0
10
0.8
8
0.6
6
0.4
4
0.2
2
0.0
Speed (km/h)
2
Weighted r.m.s. Acceleration (m/s )
1.4
0
Unsuspended
Cab suspension
Front axle & cab
suspension
Front & rear axle
suspension
Tractor
Longitudinal (X)
Transverse (Y)
Vertical (Z)
Speed
1.4
28
1.2
24
1.0
20
0.8
16
0.6
12
0.4
8
0.2
4
0.0
Speed (km/h)
2
Weighted r.m.s. Acceleration (m/s )
Figure 5.15 Cab floor WBV emission levels recorded during ploughing at SRI
0
Unsuspended
Cab suspension
Front axle & cab
suspension
Front & rear axle
suspension
Tractor
Longitudinal (X)
Transverse (Y)
Vertical (Z)
Speed
Figure 5.16 Cab floor WBV emission levels recorded during plough transport at SRI
72
Once again there is little similarity between cab floor weighted r.m.s. acceleration levels
recorded during ‘in-field’ ploughing and those obtained from the ISO test tracks (see
Figures 5.3, 5.5, 5.7 & 5.9). However, as before, influential factors such as test surface, vehicle
forward speed, tyre inflation pressures, tractor-implement weight distribution, moments of
inertia and, importantly, external (plough draught) forces acting upon the vehicle should be
taken into consideration. Given these factors, the 35 m test surface is excessively rough
compared with the field conditions (mole-drained cereal stubble), the 100 m track surface being
perhaps more appropriate. Vehicle weight distribution, moment(s) of inertia and external
forces bear little or no relation between the test conditions. Consequently, upon initial
consideration, it is hardly surprising that little similarity exists.
5.3.4
Plough transport
This operational task was performed with the same tractor-implement combinations as used for
‘in-field’ ploughing activities (see Section 5.3.3), the intention being to represent typical travel
to and from a field. A composite travel circuit was chosen, comprising sections of field
headland, farm track, ‘country’ (rough) road and ‘smooth’ road travel in approximately
20:32:38:10% relative (time) proportions. Each tractor completed the test circuit twice, taking
approximately 25 minutes per circuit; with the exception of the fully suspended (front & rear
axle) machine, which benefited from a higher (legal) maximum road speed capability on the
‘smooth’ road sections. However, the resultant effect upon the tractor’s average speed over the
entire test circuit was not substantial (see Figure 5.16). Each tractor was driven at similar
(driver comfort-limited) forward speeds during the field and farm track sections of the test
circuit. During the ‘on-road’ sections each vehicle was driven at the highest speed deemed
suitable, as limited by driver comfort, vehicle safety and maximum speed capability.
Each test tractor’s 3pt. hitch system embodied some form of active ride control, designed to
minimise the transfer of vertical shock loading from the mounted implement to the tractor
whilst in road transport (usually above 10 km/h). This feature (as described in Section 2.1.4)
was used in all instances during this task.
The WBV emission levels recorded upon the cab floor during plough transport were relatively
low (see Figure 5.16), being only slightly greater than those encountered during spraying (see
Figure 5.13). Once again the transverse (Y) axis exhibited the largest overall average r.m.s.
acceleration levels, but only marginally so, vertical (Z) axis levels being a very close second,
especially for the conventional tractors (unsuspended, suspended cab, suspended front axle &
cab). In ‘largest-single-axis’ terms, there is little difference in cab floor acceleration
magnitudes between the test vehicles (range 0.45 – 0.51 m/s2) as shown by Figures 5.13 & 5.16
and Appendix 2.5. However, the suspended cab and suspended front axle & cab tractors
possibly deliver marginally better ride than the unsuspended tractor; whereas the fully
suspended (front & rear axle) machine achieves WBV levels comparable with the best
examples whilst travelling at a higher overall average forward speed (see Figure 5.16).
In all instances the operator considered that the action of the 3pt. hitch active damping systems
improved vehicle ride comfort and made the vehicles easier to control. This was particularly
noticeable upon the ‘country’ road sections of the test circuit, but it should be emphasized that
no objective WBV data was acquired to confirm or dispel this subjective impression.
Comparing ‘plough transport’ cab floor weighted r.m.s. acceleration levels with those recorded
upon the ISO test tracks, it is first appropriate to consider the respective test conditions. In
terms of operating surface, the ISO 100 m track should bear closest similarity to the ‘farm
track’ sections of the plough transport test circuit. However, as presented here, the plough
73
transport results are a composite of the entire test circuit, discouraging direct comparison.
Additionally, it should be remembered that during this task each tractor was carrying a plough
of mass ~1500 kg and ~500 – 1000 kg front ballast, not to mention operating at higher tyre
inflation pressures (see Appendix 2.4). Add to this the effects of the 3pt. hitch active ride
control system and the significantly different dynamic behaviour of a tractor and long, heavy
mounted implement combination when compared with a solo, unladen tractor, and a disparity
between the ISO test track and ‘in-field’ results is to be expected in this instance (see
Figures 5.3, 5.5, 5.7 & 5.9). An appropriate course of action would be to revisit the WBV data
acquired during ‘farm track’ travel and compare this with data obtained by subjecting the same
tractor-implement combination to a limited 100 m ISO track test programme. However, whilst
this was performed for the self-propelled sprayers in this study (see Sections 4.2 & 4.3), further
such investigation in the case of tractors was unfortunately beyond the scope of this particular
study.
5.3.5
Cultivating
During this field task each test tractor was operated with a 4 metre wide heavy-duty ‘pigtail’
cultivator (see Figure 5.18); a popular implement for both post-harvest primary cultivation (e.g.
on cereal stubbles) and initial secondary cultivation on previously ploughed land. The test
conditions embodied both these characteristics, comprising the two distinct operating
conditions of rough ploughed / rutted ground and rutted clay cereal stubble. The resulting
operating conditions were both rough and uncomfortable for the vehicle operator, but
nonetheless were representative of ‘challenging’ conditions that are often encountered in
agriculture. To improve ride comfort marginally, whilst still achieving an adequate cultivation
/ levelling effect, the test vehicles were operated at an angle of 15-20° to the previous
ploughing / tramlines / ruts. However, driver comfort limited forward speed to approx. 6 and
7.5 km/h on the ploughed ground and stubble respectively. WBV emission levels were
recorded both upon the cab floor and driver’s seat of each vehicle throughout a 20 minute
period of operation upon each surface.
Cab floor weighted r.m.s. acceleration levels recorded during cultivating were the highest of all
‘field’ tasks investigated, being in the range 0.90–1.14 m/s2 (see Figure 5.13 and
Appendix 2.5). Given the nature of the operating conditions, this is hardly surprising.
Similarly, neither is the fact that all vehicles generated greatest WBV emission levels in the
transverse (Y) axis; followed in most cases (in decreasing magnitude) by the longitudinal (X)
and vertical (Z) axes respectively (see Figure 5.17). The higher transverse (Y) axis acceleration
levels are probably a consequence of vehicle roll whilst traversing the rough, rutted ground.
Little significant difference is evident between the cab floor WBV emission levels of test
tractors (see Figure 5.17), although a certain similarity is apparent between the performance of
the unsuspended, the suspended front axle & cab, and the fully suspended (front & rear axle)
tractors: the suspended cab tractor returning a marginally poorer ride. However, this could
possibly be due to a number of factors, including the slightly smaller overall size of the vehicle
in question and possible variation in test conditions. A greater number of test replicates would
be necessary to fully determine the significance of this apparent trend.
Comparison of ‘cultivating’ cab floor weighted r.m.s. acceleration levels with those originating
from the ISO test track programme (see Figures 5.3, 5.5, 5.7 & 5.9) indicates a certain, but not
universal, similarity. ‘Field’-generated WBV magnitudes are for once similar to those resulting
the ISO track at certain forward speeds, but the region of similarity (i.e. track type / forward
speed range) appears to be somewhat vehicle-specific and not universal across all measurement
axes. The ‘in-field’ WBV emission levels of the unsuspended and suspended front axle & cab
tractors relate most closely to their performance upon the ISO 100 m test track in the 10 –
74
15 km/h speed range: those emission levels generated upon the 35 m track by these machines
being considerably higher, especially in the transverse (Y) and longitudinal (X) axes.
However, the suspended cab tractor exhibits the exact opposite trend, greatest similarity
resulting from the 35 m track around 4 – 5 km/h. To further confuse the issue, the ‘in-field’
WBV performance of the fully suspended (front & rear axle) tractor relates most closely to its
behaviour upon the 100 m ISO track around 15 – 20 km/h forward speed.
1.4
14
1.2
12
1.0
10
0.8
8
0.6
6
0.4
4
0.2
2
0.0
0
Unsuspended
Cab suspension
Front axle & cab
suspension
Front & rear axle
suspension
Tractor
Longitudinal (X)
Transverse (Y)
Vertical (Z)
Speed
Figure 5.17 Cab floor WBV emission levels recorded during cultivating at SRI
75
Speed (km/h)
2
Weighted r.m.s. Acceleration (m/s )
What may be inferred from these results? Firstly, that the ‘in-field’ surface conditions were
considerably rougher than the ISO 100 m (smoother) track: hence comparable WBV emission
levels were only achieved upon the latter at twice or three times the ‘in-field’ vehicle forward
speed. Secondly, that the ISO 35 m (rougher) track, which was originally intended to represent
a ploughed field surface, is slightly rougher than the field conditions experienced during this
operation, but only marginally so, because during field operation the implement draught forces
(and their lines of action) would tend to stabilise the vehicles, both in pitch, yaw and possibly
roll modes. The ride vibration behaviour of an unladen vehicle will not be the same as one
operating a 3pt. linkage-mounted soil-engaging draught implement, even if the operating
surfaces are identical, as indicated by Crolla (1976). Finally, it may appear that the fully
suspended (front & rear axle) tractor failed to demonstrate its full potential for ride comfort
enhancement during this operation in comparison with the other tractors, given its superior
performance upon the ISO 100 m track (see Figures 5.9 & 5.17). However, this is probably a
result of its suspension system design, namely the incorporation of anti-roll bars on the front
and rear axles. These components generate greater roll stiffness, thereby providing better
vehicle stability during cornering manoeuvres: however, they also serve to transfer a greater
proportion of axle roll to the vehicle chassis than the freely-pivoting front axle designs utilised
by the other tractors. Operating conditions in which transverse (Y) axis vehicle roll
predominate, such as the ISO 35 m test track and driving at an angle across ruts / ploughing /
tramlines, serve to highlight this particular suspension system characteristic.
Figure 5.18
Unsuspended tractor, cultivating
Figure 5.19
Fully suspended (front & rear axle) tractor: trailer transport
76
5.3.6
Trailer transport
This task was performed in a similar manner to ‘plough transport’ (see Section 5.3.4). Each
tractor was connected, in turn, to an ‘unbalanced’ 12-tonne capacity Wootton tandem-axle
trailer (see Figure 5.19) and driven along a composite test circuit, comprising sections of field
headlands, farm tracks, ‘country’ (rough) roads and ‘smooth’ roads in approximately
38:25:27:10% relative (time) proportions. The trailer, which incorporated leaf-spring
suspension systems upon both axles and the drawbar, was ballasted to achieve the legal
maximum gross train weight (tractor + laden trailer) of approx. 24390 kg when operating with
the heaviest test tractor (JCB Fastrac 3185): this trailer load was then retained for all further
testing (see Appendix 2.4). Each tractor completed the test circuit twice, requiring approx. 25
- 30 minutes per circuit, with the exception of the fully suspended (front & rear axle) tractor,
which benefited from a higher (legal) maximum road speed capability on the ‘smooth’ road
sections. However, the resultant effect upon the tractor’s average speed over the entire test
circuit was not substantial (see Figure 5.20 and Appendix 2.5). Each tractor was driven at
similar forward speeds during the ‘field’ and ‘farm track’ sections of the test circuit: within
the on-road sections each vehicle was driven to the highest speed deemed suitable, as
constrained by driver comfort, road safety and maximum speed capability.
1.50
30
1.25
25
1.00
20
0.75
15
0.50
10
0.25
5
0.00
Speed (km/h)
2
Weighted r.m.s. Acceleration (m/s )
Weighted r.m.s. acceleration levels measured on the cab floor and averaged over the entire
(composite) test circuit for each vehicle, were of moderate to high magnitude relative to the
other ‘in-field’ tasks performed, being in the range 0.74 – 0.89 m/s2 (see Figure 5.13 and
Appendix 2.5). In virtually all cases the highest r.m.s. acceleration levels were generated in
the longitudinal (X) axis, followed closely (in decreasing magnitude) by the transverse (Y)
and vertical (Z) axes. However, given that vehicle WBV emission levels are strongly
influenced by both operating surface and forward speed, it is appropriate to consider the
different operating conditions present within the test circuit individually (see Figure 5.21 and
Appendix 2.6). By this method the following observations may be made.
0
Unsuspended
Cab suspension
Front axle & cab
suspension
Front & rear axle
suspension
Tractor
Longitudinal (X)
Figure 5.20
Transverse (Y)
Vertical (Z)
Speed
Overall cab floor WBV emission levels recorded during trailer transport
at SRI (i.e. entire ‘composite’ test circuit)
77
1.25
50
1.00
40
0.75
30
0.50
20
0.25
10
Cab suspension
Front axle & cab
suspension
1.25
50
1.00
40
0.75
30
0.50
20
0.25
10
0
Unsuspended
Front & rear axle
suspension
Cab suspension
Transverse(Y)
Vertical (Z)
Speed
Longitudinal (X)
50
1.00
40
0.75
30
0.50
20
0.25
10
2
1.25
Weighted r.m.s. Acceleration (m/s )
60
Speed (km/h)
2
Weighted r.m.s. Acceleration (m/s )
1.50
0.00
0
Cab suspension
Front axle & cab
suspension
Transverse (Y)
Figure 5.21
Vertical (Z)
Speed
1.50
60
1.25
50
1.00
40
0.75
30
0.50
20
0.25
10
0
0.00
Front & rear axle
suspension
Unsuspended
Cab suspension
Tractor
Longitudinal (X)
Transverse (Y)
Trailer transport, Smooth road: Floor accelerations (1.4 multiplier) by tractor
Trailer transport, Country road: Floor accelerations (1.4 multiplier) by tractor
Unsuspended
Front & rear axle
suspension
Tractor
Tractor
Longitudinal (X)
Front axle & cab
suspension
Front axle & cab
suspension
Front & rear axle
suspension
Tractor
Vertical (Z)
Speed
Longitudinal (X)
Transverse (Y)
Vertical (Z)
Speed
Cab floor WBV emission levels recorded during trailer transport at SRI (by test circuit section)
78
Speed (km/h)
Unsuspended
60
0.00
0
0.00
1.50
Speed (km/h)
60
2
1.50
Weighted r.m.s. Acceleration (m/s )
Trailer transport, Farm track: Floor accelerations (1.4 multiplier) by tractor
Speed (km/h)
2
Weighted r.m.s. Acceleration (m/s )
Trailer transport, Field surface: Floor accelerations (1.4 multiplier) by tractor
Field headland
This surface was a relatively soft, clay grassland field headland, but nonetheless firm enough
to enable passage of the laden tractor-trailer combinations. Vehicle forward speed was
maintained at approx. 11 km/h for all tractors, to enable comparison of results. Very similar
cab floor weighted r.m.s. acceleration levels were recorded upon all the vehicles, irrespective
of suspension system design / capability (see Figure 5.21 and Appendix 2.6), these typically
being in the range 0.9 – 1.15 m/s2. Largest (overall average r.m.s.) acceleration levels were
evident in the longitudinal (X) axis, followed (in decreasing magnitude) by the transverse (Y)
axis. Vertical (Z) axis WBV emission levels were significantly smaller.
Farm track
An un-metalled farm road, complete with characteristic potholes. Forward speed of the
conventional tractors (unsuspended, suspended cab, suspended front axle & cab) was limited
to approx. 13 km/h by driver comfort, whereas the fully suspended (front & rear axle) tractor
could comfortably maintain approx. 16 km/h (see Appendix 2.6). Despite its higher forward
speed, the fully suspended (front & rear axle) tractor returned WBV emission levels
comparable with, if not slightly lower than, the other test vehicles. In this test condition
longitudinal (X) and transverse (Y) axis acceleration levels were more comparable with each
other than in previous test conditions but, once again, vertical (Z) axis emission levels were of
significantly lower magnitudes (see Figure 5.21).
‘Country’ (rough) road
This section of the test circuit comprised undulating, minor roads between Silsoe and adjacent
villages. Road width, surface condition, slope, forward visibility, driver comfort and
oncoming traffic all served to limit vehicle forward speed to approx. 30 km/h for the
conventional tractors (unsuspended, suspended cab, suspended front axle & cab), whereas the
fully suspended (front & rear axle) tractor could comfortably achieve an average of 36 km/h
(see Appendix 2.6). The largest overall average r.m.s. acceleration levels were found in the
longitudinal (X) axis in all but one instance (see Figure 5.21), followed (in reducing
magnitude) transverse (Y) and vertical (Z) axis levels, respectively. Upon this test surface the
presence of either cab or front axle & cab suspension systems does appear to reduce the
severity of longitudinal (X) axis vibration, but additional factors such as individual vehicle
design and centre of gravity position, may have an unseen bearing upon this result. However
full (front & rear axle) suspension does undoubtedly reduce vehicle ride vibration levels (as
measured upon the cab floor) in this instance, especially given that this vehicle was indeed
travelling at a higher forward speed than the others under test.
‘Smooth’ road
A straight, level ‘A-road’ type surface upon which all vehicles could easily travel at their
maximum design speeds, subject to adequate acceleration and deceleration capabilities. Upon
this surface the conventional tractors (unsuspended, suspended cab, suspended front axle &
cab) attained approx. 40 km/h, whereas the fully suspended (front & rear axle) tractor
achieved an average of 57 km/h (see Appendix 2.6). Once more longitudinal (X) axis (overall
average r.m.s.) acceleration levels were of greatest magnitude, followed closely by the
transverse (Y) axis and, finally, by the vertical (Z) axis (see Figure 5.21). As would be
expected, WBV levels were significantly lower (in certain cases 50% less) than the average
weighted r.m.s. acceleration levels recorded upon the ‘Country’ roads. However, despite this
smooth test surface, the suspended cab and suspended front axle & cab tractors returned lower
79
(single-largest-axis) WBV levels that the unsuspended vehicle. Once more the fully
suspended (front & rear axle) tractor generated WBV emission levels comparable with the
best performing ‘conventional’ tractors, but at a significantly higher forward speed. It is
therefore reasonable to predict that at comparable operating speeds, its WBV emission levels
would be the lowest of all the vehicles tested.
Trailer transport - Summary
Given the degree of control that could exercised upon the trailer transport test conditions and
equipment, in terms of parameter control, repeatability, etc, it is possible to summarise what
may appear a complex situation by comparing the relative performance of the test vehicles /
suspension systems, as indicated by cab floor WBV emission levels. Figure 5.21 suggests
that at similar speeds upon a ‘field’ surface, there is little to choose between the ride vibration
performance of any of the test vehicles, especially in PA(V)D ‘largest-single-WBV-axis’
terms. As forward speeds increase (i.e. test conditions become more farm track / on-road
orientated), the suspended cab and suspended front axle & cab tractors show an advantage
over the unsuspended vehicle, in terms of lower WBV emission levels. However, this trend is
also demonstrated, but to a much greater degree, by the fully suspended (front & rear axle)
tractor, which proves itself a significantly more effective road transport vehicle.
Superior performance (lower WBV emission levels) may also have been expected from the
partially and fully suspended vehicles during ‘in-field’ operation (as opposed to ‘track’ or
‘road’). However, it is appropriate to recognise that the trailer represented over 70% of the
tractor-trailer combination’s gross weight, of which approx. 3900 kg was transferred to the
tractor pickup hitch, at a point behind the vehicle’s rear axle. Whilst the trailer drawbar
incorporated a rudimentary leaf-spring suspension system, which undoubtedly served to
reduce shock loadings, a variable vertical force approaching 50% of the unballasted tractor
mass was applied via the trailer drawbar during operation. Substantial forces would also be
applied to the tractor in the X and Y-axes during acceleration, braking, cornering and simply
due to trailer draught (rolling resistance). To this end it is not surprising that, in many test
conditions, the sheer ‘dynamic’ influence of the trailer (and the nature / position of its
coupling to the tractor) would have a significant effect upon the ride vibration behaviour of
the tractor, as demonstrated by Crolla and Dale (1979).
Little comparability exists between trailer transport cab floor WBV emission levels and those
obtained from the solo tractors upon the ISO test tracks (see Figures 5.3, 5.5, 5.7 & 5.9).
Perhaps this is hardly surprising, giving the vast differences in vehicle weight distributions,
tyre inflation pressures and external forces systems between the respective test conditions.
The ISO 100 m (smoother) track would relate most closely to the ‘farm track’ and possibly
‘field’ test conditions, but little similarity can be expected between the dynamic behaviour of
a 7-tonne solo tractor and a 24-tonne tractor-trailer combination. However, as discussed in
Section 5.3.4, a possible course of action would be to revisit the WBV data acquired during
‘farm track’ section of the trailer transport test circuit and compare this with data obtained by
subjecting the same tractor-trailer combination to a limited 100 m ISO track test programme.
This would, in theory, generate comparable results and perhaps provide a starting point for
the development of defined WBV test methodologies for vehicle WBV emission
determination (see Section 7.4). However, whilst this was undertaken for the self-propelled
sprayers in this study (see Section 4.3), this activity was unfortunately beyond the resources
of this investigation.
80
5.3.7
‘In-Field’ WBV Emission Measurement – Summary
The objectives of this specific part of the investigation were:• To quantify each tractor’s ‘in-field’ WBV emission levels whilst performing a selected
range of identical agricultural operations, in known / controlled conditions;
• To investigate the similarity (if any) between WBV emission levels encountered during
these operations, and those generated during ISO 5008 ride vibration track testing
(Section 5.2).
These activities generated reliable data which could be used:• To compare with WBV emission / exposure data subsequently recorded upon similar
vehicles whilst working on farms (see Section 5.4);
• To enable broad assessment of the effectiveness of the generic suspension system designs
encompassed by the investigation, in terms of WBV emission reduction.
Figure 5.13 depicts information supporting many of the important messages which may be
derived:• Greater differences in WBV emission levels exist between the target operations than
between the different tractors (suspension systems) performing each task;
• Spraying and plough transport generate low WBV emission levels
Ploughing generates moderate WBV levels
Trailer transport generates moderate to high WBV levels
(Rough Ground) Cultivating generates high WBV levels;
• WBV emission levels generated during moderate / higher speed operations are highly
dependent upon surface conditions;
• WBV emission levels recorded upon the operator’s seat during this section of the
investigation (see Figure 5.22 and Appendices 2.5 & 2.6) suggest that operators of any of
the vehicles performing any of the operations considered will exceed the proposed PA(V)D
Exposure Action Value (EAV), if the WBV levels were to continue as measured (and the
vehicles be operated) for an 8-hour working period;
• Similarly, operator seat WBV emission levels suggest that cultivating and trailer transport
operations will cause drivers to exceed the proposed PA(V)D Exposure Limit
Value (ELV), if WBV levels were to continue as measured (and the vehicles be operated)
for an 8-hour working period. Ploughing may also cause the ELV to be exceeded, but only
if the work period extends to approximately 12–14 hours;
• During all true field operations (spraying, ploughing & cultivating) and plough transport,
the highest overall average r.m.s. acceleration (Aeq) levels (recorded on the cab floor & the
seat) are found in the transverse (Y) axis, although in certain instances the differences
between WBV levels in each axial direction is small;
• During trailer transport longitudinal (X) axis (floor & seat) Aeq levels are the largest;
probably a result of vertical force input to the tractor pickup hitch (from the trailer
drawbar) accentuating vehicle pitch;
• Use of the PA(V)D-recommended ISO 2631-1 ‘Effect of Vibration on Health’ evaluation
methodology (i.e. application of a 1.4 multiplying factor to the horizontal axes and
selection of the largest single weighted axis r.m.s. acceleration: see Section 3.1.2)
undoubtedly accentuates and arguably distorts the magnitude of X and Y-axis WBV levels
reported in this investigation;
• Except during cultivating and trailer transport operations, little difference was found
between cab floor WBV emission levels of the test tractors (suspension system designs)
(see Figure 5.13) when WBV levels were evaluated by the ISO 2631-1:1997 “Effect of
Vibration on Health” method. Arguably the point vibration total value (vector sum or rootsum-of-squares: see Appendix 2.5), which represents the acceleration levels present in all
axial directions as opposed to solely the axis of the largest magnitude, is a better indicator
of the differences in vehicle ride comfort perceived by the operator during fieldwork;
81
•
•
•
Cab floor vector sum acceleration levels return the same relative ranking and distribution of
individual field operations, clarifying the relative differences between suspension system
performance (WBV emission levels) as being small during spraying and plough transport;
moderate during ploughing and trailer transport; and large during cultivating: apparently
the more extreme the application, the greater the difference between the suspension
systems;
Whilst no vehicle / suspension system design appeared to be particularly superior for all the
field operations investigated, and the differences between vehicles during certain
operations were small, cab floor and operator seat vector sum (RSS) WBV levels suggested
the fully suspended (front & rear axle) tractor and the suspended front axle & cab tractor
offer marginally superior levels of ride comfort in the majority of instances. Evaluation of
cab floor WBV levels by the largest single axis method displayed a similar trend between
vehicle types, but this was not so apparent amongst operator seat WBV values derived by
this technique: and the latter are, of course, the WBV emission levels from which operator
daily exposure would be derived;
Comparison of ISO test track WBV emission levels with those recorded during SRI ‘infield’ operations is fraught with difficulty, mainly due to differences in vehicle mass,
weight distributions, tyre inflation pressures and external force systems between the test
conditions. The ISO ride vibration tracks were originally developed as a research tool and
a method of assessing tractor suspension seat performance. The (current ISO 5008)
measurement of WBV emission levels upon solo tractors traversing these tracks bears little
relation to practical agricultural operational conditions, to the extent that any significant
correlation between ISO track and ‘in-field’ results would be a cause for concern.
Nonetheless, defined, repeatable WBV test conditions and methodologies are required for
agricultural tractors and other ‘off-road’ vehicles. There is scope for further analysis of the
results obtained from this investigation and development / refinement of test
methodologies. This is discussed further in Section 7.2.
1.60
Y-axis
X-axis
2
Weighted r.m.s. acceleration (m/s )
1.40
1.20
1.00
Y-axis
0.80
Y-axis
Y-axis
0.60
0.40
Spraying
Plough in transport
Ploughing
Trailer transport
Cultivating
Tasks
Figure 5.22
Range of operator seat r.m.s. acceleration levels recorded during SRI
agricultural tractor ‘in-field’ investigation (largest axis denoted upon each bar)
82
5.4
‘ON-FARM’ WBV EXPOSURE MEASUREMENT
5.4.1
Introduction
Following a similar methodology to that employed for the self-propelled sprayers (Section 4.4),
a programme of ‘on-farm’ WBV exposure level measurement was performed upon a range of
agricultural tractors across East Anglia. The objectives of this part of the investigation were
to:• Verify the practical applicability of the detailed agricultural tractor WBV emission data
derived from the SRI ‘in-field’ and (possibly) ISO Test Track measurement
programmes;
• Explore the variation in (and magnitudes of) WBV emission and resultant exposure
levels encountered upon ‘on-farm’ agricultural tractors during ‘typical’ half-day
(4 hour) work periods;
• Enable limited investigation of typical usage patterns of ‘on-farm’ examples of selected
test tractor designs included in the overall investigation.
5.4.2
Procedure
Given that the original objective of the investigation was “to determine WBV emission and
exposure levels associated with representative ‘state-of-the-art’ agricultural vehicles
performing agricultural operations….”, the ‘on-farm’ WBV study was intentionally restricted
to the two test tractor designs considered to embody the greatest proportion of WBV-reducing
features. These were the:•
•
Suspended front axle and cab tractor (New Holland TM 165);
Fully suspended (front & rear axle) tractor (JCB Fastrac 3185)
Whilst the JCB Fastrac can be regarded as somewhat unique in the marketplace, it is
nonetheless well established, largely as a result of its suspension, handling and high-speed
travel capabilities. A ride vibration study would therefore not be complete without its
inclusion. Equally, suspended front axle and cab tractors now represent the ‘state-of-the-art’ in
‘conventional’ tractor development (see Section 2.1), examples being offered in the (100 –
130 kW) power range by all major manufacturers. Consequently, its inclusion in this part of
the study was equally important.
To ensure comparability with the SRI ‘in-field’ WBV emission measurement programme, an
identical range of field tasks (field/road trailer transport, ploughing, cultivating,
spraying/fertiliser application) was targeted, albeit in ‘on-farm’ situations. During the period
December 2001 – March 2002 attempts were made to record WBV acceleration time histories
(thereby permitting derivation of WBV emission and exposure levels) upon 3 separate
examples of each tractor type performing each defined field task, thereby providing
3 replications of each tractor / field task combination. Theoretically this required identification
of, and subsequent logistical coordination with, 24 different tractors / owners / operators across
East Anglia: 22 tractor / task combinations were successfully completed within the seasonal
constraints present (see Table 5.5 & Appendix 2.8). Suitable ‘on-farm’ test vehicles (i.e.
correct physical specification and less than 2 years old) were identified with manufacturer /
dealer assistance: vehicle owners were then approached to determine the typical operations
performed by the vehicles. Given comparability with the target field tasks and preparedness to
participate in the study, ‘on-farm’ WBV measurements were made during a nominal ‘half-day’
(4-hour) period, as the tractor performed the target task in conjunction with the ‘on-farm’
implement typically used for that purpose.
83
Acceleration time histories were recorded simultaneously upon the operator’s seat and the cab
floor of each tractor, by use of the vehicle-mounted instrumentation described in Section 3.2,
but in this application individual Larson Davis Human Vibration meters (type HVM100) were
also used to reduce the acceleration data in real-time, record peak values and derive vibration
dose values (VDV) for each 15-minute section of the total operating period. As before, vehicle
forward speed was recorded (derived from a Doppler radar sensor mounted upon each vehicle),
to enable quantification of this important operational parameter and identification of any
stationary / inactive periods during the measurement period.
5.4.3
Results
As discussed previously (Section 3.1), the European Union Physical Agents (Vibration)
Directive (PA(V)D) defines the WBV Exposure Action Value (EAV) and Exposure Limit
Value (ELV) in two alternative ways. Either as an 8-hour energy-equivalent frequency
weighted r.m.s. acceleration value (A(8)), or as a vibration dose value (VDV). Member States
are given the option of implementing the Directive using either method, using the values stated
below (see Table 5.4). Specific details are discussed in Section 3.1, but an important difference
between the methods is as follows. The root-mean-square (r.m.s.) or A(8) method produces a
value which is an average vibration level adjusted to represent an 8 hour working day, whereas
the vibration dose value represents cumulative exposure to vibration over the working day.
The practical significance of this is clearly depicted by Figure 5.29. If, over a given working
period, frequency-weighted r.m.s. acceleration levels recorded upon the operator’s seat are
relatively consistent, the resultant equivalent continuous acceleration (Aeq) value (only A(8) if
exposure period = 8 hours) changes little, having once reached an average ‘plateau’ value.
However, in the same circumstances, the VDV increases throughout the work period in a
cumulative manner. Additionally, the A(8) method represents steady levels of vibration with
reasonable accuracy but gives poor representation of shocks and jolts, whereas the VDV
method performs well in both instances (Griffin, 1998; Coles, 2002). These issues, and those
of sampling duration, are discussed in Appendix 4.
Throughout this investigation we have primarily utilised the A(8) method but, during ‘on-farm’
exposure measurement, vibration dose values have also been derived (see Figures 5.29 – 5.32
inclusive and Appendix 2.8). At the time of writing the HSE is undertaking a public
consultation exercise regarding implementation of the PA(V)D in the UK. Whilst it is highly
likely that the ELV will be specified by the A(8) technique, debate is currently ongoing as to
whether the EAV will be implemented in VDV or A(8) terms: the implications of this stance
are discussed in Sections 3.1 & 7.4.
An important aspect of results interpretation concerns how estimates for a whole day’s
vibration exposure can be made from values measured over a shorter period (see also
Appendix 4). Nominal half-day (approx. 4-hour) measurement periods were used ‘on-farm’ to
ensure the data acquired were characteristic of the operation. If using the r.m.s. A(8) approach,
the resultant overall average frequency-weighted r.m.s. acceleration (Aeq) value, measured for
the shorter (~4-hour) period, can be considered to extend throughout the entire day’s use of the
machine. The Aeq value becomes equivalent to the daily occupational vibration exposure
(A(8)) value for that operation, if the vehicle in question were to be operated for 8 hours.
Consequently the Aeq values generated by this investigation may be compared directly with the
A(8) EAV and ELV values stipulated by the PA(V)D whenever the working day length
approximates to 8 hours. For shorter or longer working days the respective A(8) value for the
daily exposure period in question may be calculated from the Aeq value, prior to comparison
with the EAV or ELV (see Section 3.1.2, Equation 3). A similar approach is necessary for the
VDV; its cumulative nature requires a value for a shorter period be re-calculated to estimate the
VDV after the full day’s exposure. This is performed by assuming subsequent WBV emission
84
levels are similar to those recorded during the (~4 hour) measurement period (see Appendix 4).
Examples of estimated 8-hour VDV’s appear in Tables 5.5 & 5.6, Figures 5.29 – 5.32 and
Appendix 2.8.
Table 5.4 WBV exposure values specified by the EU PA(V)D
8-hour energy-equivalent
Vibration Dose Value
r.m.s. acceleration – A(8)
(m/s1.75)
(m/s2)
Exposure Action Value (EAV)
0.5
9.1
Exposure Limit Value (ELV)
1.15
21
1.6
Weighted r.m.s. acceleration (m/s 2)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Tractor
Figure 5.23 Range of average ‘energy-equivalent’ r.m.s. seat acceleration (Aeq)
values recorded during ‘on-farm’ WBV measurement programme
The range of energy-equivalent WBV (Aeq) levels (largest single axis only) recorded upon the
seats of ‘on-farm’ agricultural tractor-implement combinations is depicted in Figure 5.23,
highlighting the spread of overall average WBV magnitudes (0.36 – 1.39 m/s2) present within
typical agricultural operations. It would appear that only a minority of the applications would
exceed the PA(V)D-prescribed A(8) exposure limit value (ELV) if operated for 8 hours per day
(see Figures 5.24, 5.25 & 5.35). Seat WBV data arising from the ‘on-farm’ tractor
investigation are summarised in Table 5.5 and Figure 5.24 (suspended front axle & cab tractor)
and Table 5.6 and Figure 5.25 (fully suspended (front & rear axle) tractor). Corresponding cab
floor results appear in Appendix 2.7, and are presented graphically for comparison with
operator seat WBV levels in Figures 5.26 & 5.27 (largest single axis only). Generally the
individual ‘on-farm’ operations reflect similar relative WBV magnitudes to those obtained from
SRI ‘in-field’ measurements (see Figure 5.28), especially in the case of the fully suspended
(front & rear axle) tractor.
85
1.6
Weighted r.m.s. acceleration (m/s2)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Spraying
Ploughing
Trailer Transport
Cultivating
Tasks
X-axis
Figure 5.24
Y-axis
Z-axis
EAV (A(8)
ELV (A(8)
Range of ‘energy-equivalent’ r.m.s. (Aeq) seat acceleration levels
recorded upon ‘on-farm’ suspended front axle and cab tractors: (displayed
by measurement axis & task performed)
1.6
Weighted r.m.s. acceleration (m/s2)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Spraying
Ploughing
Trailer Transport
Cultivating
Tasks
X-axis
Figure 5.25
Y-axis
Z-axis
EAV (A(8)
ELV (A(8)
Range of ‘energy-equivalent’ r.m.s. (Aeq) seat acceleration levels
recorded upon ‘on-farm’ fully suspended (front & rear axle) tractors:
(displayed by measurement axis & task performed)
86
Seat acceleration levels were in all instances higher than those recorded upon the cab floor
(see Figures 5.26 & 5.27). In largest single-axis magnitude terms, highest overall average
(Aeq) levels were, once more, primarily encountered in the transverse (Y) axis during most
field operations, with the exception of trailer transport when the longitudinal (X) axis levels
took precedence. However, as previously discussed, whilst the Directive requires WBV
exposure levels to be assessed separately in each axial direction, and the measurement axis
with the greatest (overall average) magnitude be identified, action is required to reduce WBV
exposure in all axial directions where the EAV is exceeded (see Section 3.1.3). In practical
terms whilst, for a given vehicle / application, the longitudinal (X) or transverse (Y)
measurement axes may exhibit the highest axis-weighted overall-average acceleration levels,
marginally lower Aeq levels in the remaining axial directions may still require vibrationreducing actions on the part of the employer, if above the EAV, especially if significant peak
acceleration events (shocks and jolts) are present (see Figures 5.30 – 5.32).
Following this methodology it can be seen from the limited ‘on-farm’ survey performed
during this investigation (see Figures 5.24 & 5.25 and Tables 5.5 & 5.6)) that the EAV would
be reached or exceeded after 8 hours operation, due to WBV levels present in the following
axes upon the following machine / task combinations:Suspended Front Axle & Cab Tractor:o
Spraying / fertiliser spreading:-
X & Y-axes
o
Ploughing:-
X & Y-axes
o
Trailer transport:-
X & Y-axes
o
Cultivating:-
Y-axis
Fully Suspended (front & rear axle) Tractor:o
Spraying / fertiliser spreading:-
Y-axis
o
Ploughing:-
X & Y-axes
o
Trailer transport:-
X & Y-axes
o
Cultivating:-
X, Y & Z-axes
Seat r.m.s. acceleration levels were of sufficient magnitude in certain examples of the fully
suspended (front & rear axle) tractor to approach or exceed the ELV after 8 hours operation
upon trailer transport and cultivating operations (see Figure 5.25 & Table 5.6): a potential
situation predicted for all the test vehicles following the SRI ‘in-field’ programme. However,
these same operations resulted in only moderate / low WBV levels upon the suspended front
axle & cab tractor (see Figure 5.24 & Table 5.5), spraying and ploughing operations
frequently generating higher WBV levels upon examples of this vehicle. This evidence raises
a number of important issues. ISO test track and SRI ‘in-field’ investigations with
representative examples of these vehicles found that, in the majority of agricultural field
operations, these machines generated comparable WBV emission levels upon both the cab
floor and operator’s seat: the fully suspended tractor delivering reduced WBV levels during
(road / farm track) trailer transport operations. Why therefore were these findings not
reflected in the ‘on-farm’ data?
87
Table 5.5 ‘On-farm’ WBV seat data: suspended front axle & cab tractor
Task
Duration
(hr)
Average r.m.s. acceleration (m/s 2 )
X
Y
Z
Major axis
Aeq
(m/s 2 )
Est. 8 hr
VDV
(m/s 1.75 )
Time to
Time to
EAV (hr) EAV (hr)
(VDV)
(A(8))
Time to
ELV (hr)
(A(8))
Ploughing (1)
4.25
0.35
0.62
0.32
Y
0.62
11.7
5.16
2.96
>24
Ploughing (2)
3.25
0.58
0.86
0.47
Y
0.86
15.3
2.72
0.99
14.39
Ploughing (3)
4.25
0.39
0.49
0.26
Y
0.49
10.2
8.29
5.13
>24
Cultivating (1)
5.25
0.35
0.53
0.27
Y
0.53
13.3
7.04
1.74
>24
Cultivating (2)
4.75
0.45
0.67
0.31
Y
0.67
16.9
4.51
0.68
23.84
Spraying (1)
4.50
0.50
0.66
0.40
Y
0.66
16.0
4.63
0.84
>24
Spraying (2)
4.25
0.41
0.49
0.29
Y
0.49
12.1
8.39
2.55
>24
Spraying (3)
4.50
0.48
0.78
0.42
Y
0.78
20.7
3.27
0.30
17.32
Trailer Work (1)
3.75
0.55
0.50
0.34
X
0.55
12.0
6.61
2.63
>24
Trailer Work (2)
4.75
0.52
0.58
0.37
Y
0.58
14.3
6.00
1.31
>24
Trailer Work (3)
4.00
0.47
0.38
0.29
X
0.47
11.7
9.10
2.94
>24
Table 5.6 ‘On-farm’ WBV seat data: fully suspended (front & rear axle) tractor
Aeq
(m/s 2 )
Est. 8 hr
VDV
(m/s 1.75 )
Y
0.93
19.9
2.31
0.35
12.24
0.30
Y
0.81
21.9
3.06
0.24
16.18
0.39
Y
0.76
16.4
3.47
0.76
18.37
Average r.m.s. acceleration (m/s 2 )
Task
Duration
(hr)
X
Y
Z
Major axis
Ploughing (1)
4.00
0.54
0.93
0.33
Ploughing (2)
5.75
0.34
0.81
Ploughing (3)
4.50
0.59
0.76
Time to
Time to
EAV (hr) EAV (hr)
(A(8))
(VDV)
Time to
ELV (hr)
(A(8))
Cultivating (1)
3.75
0.54
0.85
0.46
Y
0.85
21.7
2.79
0.25
14.75
Cultivating (2)
4.50
0.86
1.36
0.65
Y
1.36
29.4
1.09
0.07
5.76
5.51
Cultivating (3)
4.00
0.89
1.39
0.63
Y
1.39
26.2
1.04
0.12
Spraying (1)
4.75
0.48
0.58
0.41
Y
0.58
14.6
5.86
1.20
>24
Spraying (2)
6.00
0.27
0.36
0.26
Y
0.36
8.5
15.32
10.72
>24
Trailer Work (1)
5.50
0.71
0.65
0.38
X
0.71
18.2
3.93
0.50
20.79
Trailer Work (2)
5.00
1.12
0.85
0.48
X
1.12
28.9
1.60
0.08
8.49
Trailer Work (3)
4.50
0.54
0.64
0.33
Y
0.64
25.3
4.94
0.13
>24
Vehicle WBV emission levels are dependent not only upon vehicle design and the presence of
vibration reduction features (e.g. suspended seats, cabs & axles), but also upon operating
surface, forward speed and personal driving technique / direction. It was noted during the ‘onfarm’ investigation that certain of the suspended front axle & cab tractor operating conditions
were not as severe as those being experienced by the fully suspended (front & rear axle)
machines. This was particularly noticeable during cultivating and trailer transport operations.
The ‘intensity’ of use of the fully suspended machines, in terms of demanded cycle times and
haul distances, also appeared to be greater. It is appropriate to highlight that the latter are
solely observations of a relatively small sample of tractors / operations, albeit made by
experienced agricultural field test personnel. Nonetheless it is probably inappropriate to
conclude that a suspended front axle & cab tractor will frequently deliver lower WBV levels
than a fully suspended (front & rear axle) machine.
88
1.6
2
Weighted r.m.s. acceleration (m/s )
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Spraying
(Y-axis)
Ploughing
(Y-axis)
Trailer
transport (X-axis)
Cultivating
(Y-axis)
Tasks
Seat
Figure 5.26
Floor
EAV (A(8))
ELV (A(8))
Range of ‘energy-equivalent’ r.m.s. (Aeq) seat & floor acceleration
values recorded upon ‘on-farm’ suspended front axle and cab tractors
(largest axis denoted beside ‘task’)
1.6
2
Weighted r.m.s. acceleration (m/s )
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Spraying
(Y-axis)
Ploughing
(Y-axis)
Trailer
transport (X-axis)
Cultivating
(Y-axis)
Tasks
Seat
Figure 5.27
Floor
EAV (A(8))
ELV (A(8))
Range of ‘energy-equivalent’ r.m.s. (Aeq) seat & floor acceleration
values recorded upon ‘on-farm’ fully suspended (front & rear axle)
tractors (largest axis denoted beside ‘task’)
89
Average rms acceleration values - JCB Floor
1
1
0.9
0.9
Weighted r.m.s. Acceleration (m/s 2)
Weighted r.m.s. Acceleration (m/s 2)
Average rms acceleration values - TM 165 Floor
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Ploughing (Y)
Cultivating (Y)
SRI (field)
Farm 1
Spraying (Y)
Farm 2
Trailer transport (X)
Ploughing (Y)
Farm 3
Average rms acceleration values - TM 165 Seat
Farm 1
Spraying (Y)
Farm 2
Trailer transport (X)
Farm 3
Average rms acceleration values - JCB Seat
1.6
Weighted r.m.s. Acceleration (m/s 2)
1.6
Weighted r.m.s. Acceleration (m/s 2)
Cultivating (Y)
SRI (field)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Ploughing (Y)
Cultivating (Y)
SRI (field)
Figure 5.28
Farm 1
Spraying (Y)
Farm 2
Trailer transport (X)
Ploughing (Y)
Farm 3
Cultivating (Y)
SRI (field)
Farm 1
Spraying (Y)
Farm 2
Trailer transport (X)
Farm 3
Comparison between SRI ‘in-field’ and ‘on-farm’ WBV levels, by vehicle and operation (largest axis denoted beside ‘operation’)
90
A more precise comparison between the WBV emission levels generated by the suspended
front axle & cab tractor and the fully suspended (front & rear axle) machine is provided by
the SRI ‘in-field’ test programme (see Figure 5.28), but no doubt performance of a greater
number of ‘on-farm’ test replications in the future would enable greater statistical confidence
to placed in data from this potentially variable (‘on-farm’) source.
Figures 5.29 – 5.32 depict the parameters arising from the ‘on-farm’ WBV measurement
programme in a generic presentation format. Figures 5.29 & 5.30 depict seat WBV data
arising from a suspended front axle & cab tractor performing ploughing and fertiliser
spreading (spraying) operations, respectively. Figures 5.31 & 5.32 depict comparable data
arising from a fully suspended (front & rear axle) tractor undertaking trailer transport and
cultivating. Tabular data specifies the measurement location (seat or floor), tractor model,
geographical location, date, operation type and measurement duration. The corresponding
graph depicts a time history of frequency-weighted 1-minute average r.m.s. acceleration
values, as recorded in the orthogonal axis which consistently generated the largest overall
average values throughout the operating period. This is supplemented by traces depicting 15minute vibration dose values (VDV) and development of equivalent continuous frequencyweighted r.m.s. acceleration (Aeq) which, as previously discussed, may be related to the A(8)
value. Tabular WBV data are presented in terms of overall average frequency-weighted
r.m.s. acceleration (Aeq) and peak values for each measurement axis, together with
corresponding root-sum-of-squares (RSS) values. Individual axis and RSS VDV values for
the measurement duration, and estimated (VDV) values for an 8-hour period, are also
included. Finally, estimated operating periods until the EAV and ELV are reached, are shown
both in relation to the A(8) and VDV calculation methods. Comments relating specifically to
each of these ‘on-farm’ WBV measurement examples appear at the base of each Figure (5.29
– 5.32 inclusive). A summary of cab floor and seat WBV data from the entire ‘on-farm’
programme is presented in Appendix 2.8.
The traces shown within Figures 5.33 & 5.34 depict the development of equivalent
continuous r.m.s. (Aeq) seat acceleration (in the largest single (major) axis) for all ‘on-farm’
tractor type / operation WBV exposure measurement replicates, thereby indicating the degree
of variation present within each ‘target’ task. The important parameter is the Aeq value at the
end of each measurement period for a particular operation: these values are also presented in
Tables 5.5 & 5.6 and their range depicted in Figures 5.24 & 5.25 (for all measurement axes).
Little WBV exposure variation is present within certain operations (suspended front axle &
cab tractor – trailer transport and cultivating; fully suspended tractor – ploughing and
spraying). Greater variation is present within the other tractor / task combinations (suspended
front axle & cab tractor – ploughing and spraying; fully suspended tractor - trailer transport
and cultivating). This absence of pattern suggests that WBV exposure levels are less
operation-dependent than the findings of the SRI ‘in-field’ programme suggest. An
alternative explanation is that insufficient ‘on-farm’ tractor / task measurement replicates
were performed to enable the ‘operation’ dependency of WBV exposure to be determined.
This also restricts generation of a robust, generic WBV emissions database for agricultural
tractor operations, which is undoubtedly a requirement to assist implementation of the
Directive within UK agriculture.
91
20.0
2
16.0
1.5
12.0
1
8.0
0.5
4.0
0
0:00
VDV (m/s1.75)
Weighted r.m.s. Acceleration (m/s2)
2.5
0.0
0:30
1:00
1:30
2:00
2:30
3:00
Elapsed Time (hrs)
Transverse (Y)
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: AO51HMY
Ploughing
Task:
Edwards, Farmers/Contractors, Mattishall
Place:
Total VDV (m/s 1.75 )
Time
X
8.6
03:15
8-hr est tot
10.8
Y
12.3
15.3
Z
6.7
8.4
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.99
>24
r.m.s./A(8)
2.72
14.39
Figure 5.29
Sum
16.4
20.5
Aeq
VDV
Day
15
Month
Jan
Year
2
Start time:
13:47
Average r.m.s. (Aeq) (m/s 2 )
X
Y
0.58
0.86
Z
0.47
Sum
1.13
Maximum peak value (m/s 2 )
X
Y
5.08
5.56
Z
5.06
Sum
6.35
Typical time history of weighted 1-minute r.m.s. accelerations (Y-axis,
TM 165 seat – ploughing) plus development of equivalent continuous
r.m.s. acceleration (Aeq) & 15-minute record of Vibration Dose Value
(VDV) and table of seat WBV parameters
Comments
•
•
•
•
•
•
A relatively consistent vibration record (Y-axis largest) with few peaks in any axis; however
the overall acceleration level is moderate to high;
The abovementioned characteristics result in a relatively constant, high Y-axis Aeq value,
which reflects the overall WBV history well;
The VDV ramps steadily throughout the measurement period, reflecting its cumulative nature.
The Aeq is the level of equivalent continuous acceleration experienced since the beginning of
the measurement period: it therefore remains relatively constant throughout, having once
attained a representative value in the first 15 minutes of operation (see Appendix 4);
The VDV Exposure Action Value (EAV) is exceeded in approx. 1-hour operation;
The A(8) Exposure Action Value (EAV) is exceeded in approx. 2¾ hours operation;
The (A(8)) Exposure Limit Value (ELV) is exceeded in approx. 14½ hours operation.
92
16.0
1.5
12.0
1.0
8.0
0.5
4.0
0.0
0:00
)
2.0
1.75
20.0
VDV (m/s
Weighted r.m.s. Acceleration (m/s2)
2.5
0.0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (Y)
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: W271DNO
Fertiliser spreading
Task:
R Melbourne, Contractor, Stevenage
Place:
Total VDV (m/s 1.75 )
Time
X
10.1
04:30
8-hr est tot
11.7
Y
13.8
16.0
Z
9.8
11.3
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.84
23.93
r.m.s./A(8)
4.63
>24
Figure 5.30
Sum
19.3
22.3
Aeq
VDV
Day
5
Month
Mar
Year
2
Start time:
08:45
Average r.m.s. (Aeq) (m/s 2 )
X
Y
0.50
0.66
Z
0.40
Sum
0.92
Maximum peak value (m/s 2 )
X
Y
7.95
10.15
Z
13.10
Sum
13.30
Typical time history of weighted 1-minute r.m.s. accelerations (Y-axis,
TM 165 seat – fertiliser spreading) plus development of equivalent
continuous r.m.s. acceleration (Aeq) & 15-minute record of Vibration
Dose Value (VDV) and table of seat WBV parameters
Comments
•
•
•
•
•
•
A variable vibration record (Y-axis largest), reflecting the cyclical (refilling, transport,
field travel) nature of the operation;
Moderate peaks, troughs and periods of inactivity (refilling) are present: the highest peaks
occur in the Y and Z-axes;
The equivalent continuous acceleration (Aeq) level is moderate: this calculation method
smoothes the time history to a degree and does not respond to the peak events as
significantly as the VDV method (see trace);
The VDV Exposure Action Value (EAV) is exceeded in less than 1-hour operation;
The A(8) Exposure Action Value (EAV) is exceeded in approx. 4½ hours operation;
The (A(8)) Exposure Limit Value (ELV) will not be exceeded in a 24-hour period
(Methods of calculating estimated exposure values are discussed in Appendix 4);
93
16.0
1.5
12.0
1.0
8.0
0.5
4.0
0.0
0:00
)
2.0
1.75
20.0
VDV (m/s
Weighted r.m.s. Acceleration (m/s2)
2.5
0.0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
Elapsed Time (hrs)
Transverse (X)
Aeq
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac
Reg No: W193BAV
Trailer Work (Sugar Beet Haulage)
Task:
David Russell Contractor (Downham Market)
Place:
Total VDV (m/s 1.75 )
Time
X
16.3
05:30
8-hr est tot
17.9
Y
16.6
18.2
Z
9.6
10.6
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.50
14.06
r.m.s./A(8)
3.93
20.79
Figure 5.31
Sum
24.4
26.8
VDV
Day
17
Month
Jan
Year
2
Start time:
11:47
Average r.m.s. (Aeq) (m/s 2 )
X
Y
0.71
0.65
Z
0.38
Sum
1.03
Maximum peak value (m/s 2 )
X
Y
11.09
9.84
Z
18.10
Sum
18.10
Typical time history of weighted 1-minute r.m.s. accelerations (X-axis,
JCB 3185 seat – trailer transport) plus development of equivalent
continuous r.m.s. acceleration (Aeq) & 15-minute record of Vibration
Dose Value (VDV) and table of seat WBV parameters
Comments
•
•
•
•
•
•
•
A variable vibration time history (X-axis largest), reflecting initial road travel to a new site,
followed by an inactive period and thereafter harvester to clamp field transport;
Whilst the overall average r.m.s. (Aeq) values identify the X-axis as largest, greatest peaks
actually occur in the Z-axis;
The Aeq reduces significantly during the idle period, but increases substantially during
subsequent fieldwork: the overall value would be higher for an entire day’s fieldwork;
The VDV Exposure Action Value (EAV) is exceeded in approx. 30 minutes operation;
The A(8) Exposure Action Value (EAV) is exceeded in approx. 4 hours operation
The (A(8)) Exposure Limit Value (ELV) is likely to be exceeded in ~20¾ hours operation;
Whilst the ELV appears unlikely to be reached during the daily performance of this task,
perhaps this example is not a truly representative working day ? Nonetheless, inter-site
travel and harvester maintenance breaks must regularly occur in practice.
94
16.0
1.5
12.0
1.0
8.0
0.5
4.0
0.0
0:00
)
2.0
1.75
20.0
VDV (m/s
Weighted r.m.s. Acceleration (m/s2)
2.5
0.0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y)
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3185
Reg No: W193BAV
Cultivating
Task:
Russell Contractors, Downham Market
Place:
Total VDV (m/s 1.75 )
Time
X
10.6
03:45
8-hr est tot
12.8
Y
18.0
21.7
Z
9.5
11.5
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.25
7.01
r.m.s./A(8)
2.79
14.75
Figure 5.32
Sum
22.4
27.1
Aeq
VDV
Day
26
Month
Mar
Year
2
Start time:
09:19
Average r.m.s. (Aeq) (m/s 2 )
X
Y
0.54
0.85
Z
0.46
Sum
1.11
Maximum peak value (m/s 2 )
X
Y
7.34
11.21
Z
13.70
Sum
13.60
Typical time history of weighted 1-minute r.m.s. accelerations (Y-axis,
JCB 3185 seat – cultivating) plus development of equivalent continuous
r.m.s. acceleration (Aeq) & 15 minute record of Vibration Dose Value
(VDV) and table of seat WBV parameters
Comments
•
•
•
•
•
•
•
An extremely variable vibration record (Y-axis largest) reflecting fieldwork in conditions
of different severity / location, plus a period of inactivity;
Moderate to high overall average r.m.s. (Aeq) and 8-hour estimated VDV values;
Substantial (1-minute average) peaks occur early on, causing a rapid increase in the VDV:
the Aeq does not respond to these events as significantly and reduces during subsequent
periods of lower r.m.s. acceleration levels;
The VDV Exposure Action Value (EAV) is exceeded in approx. 15 minutes;
The A(8) Exposure Action Value (EAV) is exceeded in approx. 2¾ hours operation;
The (A(8)) Exposure Limit Value (ELV) is likely to be exceeded in 14¾ hours operation;
Whilst it appears the ELV would only be reached during a long working day, this point
could in fact be reached much sooner if the initial high acceleration levels were
maintained through a greater proportion of the working day (see Appendix 4).
95
Equivalent Continuous r.m.s. Acceleration (Aeq) (TM 165 seat, Y-axis - Cultivation)
1.0
0.9
0.9
2
Weighted r.m.s. Acceleration (m/s )
1.0
2
Weighted r.m.s. Acceleration (m/s )
Equivalent Continuous r.m.s. Acceleration (Aeq) (TM 165 seat, X-axis - Trailer
Transport)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0:00
5:00
0:30
1:00
1:30
2:00
Elapsed Time (hrs)
TR1 - X
TR2 - X
TR3 - X
Equivalent Continuous r.m.s. Acceleration (Aeq) (TM 165 seat, Y-axis - Ploughing)
3:00
3:30
4:00
4:30
5:00
5:30
Equivalent Continuous r.m.s. Acceleration (Aeq) (TM 165 seat, Y-axis - Spraying)
1.0
0.9
0.9
2
Weighted r.m.s. Acceleration (m/s )
1.0
2
Weighted r.m.s. Acceleration (m/s )
2:30
Elapsed Time (hrs)
CT1 - Y
CT2 - Y
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
PL1 - Y
PL2 - Y
PL3 - Y
Figure 5.33
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
DR1 - Y
DR2 - Y
DR3 - Y
Equivalent continuous r.m.s. (Aeq) seat acceleration traces for suspended front axle & cab tractor (TM 165) ‘on-farm’
operations
96
Equivalent Continuous r.m.s. Acceleration (Aeq) (JCB 3185 seat, Y-axis - Cultivation)
1.6
1.6
1.4
1.4
Weighted r.m.s. Acceleration (m/s2)
2
Weighted r.m.s. Acceleration (m/s )
Equivalent Continuous r.m.s. Acceleration (Aeq) (JCB 3185 seat, X-axis - Trailer
Transport)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0:00
6:00
0:30
1:00
Elapsed Time (hrs)
TR1 - X
TR2 - X
TR3 - X
1.4
1.4
2
Weighted r.m.s. Acceleration (m/s )
2
Weighted r.m.s. Acceleration (m/s )
1.6
1.2
1.0
0.8
0.6
0.4
0.2
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
Elapsed Time (hrs)
PL1 - Y
PL2 - Y
PL3 - Y
Figure 5.34
2:30
3:00
3:30
4:00
4:30
Equivalent Continuous r.m.s. Acceleration (Aeq) (JCB 3185 seat, Y-axis - Spraying)
1.6
0:30
2:00
Elapsed Time (hrs)
CT1 - Y
CT2 - Y
CT3 - Y
Equivalent Continuous r.m.s. Acceleration (Aeq) (JCB 3185 seat, Y-axis - Ploughing)
0.0
0:00
1:30
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
Elapsed Time (hrs)
DR1 - Y
DR2 - Y
Equivalent continuous r.m.s. (Aeq) seat acceleration traces for fully suspended (front & rear axle) tractor (JCB Fastrac
3185) ‘on-farm’ operations
97
1.6
Daily vibration exposure (A(8)) (m/s 2)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Tractor
A(8)
Figure 5.35
EAV (A(8))
ELV (A(8))
Daily WBV exposure (A(8)) likely to be received by operators of
surveyed ‘on-farm’ tractors, if operated for 8 hours per day
1.8
Daily vibration exposure (A(8)) (m/s 2)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Tractor
A(8) value for 12 hr shift
Figure 5.36
EAV (A(8))
ELV (A(8))
Daily WBV exposure (A(8)) likely to be received by operators of
surveyed ‘on-farm’ tractors, if operated for 12 hours per day
98
22
As discussed earlier, whilst few (~ 9%) of the ‘on-farm’ tractor - operations surveyed would
exceed the PA(V)D A(8) exposure limit value (ELV) if worked for 8 hours per day, virtually
all the machine examples (~ 95%) would exceed the exposure action value (EAV) during the
same working period (if specified in VDV terms), but fewer (~ 82%) would reach the EAV if
it were to be specified by the A(8) method (see Tables 5.5 & 5.6 and Figures 5.35 & 5.37).
However, as discussed in Section 3.1.3, if the vehicle operating period extends beyond
8 hours per day, the weighted r.m.s. acceleration and VDV magnitudes associated with the
ELV and EAV values progressively reduce (see Figure 3.1). Alternatively the A(8) value for
a non-8-hour working day must be calculated from the prevailing Aeq value (see
Section 3.1.2, Equation 3 (reproduced below)) to reflect the (shorter or longer) exposure period.
The effect of a longer working day upon operation of the tractor – operations surveyed can be
seen by comparing Figures 5.35 & 5.36, which depict the daily WBV exposures likely to be
received by the operators if the vehicles were worked for an 8 or 12-hour period. It will be
noted that the longer operating period effectively increases the A(8) value of each vehicle,
increasing the likelihood of exceeding the EAV and ELV, but the nature of this increase (or
decrease) with exposure period (time) is not linear (see Figure 3.1 and equation below).
A(8)
=
Aeq
t
8
where:t
= daily exposure period (hours)
Aeq = the energy-equivalent continuous r.m.s. acceleration which is
representative of the exposure period (m/s2)
To this end Tables 5.5 & 5.6 and Figures 5.37 & 5.38 present the estimated operating periods
required for each surveyed tractor / task combination to reach the EAV (VDV & A(8)) and
the ELV (A(8)) respectively.
The likelihood of exceeding the EAV during a normal (8-hour) agricultural operating day is
therefore very high, necessitating employers implement WBV exposure reduction /
management actions discussed in Section 3.1.3. The ELV would, at first, not appear to be a
significant restriction to normal use of modern, state-of-the-art tractors during an 8-hour
working day, but such a working day is hardly normal practice in agriculture, especially
regarding operation of tractors of this size. If the working day were to increase, 14% of the
surveyed examples would exceed the ELV in 9 hours operation, 18% in 13 hours and 27% in
15 hours operation. Such operating periods may appear extreme, but as part of the ‘on-farm’
investigation, drivers recorded both their driving hours and the operation(s) performed by
their tractors during the (5-day) working week, which encompassed the WBV measurement
day. This effectively produced a survey of 110 tractor-days, of which 90 days (82%) were
operational: the results obtained are summarised in Table 5.7 and Figure 5.39. Whilst 57% of
tractor-days exceeded 8 hours operation per day, a significant proportion reached 12, 14 or
even 16 hours per day. Additionally, these operating hours would probably extend over a
6 day working week and the survey period (December – March) is not usually regarded as a
busy period in the farming year. Consequently, the requirements of the Directive may well
restrict UK agricultural tractor operating patterns, in terms of permissible daily operating
period (greater than 8 hours).
99
16
15
14
13
Operating Period (hours)
12
11
10
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Tractor
EAV (VDV)
Figure 5.37
EAV (A(8))
Operating period required of surveyed ‘on-farm’ tractors / tasks in order
to exceed the Exposure Action Value (EAV)
28
26
24
Operating Period (hours)
22
20
18
16
14
12
10
8
6
4
2
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Tractor
ELV (A(8))
Figure 5.38
Operating period required of surveyed ‘on-farm’ tractors / tasks in order
to exceed the A(8) Exposure Limit Value (ELV)
100
Table 5.7 ‘On-farm’ daily usage of suspended front axle & cab (TM 165) and fully
suspended (front & rear axle) (JCB 3185) tractors
Tractor
Number of
Number of
days surveyed operational days
JCB
TM
55
55
Number of
operational days
<= 8 hrs
22
17
45
45
Number of
operational days
> 8 hrs
23
28
Average operational
day length (hours)
9.5
8.3
25
Number of working days
20
15
10
5
0
4
6
8
10
12
14
16
Period of daily operation (hrs)
JCB 3185
Figure 5.39
TM 165
‘On-farm’ daily usage of suspended front axle & cab (TM 165) and fully
suspended (front & rear axle) (JCB 3185) tractors
Mitigating against these findings is the fact that this was a limited survey. Whilst the WBV
exposure measurement days were found to be representative of vehicle usage, the survey was
performed during only one seasonal period. Also of consequence is the likely daily working
pattern of the vehicle in question: rest breaks, machine maintenance and periods of general
inactivity can all contribute to a reduction in the Aeq WBV exposure value (see Figure 5.31).
This characteristic also has consequences for ‘in-field’ WBV exposure measurement. A
30 minute measurement period, as used during the SRI ‘in-field’ WBV programme, will
encompass normal variations present within an agricultural tractor field task. However, such a
period of operation will be ‘continuous’ and will not include rest or maintenance breaks. The
4-hour (half-day) measurement period, as utilised in the ‘on-farm’ WBV programme, will
almost certainly identify such breaks if they are a common / regular feature.
101
Average rms acceleration values - JCB Floor
1
Weighted r.m.s. Acceleration (m/s2)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Ploughing (Y)
Cultivating (Y)
SRI (field)
Figure 5.40
Spraying (Y)
Farm 1
Farm 2
Trailer transport (X)
Farm 3
Comparison between SRI ‘in-field’ and ‘as-recorded’ ‘on-farm’ WBV
levels
Average rms acceleration values - JCB Floor
Weighted r.m.s. Acceleration (m/ s 2)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Ploughing (Y)
Cultivating (Y)
SRI (field)
Figure 5.41
Farm 1
Spraying (Y)
Farm 2
Trailer transport (X)
Farm 3
Comparison between SRI ‘in-field’ and ‘on-farm’ ‘continuous-operation’
WBV levels
102
The potential effect of sampling duration is highlighted in Figures 5.40 & 5.41 and discussed
further in Appendix 4. Figure 5.40 indicates the degree of similarity between WBV levels
recorded SRI ‘in-field’ and comparable ‘on-farm’ measurements. Figure 5.41 depicts the
same SRI ‘in-field’ values, but the ‘on-farm’ WBV data has been processed to reflect only
periods of continuous operation. Consequently, whilst certain of the WBV levels recorded
during the SRI ‘in-field’ work may initially appear somewhat excessive and unrepresentative
of ‘on-farm’ machine operation, comparison with ‘continuous’ ‘on-farm’ operation shows this
not to be the case. Nonetheless, as far as the Directive is concerned, it is the lower,
‘interrupted’ ‘on-farm’ WBV daily exposure levels which are evaluated against the prescribed
action and limit values.
5.4.4
‘On-Farm WBV Exposure Measurement - Summary
The objectives of the ‘on-farm’ tractor WBV investigation were to:•
•
•
Verify the practical applicability of the detailed agricultural tractor WBV emissions
data derived from the SRI ‘in-field’ and (possibly) ISO Test Track measurement
programmes;
Explore the variation in (and magnitudes of) WBV emission and resultant exposure
levels encountered upon ‘on-farm’ agricultural tractors during typical half-day
(4 hour) work periods;
Enable limited investigation of typical usage patterns of ‘on-farm’ examples of
selected test tractor designs included in the overall investigation.
The findings of the ‘on-farm’ tractor WBV exposure measurement programme may be
summarised as follows:•
•
•
•
•
•
Specific ‘on-farm’ tractor / operation combinations generated WBV emission levels
similar to those experienced during the SRI ‘in-field’ measurement programme. This
was particularly true of the fully suspended (front & rear axle) tractor;
Cultivating and trailer transport generated the highest WBV emission levels upon the
fully suspended (front & rear axle) tractors, confirming the findings of the SRI ‘infield’ programme (see Figure 5.25);
Largest overall average r.m.s. (Aeq) seat acceleration levels were usually found in the
transverse (Y) axis during the majority of ‘on-farm’ operations, with the exception of
trailer transport when longitudinal (X) axis WBV took precedence (see Figures 5.24
& 5.25). However, frequently the maximum peak acceleration was found to occur in
the vertical (Z) axis;
In all instances seat acceleration levels were higher than those recorded upon the
tractor cab floor (see Figures 5.26 and 5.27);
During certain operations (cultivating and trailer transport), ‘on-farm’ examples of
the suspended front axle & cab tractor generated lower WBV emission levels than the
comparable SRI ‘in-field’ tractor and the ‘on-farm’ fully suspended (front & rear
axle) tractors. This was deemed to be due to disparate operating conditions and
intensity of machine operation;
It was considered that, in general, the ‘on-farm’ fully suspended (front & rear axle)
tractors were operated at higher forward speeds, over rougher surface conditions, than
the suspended front axle & cab tractors. This may, however, be a consequence of a
greater proportion of ‘farm contractor’ rather than ‘owner-operator’ ownership of
these machines;
103
•
•
•
•
•
•
•
•
Virtually all (~ 95%) of the ‘on-farm’ tractor-operations surveyed exceeded the
PA(V)D 8-hour Exposure Action Value (EAV) within 8 hours operation, and will
require management of employee daily WBV exposure if 8 or more hours operation
per day are common place. Possible measures are outlined in Section 3.1.3;
Few ‘on-farm’ tractor-operations (~ 9%) exceeded the Exposure Limit Value (ELV)
within 8 hours operation. However, if the working day length were to increase to
15 hours, up to 27% of the vehicles surveyed would probably exceed the ELV;
A majority (57%) of the tractors surveyed were operated for more than 8 hours per
day. A number of machines were operated for up to 16 hours per day (see
Figure 5.39);
The PA(V)D is not likely to restrict the operation of large, modern, ‘state-of-the-art’
tractors during an 8-hour day, but it will become a limitation if the working day
lengthens significantly (see Figure 5.38);
During agricultural tractor operations, the VDV-specified EAV is reached in a
considerably shorter period than the A(8) EAV (see Figure 5.37). During part-day
operation, the EAV is more likely to be exceeded (requiring implementation of WBV
exposure reduction / management measures) if specified in VDV terms. However,
over a full (8-hour) day the difference appears less significant; ~95% of the tractors
surveyed exceeded the VDV EAV in 8 hours operation, whilst ~82% exceeded the
A(8) EAV in the same period;
Daily working patterns, including rest breaks, machine maintenance and periods of
general inactivity, can all contribute to a reduction in the Aeq WBV exposure value;
Variation in WBV daily exposure level was found to be present between certain
examples of similar ‘on-farm’ tractors / operations. This is not assisted by the
relatively small number of individual tractor / operation combinations investigated;
the 3 replicates performed being adequate to indicate ‘on-farm’ WBV levels, but
insufficient to determine the degree of WBV emission variability between supposedly
identical tractors / operations;
A more detailed study of similar ‘on-farm’ format, but comprising a larger number of
measurement replications, is required to enable creation of a robust database of
generic WBV emission data for modern agricultural tractor / implement
combinations.
104
6.
ALL-TERRAIN VEHICLES
All-terrain vehicles (ATVs or “Quad Bikes”) were arguably the greatest unknown in this
investigation, but their undeniable popularity in agriculture necessitated their inclusion.
Where possible the same testing and measurement techniques were employed upon the ATVs
as had been used on the other vehicles in the investigation. Modifications to the
instrumentation used have been described (see Section 3.2) and procedures specific to the
ATVs are also described below.
6.1
TEST VEHICLES
A range of four modern, state-of-the-art 300 – 400cc ATVs (see Figure 6.1) were identified
and kindly loaned by their respective manufacturers for the purposes of the ISO test track and
‘in-field’ vibration investigations at SRI (see Sections 6.2 & 6.3). All machines were fourwheel-drive models with the exception of the Honda, which was two-wheel-drive: a fact
reflected in its slightly different weight distribution and lower overall mass (see Table 6.1).
Three examples of one of the ATVs tested at SRI (Machine ‘A’) were subsequently located
on working farms and subjected to vibration measurements during typical ‘on-farm’ operation
(see Section 6.4). A summary of the relevant specifications of the four ATV models is given
in Table 6.1 below.
Table 6.1 ATVs used in the investigation at SRI
Make
Honda
Kawasaki
Suzuki
Yamaha
Model
TRX 350 TM
(Four Trax)
KLF300 (-C)
4x4
LT-F-300
(King Quad)
400
Big Bear
Front (kg)
Rear (kg)
Total (kg)
140
186
326
173
200
373
182
211
393
171
207
378
Wheelbase (m)
1.25
1.20
1.16
1.23
Track width (m)
0.85
0.84F / 0.86R
0.86
0.82
Front tyres
AT24 8-12
AT24 8-11
AT24 8-11
AT25 8-12
Pressure (lb/in2)
2.8
5.0
4.4
3.6
Rear tyres
AT24 9-11
AT24 10-11
AT25 10-12
AT25 10-12
Pressure (lb/in2)
2.8
4.0
4.0
3.6
Front suspension
Independent,
twin coil spring
& damper
Independent,
twin coil spring
& damper
Independent,
twin coil spring
& damper
Independent,
twin coil spring
& damper
Rear suspension
Trailing live
axle, single coil
spring & damper
Trailing live
axle, twin coil
spring & damper
Independent,
twin coil spring
& damper
Trailing live
axle, single coil
spring & damper
Weight with 77 kg
operator:-
105
Figure 6.1 ATVs used in the investigation at SRI
Figure 6.2 ATV traversing the ISO 100 m (smoother) ride vibration test track
106
6.2
ISO TEST TRACK VIBRATION EMISSION MEASUREMENT
6.2.1
Procedure
Whole-body vibration (WBV) emission levels were recorded in three mutually-perpendicular
directions (X-longitudinal, Y-transverse, Z-vertical), both upon the seat and the right-hand
footrest of each machine (see Figures 3.5 & 3.6 respectively), as a 77 kg (mass) operator rode
each over the SRI ISO 100 m (smoother) ride vibration test track, as defined in
ISO 5008:2002. Three measurement replications were made of each ATV traversing the ISO
track at each of the ISO 5008:2002-defined forward speeds (10, 12 & 14 km/h). Additional
measurements were also made at 16, 18 and 20 km/h. WBV data was acquired and analysed
by the methods previously described in Sections 3.2 & 3.3, in accordance with the
recommendations of ISO 2631-1:1997. After some preliminary trials, measurements when
driving over the ISO 35m (rougher) track were abandoned, because of the difficulty of
maintaining a constant forward speed upon the test vehicles.
Hand-arm (transmitted) vibration (HAV) was measured upon both handlebars of each ATV,
using equipment described in Section 3.2, whilst driving over the ISO 100 m (smoother) track
at the same range of speeds specified above. HAV was also measured during constant
forward speed tests whilst driving upon a smooth concrete surface, during which the
maximum forward speed attainable in each forward gear was held for at least 10 seconds
whilst vibration measurements were made. Because of the differences in gear ratios between
the test vehicles, a simple average of the frequency-weighted overall three-axis sum (RootSum-of-Squares - RSS) r.m.s. acceleration levels at all forward speeds was calculated for
each machine.
6.2.2
Results
Whole-body vibration - Seat
Operator seat WBV emission levels recorded upon each of the four ATVs whilst traversing
the ISO 100 m test track, are presented graphically within the line graph sections of
Figures 6.3 – 6.6 inclusive. For three of the machines the vertical (Z) axis WBV component
was consistently greater than those recorded upon the longitudinal (X) and transverse (Y)
axes, despite the effect of the PA(V)D-stipulated 1.4 multiplying factor that increases the
magnitude of the horizontal acceleration components. However, for one machine the
transverse (Y) axis acceleration levels were of similar magnitude because, in that particular
case, the Z-axis component was of lower magnitude than those recorded upon the other
machines. In all cases, Z-axis acceleration levels increased steadily with increasing forward
speed, at least up to approx. 15 km/h: however, two machines exhibited a tendency to lower
acceleration magnitudes at 20 km/h. Across the test vehicles, Z-axis frequency-weighted
acceleration magnitudes at 15 km/h forward speed ranged from less than 1.5 m/s2 to more
than 3 m/s2.
(Continued)
107
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Track
Field
Overall
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 6.3 ATV ‘A’ seat acceleration (1.4 multiplier)
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
Weighted r.m.s. Acceleration (m/s2)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Track
Field
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 6.4 ATV ‘B’ seat acceleration (1.4 multiplier)
108
Overall
30
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Road
ISO 100m Test Track
Track
Field
Overall
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 6.5 ATV ‘C’ seat acceleration (1.4 multiplier)
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
Weighted r.m.s. Acceleration (m/s2)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Road
ISO 100m Test Track
Track
Field
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 6.6 ATV ‘D’ seat acceleration (1.4 multiplier)
109
Overall
30
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Road
ISO 100m Test Track
Track
Field
Overall
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure
ure 6.7 ATV ‘A’ footrest acceleration (1.4 multiplier)
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
Weighted r.m.s. Acceleration (m/s2)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Road
ISO 100m Test Track
Track
Field
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 6.8 ATV ‘B’ footrest acceleration (1.4 multiplier)
110
Overall
30
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Road
ISO 100m Test Track
Track
Field
Overall
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 6.9 ATV ‘C’ footrest acceleration (1.4 multiplier)
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
Weighted r.m.s. Acceleration (m/s2)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Road
ISO 100m Test Track
Track
Field
Task Segments
Task Longitudinal (X)
Track Longitudinal (X)
Task Transverse (Y)
Track Transverse (Y)
Task Vertical (Z)
Track Vertical (Z)
Figure 6.10 ATV ‘D’ footrest acceleration (1.4 multiplier)
111
Overall
30
6.2.2
Results (continued)
Whole-body vibration - Footrests
WBV emission levels recorded upon the footrests of the four test ATVs whilst traversing the
ISO 100 m test track, are presented graphically within the line graph sections of Figures 6.7 –
6.10 inclusive. In all cases, the vertical (Z) axis acceleration component was of far greater
magnitude than either X- or Y-axis components, reaching a maximum of 3 - 3.5 m/s2 for all
the test machines. Without the smoothing effect produced by the saddle, one ATV
demonstrates a complex relationship between footrest WBV emission levels and forward
speed (see Figure 6.9). This is thought to be a result of the spacing of the wooden slats of
which the ISO test track is constructed (see Figure 6.2), insofar as the vibration generated by
the slats interacts with the dynamic response of the test vehicles.
Hand-arm vibration (handlebars)
The frequency-weighted RSS handlebar (hand-arm) vibration levels derived from the ISO test
track, range from 5 m/s2 to nearly 10 m/s2, as depicted by the line graph sections of
Figures 6.11 – 6.14. These HAV emission levels are considerably greater than the average
levels recorded upon the smooth concrete surface, as shown by the left-hand bar graph pair in
Figures 6.11 – 6.14. The difference in vibration magnitudes is thought to result from
excitation received by the ATV tyres as they ran over the spaced wooden slats which form the
ISO track (see Figure 6.2), this being at a frequency that can pass through the HAV weighting
filter with little or no attenuation.
6.2.3
ISO Test Track Vibration Emission Measurement - Summary
The results of the ATV ISO test track vibration measurement programme may be summarised
as follows:• Seat WBV emission levels in the vertical (Z) axis were significantly greater than
those in the longitudinal (X) or transverse (Y) axes, irrespective of vehicle forward
speed, with the exception of Machine D whose Y-axis WBV levels initially shadowed
and then marginally exceeded those of the Z-axis above 14 km/h;
• Seat Z-axis WBV emission levels at 15 km/h forward speed ranged from less than
1.5 m/s2 to more than 3.0 m/s2, depending upon the ATV model;
• In the majority of instances seat X and Y-axis WBV levels were not affected
substantially by forward speed (9 – 19 km/h) (see Figures 6.3 – 6.6);
• Footrest longitudinal (X) and transverse (Y) axis WBV emission levels were
consistently low (0.5 – 0.8 m/s2) and not affected by vehicle forward speed.
Generally footrest Z-axis WBV levels increased significantly with forward speed,
frequently approaching 3.0 – 3.5 m/s2 (see Figures 6.7 – 6.10);
• Hand-arm RSS vibration emission levels increased significantly at higher forward
speeds, doubling in many instances (e.g. ~5 to ~10 m/s2) (see Figures 6.11 – 6.14);
• ISO test track (wooden) slat spacing is believed to affect (increase) ATV footrest
WBV & handlebar HAV levels. ISO test track HAV emission levels were
substantially greater than those recorded upon a smooth concrete surface;
• The ISO 5008 test track was not conceived for vibration measurement on small
vehicles such as ATVs (low mass & small diameter tyres), and consequently would
benefit from modification to better-suit vehicles of this type.
112
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
Concrete
ISO 100m Test Track
Field
Farm
Driving Surface
Left Handgrip
Left Handgrip
Right Handgrip
Right Handgrip
Figure 6.11 ATV ‘A’ hand-arm vibration emission levels
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
ISO 100m Test Track
Concrete
Field
Driving Surface
Left Handgrip
Left Handgrip
Right Handgrip
Right Handgrip
Figure 6.12 ATV ‘B’ hand-arm vibration emission levels
113
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
Concrete
ISO 100m Test Track
Field
Driving Surface
Left Handgrip
Left Handgrip
Right Handgrip
Right Handgrip
Figure 6.13 ATV ‘C’ hand-arm vibration emission levels
Speed (km/h)
8
10
12
14
16
18
20
22
24
26
28
30
Weighted r.m.s. Acceleration (m/s2)
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
ISO 100m Test Track
Concrete
Field
Driving Surface
Left Handgrip
Left Handgrip
Right Handgrip
Right Handgrip
Figure 6.14 ATV ‘D’ hand-arm vibration emission levels
114
6.3
SRI ‘IN-FIELD’ VIBRATION EMISSION MEASUREMENT
6.3.1
Procedure
A repeatable, composite ‘in-field’ test circuit was devised comprising 0.5 km each of smooth
road and farm track, followed by driving twice around a field headland. The headland was
chosen for the (tractor) wheel ruts present upon it, which provided an approximate simulation
of off-road conditions for the ATVs under test. The entire circuit took approx. 10 minutes to
complete, the test rider selecting a consistent forward speed between the vehicles. For each
machine, seat and footrest WBV emission levels were recorded in three mutuallyperpendicular axes during two circuits of the test route: HAV emission levels were recorded
during one circuit. Frequency-weighted r.m.s. WBV emission levels were calculated for both
the complete (overall) circuit and for each individual section (road, track and field).
Vibration Dose Values (VDV) were also calculated these tests. Frequency-weighted
RSS (r.m.s.) hand-arm vibration (HAV) emission levels were calculated for the complete
(overall) test circuit, but the resulting values are labelled as ‘field’ in Figures 6.11 – 6.14
inclusive.
During this phase of the investigation, a device was developed to enable operator presence
upon the ATV seat to be recorded upon the 8th channel of the PC card recorder. However,
consistent operation of this device was not achieved early enough for it to be used during the
‘in-field’ test programme, so any effect of the driver losing contact with the ATV seat was
ignored.
6.3.2
Results
Whole-body vibration - Seat
The bar graph sections of Figures 6.3 – 6.6 inclusive, depict operator seat WBV emission
levels for the four ATVs. In general, ‘overall’ ‘in-field’ WBV emission levels were of the
same orders of magnitude as those arising from the ISO 100 m test track: overall levels of the
vertical (Z) axis component being around 1.5 m/s2, and the longitudinal (X) and
transverse (Y) axis components both being lower. The expected trend can be seen where
‘field’ seat WBV emission levels are greater than those recorded upon the (farm) ‘track’,
which in turn are greater than those resulting from the ‘road’ section of the composite test
circuit.
Whole-body vibration - Footrests
Footrest WBV emission levels for the four machines are depicted by the bar graph sections of
Figures 6.7 – 6.10 inclusive. As in the case of the ISO test track measurements, the
vertical (Z) axis component dominates, but the ‘overall’ ‘in-field’ footrest vibration
magnitudes were somewhat lower, between 2.0 – 2.5 m/s2. Differences between ‘road’,
‘track’ and ‘field’ emission levels are smaller than those between corresponding WBV values
recorded upon the operator’s seat. This suggests that some engine vibration feeds through the
footrests (and through the wk weighting filter). It also supports the hypothesis that the ISO
test track vibration emission values are affected by the spaced wooden slat construction of the
track (see Section 6.2.2), the characteristic vibration frequency of which would also feed
through the wk filter.
115
Hand-arm vibration (handlebars)
Handlebar (hand-arm) vibration emission levels are depicted by the right-hand bar graph
sections of Figures 6.11 – 6.14 inclusive. These frequency-weighted sum (root-sum-ofsquares - RSS) r.m.s. HAV values, recorded over the entire (overall) composite ‘in-field’ test
circuit (see Section 6.3.1) were generally found, at 3 - 4 m/s2, to be only slightly greater than
those obtained from the smooth concrete surface (see Section 6.2.1).
6.3.3
ATV ‘in-field’ and ISO test track performance comparison
The four models of ATV included in the study at SRI (see Figure 6.1 & Table 6.1) may be
compared by means of the vibration data arising from the SRI ‘in-field’ or ISO 5008 test track
investigations (see Figures 6.15 – 6.18). It is also of interest to evaluate the ISO test track
data as a potential predictor of ‘in-field’ vibration emission levels. To provide a consistent
basis for machine comparison, an average of vibration emission levels recorded at 10, 12 and
14 km/h upon the ISO test track are depicted, as directed by ISO 5008 for tractor driver WBV
measurement. An overall average of the vibration levels arising from the different sections of
the SRI ‘in-field’ composite test circuit (road, farm track & field) are depicted for each
machine. An average of RSS hand-arm vibration levels recorded at all forward speeds upon
the smooth concrete track, are also displayed (see Figures 6.17 & 6.18).
The ISO test track was developed to enable consistent, comparative measurement of WBV
emission levels upon tractors and other field machines. However, these vehicles are typically
heavier and have larger diameter tyres than ATVs, and consequently it is possible that the
passing frequency of the spaced wooden slats, of which the test track is constructed, may have
a large influence on the frequency-weighted vibration emission values recorded on this test
surface. This could potentially result in ISO track vibration levels being unduly high.
Whole-body vibration - Seat
Although the ‘overall in-field’ vertical (Z) axis seat WBV magnitudes from the different
machines were of a similar order of magnitude, it can be seen from Figure 6.15 that one of the
ATVs (Machine C) amplified the ISO test track-induced vibration nearly twice as much as the
others. Although this machine also generated higher seat WBV emission levels than the other
vehicles ‘in-field’, the difference was very much smaller. Additionally, any comparison of
‘in-field’ seat WBV levels between these other machines (A, B & D) did not correlate very
well with their comparison gained upon the ISO test track. However, the differences between
machines were quite small in both the ISO track and ‘in-field’ instances, and it would perhaps
be unreasonable to expect the machines to be distinguished by the ISO track test, given its
questionable suitability for machines of this type.
Whole-body vibration - Footrests
A closer correlation exists between the vertical (Z) axis footrest WBV emission levels of the
ATVs resulting from the ISO test track and ‘in-field’ measurements (see Figure 6.16). In the
case of footrest vibration, it may be that engine vibration has a greater influence than groundinduced (tyre) vibration: otherwise, similar relative differences in WBV levels to those found
upon the seats would be expected (see Figure 6.15). The footrest WBV results are also
consistent with the hypothesis whereby the ISO test track provides an additional vibrational
input (from the slat spacing), this being common to all the machines tested.
116
3
Weighted r.m.s. Acceleration (m/s2)
2.5
2
1.5
1
0.5
0
ISO 100m Track
Machine A
Overall 'In-Field'
Machine B
Machine C
Machine D
Figure 6.15 ATV seat vertical (Z) axis whole-body vibration: machines A, B, C & D
3.5
Weighted r.m.s. Acceleration (m/s2)
3
2.5
2
1.5
1
0.5
0
ISO 100m Track
Machine A
Overall 'In-Field'
Machine B
Machine C
Machine D
Figure 6.16 ATV footrest vertical (Z) axis vibration: machines A, B, C & D
117
6
Weighted r.m.s. Acceleration (m/s2)
5
4
3
2
1
0
Smooth Concrete
ISO 100m Track
Machine A
Machine B
Machine C
Overall 'In-Field'
Machine D
Figure 6.17 ATV left handgrip vibration (RSS): machines A, B, C & D
6
Weighted r.m.s. Acceleration (m/s2)
5
4
3
2
1
0
Smooth Concrete
ISO 100m Track
Machine A
Machine B
Machine C
Overall 'In-Field'
Machine D
Figure 6.18 ATV right handgrip vibration (RSS): machines A, B, C & D
118
Hand-arm vibration (handlebars)
In this case, the ISO 100 m (smoother) test track data again exhibits a characteristic that does
not correlate with the SRI ‘overall’ ‘in-field’ results (see Figures 6.17 & 6.18). On the ISO
track, one machine exhibits a lower level of RSS vibration emission than the other three, yet
in the field the differences between the test machines are smaller and they are rated in a
different relative order. However, the ‘in-field’ HAV magnitudes compare more favourably
with those arising from the tests on a smooth concrete surface, particularly with regard to
rating by magnitude. The ‘in-field’ HAV emission levels were slightly higher than those
from the smooth concrete surface. This could indicate that some ground-induced vibration
from the (predictably rougher) field surface is feeding through the frequency-weighting filter.
Alternatively, the ‘in-field’ tests may have included periods of operation at engine speeds
other than maximum, whereas the smooth surface tests were all conducted at full throttle.
6.3.4
Comments (conclusions) regarding standardised tests
The ISO 5008 100 m (smoother) test track is not suitable in its present (constructional) form
for providing a representative comparison of different ATVs, whether the interest is wholebody or hand-arm vibration. If the present (wooden slat) construction, which is currently
endorsed by ISO 5008, were replaced with a smoothed concrete surface of appropriate
contour – a method which has been used at some test facilities - then the vibrational problems
arising from slat spacing would be eliminated, and better correlation with ‘in-field’ behaviour
might be achieved.
As ‘in-field’ levels of handlebar (hand-arm) vibration were best predicted by that measured
when the machines were driven over a smooth surface, it may well be that a static test (albeit
with the engine running) would provide an adequate prediction. In that case, it would be
useful to investigate what engine speed settings would be most appropriate, as vibration
emission values derived from a single-speed test could be compromised by resonance effects
in the machine structure.
6.3.5
‘In-Field’ Vibration Emission Measurement - Summary
The objectives of this specific part of the investigation were:• To quantify for each model of ATV the WBV and HAV emission levels, averaged
over a set of controlled conditions that were representative of a common use of these
machines in UK agriculture;
• To investigate the similarity between these vibration levels and those found during
tests on the ISO 5008 track (Section 6.2).
The results may be summarised as follows:• The largest seat WBV emission levels were generally evident in the vertical (Z) axis,
typically being in the region of 1.5 m/s2;
• Footrest WBV emission levels were dominated by the vertical (Z) axis component,
and were in the range 2.0 - 2.5 m/s2;
• ‘Overall’ ‘in-field’ HAV levels (RSS) were between 3.0 – 4.0 m/s2 and were only
slightly greater than those values recorded upon a smooth concrete surface;
119
•
•
•
•
•
•
Seat (Z-axis) WBV levels recorded upon the ISO 5008 track were of a similar
magnitude to those recorded ‘in-field’, but did they not reflect differences between
the machines in the same manner; ‘in-field’ differences between machines being
much smaller than those arising from the ISO track (see Figure 6.15);
Footrest (Z-axis) WBV levels recorded upon the ISO track were slightly higher than
those recorded ‘in-field’, but reflected differences between the individual machines
quite closely (see Figure 6.16);
HAV (RSS) emission levels recorded upon a smooth concrete surface were slightly
lower than those measured ‘in-field’, but demonstrated very similar differences in
magnitude between the machines (see Figures 6.17 & 6.18);
ISO track HAV values were higher than those recorded ‘in-field’, and demonstrated
larger differences between individual machines, which were not consistent with those
found ‘in-field’;
An ISO test track of wooden slat construction is of questionable suitability for
quantification of vibration emission levels from machines of this type (ATVs);
A static test may be suitable for assessment of engine-induced HAV upon ATVs.
120
6.4
‘ON-FARM’ VIBRATION EXPOSURE MEASUREMENT
6.4.1
Farm description and ATV utilisation
In association with an ATV manufacturer’s agent, a number of farmers were approached to
participate in an investigation of admittedly restricted scope: three enterprises kindly agreed.
Two of these were Welsh hill farms; one (Hill Farm#1) of approx. 230 hectares, the other
(Hill Farm#2) rather smaller. The third enterprise was a 200-hectare holding in the Welsh
Borders, which operated as a commercial shoot, the ATV being used by the Gamekeeper.
Hill Farm#1 was operated by the farmer/owner, with the assistance of one stockman. The
stockman (estimated weight ~70 kg) generally used the ATV, primarily to inspect the stock
immediately after arriving for work. Generally this ‘round’ took ½ – 1-hour.
Hill Farm#2 was run by a young farmer, with help from his mother. In this instance the
farmer’s mother (estimated weight ~70 kg) used the ATV for the stock inspection ‘round’,
which was undertaken at whatever time was convenient and took about ½-hour.
The Gamekeeper (estimated weight ~90 kg) used his ATV for two slightly different tasks. In
one case a game feed distributor was attached to the rear load-carrying rack. The operator
would then drive out to a given plantation, slow down whilst spreading food, before returning
at high speed to re-fill the hopper. The other task involved placing sacks of feed on the loadcarrying rack and driving around plantations, dismounting frequently to re-fill freestanding
feeders in these locations. Between ½ & 1-hour was required for either operation, which
were performed as the first task each morning. Sometimes both tasks would be performed on
the same day, the feed distributor being removed during a break. This was the case on the
WBV measurement day.
All the above routines would vary with the season and if there was also a need to move stock
around the enterprises. However, the days on which measurements were made were
considered by the drivers to be typical of most working days. The only exception to this was
the WBV recording for the Gamekeeper, who had held back some work from the previous
day “to make sure that there was enough work to measure”, resulting in a recording period in
excess of 2 hours on the day in question (see Table 6.3).
6.4.2
Procedure
A preliminary visit was made to each enterprise to confirm the farmer’s agreement to
participate and the suitability of the machine on-site. Also to check upon the daily routine of
ATV use and in particular when it was convenient to fit and remove the measurement
instrumentation. In some cases the instrumentation was fitted at the end of the preceding day;
otherwise it was installed early in the morning before the machine was needed. The
equipment was checked in the laboratory before travel to each farm.
The Human Vibration Meters and PC card recorder (see Section 3.2.3) were set to record as
close to the start of each daily ‘round’ as practicable, and stopped at the end of the ‘round’,
the aim being to obtain one dataset each of WBV (seat & footrest) and HAV (handlebar) on
each farm, this necessitating measurement on successive days. Because of the terrain, it was
not possible to observe the use of the machine once it had left the farmyard. Only in the case
of the Gamekeeper’s machine could progress be monitored, because of frequent returns to the
farmyard to re-fill the feed distributor or to collect further sacks of feed.
121
6.4.3
Results
As discussed previously (Section 3.1), the European Union Physical Agents (Vibration)
Directive (PA(V)D) (EEC, 2002) defines the WBV Exposure Action Value (EAV) and
Exposure Limit Value (ELV) in two alternative ways. Either as an 8-hour energy-equivalent
frequency-weighted r.m.s. acceleration value (A(8)), or as a vibration dose value (VDV).
Member States are given the option of implementing the Directive using either method, using
the values stated below (see Table 6.2). Specific details are discussed in Section 3.1, but an
important difference between the methods is as follows. The root-mean-square (r.m.s.) or
A(8) method produces a value which is an average vibration level adjusted to represent an
8 hour working day, whereas the vibration dose value represents cumulative exposure to
vibration over the working day. The practical significance of this is clearly depicted by
Figure 5.29 & 6.19. If, over a given period of work, frequency-weighted r.m.s. acceleration
levels recorded upon the operator’s seat are relatively consistent, the resultant Aeq value
(only A(8) if duration equals 8 hours) changes little, having once reached an average ‘plateau’
value. However, in the same circumstances, the VDV increases throughout the work period
in a cumulative manner. Additionally, the A(8) method represents steady levels of vibration
with reasonable accuracy but gives poor representation of shocks and jolts, whereas the VDV
method performs well in both instances (Griffin, 1998; Coles, 2002). These issues, and those
of data sampling duration, are discussed in Appendix 4.
Throughout this investigation we have primarily utilised the A(8) method but, during ‘onfarm’ exposure measurement, vibration dose values have also been derived (see Figures 6.19
and Appendix 3.3). At the time of writing the HSE is undertaking a public consultation
exercise regarding implementation of the PA(V)D in the UK. Whilst it is highly likely that
the ELV will be specified by the A(8) technique, debate is currently ongoing as to whether the
EAV will be implemented in VDV or A(8) terms: the implications of this stance are discussed
in Sections 3.1 & 7.4.
An important aspect of results interpretation concerns how estimates for a whole day’s
vibration exposure can be made from values measured over a shorter period (see also
Appendix 4). In the case of the ATV’s, the ‘on-farm’ measurement period of ½ - 1-hour
encompassed the entire day’s exposure for each vehicle, but in other businesses longer
exposures might be involved. Where the r.m.s. A(8) approach is used, the resultant overall
average frequency-weighted r.m.s. acceleration (Aeq) value measured for a shorter period,
can be considered to extend throughout the entire day’s use of the machine. If this use
extends for 8 hours, the Aeq value becomes equivalent to the daily occupational vibration
exposure (A(8)) value for that operation. Consequently the Aeq values generated by this
investigation may be compared directly with the A(8) EAV and ELV values stipulated by the
PA(V)D whenever the working day length approximates to 8 hours. For shorter or longer
working days the respective A(8) value for the daily exposure period in question may be
calculated from the Aeq value, prior to comparison with the EAV or ELV (see Section 3.1.2,
Equation 3). A similar approach is necessary for the VDV; its cumulative nature requires a
value for a shorter period be re-calculated to estimate the VDV after the full day’s exposure.
This is performed by assuming subsequent WBV emission levels are similar to those recorded
during the (~4 hour) measurement period (see Appendix 4). .
This, however, is not the case for the VDV: its cumulative nature requires a value for non8 hour period be re-calculated to estimate the VDV after 8 hours exposure, this being
performed by assuming subsequent WBV emission levels are similar to those recorded during
the (½ - 1 hour) measurement period. Estimated 8-hour (seat WBV) VDV’s for the ‘on-farm’
ATVs appear in Table 6.5 and Appendix 3.3.
122
Table 6.2 WBV exposure values specified by the EU PA(V)D
8-hour energy-equivalent
Vibration Dose Value
r.m.s. acceleration – A(8)
(m/s1.75)
(m/s2)
Exposure Action Value (EAV)
0.5
9.1
Exposure Limit Value (ELV)
1.15
21
Following the procedure used during both the ISO test track and SRI ‘in-field’ measurement
programmes, WBV was recorded both upon the ATV seat and footrests. However, no
guidance is provided by the PA(V)D regarding evaluation of WBV which originates from
multiple sources (e.g. the operator’s posterior and feet). Given that it is common practice to
ride ATV’s whilst standing upon the footrests, particularly when traversing rough terrain,
‘simple’ acceleration data from a seat-mounted accelerometer may be misleading. To guard
against this an array of thin-film force transducers was incorporated into the accelerometer
‘seat-pad’ installation (see Figure 3.5), their output being recorded by the data acquisition
system. This device was able to indicate the operator’s presence upon the seat and
consequently the periods when he/she was being exposed to the WBV being recorded by the
seat accelerometer pad. The difference between ‘overall’ (total) seat WBV exposure and that
received during ‘seat contact’ is highlighted for each ‘on-farm’ application within Tables 6.4
& 6.5. Regrettably, whilst this technique indicated ‘seat presence’, it was unable to
differentiate between periods of ‘seat absence’ when the operator was standing on the
footrests, or when he/she had dismounted from the machine. Further analysis of vehicle
forward speed time-histories could possibly clarify this issue, but unfortunately this was
beyond the resources of this particular investigation. In the interim, estimated operating
periods to reach the (seat WBV) EAV and ELV (see Table 6.6) were calculated using driver
‘on-seat’ WBV data.
Footrest WBV emission and exposure levels were recorded & calculated and are depicted for
the reader’s information (see Tables 6.7 & 6.8), but further evaluation is restricted by the
current form of the PA(V)D, namely a lack of guidance regarding how to evaluate wholebody vibration exposure in instances where an individual receives vibration both through
his/her seat and feet.. The Directive specifies an EAV and ELV for hand-arm vibration
(HAV), these being 2.5 m/s2 and 5 m/s2 respectively. However, in instances where an
operator is subjected simultaneously to both HAV and WBV, these physical agents are
considered separately. If either should exceed the EAV, the preventative steps stated in
Section 3.1 must be implemented, and under no circumstances should either WBV or HAV
exposure levels be allowed to exceed the ELV.
Because of a suspicion concerning the data resulting from the first WBV measurement on
Hill Farm#1, and because the farmer was particularly co-operative, WBV emission and
exposure levels were recorded once more on a second day, with hand-arm vibration being
measured on a third day. Both WBV and HAV were also recorded for the Gamekeeper.
However, there were time constraints on Hill Farm#2, so that only one day was available and
this was used for WBV measurement purposes. The activities associated with each recording
are illustrated in Appendix 3.4 in the form of time-history graphs of forward speed and
operator ‘seat presence’.
123
18
2.5
15
2.0
12
1.5
9
1.0
6
0.5
3
0.0
0:00
VDV (m/s1.75)
Weighted r.m.s. Acceleration (m/s2)
3.0
0
0:15
0:30
0:45
1:00
Elapsed Time (hrs)
Vertical (Z-axis) seat
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Total VDV
Time
00:45
8-hr est tot
VDV
SN:00215
Seat
ATV
Day
24
Month
Sep
Year
2
Start time:
07:55
Z
1.39
Sum
2.20
Z
22.10
Sum
22.10
Stock tour
Hill Farm #1 (1)
X
12.6
22.8
Y
16.1
29.1
Z
17.0
30.7
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.06
1.75
r.m.s./A(8)
1.03
5.46
Figure 6.19
Aeq
Average rms (Leq)
X
1.06
Sum
26.5
48.0
Y
1.39
2
Maximum peak value (m/s )
X
Y
8.53
12.84
Typical time history of weighted 1-minute r.m.s. accelerations (Z-axis, ATV
seat – Hill Farm#1 (1)) plus development of equivalent continuous r.m.s.
acceleration (Aeq) & 15-minute record of Vibration Dose Value (VDV) and
table of seat WBV parameters
Table 6.3 ATV ‘on-farm’ WBV recording durations and forward speeds used
Farm
Forward speed (km/h)
Measurement
duration
(hours:mins)
Average
Maximum
Hill Farm#1 (1)
0:55
10.8
46
Hill Farm#1 (2)
1:10
10.1
53
Hill Farm#2
0:35
9.4
34
Gamekeeper
2:20*
7.5
41
* Included 20-minute break for removing the feed distributor
124
Table 6.4 ‘On-farm’ ATV weighted r.m.s. (Aeq) seat WBV exposure values
Farm
Energy-equivalent weighted r.m.s. (Aeq) seat acceleration
(m/s2)
Circumstance
X-axis
Y-axis
Z-axis
‘Overall’
1.06
1.39
1.39
Driver ‘on-seat’
1.00
1.32
1.26
Difference (%)
6
5
9
‘Overall’
0.90
1.29
1.21
Driver ‘on-seat’
0.84
1.20
1.09
Difference (%)
7
7
10
‘Overall’
0.72
0.65
0.87
Driver ‘on-seat’
0.69
0.62
0.77
Difference (%)
4
4
12
‘Overall’
0.55
0.76
0.85
Driver ‘on-seat’
0.53
0.74
0.66
Difference (%)
4
3
22
Major
axis
Y/Z
Hill Farm#1 (1)
Y/Z
Hill Farm#1 (2)
Z
Hill Farm#2
Y/Z
Gamekeeper
-
Whole-body vibration - Seat
As mentioned previously, the ATV ‘on-farm’ WBV exposure data acquired mainly resulted
from stock monitoring rounds of ½ - 1-hour duration, with the exception of the Gamekeeper
who provided an unusually long period of use (see Table 6.3). The seat WBV (Aeq) exposure
values recorded upon the ‘on-farm’ ATVs are shown in Table 6.4, highlighting the range of
(‘on-seat’) WBV magnitudes (0.62 – 1.32 m/s2) common during typical ‘on-farm’ ATV
operations. In the majority of ‘on-farm’ applications, the vertical (Z) and transverse (Y) axis
vibration components were greater than those present in the longitudinal (X) axis. This
departs somewhat from the findings of the SRI ‘in-field’ test programme (see Section 6.3),
where longitudinal (X) and transverse (Y) axis vibration magnitudes were similar and
markedly lower than those experienced in the Z-axis. However, in these ‘in-field’ test
conditions the Z-axis vibration levels were generally higher than those encountered ‘on-farm’,
suggesting that the SRI ‘in-field’ composite test circuit probably provided a smoother
operating surface for the test vehicles, which generated less vehicle (Y-axis) roll, but
conversely higher vertical (Z) axis vibration levels because of higher forward speed.
In ‘on-farm’ conditions, longitudinal (X) axis vibration magnitudes appear to be
approximately 10 - 30% lower than the levels experienced in the transverse (Y) or vertical (Z)
axes. Differences in acceleration levels between individual farms appear to be as great as two
to one, irrespective of the measurement axis: this is probably attributable to differences in
personal driving style.
125
It would appear that only one of the ‘on-farm’ ATV applications investigated (two
measurement instances) generated actual daily WBV exposure levels that would exceed the
PA(V)D-prescribed A(8) Exposure Limit Value (ELV) during 8 hours of operation (see
Table 6.6). It seems that the operator in question (Hill Farm#1) rode his ATV in a rather
harder manner than the other two operators, with the result that he returned higher values of
both energy-equivalent r.m.s. acceleration (Aeq) and VDV (see Tables 6.4 & 6.5
respectively). This consequently led to considerably shorter operating periods until the
PA(V)D-prescribed WBV Exposure Action Value (EAV) and Exposure Limit Value (ELV)
would be reached (see Table 6.6). However, all the ‘on-farm’ ATVs exceeded the PA(V)D
Exposure Action Value in less than ½-hour operation when this parameter is expressed in
terms of VDV (see Tables 6.2 & 6.6).
Table 6.5 ‘On-farm’ ATV seat whole-body vibration exposure values:Vibration Dose Value (VDV)
ATV seat vibration dose value (VDV) (m/s1.75)
Farm
Circumstance
X-axis
Y-axis
Z-axis
‘Overall’ VDV
12.6
16.1
17.0
Driver ‘on-seat’
11.7
15.1
15.5
Difference (%)
7
6
9
Est 8-hr VDV
21.1
27.3
28.0
‘Overall’ VDV
12.4
17.5
18.4
Driver ‘on-seat’
11.5
16.1
16.0
Difference (%)
7
8
13
Est 8-hr VDV on seat
18.3
25.6
25.4
‘Overall’ VDV
10.0
8.1
10.9
Driver ‘on-seat’
9.5
7.9
10.2
Difference (%)
5
3
6
Est 8-hr VDV
17.2
14.3
18.4
‘Overall’ VDV
11.3
11.9
15.6
Driver ‘on-seat’
11.0
11.7
14.7
Difference (%)
3
2
6
Est 8-hr VDV
15.1
16.1
20.2
Major
axis
Z/Y
Hill Farm#1 (1)
-
Z/Y
Hill Farm#1 (2)
-
Z/X
Hill Farm#2
-
Z
Gamekeeper
-
126
Table 6.6 Estimated ‘on-farm’ ATV operating periods to reach PA(V)D-prescribed
WBV Exposure Action Value (EAV) & Exposure Limit Value (ELV)
(based upon seat ‘overall’ Z-axis WBV magnitudes)
Estimated time to EAV (hours:mins)
Estimated time to ELV (hours:mins)
Farm
VDV
A(8)
VDV
A(8)
Hill Farm#1 (1)
0:5
1:2
2:8
5:29
Hill Farm#1 (2)
0:4
1:22
1:59
7:14
Hill Farm#2
0:17
2:39
8:2
13:59
Gamekeeper
0:16
2.46
7:40
14:39
NB:- HSE is proposing to utilise A(8) for the ELV and is consulting regarding either A(8) or VDV for the EAV
In general, the effect of calculating WBV exposure values only during times of driver ‘seat
presence’ was a reduction of less than 10% (see Tables 6.4 & 6.5). An exception was found
in the case of the Gamekeeper, when the ‘overall’ vs. ‘on-seat’ difference in the vertical (Z)
axis was more than 20%. In this case the driver himself pointed out the clearly visible
vibration of the ATV seat cushion when he was dismounted and the engine was idling. This
would have added to the Aeq WBV calculation whenever the driver dismounted to fill a sack
or feed hopper, as he seldom stopped the engine for this. It would not however have
contributed much to the VDV WBV figures, these values being dominated by the peak
acceleration events encountered during off-road travel.
Whole-body vibration - Footrests
Whole-body vibration magnitudes obtained from the footrests of the ‘on-farm’ ATVs are also
consistent with the results of the SRI ‘in-field’ experimental programme, in that the
vertical (Z) axis component is greatest and considerably larger than the corresponding value
recorded upon the seat. (see Tables 6.7 & 6.8). These values have not been corrected for
times when the driver had dismounted from the ATV seat because, as discussed previously,
such periods of ‘seat absence’ were not always consistent with the operator’s feet being off
the footrests. As discussed earlier, it is currently unclear how to evaluate whole-body
vibration exposure in instances where an individual receives vibration both through his/her
seat and feet. Consequently, the information provided in Tables 6.7 & 6.8 is primarily for the
reader’s information.
127
Table 6.7 ‘On-farm’ ATV footrest weighted r.m.s. (Aeq) vibration exposure values
Energy-equivalent weighted r.m.s.(Aeq) footrest acceleration (m/s2)
Farm
Major
axis
X-axis
Y-axis
Z-axis
Hill Farm#1 (1)
0.71
0.76
3.62
Z
Hill Farm#1 (2)
0.64
0.74
3.05
Z
Hill Farm#2
0.49
0.43
2.07
Z
Gamekeeper
0.57
0.53
3.30
Z
Table 6.8 ‘On-farm’ ATV footrest vibration exposure values:Vibration Dose Value (VDV)
ATV footrest vibration dose value (VDV) (m/s1.75)
Major
axis
Farm
X-axis
Y-axis
Z-axis
Hill Farm#1 (1)
9.3
8.9
38.7
Z
Hill Farm#1 (2)
9.6
9.8
37.8
Z
Hill Farm#2
7.7
5.2
23.5
Z
Gamekeeper
10.1
9.0
47.5
Z
Hand-arm vibration
Vibration of the ATV handlebars was measured for durations of 35 and 45 minutes
respectively at Hill Farm#1 and for the Gamekeeper. In the first of these instances, the PC
card recorder shut down at an early stage, necessitating some improvement to the mounting
arrangement. However, the short-term frequency-weighted r.m.s. acceleration values stored
in the human vibration meters were available, and so these have been used for both sets of
recordings. The overall three-axis sum (Root-Sum-of-Squares - RSS) values are shown in
Table 6.9 below.
Table 6.9 ‘On-farm’ ATV hand-arm vibration exposure
RSS weighted r.m.s. (Aeq) hand-arm acceleration (m/s2)
Farm
Left hand
Right hand
Hill Farm#1
8.1
9.3
Gamekeeper
3.9
4.8
The machine used by the Gamekeeper was very much newer than that used at Hill Farm#1,
which may partially account for the higher acceleration magnitudes found on the latter.
However, the Gamekeeper’s machine exhibited unusually large vibration at idle, as
128
mentioned earlier. An alternative explanation could be that the hard-driving technique of the
stockman on Hill Farm#1 led to some ground-induced vibration being transmitted through to
the handlebars. If that were the case, it would pass through the HAV weighting filter with
relatively little attenuation. Certainly the whole-body vibration levels recorded upon the Hill
Farm#1 machine were greater than those arising from the simulated field tests at SRI (see
Figure 6.3), almost certainly due to higher levels of ground surface-induced vibration on the
farm. Given that, in this application, the vibration from this source was able to pass through
the WBV signal filter, it is likely that it was also able to pass through the HAV filter, possibly
resulting in higher recorded vibration levels. In either case, we have to conclude that a HAV
magnitude spread of two to one may be expected in typical ‘on-farm’ use of ATVs.
Table 6.10 Estimated ‘on-farm’ ATV operating periods to reach PA(V)D-prescribed
HAV Exposure Action Value (EAV) & Exposure Limit Value (ELV)
(based upon weighted RSS r.m.s .vibration magnitude upon worst hand)
Farm
Estimated time to EAV
(hours:minutes)
Estimated time to ELV
(hours:minutes)
Hill Farm #1
0:36
2:18
Gamekeeper
2:12
8:42
The HAV emission levels generated by the majority of the ATV’s during the SRI ‘in-field’
tests were only slightly greater than those arising from the smooth concrete test surface (see
Figures 6.12 - 6.14 inclusive), typically being in the range 3.0 – 4.0 m/s2. However, one ATV
(Machine A) – the model targeted during the ‘on-farm’ test programme - displayed a
significant increase in HAV emission levels between the smooth concrete, the SRI ‘in-field’
and the Hill Farm#1 test conditions (see bar-graph sections of Figure 6.11), whereas HAV
levels recorded upon the Gamekeeper’s machine (see Table 6.9) were comparable with those
experienced during the SRI ‘in-field’ test programme (see Figures 6.17 & 6.18).
As discussed earlier, the PA(V)D does specify an EAV and ELV for hand-arm vibration
(HAV), these being 2.5 m/s2 and 5 m/s2 (A(8)) respectively. However, in instances where an
operator is subjected simultaneously to both HAV and WBV, these physical agents are
considered separately, exposure to vibration exceeding either the HAV or WBV Exposure
Action Value (EAV) necessitating the implementation of vibration reduction and
management measures (see Section 3.1.3). As previously discussed, on no account should
workers receive daily exposure to vibration (either HAV or WBV) in excess of the Exposure
Limit Value (ELV). If the ELV is exceeded, immediate action must be taken to reduce
vibration exposure below the ELV and measures be implemented to prevent it being exceeded
again. Consequently regarding limitation of machine operating period, HAV and WBV are
considered separately in relation to their respective ELV’s, on a “first-past-the-post” basis.
As stated earlier, at the time of writing the HSE is undertaking a public consultation exercise
regarding implementation of the PA(V)D in the UK. It appears likely that the WBV ELV will
be specified as a r.m.s. A(8) value (1.15 m/s2), but debate is currently ongoing as to whether
the WBV EAV will be implemented in VDV (9.1 m/s1.75) or A(8) (0.5 m/s2) terms. No option
is provided for HAV by the Directive, the EAV and ELV being the A(8) values stated above.
129
Consequently, in the two ‘on-farm’ instances where HAV was recorded (see Tables 6.9 &
6.10), seat (whole-body) vibration caused the (WBV) EAV to be exceeded first, in less than
20 minutes. The HAV EAV was not reached until between 30 minutes and 1-hour 50 minutes
later. However, on both farm ATVs, hand-arm vibration levels caused the (HAV) ELV to be
reached in a shorter period than the WBV ELV (see Tables 6.6 & 6.10). However, given the
short daily use periods of these vehicles, neither WBV nor HAV exposure is likely to present
an operational restriction to typical stock farmers. The ELV could possibly pose a restraint to
daily use of ATVs by more intensive users, but the vibration exposures likely in these
applications and their consequent risk are not currently known.
6.4.4
‘On-Farm’ Vibration Exposure Measurement - Summary
The objectives of the ‘on-farm’ ATV vibration exposure measurement programme were:•
•
To quantify typical daily exposure to WBV and HAV of farmers who use ATVs for
fieldwork whilst tending livestock;
To investigate the relationship between vibration levels measured under controlled
conditions, either ‘in-field’ or on a (ISO) test track, and what characterises daily
vibration exposure ‘on-farms’.
The findings may be summarised as follows:•
•
•
•
•
•
•
•
•
‘On-farm’ ATV seat WBV levels vary by at least ±50%, giving anything from 0.66 1.26 m/s2 in the vertical (Z) axis, depending upon the application;
Short daily exposure times, generally of less than 1½ hours, ensure that even the
highest of these WBV levels does not cause the PA(V)D Exposure Limit
Value (ELV) to be exceeded during normal daily use;
In several instances, the WBV Exposure Action Value (EAV) is not exceeded (during
typical daily use) if expressed in r.m.s. A(8) terms. However, if specified as a VDV,
the EAV is exceeded in all cases;
Hand-arm vibration (HAV) levels also vary widely, and approach or exceed the ELV.
It is not clear how much of this difference in levels is the result of differences in
ground conditions, driving technique or machine (condition) between the enterprises
studied;
In the case of HAV, the short daily exposure periods ensure that the ELV is not
exceeded in typical ‘on-farm’ use, but the EAV may well be exceeded, and if so will
require management of employee daily vibration exposure. Possible measures are
outlined in Section 3.1.3;;
Footrest WBV levels are greater than those generated upon the seat (saddle);
If footrest vibration is treated in the same way as seat vibration, then even the short
daily exposure times found on farms will result in transgression of the ELV;
Given that the WBV requirements of the PA(V)D have been determined according to
what is needed to protect the worker’s lower back, and that there is very little data for
transmission of vibration from the feet to the lumbar spine in postures similar to those
of ATV riders, nor to correlate foot vibration with low back problems, it is suggested
that this result provides a reason for further research rather than for restricting the use
of these vehicles;
On the basis of the limited evidence available from the investigation, vibration values
arising from the controlled (SRI) ‘in-field’ conditions generally provide a fairly good
indication of ‘on-farm’ longitudinal (X) axis WBV levels, averaged over the daily
exposure period, but ‘on-farm’ transverse (Y) axis values were greater and conversely
vertical (Z) axis values lower than the corresponding ‘in-field’ levels;
130
•
•
On the basis of even more limited evidence, HAV measured in controlled ‘in-field’
conditions is of a similar order of magnitude to that found on some farms;
Results from the ISO 5008 test track do not provide a good indication of vibration
magnitudes in controlled (SRI) ‘in-field’ conditions, and are therefore even less
useful for predicting ‘on-farm’ vibration exposures. Given that an ISO test track of
wooden slat construction is of questionable suitability for quantification of vibration
emission levels from machines of this type (ATVs), arguably this is to be expected.
131
132
7.
DISCUSSION
The overall objective of this investigation was to determine Whole-Body Vibration (WBV)
emission and exposure levels associated with representative ‘state-of-the-art’ agricultural
vehicles, both whilst traversing ISO 5008 standard ride vibration test tracks and whilst
performing typical agricultural operations, both in (representative) controlled ‘in-field’
conditions and during normal operation on working farms. Additionally, the investigation
considered the consequences of prescribing limits for operator WBV daily exposure, upon
agricultural vehicle usage patterns in the U.K. The investigation targeted three generic types
of agricultural vehicle (self-propelled sprayers, all-terrain vehicles (ATVs), and agricultural
tractors), all whilst operating (‘in-field’ and ‘on-farm’), the latter with a range of attached
agricultural implements.
7.1
SELF-PROPELLED SPRAYERS
The section of the investigation concerning self-propelled sprayers (Section 4) followed the
established format described above, studying two suspension design variants of otherwise
identical machines. When attempting to compare WBV emission levels recorded ‘in-field’
and upon the ISO test tracks, it is important to select appropriate track and field test
conditions (and vehicle states) for comparison. Fortunately, this was probably one of the few
instances where a degree of comparability existed between certain of the test conditions,
namely the ISO 100 m ‘smoother’ track (at approx. 12 km/h) and the SRI ‘farm track’, the
former having originally been designed to represent something rather like the latter.
Additionally, the ‘laden’ sprayer condition in which some of the ISO track work was
conducted was identical to that used during the SRI ‘in-field’ work. The resulting similarity
(or lack of it) between results is therefore of interest.
Upon the ISO test track (only the 100 m ‘smoother’ version used), vertical (Z) axis WBV
emission levels were consistently higher than those recorded in the longitudinal (X) or
transverse (Y) axes, irrespective of vehicle forward speed or suspension system capability.
However, in many instances, Y-axis WBV levels approached those recorded in the Z-axis.
The (forward control) position of the operator’s cab, well forward of the sprayer’s pitch
centre, probably caused a proportion of vehicle pitch to be translated into near vertical
movement of the cab floor, hence the high acceleration levels in this axis. Fitting softer
‘flotation’ tyres, rather than the stiffer ‘standard’ variants, caused significant increases in cab
floor transverse (Y) axis acceleration levels during both the ISO track and ‘in-field’ test
programmes, almost certainly because the lower inflation pressures of the flotation tyres
resulted in lower dynamic stiffness and hence greater low-frequency transverse roll motion of
the vehicle. Consequently, during the ‘in-field’ test programme, when fitted with ‘flotation’
tyres, machine transverse (Y) axis WBV emission levels were almost always the largest.
The most significant physical difference between the test machines concerned the designs of
their suspension systems (coil spring & hydraulic damper and self-levelling air spring &
hydraulic damper). In theory the ISO track provided a good opportunity to investigate the
relative practical benefits of these designs. Whilst longitudinal (X) and transverse (Y) axis
cab floor acceleration levels upon the ISO track were comparable between the vehicles, the
vertical (Z) axis WBV levels recorded upon the air spring suspension vehicle were
significantly (up to 30%) lower than those of the coil spring suspension machine. ‘In-field’
performance indicated lower WBV levels upon the air spring vehicle in both vertical (Z) and
longitudinal (X) axial directions.
133
Additionally, WBV emission levels upon the coil spring suspension vehicle were found to
increase when in ‘laden’ condition, whereas the air suspension machine did not exhibit this
undesirable characteristic. However, one word of caution when comparing vehicle WBV
emission levels: the air spring suspension seat fitted to the air spring suspension vehicle was
more effective in reducing vertical (Z) axis vibration than the (rather ‘tired’) mechanical
suspension seat fitted to the coil spring suspension machine. Operator ‘seat’ WBV emission
levels were always higher than those measured upon the cab floor, but this trend was less
pronounced upon the air suspension machine, almost certainly due to the disparate suspension
seats (of both different design and age) fitted to the test machines. Consequently, the degree
of effectiveness of different suspension seats upon ‘seat’ WBV level reduction should not be
confused with the performance of the vehicle suspension system. For this reason, cab floor
WBV levels often provide a more reliable basis for vehicle suspension system evaluation (but
not operator WBV exposure assessment).
Travelling over the ISO track with the sprayer booms (24 m) extended (rather than ‘stowed’),
consistently increased longitudinal (X) axis and, less frequently, vertical (Z) axis WBV levels.
Transverse (Y) axis levels decreased slightly or remained the same. The coil spring
suspension machine demonstrated these trends more consistently than air spring suspension
vehicle. Vehicle loading condition (laden or unladen) had no effect upon these trends, which
are probably a result of the sprayer weight distribution and pitch centre moving rearwards
when the booms are unfolded, their stowed position being forwards alongside the operator’s
cab.
During the SRI ‘in-field’ programme, farm ‘track’ travel was understandably found to
generate the highest WBV emission levels of all test conditions investigated, irrespective of
vehicle suspension system design, tyre fitment or the measurement location. During farm
‘track’ travel the largest WBV levels were always found in the transverse (Y) axial direction.
WBV emission levels were lower during both ‘road’ travel and ‘spraying’ operations but,
when fitted with ‘flotation’ tyres, the highest overall average r.m.s. (Aeq) WBV levels
generated upon the vehicles in these conditions were still found in the transverse (Y) axis.
However, when fitted with ‘standard’ tyres, the behaviour of the vehicles changed,
vertical (Z) axis WBV emissions becoming greater than those of the longitudinal (X) or
transverse (Y) axes during ‘road’ travel and ‘spraying’, irrespective of the vehicle design or
measurement location (floor or seat). The apparent superiority of transverse (Y) axis WBV
would not necessarily have been so prevalent were it not for the 1.4x multiplying factor,
stipulated by the Directive for application to horizontal axes values (see Section 3.1.2).
Comparison of ‘in-field’ and ISO test track data (as discussed above) illustrated very good
agreement between transverse (Y) axis WBV levels, but a less agreement between
longitudinal (X) axis WBV and very poor agreement in the vertical (Z) axis. Vehicle tyre
equipment was found to have no effect upon the degree of agreement observed.
The majority of ‘on-farm’ self-propelled sprayers, all of which were fitted with ‘standard’
tyres, were found to generate similar WBV emission levels to those experienced during the
SRI ‘in-field’ programme, vibration magnitudes being significantly different in only one ‘onfarm’ instance, which was deemed a result of disparate (unusually rough) ‘on-farm’ operating
conditions. ‘On-farm’ seat acceleration levels were higher than those recorded upon the
sprayer cab floor in all instances, transverse (Y) axis WBV emissions generally being the
largest of those measured upon the operator’s seat, but vertical (Z) axis emissions frequently
taking precedence amongst measurements made upon the cab floor. However, in many
instances the differences between individual axis WBV magnitudes was small (see Tables 4.5
134
& 4.6). The greater (vertical) distance between the vehicle’s roll centre and the seat surface
undoubtedly assists the apparent superiority of the ‘operator’s seat’ Y-axis values.
Of the ‘on-farm’ sprayers surveyed, a majority (57%) were operated for more than 8 hours
per day during the survey week, a number being operated for up to 14 hours per day. Despite
this, the total weekly operation period was a remarkably consistent average of 45 hours.
Considering the likely impact of the PA(V)D, all of the ‘on-farm’ sprayers surveyed exceeded
the 8-hour Exposure Action Value (EAV) within 8 hours operation, and will require
implementation of measures to reduce and manage employee daily WBV exposure if 8 or
more hours operation per day are common place. Possible measures are outlined in
Section 3.1.3. Only one example exceeded the Exposure Limit Value (ELV) within 8 hours
operation, in an uncommonly rough application. Working day length would have to increase
to unsustainable levels (greater than 22 hours per day) for the other sprayers surveyed to
exceed the A(8) ELV. Consequently, the requirements of the PA(V)D are not likely to
restrict the operation of large, modern, ‘state-of-the-art’ self-propelled sprayers during an
8 hour day, and will not become a limitation even if the working day were to lengthen
significantly (see Table 7.1). Daily working patterns, including rest breaks, machine
maintenance, re-filling and periods of general inactivity, can all contribute to a reduction in
the Aeq WBV exposure value.
However, variation in WBV exposure levels was found to be present between certain ‘onfarm’ example sprayers. This was not assisted by the relatively small number of individual
machines investigated; the 3 replicates performed being adequate to indicate ‘on-farm’ WBV
levels, but insufficient to determine the degree of WBV emission level variability between
supposedly identical vehicles / operations. Therefore, whilst the consistency between WBV
emissions encountered during ‘on-farm’ sprayer operation is encouraging, a more detailed
investigation of similar format, but comprising a larger number of measurement replications,
is advisable in order to enable creation of a robust database of generic WBV emission data for
modern self-propelled agricultural sprayers. Additionally, differences between ISO test track
and ‘in-field’ WBV data require closer investigation if improved test track WBV assessment
methodologies are to be developed to assist the industry to embrace the Directive.
Nonetheless, given the evidence provided by this investigation, it seems unlikely that the
requirements of the Directive will restrict the daily or weekly usage of self-propelled
agricultural sprayers in the UK.
135
7.2
AGRICULTURAL TRACTORS
As discussed previously in greater detail (see Section 5), four 4wd tractors in the 90 – 130 kW
engine power range were selected for WBV measurement during travel upon ISO ride
vibration test tracks and operation in controlled (SRI) ‘in-field’ conditions. Each vehicle
embodied different levels of suspension system complexity, these being:•
•
•
•
Unsuspended
Suspended cab
Suspended front axle & cab
Fully suspended (front & rear axle).
Only examples of the suspended front axle & cab tractor and the fully suspended (front & rear
axle) tractor participated in the subsequent ‘on-farm’ WBV evaluation, but these vehicles
performed field operations largely identical to those undertaken previously at SRI, namely
ploughing, plough transport, cultivating, spraying / fertiliser spreading, and trailer transport,
thereby providing a direct comparison with the SRI ‘in-field’ work.
The SRI ‘in-field’ WBV emission measurement programme demonstrated that the type of
agricultural operation / task performed has a greater influence upon resulting WBV emission
levels than the suspension system capability of the test tractors performing each task (see
Figures 5.13 & 5.22 and Appendices 2.5 & 2.6). Spraying and plough transport generated
low WBV emission levels: ploughing generated moderate levels, whereas trailer transport
generated moderate to high levels and cultivating generated high WBV levels (see Tables 7.1
& 7.2). This confirmed the previous belief that the WBV levels generated during moderatehigher speed operations are highly dependent upon prevailing surface conditions.
The WBV levels recorded upon the operator’s seat during the SRI controlled ‘in-field’ test
programme (see Figure 5.22) suggested that operators performing any of the tractoroperations with any of the surveyed vehicles will exceed the proposed PA(V)D A(8)
Exposure Action Value (EAV) within 8 hours operation, requiring implementation of
measures to reduce and manage employee daily WBV exposure if 8 or more hours operation
per day are commonplace. Additionally, (rough ground) cultivating and trailer transport
operations will cause the proposed PA(V)D A(8) Exposure Limit Value (ELV) to be
exceeded during an 8-hour working period, potentially necessitating changes in operating
methods or equipment to reduce WBV levels or, alternatively, limitation of daily operating
duration. Ploughing may also cause the ELV to be exceeded, but only if the work period
extends to approx. 12 – 14 hours per day. In all instances seat acceleration levels were higher
than those recorded upon the tractor cab floor (see Figures 5.13 & 5.22 and Appendices 2.5 &
2.6).
With the exception of cultivating and trailer transport, little significant difference was found
between the cab floor WBV emission levels of the test tractors (suspension system designs)
whilst performing the selected ‘in-field’ operations (see Figure 5.13); at least when WBV
levels were evaluated by the ISO 2631-1:1997 “Effect of Vibration on Health” methodology
favoured by the Directive (‘largest single weighted axis’: see Section 3.1.2). Arguably the
point vibration total value (vector sum or root-sum-of-squares: see Appendices 2.5 & 2.6),
which represents the acceleration levels present in all axial directions as opposed to solely the
axis of the largest magnitude, is a better indicator of the differences in vehicle ride comfort
perceived by the operator during fieldwork. The technique employed also relates more
closely to the ISO 2631-1:1997 “Effect of Vibration on Comfort” evaluation methodology,
but retains the additional weighting of horizontal axis values.
136
Table 7.1 Relative WBV magnitudes arising from agricultural tractor operations
performed during the SRI ‘in-field’ investigation
WBV Emission Level (energy-equivalent continuous (overall average) r.m.s. acceleration)
Low
Moderate
High
Spraying / Fertiliser Spreading
Ploughing
Cultivating (rough ground)
Plough Transport
Trailer Transport
Calculation of cab floor vector sum acceleration levels by this method returned the same
relative ranking and distribution of individual field operations, clarifying the relative
differences between suspension system performance (resultant WBV emission levels) as
being small during spraying and plough transport; moderate during ploughing and trailer
transport; and large during cultivating: a case of the more extreme the application, the greater
the difference between the suspension systems.
Whilst no vehicle / suspension system design appeared to be particularly superior for all the
field operations investigated, and it should be noted that during certain operations the
differences between the vehicles were small, evaluation of cab floor or operator seat WBV
levels by the vector sum (RSS) method did suggest the ride comfort of the fully
suspended (front & rear axle) tractor and the suspended front axle & cab tractor to be
marginally superior to that of the other test vehicles in the majority of instances. Evaluation
of cab floor WBV levels by the largest single axis method displayed a similar trend between
vehicle types, but this was not so apparent amongst operator seat WBV values derived by this
technique: and the latter are, of course, the WBV emission levels from which operator daily
exposure would be derived.
Specific ‘on-farm’ tractor / operation combinations generated WBV emission levels similar to
those experienced during the SRI ‘in-field’ measurement programme, particularly in the case
of ‘on-farm’ examples of the fully suspended (front & rear axle) tractor, which generated its
highest WBV levels during cultivating and trailer transport operations. However, whilst SRI
‘in-field’ WBV levels initially appeared higher than those from corresponding ‘on-farm’
machines / operations (see Figure 5.40), closer investigation showed that ‘on-farm’ daily
working patterns, including rest breaks, machine maintenance and periods of general
inactivity, all contributed to a reduction in the r.m.s. Aeq WBV exposure value, but not in the
vibration dose value (VDV). Removal of these periods of inactivity resulted in much greater
similarity between SRI ‘in-field’ and ‘on-farm’ WBV levels (see Figure 5.41).
During the majority of field operations (spraying / fertiliser spreading, ploughing &
cultivating) and plough transport, the largest operator seat WBV levels (overall average r.m.s.
(Aeq) acceleration) were mainly encountered in the transverse (Y) axis, when WBV was
evaluated by the largest single weighted axis method. However, during trailer transport
longitudinal (X) axis acceleration took precedence (see Figures 5.24 & 5.25), probably a
result of vertical force input to the tractor pickup hitch (from the trailer drawbar) accentuating
vehicle pitch, as discussed in Section 5.3.6. Horizontal (X & Y) axis seat Aeq acceleration
levels were in all instances higher than those recorded upon the cab floor (see Figures 5.26 &
137
5.27 and further discussion in Section 7.4). Nonetheless, maximum peak accelerations were
frequently found to occur in the vertical (Z-axis) direction.
The apparent importance of the horizontal (X & Y) axes WBV levels reported in this
investigation is undoubtedly accentuated (and arguably distorted) by use of the ISO 26311:1997 “Effect of Vibration on Health” methodology favoured by the Directive (‘largest
single weighted axis’: see Section 3.1.2). WBV levels in each axial direction are compared
individually with the EAV and ELV following application of frequency weightings and axis
weighting factors (1.4x for X & Y axes): the latter effectively increasing the magnitudes of
the horizontal (X & Y) axes WBV values.
However, as previously discussed, whilst the Directive requires WBV exposure levels to be
assessed separately in each axial direction, and the measurement axis with the greatest
(overall average) magnitude be identified, action is required to reduce WBV exposure in all
axial directions where the EAV is exceeded (see Section 3.1.3). In practical terms whilst, for
a given vehicle / application, the longitudinal (X) or transverse (Y) measurement axes may
exhibit the highest axis-weighted overall-average acceleration levels, marginally lower Aeq
levels in the remaining axial directions will also require implementation of appropriate
vibration exposure-reducing measures if daily exposure levels exceed the EAV, and
especially if significant peak acceleration events (shocks and jolts) are present.
Virtually all (~ 95%) of the ‘on-farm’ tractor-operations surveyed exceeded the PA(V)D
8 hour Exposure Action Value (EAV) within 8 hours operation, and will require
implementation of measures to reduce and manage employee daily WBV exposure if 8 or
more hours operation per day are common place. Possible measures are outlined in
Section 3.1.3. Relatively few tractor-operations (~ 9%) exceeded the Exposure Limit
Value (ELV) within 8 hours operation. However, if the working day length were to increase
to 15 hours, up to 27% of the vehicles surveyed would probably exceed the ELV.
During agricultural tractor operations, the VDV-specified EAV represents a considerably
lower operating duration threshold than the corresponding A(8) EAV (see Figure 5.37).
Arguably this disparity offers greater overall protection to the vehicle operator. For instance,
during part-day operation the EAV is more likely to be exceeded (requiring implementation
of WBV exposure reduction / management measures) if specified in VDV terms. However,
over a full (8-hour) working day the difference appears less significant; ~95% of the ‘onfarm’ tractors surveyed exceeded the VDV EAV in 8 hours operation, whilst ~82% exceeded
the A(8) EAV in the same period. This issue is discussed further in Section 7.4.
A majority (57%) of the tractors surveyed were operated for more than 8 hours per day and a
number were used for up to 16 hours per day (see Figure 5.39). Consequently, whilst the
requirements of the Directive are not likely to restrict the operation of large, modern, ‘stateof-the-art’ tractors during an 8-hour working day, they may well pose a restriction, in terms
maximum permissible daily operating period, if the working day were to lengthen
significantly (greater than 8 hours). The onset of this limitation would be more rapid if the
vehicles in question are smaller (lighter) or offer lower levels of operator comfort, WBV
levels having been shown to be higher on smaller, more basic tractors in comparable
operating conditions (Scarlett et al., 2002). Nonetheless over 50% of the ‘on-farm’ tractors /
operations surveyed would have to work for approaching 24 hours per day to reach the ELV
(see Figure 5.38).
138
As discussed earlier (see Section 3.1.2), the Directive provides a derogation permitting
weekly averaging of daily personal vibration exposures, but this is intended for use in
circumstances where occasional high vibration exposure levels (greater than the ELV) are
likely to be encountered during the working week, but otherwise levels are usually low
(below the EAV). Such qualifying circumstances would appear to be extremely rare in
agricultural tractor operations. The situation is (possibly) complicated further by the fact that
the resulting weekly average personal vibration exposure (A(8)week) represents the total
exposure occurring within a period of seven consecutive days, but normalised to a reference
duration of 40 hours, whereas modern agricultural practices can frequently cause the working
week duration to exceed 80 hours at peak times. Issues of seasonal timeliness, primarily
relating to utilisation of favourable soil and weather conditions, place somewhat unique
demands upon agricultural operations, requiring extended working day lengths at peak times.
The true extent of the impact the PA(V)D will have upon industries which interact strongly
with the natural environment will not be realised until some time after the attempted
implementation of the Directive. However, it is probable that by selection of appropriate
work equipment and the provision of adequate operator training in methods of WBV exposure
reduction, the impact of the Directive upon such industries may be minimised.
During certain operations (cultivating and trailer transport), ‘on-farm’ examples of the
suspended front axle & cab tractor generated lower WBV emission levels than the
comparable model SRI ‘in-field’ tractor and also the ‘on-farm’ examples of the fully
suspended (front & rear axle) tractor. This was deemed to be due to disparate operating
conditions and intensity of machine operation, the ‘on-farm’ fully suspended (front & rear
axle) tractors being, in general, operated at higher forward speeds, over rougher surface
conditions, than the suspended front axle & cab tractors. This may, however, be a
consequence of a greater proportion of farm contractor rather than owner-operator ownership
of these (fully suspended) machines. Additionally, the higher cost of these vehicles
frequently necessitates more intense ‘on-farm’ utilisation compared with tractors of more
‘conventional’ design.
Comparison of ISO test track WBV emission levels with those recorded during SRI ‘in-field’
operations is fraught with difficulty, mainly due to differences in vehicle mass, axle weight
distributions, tyre inflation pressures and external force systems between the test conditions.
The ISO ride vibration tracks were originally developed as a research tool and a method of
assessing tractor suspension seat performance. As such it is still useful in comparative testing
of axle and cab suspension systems, although suspension seat testing has long since been
transferred to the laboratory (ISO 5007:2003). The (current ISO 5008) measurement of WBV
emission levels upon a solo tractor traversing these tracks bears no relation to practical
agricultural operating conditions, to the extent that any significant correlation between ‘track’
and ‘field’ results would be a cause for concern. The recent updating of ISO 5008
(ISO, 2002) has done little to improve this situation.
Nonetheless, defined, repeatable WBV test conditions and methodologies are required for
agricultural tractors and other ‘off-road’ vehicles. In the future (2007 onwards) it is probable
that new tractor customers, particularly high intensity users who expect their employees’ daily
WBV exposure to frequently exceed the EAV, will favour cost-effective equipment
embodying WBV-reducing design features, thereby assisting compliance with the PA(V)D.
139
It seems reasonable to expect those customers will also desire WBV emission data from
manufacturers to support the claimed effectiveness of the aforesaid features and assist
justification of purchase decisions. If so, that data should:i)
Enable direct comparison between different vehicle models, ranges and competitive
brands;
ii)
Relate closely to the likely WBV emissions of the said vehicle(s) in agricultural
applications / operating conditions.
The ISO 5008 test methodology currently satisfies (i) but falls significantly short of (ii).
The PA(V)D does not require equipment manufacturers to state likely WBV emission levels
of their products, but the EU Machinery Directive (98/37/EC) (EEC, 1998) does require such
a declaration in the operators handbook if WBV emission levels equal or exceed 0.5 m/s2.
These emission levels were regularly exceeded by all tractors during the SRI ‘in-field’ trials
(see Figure 5.22). However, agricultural tractors are not currently included within the scope
of the Machinery Directive, but all other agricultural machinery (self-propelled or otherwise)
is, i.e. both self-propelled sprayers and ATVs. Consequently there is scope for further
analysis of the results obtained from this investigation and development / refinement of ride
vibration track test methodologies, with a view to providing a consistent, realistic, ideally
independent method of agricultural tractor WBV assessment. Without such a reliable
method, vehicle customers will be unable to have confidence in the relative WBV emission
levels stated by manufacturers (either voluntarily or for legislative compliance) for their
respective machines.
Variation in WBV exposure values was found between certain examples of similar ‘on-farm’
tractors / operations (see Figures 5.33 & 5.34). This was not assisted by the relatively small
number of individual tractor / operation combinations investigated; the 3 replicates performed
being adequate to indicate ‘on-farm’ WBV levels, but insufficient to determine the degree of
WBV emission variability between supposedly identical tractors & operations. A more
detailed study of similar ‘on-farm’ format, but comprising a larger number of measurement
replications, is required to enable creation of a robust database of generic WBV emission data
for modern agricultural tractor / implement combinations, in order to enable employers to
estimate the potential daily occupational vibration exposure of their employee’s and thereby
comply with the requirements of the Directive.
In theory such a database need only be sufficiently detailed to enable an employer to
determine whether exceedance of the EAV and/or ELV during a given (typical) operating
period is unlikely, possible or probable. However, as indicated by Table 7.3, the
recommended methods for determining employee daily WBV exposure levels (and their
subsequent complexity & cost) are dependent upon the magnitudes of the exposure levels
likely to be encountered. If daily vibration exposure is likely to approach the ELV (and most
certainly if it may exceed it), then a representative workplace measurement of vibration
exposure may be either advisable or necessary. For this reason, especially given the location
of tractor operation WBV daily exposure levels between the EAV and ELV (see Table 7.2), a
robust database of generic WBV emission data would be of value, enabling an employer to
target specific operations of concern in greater detail, whilst utilising recommended WBV
estimation / calculation techniques for other (lower exposure level) operations, with
confidence.
140
7.3
ALL-TERRAIN VEHICLES (ATVs)
It is the case with drivers of ATVs, probably more so than those of any other farm vehicle,
that they have freedom of choice with regard to travel speed. They may also have to cross the
roughest ground. It is therefore not surprising that the range of seat WBV magnitudes for
similar vehicles performing similar tasks is of the order of ±50% (see Section 6). This is
greater than the difference between different machines (ATVs) travelling over the same
ground at the same speed (see Figure 6.15). The advantage of the lower vibration machines
may be taken by drivers in the form of lower vibration exposure. However, it is just as likely
to be transformed into higher operating speeds for those who control their speed according to
their personal comfort. Therefore the exposure levels that we have measured are likely to be
representative of all ATVs of this size (300-400 cc engine capacity).
As long as stock farmers use these machines for only ½ - 1 hour per day, they are unlikely to
exceed the PA(V)D 8-hour Exposure Limit Value: whether they exceed the Exposure Action
Value depends on whether one uses the VDV or the A(8) assessment criterion.
However, ATVs are also used for recreational purposes, often by hill farmers seeking to
diversify into a sport or entertainment enterprise. In such cases it is to be expected that
drivers, particularly instructors, will use such machines for considerably longer than 1-hour
per day. In these cases they will require management of vibration exposure, including
advising of the vibration risk to health. It is also likely that drivers will intentionally seek to
travel at higher speeds and/or over rougher terrain as part of the desired ‘experience’. Such
vehicle use is beyond the scope of the present study, but it would be irresponsible not to
mention the probability that it could lead to vibration exposures in excess of the ELV.
One reason for recording driver presence upon the seat had been to exclude those rough parts
of any journey during which the driver stood up to make his/her ride more comfortable. In
the event, eliminating periods when the driver was not on the vehicle seat made only a small
difference (generally less than 10%) to his/her overall exposure, and the difference was no
greater when measured in terms of VDV rather than as r.m.s. (A(8)). Therefore, the
anticipated effect was not found. However, the drivers did spend some time out of the saddle,
and this did reduce their overall exposure slightly. Time off the seat does not equate to time
spent standing on the footrests, but rather was mostly time during which the operator
dismounted. From the records obtained in this investigation, it is not possible to identify any
time the operator spent standing on the footrests.
In the ‘on-farm’ data, both transverse (Y) and vertical (Z) axes exhibited similar magnitudes
of WBV on the seat, with longitudinal (X) axis WBV being rather lower. This would not
have been the case without the 1.4x multiplying factor stipulated for the horizontal axes (see
Section 3.1.2). It was also different from what was found in the SRI controlled ‘in-field’
trials, where WBV levels in the vertical (Z) axis clearly dominated. A likely explanation is
that the operating surfaces at SRI were not as severe as those found on the farms. This would
have allowed higher vehicle forward speeds, with more vertical (Z) and less roll (Y-axis)
motion than on the farms. A similar effect has been observed with tractors driven over the
two different ISO 5008 tracks. The ‘rougher’ (35 m) track, traversed at lower speeds,
produces more transverse (y-axis) and less vertical (Z-axis) vibration than the ‘smoother’
(100 m) track. It may be concluded that the SRI ‘in-field’ test circuit was not rough enough
to be representative of ‘on-farm’ conditions. Nevertheless, that circuit did provide a better
comparison between the different machines than did the ISO 5008 track.
141
ISO 5008 specifies ordinates for two pairs of test tracks, each pair being the left and right
wheel tracks. The standard allows the tracks to be constructed of separate slats, usually
wooden, for each ordinate, or of moulded concrete, which can be smoothed between
ordinates. The separate slats were deemed to be acceptable for use by tractors and other
vehicles with tyres of large diameter. The results obtained in this study suggest that they are
not suitable for ATVs, whose tyre diameter and chassis structural stiffness are different to that
of a ‘conventional’ tractor. A moulded concrete track may well have been more appropriate
for ATV evaluation, but unfortunately could not be compared in this study. However, while
the ‘smoother’ (100 m) track did not produce the equivalent transverse (Y-axis) motion found
on farms, attempts to use the ‘rougher’ (35 m) track had to be abandoned because of the
difficulty of maintaining a constant forward speed, and because the driver had to stand out of
the seat in order to control the vehicle. It is difficult to see how ISO 5008 could be adapted to
be suitable for ATV WBV measurement.
Although only two sets of hand-arm vibration data were obtained from farms, these were
consistent with data obtained from the controlled ‘in-field’ tests. The data suggests that the
EAV and ELV are likely to be reached sooner for hand-arm vibration than for whole-body
vibration on these machines. However, as for WBV, the short durations of use encountered
on livestock farms enables the vehicles to be used without exceeding the daily ELV.
The same cannot be said for the vibration on the footrests. If the directive is followed
precisely, this has to be assessed as whole-body vibration in the same way as that on the seat.
And in that case, all the ‘on-farm’ example vehicles exceeded the ELV. However, a layman
who is concerned about the amount of vibration reaching the lower back might be moved to
ask how it is that the two inputs of seat and footrest(s) come to be considered equivalent?
People stand up to enable their legs to cushion the effect of rough rides, and subjectively it
works. The authors of this study believe more research relevant to this condition is required.
7.4
OVERALL DISCUSSION
Although the UK agricultural workforce has reduced substantially in recent years, the
remaining workers are spending a greater proportion of their time operating mobile machines
which can create exposure to whole-body vibration. This is primarily a result of the use of
fewer, larger (higher power) tractors in the UK (see Figures 2.9 & 2.10). Their smaller
number and their higher initial cost requires greater annual utilisation of these vehicles, which
translates into a greater number of working hours spent ‘in the driving seat’. A similar
scenario applies to specialist self-propelled vehicles such as self-propelled sprayers, forage
and sugar beet harvesters. The increased popularity of agricultural contractors and contract
farming operations may potentially lead to operators spending a greater number of longer
working days performing specific operations at peak times of the year. Whole-body vibration
exposure data for the ‘on-farm’ tractors in this survey suggests that there is a wide variation
of exposure levels for similar agricultural operations / tasks (see Table 7.2). One possible
(but unsubstantiated) explanation for this is the potential difference in driver operating
technique / style between farmers who may perhaps be owner-drivers of the machines in
question, and have fixed volumes of work to undertake without excessive time pressures (in a
normal season). Alternatively, the staff of contractors may need to work more intensely /
faster and for longer periods in each day, in order to maximise work volumes and potential
business income.
142
Table 7.2 Summary of ‘on-farm’ agricultural vehicle operations investigated
Vehicle / Activity
S.P. Sprayer
Tractor – Spraying
Seat overall
average r.m.s.
(Aeq) WBV
level (m/s2)
Time to EAV
(A(8))
(hrs:mins)
0.53 – 0.69
4:12 – 7:7
22 - >24
0.36 – 0.78
3:17 – 15:26
17:23 - >24
2:19 – 8:20
12:14 - >24
1:36 – 9:3
8:26 - >24
1:2 – 7:7
1:2 – 2:46
Time to ELV
(A(8))
(hrs:mins)
Average
Working
Day
(hrs)
Likelihood of Exceeding
Value in a Normal
Working Day:EAV
ELV
10.1
Yes
No
8.9
Probably
No
8.9
Yes
Unlikely
8.9
Yes
Possibly
5:29 - >24
8.9
Yes
Possibly
5:29 – 14:39
1-2
Possibly
V.unlikely
(0.5 – 0.74)
Tractor - Ploughing
0.49 – 0.93
(0.73 – 0.89)
Tractor – Trailer
Transport
Tractor – Cultivating
0.47 – 1.12
(1.05 – 1.32)
0.53 – 1.39
(1.2 – 1.49)
ATV
NB:-
0.85 – 1.39
Tractor WBV data in parentheses originates from SRI ‘in-field’ measurements (performed in controlled
field conditions) and encompasses all tractor suspension system designs investigated;
All other WBV data above relates to ‘on-farm’ measurements and, in the case of tractors, only includes
suspended front axle & cab, and fully suspended (front & rear axle) tractor models.
This limited survey has provided reasonable indication of the factors that affect WBV daily
exposure during ‘on-farm’ use of selected agricultural vehicles, but the range of WBV levels
within operations is large (frequently +/- 50%: see Table 7.2), particularly in the case of
specific ‘on-farm’ tractor-implement operations. If a comprehensive, generic database of
agricultural vehicle WBV emission levels is deemed desirable, to provide farmers with
adequately robust data to enable estimation of likely WBV daily exposure levels (as required
by the Directive), or alternatively to identify the need for workplace measurement of WBV
exposure levels (see Table 7.3), then a more comprehensive study is required, embodying a
greater number of measurement replications. This issue, which applies primarily to tractorimplement operations, is discussed in greater detail in Section 7.2.
Operators of virtually all the ‘on-farm’ examples of tractor operations and the self-propelled
sprayers would have received WBV daily exposures in excess of the Exposure Action
Value (EAV) within 8 hours operation, whether the EAV was evaluated according to the
r.m.s. (A(8)) or the VDV criterion (see Table 7.2). Given their generally short daily operating
periods of ½ - 1 hour, the ATVs would have exceeded the EAV only if specified according to
the VDV criterion (see Table 6.6). However, these vehicles may also exceed the EAV for
hand-arm vibration (see Section 6.4.3). In all of these instances, daily vibration exposure in
143
excess of the EAV will require action to be taken on the part of the employer, including
implementation of measures to reduce and manage worker vibration exposure, and advising
workers of the associated health risk (see Section 3.1.3).
With regard to the PA(V)D Exposure Limit Value (ELV), of the tractor operations studied
‘on-farm’, only cultivating provided examples where worker daily exposure would have
exceeded the ELV within an 8-hour working day, although trailer transport operations
approached the ELV in certain instances (see Table 7.2). Longer working days, extending to
12-14 hours, could lead to some ploughing and some trailer transport operations causing
operator WBV exposure to exceed the ELV. Of the self-propelled sprayers, only on one,
brief occasion were ‘on-farm’ WBV exposure levels severe enough to exceed the ELV, if the
exposure had continued for 8 hours. However, that particular application seemed to be
sufficiently unusual for such extreme conditions to be experienced for the entire (~4-hour)
measurement period. Finally, the ATVs used on stock farms were not operated for
sufficiently long (total) periods in each given day for the ELV to be exceeded, although the
case might be different for recreational use of these vehicles.
The controlled ‘in-field’ tests performed at SRI generally produced average weighted r.m.s.
(Aeq) acceleration levels of a similar order of magnitude to those found ‘on-farm’. For the
agricultural tractor operations, the SRI ‘in-field’ WBV levels were slightly higher than those
from ‘on-farm’, as would be expected because of the lack of (maintenance or rest) breaks
during the measurement periods at SRI. For the self-propelled sprayers, one farm record
generated considerably higher WBV levels than either the SRI ‘in-field’ or the other ‘onfarm’ instances (see Figure 4.19). This may have been, and indeed is believed to be, an
unusual occurrence, but it indicates the need for some care in establishing generic vibration
values for certain operations. With that exception, it is probably fair to conclude that the SRI
controlled ‘in-field’ tests were reasonably representative of more general farm work.
However, for the ATVs a more severe ground surface might have given more representative
transverse (Y-axis) motion, with the necessarily lower forward speeds leading to relatively
lower vertical (Z-axis) vibration levels (see Section 6.4.3).
The ISO 5008:2002 WBV test tracks yielded much larger WBV magnitudes for the tractors
and self-propelled sprayers, than were found in the controlled field trials. This is a natural
result of the origins of the track, these being to represent the most severe ride conditions
found in normal farm vehicle operation. The relevance to WBV levels found upon tractors in
normal work is further compromised by the lack of any attached implements or trailers, the
applied forces from which can have a large effect on the dynamics of the tractor.
Consideration needs to be given to practical ways of including these aspects within future
attempts to improve this standardised test methodology, and indeed the role such a
methodology can play in off-road vehicle WBV emissions assessment (discussed in greater
detail within Section 7.2). ATVs, whose use is more usually over rough ground surfaces,
were tested more appropriately by the ISO 5008 (100 m ‘smoother’) track. However, the
current form of SRI ISO 5008 track construction, comprising separate wooden slats, was a
probable cause of discrepancies in the footrest and handlebar vibration levels, and in some
cases possibly also in the seat vibration. This difficulty might be overcome if a moulded
concrete form of the track construction (an intended future modification at SRI) were to be
used.
144
Table 7.3 Proposed method(s) for determination of WBV daily exposure level
Likely WBV daily exposure level
Less than EAV
~ EAV
→ ELV
Calculate likely daily exposure
level from manufacturer’s stated
WBV emission values
Calculate likely daily exposure
level from manufacturer’s stated
WBV emission values
Measure WBV exposure levels
in the workplace
Or
Or
Derive from published WBV
exposure data for the generic
machine type/operation
(via proposed HSE website
calculator)
Derive from published WBV
exposure data for the generic
machine type/operation
(via proposed HSE website
calculator)
The differences between WBV emission levels generated by individual tractor (axle and cab)
suspension designs were generally less than those evident between the different agricultural
tasks performed (spraying / fertiliser spreading, ploughing, plough transport, cultivating,
trailer transport), particularly when evaluated by the ‘largest single weighted axis’
methodology favoured by the Directive. Every effort was made to minimise variation in the
controlled ‘in-field’ test conditions, in order to highlight differences in tractor (suspension
system) performance, but small differences no doubt existed between ground surface
conditions for the same field task. Nonetheless, whilst no vehicle / suspension system design
appeared to be particularly superior for all the field operations investigated, and it should be
noted that during certain operations the differences between the vehicles were small,
evaluation of cab floor or operator seat WBV levels by the vector sum (RSS) method did
suggest the ride comfort of the fully suspended (front & rear axle) tractor and the suspended
front axle & cab tractor to be marginally superior to that of the other test vehicles in the
majority of instances. Evaluation of cab floor WBV levels by the largest single axis method
displayed a similar trend between vehicle types, but this was not so apparent amongst
operator seat WBV values derived by this technique: and the latter are, of course, the WBV
emission levels from which operator daily exposure would be derived. Nonetheless, it is
possible to conclude that, for a given task and given operating conditions, there are
advantages in selecting the tractor with the most appropriate suspension system capability.
For the self-propelled sprayers, the recently developed self-levelling air spring suspension
system was found to offer useful advantages over the earlier mechanical coil spring and
damper design in both ISO track and controlled ‘in-field’ trials. The flotation tyres, despite
the apparent advantage of being softer, actually contributed to greater levels of WBV by
increasing the vehicles’ transverse (Y-axis) roll motion.
A feature common to whole-body vibration on the tractor and self-propelled sprayer
operations investigated is the predominance of high (axis-weighted) overall average WBV
levels in the transverse (Y) axial direction. The apparent importance of the horizontal (X &
Y) axes WBV levels reported in this investigation is undoubtedly accentuated (and arguably
distorted) by use of the ISO 2631-1:1997 “Effect of Vibration on Health” methodology
favoured by the Directive (‘largest single weighted axis’: see Section 3.1.2). WBV levels in
each axial direction are compared individually with the EAV and ELV following application
of frequency weightings and axis weighting factors (1.4x for X & Y axes): the latter
145
effectively increasing the magnitudes of the horizontal (X & Y) axes WBV values. However,
in some of the instances the transverse (Y) axis would have produced the largest WBV levels
prior to the addition of 40% from the multiplying factor. The remaining (majority of)
instances do raise a question regarding the foundation upon which use of the 1.4x multiplier is
based, as this factor is not found in the nearly-equivalent British Standard, BS 6841:1987.
This is, however, a largely technical (procedural) issue, for although the Directive requires
WBV exposure levels to be assessed separately in each axial direction, and the measurement
axis with the greatest (overall average) r.m.s. acceleration magnitude be identified, action is
required to reduce WBV exposure in all axial directions where the EAV is exceeded (see
Section 3.1.3). In practical terms whilst longitudinal (X) or transverse (Y) axes may exhibit
the highest axis-weighted overall-average (Aeq) acceleration levels, marginally lower levels
in the remaining axial directions will also require implementation of appropriate vibration
exposure-reducing measures if daily exposure levels exceed the EAV (as outlined in
Section 3.1.3). This is particularly pertinent if, for a given vehicle / application, significant
peak acceleration events (shocks and jolts), possibly not well represented by the r.m.s. (A(8))
evaluation method, are present in any of the other axial directions.
A feature that is highlighted, if not exaggerated, by the horizontal axes multiplying factors, is
the importance of height of the operator’s position above ground level, and above the
vehicles’ roll centre. The gradual increase in this height as agricultural vehicles (particularly
tractors) have become more powerful / larger is not a desirable development from the point of
view of whole-body vibration. Furthermore, it is a motion whose effect it is difficult to
mitigate by additional seat suspension capability. Horizontal (Y-axis) seat suspensions are
now available, and indeed an example was fitted upon a test tractor in this investigation.
During operations typified by high transverse (Y-axis) acceleration levels, this facility
appeared to moderate the increase between cab floor and operator seat WBV levels in that
axial direction. However, this characteristic was not investigated in isolation and further
study would be required to determine its significance.
In practice there are a number of factors that may complicate and potentially limit the
effectiveness of this solution. Firstly, there is restricted space within the majority of
agricultural vehicle cabs for transverse (Y-axis) suspension travel, and the low roll
frequencies of these vehicles requires long suspension travel in order to be effective.
Secondly, were such long suspension travels to be practical, there would be the ergonomic
problem of relative movement between the operator and cab-mounted controls, although the
current tendency to mount vehicle controls upon the operator’s seat could potentially address
this problem to an extent. In the future engineering solutions to these problems may well be
found.
There is not the scope within the constraints of this investigation to thoroughly analyse the
part played by seat suspension systems in the WBV exposure of the tractor driver. What has
given some concern is the apparent amplification of vibration between the cab floor and the
seat above the suspension. For horizontal motion, this can mainly be explained by the
increase in height above the vehicle’s roll centre. The position regarding vertical (Z) axis
vibration is more complex. Seat vertical suspension systems have traditionally been designed
to protect the occupant from relatively large magnitude motion, between approx. 1.0 2.0 m/s2 weighted r.m.s. magnitude (ISO 5007:2003). For larger motions, it is possible that
the suspension travel limits will be reached. For lower level motions, friction will
progressively reduce the suspension system’s effectiveness.
146
Another issue of relevance to seat suspension performance is the appropriateness of the emarking system. This was originally based upon ensuring the suitability of seat suspension
system performance when fitted upon unsuspended tractors, but was extended to include
tractors fitted with forms of axle and/or cab suspension without adequate technical
verification. This may have led to suspended seats being fitted into cabs where the primary
vertical motion may be at a frequency lower than that for which the seat was designed,
leading to the possibility of resonant amplification.
When there is a strong likelihood of seat suspension over-travel, operators often adjust the
suspension seat mid-ride position to a position higher than is optimum, sometimes even
jamming the suspension system against the upper travel limit stop, thereby reducing the risk
of a jarring blow at the bottom of suspension travel, but also leading to greater transmission of
low-level vibration. If seat suspension systems are to protect the driver against the more
severe shocks / jolts, they will require generally higher damping than is consistent with
achieving low transmission of vibration in the standard (ISO 5007) tests. It also poses a
problem for implementation of the PA(V)D, as this is predicated upon reducing average
vibration levels rather than shocks. It is entirely possible that efforts to satisfy the Directive
could result in drivers being more exposed to shocks / jolts than they may have otherwise
been, even if the criterion VDV is used rather than the A(8).
The difference between the r.m.s. (A(8)) and VDV assessment criteria is very large for this
application area (agricultural vehicles), manifesting itself in terms of the exposure duration
required to reach the EAV or ELV. This probably arises because the equivalence was based
on a calculation of estimated vibration dose values, or eVDVs, which can be derived from
r.m.s. acceleration data (see ISO 2631-1:1997 & Section 3.1.2). Real, measured VDVs are
intended for use with vibration signals that fail by a long way to satisfy the criteria for using
eVDV, the latter being namely:•
•
Crest factor greater than 6;
Nearly constant level of r.m.s. acceleration (stationary data)
WBV measurement upon agricultural vehicles can generate crest factors as high as 20, and
the time-histories of 1-minute r.m.s. acceleration recorded in this investigation (see
Figures 5.30, 5.31 and 5.32) display very wide variations in level. Issues concerning
estimation of WBV exposure levels (in A(8) & VDV format) from measured data are
explored further in Appendix 4. The VDV criterion does provide a better indication of shocks
and transients in WBV exposure than the simpler r.m.s. (A(8)) evaluation method (Coles,
2002). It is also more able to identify short-duration / high vibration intensity incidents which
may require particular control measures and, by consequence, may well provide better
indication of WBV risks present and the effectiveness of subsequent control measures.
However, there is the issue of the strange units (m/s1.75) and the more complex method of
calculation of VDV, if more widespread / general use is desired. A(8) daily exposure values
may be estimated more easily and accurately from manufacturer’s stated machine WBV
emissions values and, as shown, the A(8) EAV and ELV are likely to be less stringent where
shocks and jolts are present in the acceleration time history. It has been proposed elsewhere
(Stayner, 2001) that some feature of the amplitude or peak distribution of a vibration time
signal might be a more appropriate measure of WBV health risk than those presently in use.
However, this matter is not at present open for discussion.
147
148
8.
CONCLUSIONS AND RECOMMENDATIONS
At the potential risk of over-simplification, the following may be concluded from this
substantial investigation:•
Virtually all the agricultural vehicle operations investigated, involving modern, state-ofthe-art tractors, self-propelled sprayers or ATVs, will result in operator WBV daily
exposure exceeding the PA(V)D Exposure Action Value (EAV) during a normal working
day (see Table 7.2), thereby requiring employers to implement measures to reduce &
manage worker vibration exposure, as proposed by the Directive (see Section 3.1.3);
•
During the majority of agricultural vehicle operations investigated, WBV daily exposure
is unlikely to exceed the Exposure Limit Value (ELV) during a typical working day,
either due to sufficiently low WBV emission levels upon the vehicles concerned, or
suitably short (total) periods of exposure within the day (see Table 7.2). However,
exceptions include tractors cultivating (on rough ground) and tractor-trailer transport
operations. Longer shifts, extending to 12 – 14 hours per day, which are common at peak
times in agriculture, could result in other tractor operations (e.g. ploughing) causing
operator WBV exposure to exceed the ELV. In longer days such as these, over 25% of
the large, modern ‘on-farm’ tractor-operations surveyed would cause the ELV to be
exceeded. Also, under comparable operating conditions, WBV emission levels upon
smaller tractors are likely to be higher than upon the larger models investigated here,
resulting in higher WBV daily exposure levels. However, over 50% of the ‘on-farm’
tractors / operations surveyed would have to work for approaching 24 hours per day to
exceed the ELV (see Figure 5.38);
•
It should be stressed that the WBV Exposure Limit Value (ELV) should not be
considered a ‘safe’ level of vibration exposure in the workplace, but rather as a high,
undesirable level of vibration exposure (and a legal threshold) to be avoided at all costs.
It is for this reason the Directive requires action to be taken, so far as is reasonably
practicable, to minimise vibration exposure once levels exceed the Exposure Action
Value (EAV);
•
Differences between overall average (Aeq) WBV emission levels generated by individual
tractor (axle and cab) suspension designs were generally less than those evident between
the different agricultural operations performed (spraying / fertiliser spreading, ploughing,
plough transport, cultivating, trailer transport), particularly when evaluated by the
‘largest single weighted axis’ (ISO 2631-1:1997 ‘Effect of Vibration on Health’)
methodology favoured by the Directive;
•
Developments in suspension system design have been shown to reduce the WBV
emission levels of self-propelled sprayers. Developments in tractor (cab and axle)
suspension systems appear to yield improvements in subjective ride comfort: a fact
confirmed by evaluation of cab floor and operator seat WBV levels by the vector
sum (RSS) method. The latter suggested the ride comfort of the fully suspended (front &
rear axle) tractor and the suspended front axle & cab tractor to be marginally superior to
that of the other test vehicles in the majority of instances. Cab floor WBV levels derived
by the largest single axis method displayed a similar trend between tractor designs, but
this was not so apparent amongst operator seat WBV values derived by the technique:
and the latter are, of course, the WBV emission levels from which operator daily
exposure would be derived;
149
•
WBV exposure levels during ‘on-farm’ agricultural vehicle operations can vary by as
much as ±50% or more for the same task, depending upon ground conditions, driving
technique and operational requirements (‘the need for speed’). This is much greater
than the likely differences in WBV levels generated by alternative types (capabilities)
of tractor cab and/or axle suspension system, whilst operating in similar conditions;
•
The Directive requires WBV levels in each axial direction to be assessed separately,
and the axis with greatest (overall average) magnitude be identified. However, action is
required to reduce exposure to vibration in all axial directions in which the EAV is
exceeded (see Section 7.4). A given vehicle / application may exhibit high overall
average longitudinal (X) or transverse (Y) axis WBV levels, whilst significant peak
acceleration events (shocks and jolts) are generated in one or more of the other axial
directions, and are possibly not well represented by the r.m.s. (A(8)) evaluation
method;
•
During the majority of self-propelled sprayer and tractor-implement operations, largest
(overall average, axis weighted) WBV magnitudes were generated in the transverse (Y)
axis: during tractor-trailer transport the longitudinal (X) axis WBV took precedence.
However, maximum peak acceleration levels frequently occurred in the vertical (Z)
axis, and vertical (Z) axis WBV levels dominated ATV operation. The apparent
importance of horizontal (X & Y) axes WBV levels reported in this investigation is
undoubtedly accentuated (and arguably distorted) by use of the ‘largest single weighted
axis’ (ISO 2631-1:1997 ‘Effect of Vibration on Health’) methodology favoured by the
Directive. Were 1.4x multiplying factors not applied to horizontal vibration
components, vertical (Z) axis WBV levels would be the largest for a greater number of
vehicles / operations investigated;
•
If a comprehensive, generic database of agricultural vehicle WBV emission levels is
deemed desirable, to provide farmers with adequately robust data to enable estimation /
calculation of likely WBV daily exposure levels (as required by the Directive) and/or to
identify the need for workplace measurement of WBV exposure levels, where these
may approach the ELV (see Table 7.3), then a more comprehensive study is required,
embodying a greater number of measurement replications. This issue is particularly
pertinent to tractor-implement operations, which typically generate WBV daily
exposure levels between the EAV and ELV (see Table 7.2). Such a database would be
of value, enabling an employer to target specific operations of concern in greater detail
(workplace exposure measurement), whilst permitting recommended WBV estimation /
calculation techniques to be used for other (lower exposure level) operations, with
confidence;
•
For agricultural operating conditions, there is little equivalence between the 8-hour
energy-equivalent, frequency-weighted r.m.s. acceleration (A(8)) and vibration dose
value (VDV) methods of WBV exposure assessment, as specified by the Directive.
This is because the equivalence is based upon the estimated vibration dose
value (eVDV), and the requirements for use of the eVDV are not met by the WBV
encountered in real agricultural conditions. In agricultural operating conditions the
A(8) EAV and ELV appear to be less stringent (equate to longer operating durations)
than their VDV-specified equivalents;
150
•
The ISO 5008 ride vibration track tests provide a reasonable basis for comparing selfpropelled sprayer WBV emission levels. However, for agricultural tractors, the results
of the ISO 5008 tests bear little resemblance to WBV levels measured under ‘in-field’
or ‘on-farm’ conditions. This is largely because of the lack of attached implements or
trailers and consequent differences in vehicle mass, weight distribution, tyre inflation
pressures and external force systems acting upon the vehicle. Consequently, current
test track techniques require development / adaptation to improve their suitability for
tractor-implement combination WBV emission assessment. Such developments would
ideally deliver standardised testing methodologies, capable of quantifying the
effectiveness of tractor WBV-reducing design features when operating in typical
agricultural conditions (see Section 7.2);
•
For ATVs, hand-arm vibration exposure is more likely to restrict vehicle daily
operating duration (due to exposure in excess of the ELV), rather than exposure to
whole-body vibration. The slatted construction form of the ISO 5008 test track is
inappropriate for ATVs, because of vibration generated by the inter-slat spacing. The
suitability of the alternative moulded concrete type of track has not as yet been
evaluated.
151
152
9.
REFERENCES
BSI (1997) BS 6841 Guide to Measurement and Evaluation of Human Exposure to WholeBody Mechanical Vibration and Repeated Shock. British Standards Institution, London.
Bovenzi, M. & Betta, A. (1994) Low Back Disorders in Agricultural Tractor Drivers
Exposed to Whole-Body Vibration and Postural Stress. Applied Ergonomics 25, 231-240.
Coles, B. (2002) The Physical Agents (Vibration) Directive. Exposure Action and Limit
Values for Whole-Body Vibration: an important choice. HSE Discussion Paper (unpubl.),
Southwark, UK.
Crolla, D.A. (1976) The Effect of Cultivation Implements on Tractor Ride Vibration and
Implications for Implement Control. J agric Engng Res 21, 247-261.
Crolla, D.A. & Dale, A.K. (1979) The Ride Vibration of Tractor and Trailer Combinations.
NIAE Departmental Note No. DN/ER/915/05005 (unpubl.), Silsoe, UK.
DEFRA (Department for Environment, Food & Rural Affairs) (2001) Agriculture in the
United Kingdom: 2000 (and previous years).
Dufner, D.L. & Schick, T.E. (2002) John Deere Active SeatTM: a new level of seat
performance. Proc. VDI Agritechnik Conference ‘Agricultural Engineering for
Environmental Protection’, Martin Luther Universitat, Halle-Wirttenburg, Germany.
EEC (1978) Council Directive on the Approximation of the Laws of Member States Relating
to the Driver’s Seat on Wheeled Agricultural and Forestry Tractors (78/764/EEC). Journal of
the European Communities No. L 183/9-32.
EEC (1998) Council Directive on the Approximation of the Laws of Member States Relating
to Machinery (98/37/EC). Journal of the European Communities No. L 207, 23rd July, 46pp
EEC (2002) Council Directive on the Minimum Health and Safety Requirements Regarding
the Exposure of Workers to the Risks Arising from Physical Agents (Vibration)
(2002/44/EC). Journal of the European Communities No. OJ L 177, 6th July, 13pp.
Griffin, M.J. (1998) A Comparison of Standardised Methods for Predicting the Hazards of
Whole-Body Vibration and Repeated Shocks. Journal of Sound and Vibration, 215 (4), 883914.
ISO (1997) ISO 2631-1:1997 Mechanical Vibration and Shock - Evaluation of Human
Exposure to Whole-Body Vibration - Part 1: General requirements. International
Organisation for Standardisation, Geneva.
ISO (2001) ISO 5349-1:2001 Mechanical Vibration – Measurement and Evaluation of
Human Exposure to Hand-Transmitted Vibration - Part 1: General requirements.
International Organisation for Standardisation, Geneva.
ISO (2002) ISO 5008:2002 Agricultural Wheeled Tractors and Field Machinery Measurement of Whole-Body Vibration of the Operator. International Organisation for
Standardisation, Geneva.
153
+ISO (2003) ISO 5007:2003 Agricultural Wheeled Tractors – Operator’s Seat – Laboratory
Evaluation of Transmitted Vibration. International Organisation for Standardisation, Geneva.
Lines, J.A.; Whyte, R.T. & Stayner, R.M. (1989) Agricultural Vehicle Suspensions:
Suspensions for Tractor Cabs. Proc. 3rd Int. Symposium of Int. Section of ISSA for Research
on Prevention of Occupational Risks, Vienna.
Lines, J.A.; Stiles, M. & Whyte, R.T. (1995) Whole Body Vibration During Tractor
Driving. Journal of Low Frequency Noise and Vibration, 14(2), 87-104.
Matthews, J. (1966) Ride Comfort for Tractor Operators: II Analysis of Ride Vibrations on
Pneumatic Tyred Tractors. J agric Engng Res 9(2), 147-158.
Paddan, G.S.; Haward, B.M.; Griffin, M.J. & Palmer, K.T. (1999) Whole-Body
Vibration: Evaluation of Some Common Sources of Exposure in Great Britain. HSE Contract
Research Report 235/1999. HSE Books, ISBN 0 7176 2481 1, 70pp.
Peachey, R.O.; Lines, J.A. & Stayner, R.M. (1989) Agricultural Vehicle Suspensions:
Tractor Front Axle Suspension. Proc. 3rd Int. Symposium of Int. Section of ISSA for Research
on Prevention of Occupational Risks, Vienna.
Scarlett, A. J.; Price, J.S. & Stayner, R.M. (2002) Whole-Body Vibration: Initial
Evaluation of Emissions Originating from Agricultural Tractors. HSE Contract Research
Report 413/2002. HSE Books, ISBN 0 7176 2276 2, 18pp.
Stayner, R.M. & Bean, A.G.M. (1975) Tractor Ride Investigations: A survey of vibrations
experienced by drivers during field work. NIAE Departmental Note No. DN/E/578/1445
(unpubl.), Silsoe, UK.
Stayner, R.M.; Hilton, D.J. & Moran, P. (1975) Protecting the Tractor Driver from LowFrequency Ride Vibration. Proc. IMechE Conf. “Off-Highway Vehicles”, Tractors &
Equipment, CP 11/75, IMechE, London.
Stayner, R.M. (2001) Whole-Body Vibration and Shock - A Literature Review. HSE
Contract Research Report 333/2001. HSE Books, ISBN 0 7176 2004 2.
154
APPENDICES
APPENDIX 1.1:
Self-Propelled Sprayer Specifications:– ISO Test
Track and SRI ‘In-Field’ Test Programmes
A1.1.1 Coil Spring Suspension Sprayer
Make:Househam
Model:Super Sprint
Year of manufacture:- 1997
Registration No.:P820 BCT
Spray tank capacity:- 2500 l
Spray boom width:- 24 m
Engine:118 kW 6-cylinder turbocharged diesel
Driveline:2-speed hydrostatic, infinitely-variable
Wheelbase:3.10 m
Track width:1.83 m
Suspension features (in addition to operator’s seat):Twin coil springs & dampers on both front & rear axles
Front axle may oscillate relative to chassis – lateral location provided
by a Panhard rod
Operator’s seat:Isringhausen – Vertical (Z)-axis adjustable mechanical
spring & damper; ‘scissor’ linkage suspension system
(tired)
Operator’s mass:77.5 kg
Ground drive system:-
Equal wheel four wheel drive
Axle loadings, tyre equipment & tyre pressures:Standard Tyres, Unladen
Axle loadings:Tyre sizes:Tyres pressures:-
Front
Rear
Total
3000 kg
2320 kg
5320 kg
Continental Contract AC90 12.4 R32 radials all round
1.6 bar (24 lb/in2)
1.1 bar (16 lb/in2)
Standard Tyres, Laden (~2000 l)
Front
Rear
Total
Axle loadings:3642 kg
3699 kg
7341 kg
Tyre sizes:Continental Contract AC90 12.4 R32 radials all round
Tyres pressures:2.1 bar (31 lb/in2)
2.1 bar (31 lb/in2)
Flotation Tyres, Unladen
Axle loadings:Tyre sizes:Tyres pressures:-
Front
Rear
Total
3150 kg
2514 kg
5664 kg
Nokian ELS 600/55 R26.5 tubeless radials all round
0.9 bar (13 lb/in2)
0.8 bar (12 lb/in2)
Flotation Tyres, Laden (~2000 l)
Front
Rear
Total
Axle loadings:3708 kg
3734 kg
7442 kg
Tyre sizes:Nokian ELS 600/55 R26.5 tubeless radials all round
Tyres pressures:1.2 bar (17 lb/in2)
1.2 bar (17 lb/in2)
155
A1.1.2 Air Spring Suspension Sprayer
Make:Househam
Model:AR 2500 (Super Sprint Air-Ride)
Year of manufacture:- 2002
Registration No.:FY02 GPU
Spray tank capacity:- 2500 l
Spray boom width:- 24 m
Engine:118 kW 6-cylinder turbocharged diesel
Driveline:2-speed hydrostatic, infinitely-variable
Wheelbase:3.10 m
Track width:1.83 m
Suspension features (in addition to operator’s seat):Twin, self-levelling air springs & dampers on both front & rear axles
Front axle may oscillate relative to chassis – lateral location provided
by a Panhard rod
Operator’s seat:KAB 856 series air suspension seat
– Vertical (Z)-axis adjustable air spring & fixed damper;
‘scissor’ linkage suspension system
- Longitudinal (X)-axis fixed mechanical spring & fixed
damper
Operator’s mass:77.5 kg
Ground drive system:-
Equal wheel four wheel drive
Axle loadings, tyre equipment & tyre pressures:Standard Tyres, Unladen
Axle loadings:Tyre sizes:Tyres pressures:-
Front
Rear
Total
3314 kg
2514 kg
5828 kg
Continental Contract AC90 12.4 R32 radials all round
1.9 bar (27 lb/in2)
1.2 bar (18 lb/in2)
Standard Tyres, Laden (~2000 l)
Front
Rear
Total
Axle loadings:4064 kg
3784 kg
7848 kg
Tyre sizes:Continental Contract AC90 12.4 R32 radials all round
Tyres pressures:2.4 bar (35 lb/in2)
2.2 bar (32 lb/in2)
Flotation Tyres, Unladen
Axle loadings:Tyre sizes:Tyres pressures:-
Front
Rear
Total
3429 kg
2616 kg
6045 kg
Nokian ELS 600/55 R26.5 tubeless radials all round
1.0 bar (15 lb/in2)
0.8 bar (12 lb/in2)
Flotation Tyres, Laden (~2000 l)
Front
Rear
Total
Axle loadings:4140 kg
3835 kg
7975 kg
Tyre sizes:Nokian ELS 600/55 R26.5 tubeless radials all round
Tyres pressures:1.3 bar (19.5 lb/in2) 1.2 bar (18 lb/in2)
156
APPENDIX 1.2:
A1.2.1
Self-Propelled Sprayer WBV Emission Data:- ISO Test
Track Programme
Coil Spring and Air Spring Suspension Systems:- Unladen
Coil Spring Suspension Sprayer - Standard tyres – Unladen (Empty tank)
Spray booms open (extended)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
9.93
12.00
13.99
SD
0.288
0.246
0.265
X
Mean
0.68
0.83
0.84
Y
SD
0.128
0.062
0.010
Mean
2.08
2.59
2.69
Z
SD
0.738
0.575
0.454
Mean
1.33
1.43
1.42
RSS
SD
0.081
0.030
0.021
Mean
2.60
3.09
3.16
SD
0.535
0.488
0.372
Spray booms closed (stowed)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.17
0.029
12.22
0.063
13.04
14.25
0.142
15.00
16.22
18.09
20.45
X
Mean
0.48
0.58
0.56
0.60
0.73
0.72
0.78
0.91
Y
SD
0.009
0.040
0.020
Mean
1.28
1.15
0.91
0.96
1.38
1.30
1.54
1.56
Z
SD
0.150
0.222
0.007
Mean
1.08
1.21
1.24
1.30
1.33
1.34
1.55
1.71
SD
0.004
0.020
0.025
RSS
Mean
SD
1.74 0.115
1.77 0.149
1.64
1.72 0.020
2.05
2.00
2.32
2.49
Spray booms open (extended)
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.93
0.288
12.00
0.246
13.99
0.265
X
Mean
0.47
0.54
0.56
Y
SD
0.012
0.012
0.012
Mean
0.70
0.69
0.68
Z
SD
0.013
0.028
0.017
Mean
1.29
1.31
1.39
SD
0.038
0.016
0.009
RSS
Mean
SD
1.54 0.030
1.57 0.014
1.64 0.011
Closed (Stowed), 1.4 multiplier
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.17
0.029
12.22
0.063
13.04
14.25
0.142
15.00
16.22
18.09
20.45
X
Mean
0.38
0.42
0.41
0.43
0.48
0.46
0.44
0.48
Y
SD
0.009
0.003
0.008
Mean
0.72
0.72
0.68
0.66
0.64
0.67
0.61
0.59
157
Z
SD
0.017
0.018
0.018
Mean
1.16
1.29
1.34
1.34
1.36
1.42
1.72
1.75
SD
0.021
0.018
0.012
RSS
Mean
SD
1.42 0.014
1.53 0.010
1.56
1.56 0.011
1.58
1.64
1.87
1.91
Air Spring Suspension Sprayer - Standard tyres – Unladen (Empty tank)
Spray booms open (extended)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
9.83
11.74
13.33
SD
0.201
0.117
0.085
X
Mean
0.51
0.53
0.62
Y
SD
0.015
0.006
0.016
Mean
0.68
0.72
0.73
Z
SD
0.013
0.004
0.032
Mean
0.67
0.73
0.79
RSS
SD
0.008
0.003
0.011
Mean
1.08
1.15
1.24
SD
0.018
0.002
0.006
Spray booms closed (stowed)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.94
0.057
11.70
0.058
12.77
13.74
0.090
14.52
15.86
17.82
19.67
X
Mean
0.40
0.42
0.52
0.51
0.49
0.48
0.53
0.60
Y
SD
0.002
0.003
0.009
Mean
0.66
0.71
0.74
0.72
0.69
0.74
0.68
0.64
Z
SD
0.025
0.009
0.013
Mean
0.63
0.69
0.72
0.75
0.74
0.80
0.87
0.98
SD
0.004
0.009
0.016
RSS
Mean
SD
0.99 0.016
1.07 0.002
1.16
1.16 0.003
1.12
1.19
1.22
1.32
Spray booms open (extended)
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.83
0.201
11.74
0.117
13.33
0.085
X
Mean
0.37
0.38
0.42
Y
SD
0.002
0.006
0.016
Mean
0.65
0.67
0.65
Z
SD
0.010
0.013
0.023
Mean
0.80
0.90
1.02
SD
0.005
0.022
0.017
RSS
Mean
SD
1.10 0.004
1.18 0.023
1.27 0.022
Closed (Stowed), 1.4 multiplier
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.94
0.057
11.70
0.058
12.77
13.74
0.090
14.52
15.86
17.82
19.67
X
Mean
0.32
0.34
0.37
0.38
0.36
0.37
0.40
0.45
Y
SD
0.002
0.008
0.004
Mean
0.69
0.68
0.70
0.64
0.65
0.66
0.64
0.58
158
Z
SD
0.020
0.025
0.043
Mean
0.73
0.83
0.91
0.92
0.93
1.02
1.11
1.23
SD
0.002
0.006
0.015
RSS
Mean
SD
1.05 0.015
1.13 0.013
1.21
1.18 0.020
1.19
1.27
1.34
1.43
Coil Spring Suspension Sprayer - Flotation tyres – Unladen (Empty tank)
Spray booms open (extended)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
10.20
12.21
14.21
SD
0.307
0.207
0.262
X
Mean
0.69
0.73
0.76
Y
SD
0.029
0.006
0.004
Mean
1.05
0.98
0.91
Z
SD
0.032
0.074
0.090
Mean
1.26
1.18
1.31
RSS
SD
0.019
0.010
0.026
Mean
1.78
1.70
1.77
SD
0.026
0.047
0.064
Spray booms closed (stowed)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.18
0.144
12.39
0.193
13.28
14.34
0.152
15.13
16.29
18.27
20.57
X
Mean
0.52
0.54
0.54
0.55
0.55
0.60
0.74
0.90
Y
SD
0.011
0.012
0.007
Mean
0.75
0.83
0.96
0.85
0.83
0.81
0.87
0.91
Z
SD
0.034
0.013
0.029
Mean
0.96
1.04
1.08
1.10
1.10
1.12
1.29
1.50
SD
0.011
0.007
0.018
RSS
Mean
SD
1.33 0.028
1.43 0.008
1.54
1.49 0.019
1.48
1.50
1.72
1.97
Spray booms open (extended)
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.20
0.307
12.21
0.207
14.21
0.262
X
Mean
0.44
0.46
0.48
Y
SD
0.006
0.004
0.002
Mean
0.66
0.71
0.70
Z
SD
0.024
0.063
0.043
Mean
1.12
1.14
1.28
SD
0.009
0.008
0.022
RSS
Mean
SD
1.37 0.018
1.42 0.038
1.54 0.030
Closed (Stowed), 1.4 multiplier
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.18
0.144
12.39
0.193
13.28
14.34
0.152
15.13
16.29
18.27
20.57
X
Mean
0.37
0.38
0.38
0.38
0.39
0.42
0.44
0.51
Y
SD
0.006
0.010
0.007
Mean
0.75
0.78
0.87
0.79
0.77
0.75
0.72
0.76
159
Z
SD
0.010
0.045
0.020
Mean
1.12
1.22
1.25
1.24
1.24
1.30
1.43
1.53
SD
0.015
0.005
0.003
RSS
Mean
SD
1.40 0.009
1.50 0.023
1.57
1.52 0.011
1.51
1.56
1.66
1.79
Air Spring Suspension Sprayer - Flotation tyres – Unladen (Empty tank)
Spray booms open (extended)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
9.80
11.74
13.38
SD
0.085
0.144
0.149
X
Mean
0.51
0.52
0.59
Y
SD
0.015
0.014
0.001
Mean
0.78
0.72
0.78
Z
SD
0.027
0.030
0.016
Mean
0.63
0.69
0.78
RSS
SD
0.013
0.013
0.020
Mean
1.13
1.12
1.25
SD
0.023
0.030
0.012
Spray booms closed (stowed)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.93
0.129
11.83
0.081
12.72
13.83
0.111
14.75
15.72
17.82
19.35
X
Mean
0.44
0.43
0.47
0.54
0.55
0.56
0.59
0.68
Y
SD
0.011
0.005
0.015
Mean
0.89
0.76
0.77
0.81
0.89
0.84
0.86
0.88
Z
SD
0.053
0.018
0.037
Mean
0.62
0.68
0.71
0.75
0.76
0.84
0.91
0.96
SD
0.010
0.007
0.014
RSS
Mean
SD
1.17 0.047
1.11 0.016
1.14
1.23 0.031
1.30
1.31
1.38
1.47
Spray booms open (extended)
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.80
0.085
11.74
0.144
13.38
0.149
X
Mean
0.36
0.37
0.41
Y
SD
0.009
0.002
0.016
Mean
0.81
0.84
0.90
Z
SD
0.025
0.038
0.050
Mean
0.71
0.78
0.93
SD
0.005
0.013
0.006
RSS
Mean
SD
1.14 0.015
1.20 0.034
1.36 0.041
Closed (Stowed), 1.4 multiplier
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.93
0.129
11.83
0.081
12.72
13.83
0.111
14.75
15.72
17.82
19.35
X
Mean
0.32
0.34
0.36
0.38
0.38
0.41
0.42
0.46
Y
SD
0.006
0.001
0.007
Mean
0.96
0.88
0.96
0.98
1.08
1.04
1.09
1.09
160
Z
SD
0.012
0.027
0.065
Mean
0.70
0.81
0.84
0.92
0.97
1.04
1.20
1.28
SD
0.015
0.005
0.010
RSS
Mean
SD
1.24 0.002
1.24 0.022
1.33
1.40 0.039
1.50
1.53
1.68
1.74
A1.2.2
Coil Spring and Air Spring Suspension Systems:- Laden
Coil Spring Suspension Sprayer - Standard tyres – Laden (Full tank)
Spray booms open (extended)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
9.86
11.99
13.85
SD
0.148
0.260
0.092
X
Mean
0.78
0.92
1.04
Y
SD
0.031
0.058
0.037
Mean
1.11
1.40
1.62
Z
SD
0.155
0.173
0.062
Mean
1.35
1.56
1.75
RSS
SD
0.057
0.048
0.068
Mean
1.92
2.28
2.61
SD
0.103
0.156
0.097
Spray booms closed (stowed)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.90
0.110
12.19
0.024
13.43
14.14
0.180
15.19
16.36
18.56
20.57
X
Mean
0.60
0.71
0.77
0.84
0.76
0.79
0.91
1.09
Y
SD
0.019
0.008
0.030
Mean
1.47
1.37
1.56
1.70
1.43
1.71
1.78
1.90
Z
SD
0.194
0.185
0.134
Mean
1.09
1.37
1.50
1.52
1.49
1.52
1.79
2.04
SD
0.014
0.022
0.046
RSS
Mean
SD
1.93 0.156
2.07 0.136
2.30
2.43 0.081
2.20
2.42
2.68
2.99
Spray booms open (extended)
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.86
0.148
11.99
0.260
13.85
0.092
X
Mean
0.43
0.51
0.60
Y
SD
0.012
0.028
0.046
Mean
0.78
0.73
0.78
Z
SD
0.027
0.021
0.023
Mean
1.26
1.44
1.64
SD
0.016
0.083
0.111
RSS
Mean
SD
1.54 0.006
1.69 0.083
1.91 0.116
Closed (Stowed), 1.4 multiplier
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.90
0.110
12.19
0.024
13.43
14.14
0.180
15.19
16.36
18.56
20.57
X
Mean
0.36
0.43
0.47
0.53
0.48
0.50
0.53
0.60
Y
SD
0.005
0.016
0.033
Mean
0.84
0.74
0.75
0.78
0.74
0.74
0.73
0.74
161
Z
SD
0.022
0.036
0.032
Mean
1.13
1.38
1.52
1.53
1.51
1.60
1.96
2.17
SD
0.027
0.025
0.009
RSS
Mean
SD
1.45 0.035
1.62 0.029
1.76
1.79 0.030
1.74
1.83
2.16
2.37
Air Spring Suspension Sprayer - Standard tyres – Laden (Full tank)
Spray booms open (extended)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
10.04
11.80
13.63
SD
0.063
0.113
0.198
X
Mean
0.53
0.58
0.63
Y
SD
0.031
0.011
0.018
Mean
0.76
0.75
0.79
Z
SD
0.082
0.020
0.028
Mean
0.75
0.80
0.84
RSS
SD
0.009
0.002
0.019
Mean
1.20
1.24
1.31
SD
0.067
0.016
0.016
Spray booms closed (stowed)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.03
0.159
12.01
0.195
13.07
13.79
0.024
14.63
16.00
17.78
19.81
X
Mean
0.39
0.44
0.54
0.52
0.50
0.48
0.49
0.61
Y
SD
0.002
0.017
0.020
Mean
0.71
0.70
0.79
0.81
0.78
0.70
0.73
0.77
Z
SD
0.006
0.020
0.037
Mean
0.72
0.76
0.79
0.81
0.86
0.94
0.98
1.15
SD
0.008
0.006
0.002
RSS
Mean
SD
1.08 0.006
1.13 0.011
1.24
1.26 0.031
1.27
1.26
1.32
1.51
Spray booms open (extended)
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.04
0.063
11.80
0.113
13.63
0.198
X
Mean
0.39
0.40
0.44
Y
SD
0.007
0.001
0.011
Mean
0.72
0.69
0.71
Z
SD
0.014
0.015
0.017
Mean
0.95
1.10
1.13
SD
0.023
0.018
0.016
RSS
Mean
SD
1.26 0.025
1.36 0.020
1.41 0.021
Closed (Stowed), 1.4 multiplier
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.03
0.159
12.01
0.195
13.07
13.79
0.024
14.63
16.00
17.78
19.81
X
Mean
0.33
0.35
0.39
0.40
0.40
0.39
0.40
0.50
Y
SD
0.006
0.012
0.008
Mean
0.80
0.74
0.72
0.73
0.78
0.69
0.69
0.67
162
Z
SD
0.028
0.027
0.016
Mean
0.85
1.01
1.04
1.10
1.05
1.06
1.14
1.28
SD
0.020
0.020
0.009
RSS
Mean
SD
1.22 0.009
1.30 0.031
1.32
1.38 0.015
1.37
1.32
1.40
1.53
Coil Spring Suspension Sprayer - Flotation tyres – Laden (Full tank)
Spray booms open (extended)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
10.22
12.18
13.71
SD
0.146
0.331
0.080
X
Mean
0.79
0.81
0.87
Y
SD
0.084
0.020
0.041
Mean
1.28
1.05
1.04
Z
SD
0.188
0.055
0.104
Mean
1.33
1.35
1.43
RSS
SD
0.067
0.009
0.038
Mean
2.01
1.89
1.97
SD
0.196
0.036
0.094
Spray booms closed (stowed)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.45
0.114
12.16
0.143
13.28
14.29
0.098
15.38
16.36
18.00
20.57
X
Mean
0.57
0.59
0.64
0.64
0.67
0.67
0.79
1.01
Y
SD
0.004
0.007
0.011
Mean
1.13
0.94
1.03
1.04
1.04
1.01
1.06
1.11
Z
SD
0.019
0.073
0.100
Mean
1.14
1.22
1.29
1.22
1.27
1.33
1.59
1.74
SD
0.010
0.012
0.016
RSS
Mean
SD
1.70 0.019
1.65 0.037
1.77
1.73 0.053
1.77
1.80
2.07
2.30
Spray booms open (extended)
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.22
0.146
12.18
0.331
13.71
0.080
X
Mean
0.44
0.49
0.51
Y
SD
0.032
0.002
0.018
Mean
0.97
0.99
1.01
Z
SD
0.031
0.019
0.067
Mean
1.28
1.40
1.49
SD
0.031
0.020
0.004
RSS
Mean
SD
1.67 0.050
1.79 0.019
1.87 0.031
Closed (Stowed), 1.4 multiplier
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
10.45
0.114
12.16
0.143
13.28
14.29
0.098
15.38
16.36
18.00
20.57
X
Mean
0.38
0.41
0.44
0.45
0.45
0.46
0.51
0.56
Y
SD
0.006
0.010
0.010
Mean
1.16
1.00
1.10
1.18
1.14
1.16
1.09
1.08
163
Z
SD
0.046
0.040
0.068
Mean
1.33
1.46
1.47
1.43
1.43
1.49
1.79
1.77
SD
0.025
0.022
0.005
RSS
Mean
SD
1.81 0.043
1.82 0.025
1.89
1.90 0.047
1.88
1.94
2.15
2.15
Air Spring Suspension Sprayer - Flotation tyres – Laden (Full tank)
Spray booms open (extended)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
9.64
11.48
13.65
SD
0.127
0.172
0.060
X
Mean
0.52
0.52
0.66
Y
SD
0.025
0.009
0.007
Mean
1.02
0.99
1.06
Z
SD
0.076
0.033
0.016
Mean
0.81
0.83
0.89
RSS
SD
0.016
0.014
0.010
Mean
1.40
1.39
1.54
SD
0.048
0.029
0.008
Spray booms closed (stowed)
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.95
0.079
11.91
0.239
12.90
13.76
0.170
15.00
15.86
17.82
20.11
X
Mean
0.48
0.49
0.55
0.62
0.66
0.63
0.66
0.78
Y
SD
0.002
0.018
0.006
Mean
0.95
0.84
0.88
0.93
0.96
0.91
1.22
1.06
Z
SD
0.073
0.013
0.035
Mean
0.81
0.79
0.79
0.83
0.95
0.95
1.13
1.15
SD
0.013
0.009
0.017
RSS
Mean
SD
1.34 0.058
1.25 0.019
1.30
1.39 0.012
1.50
1.46
1.78
1.75
Spray booms open (extended)
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.64
0.127
11.48
0.172
13.65
0.060
X
Mean
0.36
0.37
0.43
Y
SD
0.012
0.007
0.008
Mean
0.91
0.90
0.93
Z
SD
0.055
0.037
0.005
Mean
0.91
0.99
1.07
SD
0.010
0.010
0.009
RSS
Mean
SD
1.34 0.045
1.39 0.033
1.48 0.008
Closed (Stowed), 1.4 multiplier
Average r.m.s. floor acceleration (1.4 multiplier) (m/s2)
Actual speed (km/h)
Mean
SD
9.95
0.079
11.91
0.239
12.90
13.76
0.170
15.00
15.86
17.82
20.11
X
Mean
0.34
0.35
0.37
0.40
0.42
0.39
0.44
0.48
Y
SD
0.005
0.008
0.004
Mean
1.03
0.96
0.99
0.98
1.02
0.97
1.05
1.03
164
Z
SD
0.046
0.030
0.054
Mean
0.94
0.96
0.99
1.01
1.06
1.12
1.23
1.30
SD
0.039
0.010
0.010
RSS
Mean
SD
1.44 0.053
1.40 0.026
1.45
1.47 0.032
1.54
1.54
1.68
1.73
APPENDIX 1.3:
Self-Propelled Sprayer WBV Emission Data:SRI ‘In-Field’ Programme
Coil spring suspension - Standard tyres
Average r.m.s. floor acceleration
Average r.m.s. seat acceleration
2
(1.4 multiplier) (m/s2)
(1.4 multiplier) (m/s )
X
Y
Z
RSS
X
Y
Z
RSS
Road
0.10
0.19
0.38
0.43
0.14
0.26
0.43
0.53
Track
0.31
0.73
0.65
1.02
0.39
0.98
0.76
1.30
Spraying
0.34
0.38
0.64
0.82
0.43
0.52
0.80
1.04
Overall
0.32
0.43
0.61
0.81
0.40
0.57
0.75
1.03
Air spring suspension - Standard tyres
Average r.m.s. floor acceleration
Average r.m.s. seat acceleration
2
(1.4 multiplier) (m/s2)
(1.4 multiplier) (m/s )
X
Y
Z
RSS
X
Y
Z
RSS
Road
0.09
0.17
0.28
0.34
0.09
0.21
0.30
0.53
Track
0.28
0.68
0.49
0.88
0.28
0.80
0.56
1.02
Spraying
0.29
0.40
0.44
0.66
0.31
0.46
0.47
0.72
Overall
0.28
0.43
0.43
0.67
0.29
0.50
0.47
0.74
Coil spring suspension - Flotation tyres
Average r.m.s. floor acceleration
Average r.m.s. seat acceleration
2
(1.4 multiplier) (m/s2)
(1.4 multiplier) (m/s )
X
Y
Z
RSS
X
Y
Z
RSS
Road
0.10
0.37
0.33
0.51
0.17
0.55
0.39
0.69
Track
0.27
0.92
0.62
1.14
0.33
1.23
0.70
1.45
Spraying
0.26
0.46
0.51
0.73
0.31
0.63
0.60
0.92
Overall
0.25
0.55
0.51
0.79
0.31
0.75
0.59
1.00
165
Air spring suspension - Flotation tyres
Average r.m.s. floor acceleration
Average r.m.s. seat acceleration
2
(1.4 multiplier) (m/s2)
(1.4 multiplier) (m/s )
X
Y
Z
RSS
X
Y
Z
RSS
Road
0.08
0.28
0.21
0.36
0.09
0.37
0.23
0.44
Track
0.26
0.95
0.48
1.10
0.26
1.08
0.54
1.23
Spraying
0.21
0.48
0.37
0.64
0.24
0.55
0.41
0.72
Overall
0.21
0.56
0.38
0.71
0.23
0.64
0.41
0.80
166
APPENDIX 1.4:
Self-Propelled Sprayer ‘On-Farm’ WBV Exposure Data:Synopsis of Results
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: Househam Air Suspended
Reg No: FY02GAO
Spraying
Task:
H L Crops (Contractors)
Place:
Day
23
1.75
)
Total VDV (m/s
Time
X
6.0
03:30
Month
May
Year
2
Start time:
08:40
Z
0.39
Sum
0.61
Maximum peak value (m/s )
X
Y
6.20
5.42
Z
12.80
Sum
12.80
Day
23
Month
May
Year
2
Start time:
08:47
Z
0.53
Sum
0.79
Z
14.80
Sum
14.80
2
Y
8.6
Z
8.7
Average r.m.s. (Aeq) (m/s )
X
Y
0.26
0.39
Sum
13.5
2
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: Househam Air Suspended
Reg No: FY02GAO
Spraying
Task:
H L Crops (Contractors)
Place:
1.75
2
)
Total VDV (m/s
Time
X
6.3
03:30
8-hr est tot
7.7
Y
11.2
13.8
Z
10.1
12.4
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
1.52
>24
r.m.s./A(8)
7.12
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.28
0.52
Sum
16.0
19.7
2
Maximum peak value (m/s )
X
Y
6.38
6.99
Weighted r.m.s. Acceleration (m/s2)
1.8
1.5
1.3
1.0
0.8
0.5
0.3
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
167
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: Househam Air Suspended
Reg No: FY02GRU
Spraying
Task:
Bush & Sons (Farmers)
Place:
Day
29
1.75
)
Total VDV (m/s
Time
X
7.4
04:30
Month
May
Year
2
Start time:
08:49
Z
0.37
Sum
0.61
Z
7.13
Sum
7.29
Month
May
Year
2
Start time:
08:50
Z
0.37
Sum
0.80
Z
17.20
Sum
17.10
2
Y
8.0
Z
7.5
Average r.m.s. (Aeq) (m/s )
X
Y
0.31
0.36
Sum
12.9
2
Maximum peak value (m/s )
X
Y
4.42
4.76
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: Househam Air Suspended
Reg No: FY02GRU
Spraying
Task:
Bush & Sons (Farmers)
Place:
Day
29
1.75
2
)
Total VDV (m/s
Time
X
8.6
04:30
8-hr est tot
9.9
Y
13.7
15.8
Z
8.8
10.2
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.88
>24
r.m.s./A(8)
5.73
>24
0:30
1:00
Average r.m.s. (Aeq) (m/s )
X
Y
0.38
0.59
Sum
17.7
20.5
2
Maximum peak value (m/s )
X
Y
5.12
9.44
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
0:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
168
4:30
Larson Davis HVM100
SN:00215
Floor
Location:
Machine: Househam Air Suspended
Reg No: FY02VFK
Spraying
Task:
R Lane (Contractor)
Place:
Day
18
1.75
)
Total VDV (m/s
Time
X
8.5
01:45
Month
Jun
Year
2
Start time:
10:50
Z
0.78
Sum
1.13
Z
8.55
Sum
8.95
Month
Jun
Year
2
Start time:
10:49
Z
0.88
Sum
1.81
Z
30.80
Sum
31.80
2
Y
8.4
Z
11.4
Average r.m.s. (Aeq) (m/s )
X
Y
0.57
0.59
Sum
16.3
2
Maximum peak value (m/s )
X
Y
4.72
5.29
Larson Davis HVM100
SN:00272
Seat
Location:
Machine: Househam Air Suspended
Reg No: FY02VFK
Spraying
Task:
R Lane (Contractor)
Place:
Day
18
1.75
2
)
Total VDV (m/s
Time
X
13.9
01:45
8-hr est tot
20.3
Y
22.8
33.3
Z
16.8
24.5
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.04
1.27
r.m.s./A(8)
1.23
6.52
Average r.m.s. (Aeq) (m/s )
X
Y
0.94
1.27
Sum
30.1
44.0
2
Maximum peak value (m/s )
X
Y
8.76
14.98
Weighted r.m.s. Acceleration (m/s2)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
169
Larson Davis HVM100
SN:00215
Floor
Location:
Machine: Househam Air Suspended
Reg No: FY02VFK
Spraying (second part)
Task:
R Lane (Contractor)
Place:
Day
18
1.75
)
Total VDV (m/s
Time
X
6.7
02:00
Month
Jun
Year
2
Start time:
19:08
Z
0.65
Sum
0.95
Z
8.46
Sum
8.57
Month
Jun
Year
2
Start time:
19:07
Z
0.68
Sum
1.18
Z
25.50
Sum
25.50
2
Y
7.6
Z
9.5
Average r.m.s. (Aeq) (m/s )
X
Y
0.44
0.54
Sum
13.8
2
Maximum peak value (m/s )
X
Y
4.52
4.16
Larson Davis HVM100
SN:00272
Seat
Location:
Machine: Househam Air Suspended
Reg No: FY02VFK
Spraying (second part)
Task:
R Lane (Contractor)
Place:
Day
18
1.75
2
)
Total VDV (m/s
Time
X
10.5
02:00
8-hr est tot
14.8
Y
11.2
15.9
Z
13.2
18.6
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.46
12.96
r.m.s./A(8)
4.23
22.39
Average r.m.s. (Aeq) (m/s )
X
Y
0.69
0.68
Sum
19.7
27.8
2
Maximum peak value (m/s )
X
Y
6.64
13.73
Weighted r.m.s. Acceleration (m/s2)
1.5
1.3
1.0
0.8
0.5
0.3
0.0
0:00
0:30
1:00
1:30
2:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
170
APPENDIX 2.1:
A2.1.1
Agricultural Tractor Specifications:– ISO Test Track
Programme
Unsuspended Tractor
Make:John Deere
Model:7810
Year of manufacture:- 2001
Engine:129 kW 6-cylinder turbocharged diesel
Transmission:18-speed full powershift
Wheelbase:2.80 m
Track width:1.86 m
Suspension features (in addition to operator’s seat):None
Operator’s mass:-
77 kg
Ground drive system:-
Front
2565 kg
16.9 R28
0.6 bar (8.7 lb/in2)
Axle loadings:Tyre sizes:Tyres pressures:A2.1.2
Unequal wheel four-wheel-drive
Goodyear Super Traction Radial tyres
Rear
Total
4471 kg
7036 kg
20.8 R38
0.6 bar (8.7 lb/in2)
Suspended Cab Tractor
Make:Renault
Model:Ares 630 RZ
Year of manufacture:- 2001
Engine:88 kW 6-cylinder diesel
Transmission:16-speed semi-powershift
Wheelbase:2.75 m
Track width:1.90 m
Suspension features
(in addition to operator’s seat):‘Hydrostable RZ’ cab suspension
system, comprising coil spring/damper
units, Panhard rods, longitudinal struts &
rear anti-roll bar (see Section 2.1.2)
Operator’s mass:-
77 kg
Ground drive system:-
Axle loadings:Tyre sizes:Tyres pressures:-
Unequal wheel four-wheel-drive
Michelin Agri Bib tyres
Front
2577 kg
14.9 R28
0.7 bar (10.2 lb/in2)
171
Rear
Total
2960 kg
5537 kg
18.4 R38
0.6 bar (8.7 lb/in2)
A2.1.3
Suspended Front Axle & Cab Tractor
Make:New Holland
Model:TM 165
Year of manufacture:- 2001
Engine:120 kW 6-cylinder turbocharged diesel
Transmission:18-speed semi-powershift
Wheelbase:2.787 m
Track width:1.925 m
Suspension features
(in addition to operator’s seat):‘Comfort Ride’ cab suspension system,
comprising coil spring/damper units &
Panhard rods at cab rear (see
Section 2.1.2)
‘Terraglide’ self-levelling, gas-over-oil,
hydro-pneumatic front axle suspension
system (see Section 2.1.3)
Operator’s mass:77 kg
Ground drive system:Unequal wheel four-wheel-drive
Michelin XM108 tyres
Axle loadings:Tyre sizes:Tyres pressures:A2.1.4
Front
2765 kg
540/65 R28
0.6 bar (8.7 lb/in2)
Rear
Total
3737 kg
6502 kg
650/65 R38
0.6 bar (8.7 lb/in2)
Fully Suspended (front & rear axle) Tractor
Make:JCB
Model:Fastrac 3185
Year of manufacture:- 2001
Engine:127 kW 6-cylinder turbocharged diesel
Transmission:54-speed semi-powershift
Wheelbase:3.05 m
Track width:2.01 m
Suspension features
(in addition to operator’s seat):Front axle:- twin coil springs, telescopic
dampers, radius rods & Panhard rod
Rear axle:- self-levelling, gas-over-oil,
hydro-pneumatic suspension system
(see Section 2.1.3)
Operator’s mass:77 kg
Ground drive system:Equal wheel four-wheel-drive
Alliance Super Power Drive A-360 tyres
Axle loadings:Tyre sizes:Tyres pressures:-
Front
3762 kg
540/65 R30
1.2 bar (17.4 lb/in2)
172
Rear
Total
3483 kg
7245 kg
540/65 R30
1.2 bar (17.4 lb/in2)
APPENDIX 2.2: Tractor Suspension Seat Specifications
A2.2.1
Unsuspended Tractor (John Deere 7810)
Operator’s seat:-
Manufacturer:- Sear Manufacturing Co.
Model:JD Air FS 92/01
e11 – I, II & III. 0445
Serial No.:2873960
Suspension type:-
Vertical (Z) axis:Longitudinal (X) axis:Transverse (Y) axis:-
A2.2.2
Suspended Cab Tractor (Renault Ares 630 RZ)
Operator’s seat:-
Manufacturer:- Grammer
Model:MSG 85/731
e1 – II & III
Serial No.:-
Suspension type:- Vertical (Z) axis:Longitudinal (X) axis:Transverse (Y) axis:-
A2.2.3
air spring (adjustable) & damper
(adjustable), ‘scissor’ linkage
mechanical spring (fixed) & damper
(fixed)
mechanical spring (fixed) & damper
(fixed)
mechanical spring (adjustable) & damper
(fixed), ‘scissor’ linkage
mechanical spring (fixed) & damper
(fixed)
None
Suspended Front Axle & Cab Tractor (New Holland TM 165)
Operator’s seat:-
Manufacturer:- Sear Manufacturing Co.
Model:De Luxe Air Suspension Seat
SA15803 seat unit
SA15748 suspension unit
e11 – I, II & III. 1294
Serial No.:CNH 82016027
Suspension type:- Vertical (Z) axis:Longitudinal (X) axis:Transverse (Y) axis:-
173
air spring (adjustable) & damper
(adjustable), ‘scissor’ linkage
mechanical spring (fixed) & damper
(adjustable)
None
A2.2.4
Fully Suspended (front & rear axle) Tractor (JCB Fastrac 3185)
Operator’s seat:-
Manufacturer:- Grammer
Model:MSG 95A/721 12V
e1 – II & III.
Suspension type:- Vertical (Z) axis:Longitudinal (X) axis:Transverse (Y) axis:-
174
air spring (adjustable) & damper (fixed),
‘scissor’ linkage
mechanical spring (fixed) & damper
(adjustable)
None
APPENDIX 2.3:
A2.3.1
Unsuspended Tractor (John Deere 7810)
Actual
Speed (km/h)
4.0
5.1
6.1
7.0
10.1
12.0
13.0
14.1
15.4
16.1
18.0
19.8
24.3
30.5
Actual
Speed (km/h)
4.0
5.1
6.1
7.0
10.1
12.0
13.0
14.1
15.4
16.1
18.0
19.8
24.3
30.5
Agricultural Tractor WBV Emission Data:- ISO Test
Track Programme
Average r.m.s. floor acceleration (1.4 multiplier) (m/s 2 )
X
Y
Z
RSS
SD
SD
SD
SD
Mean
Mean
Mean
Mean
0.97
0.025
1.23
0.059
0.55
0.02
1.66
0.065
1.09
0.022
1.62
0.006
0.68
0.01
2.08
0.015
1.18
1.78
0.79
2.27
1.31
0.025
1.72
0.011
0.88
0.01
2.34
0.001
0.53
0.61
0.66
0.74
0.75
0.81
0.82
0.91
1.00
1.56
0.025
0.040
0.051
0.91
1.04
1.10
1.22
1.27
1.26
1.35
1.41
1.43
1.27
0.035
0.025
0.014
0.69
0.67
0.70
0.77
0.86
1.00
1.10
1.42
1.64
1.94
0.00
0.00
0.01
1.26
1.38
1.46
1.62
1.70
1.80
1.93
2.20
2.40
2.79
0.033
0.031
0.010
Average r.m.s. seat acceleration (1.4 multiplier) (m/s 2 )
X
Y
Z
RSS
SD
SD
SD
SD
Mean
Mean
Mean
Mean
1.43
0.041
1.53
0.052
0.63
0.017
2.19
0.060
1.59
0.037
1.98
0.049
0.78
0.012
2.66
0.056
1.77
2.31
0.87
3.04
2.04
0.093
1.03
0.018
3.01
0.076
1.96
0.029
0.83
0.86
0.95
1.13
1.25
1.46
1.46
1.76
1.69
2.53
0.061
0.083
0.030
1.10
1.29
1.27
1.46
1.61
1.54
1.68
1.79
1.66
1.55
0.080
0.032
0.074
175
0.69
0.60
0.60
0.71
0.73
1.01
1.05
1.52
1.71
1.97
0.024
0.009
0.023
1.54
1.67
1.70
1.98
2.16
2.36
2.46
2.94
2.93
3.56
0.051
0.034
0.039
A2.3.2
Suspended Cab Tractor (Renault Ares 630 RZ)
Actual
Speed (km/h)
4.1
5.1
6.0
7.1
10.6
12.7
13.8
14.9
16.1
17.1
19.1
21.6
24.0
30.0
Actual
Speed (km/h)
4.1
5.1
6.0
7.1
10.6
12.7
13.8
14.9
16.1
17.1
19.1
21.6
24.0
30.0
Average r.m.s. floor acceleration (1.4 multiplier) (m/s 2 )
X
Y
Y
RSS
SD
SD
SD
SD
Mean
Mean
Mean
Mean
0.99
0.045
1.19
0.074
0.44
0.01
1.61
0.052
0.009
1.53
0.015
0.52
0.01
1.98
0.016
1.15
1.32
1.55
0.65
2.14
0.017
1.48
0.019
0.90
0.01
2.23
0.005
1.41
0.50
0.57
0.62
0.69
0.74
0.72
0.69
0.68
0.93
1.37
0.006
0.013
0.019
0.82
0.89
0.99
1.04
1.02
1.11
1.07
1.13
1.10
0.97
0.008
0.015
0.029
0.62
0.55
0.54
0.62
0.71
0.83
1.03
1.24
1.41
1.42
0.01
0.01
0.01
1.14
1.19
1.29
1.39
1.44
1.56
1.64
1.81
2.01
2.19
0.009
0.002
0.024
Average r.m.s. seat acceleration (1.4 multiplier) (m/s 2 )
X
Y
Y
RSS
SD
SD
SD
SD
Mean
Mean
Mean
Mean
0.066
1.33
0.070
0.62
0.022
2.04
0.040
1.41
0.030
1.75
0.053
0.71
0.041
2.57
0.040
1.74
2.07
1.70
0.91
2.83
0.012
1.66
0.017
1.29
0.020
3.23
0.011
2.46
0.88
1.04
1.14
1.28
1.46
1.31
1.25
1.27
1.88
2.61
0.024
0.019
0.046
1.03
1.13
1.25
1.32
1.34
1.28
1.23
1.66
1.56
1.33
0.087
0.090
0.101
176
0.80
0.64
0.70
0.78
0.93
1.13
1.42
1.66
1.82
1.75
0.016
0.015
0.024
1.57
1.66
1.83
1.99
2.19
2.15
2.26
2.67
3.04
3.41
0.077
0.078
0.081
A2.3.3
Suspended Front Axle & Cab Tractor (New Holland TM 165)
Actual
Speed (km/h)
3.9
4.8
5.9
6.7
9.7
11.8
12.5
13.7
14.6
15.6
17.5
19.6
24.2
28.7
Actual
Speed (km/h)
3.9
4.8
5.9
6.7
9.7
11.8
12.5
13.7
14.6
15.6
17.5
19.6
24.2
28.7
Average r.m.s. floor acceleration (1.4 multiplier) (m/s 2 )
X
Y
Y
RSS
SD
SD
SD
SD
Mean
Mean
Mean
Mean
0.90
0.044
1.21
0.074
0.50
0.01
1.59
0.050
0.007
1.83
0.061
0.72
0.02
2.21
0.046
1.02
1.20
1.74
1.02
2.34
0.021
1.73
0.021
1.07
0.04
2.39
0.021
1.25
0.45
0.51
0.55
0.57
0.59
0.57
0.60
0.63
0.84
1.03
0.008
0.002
0.011
0.92
0.97
1.01
1.10
1.17
1.14
1.34
1.24
1.21
1.34
0.053
0.046
0.040
0.82
0.72
0.70
0.79
0.91
1.07
1.10
1.28
1.81
1.81
0.02
0.03
0.02
1.31
1.31
1.35
1.47
1.60
1.67
1.84
1.89
2.33
2.47
0.026
0.020
0.019
Average r.m.s. seat acceleration (1.4 multiplier) (m/s 2 )
X
Y
Y
RSS
SD
SD
SD
SD
Mean
Mean
Mean
Mean
0.055
1.30
0.136
0.55
0.024
1.86
0.089
1.22
0.020
1.99
0.130
0.76
0.030
2.57
0.098
1.43
1.75
1.74
1.12
2.71
0.045
1.88
0.020
1.23
0.084
2.91
0.027
1.85
0.68
0.78
0.84
0.88
0.91
0.91
1.05
1.10
1.51
1.87
0.009
0.006
0.028
1.16
1.22
1.16
1.38
1.36
1.31
1.91
1.51
1.55
1.57
177
0.181
0.230
0.233
0.78
0.65
0.67
0.74
0.93
1.09
1.11
1.27
1.46
1.42
0.015
0.024
0.013
1.55
1.59
1.58
1.79
1.88
1.93
2.45
2.26
2.61
2.82
0.133
0.167
0.171
A2.3.4
Fully Suspended (front & rear axle) Tractor (JCB Fastrac 3185)
Actual
Speed (km/h)
4.0
4.8
5.8
6.8
10.0
11.7
12.9
13.8
14.8
15.9
17.7
19.9
23.8
30.0
Actual
Speed (km/h)
4.0
4.8
5.8
6.8
10.0
11.7
12.9
13.8
14.8
15.9
17.7
19.9
23.8
30.0
Average r.m.s. floor acceleration (1.4 multiplier) (m/s 2 )
X
Y
Y
RSS
SD
SD
SD
SD
Mean
Mean
Mean
Mean
1.17
0.041
1.32
0.025
0.35
0.01
1.79
0.014
0.023
1.67
0.019
0.50
0.01
2.12
0.024
1.21
1.20
1.75
0.65
2.22
0.011
1.59
0.029
0.82
0.02
2.18
0.022
1.25
0.43
0.52
0.53
0.58
0.62
0.67
0.68
0.71
0.93
1.09
0.010
0.008
0.008
0.64
0.73
0.75
0.79
0.81
0.84
0.87
0.89
0.90
0.86
0.027
0.030
0.018
0.41
0.46
0.48
0.52
0.55
0.59
0.64
0.70
0.78
0.89
0.01
0.01
0.01
0.87
1.00
1.03
1.10
1.16
1.22
1.27
1.33
1.51
1.65
0.025
0.026
0.015
Average r.m.s. seat acceleration (1.4 multiplier) (m/s 2 )
X
Y
Y
RSS
SD
SD
SD
SD
Mean
Mean
Mean
Mean
0.074
1.53
0.101
0.44
0.037
2.27
0.019
1.61
0.015
2.04
0.085
0.71
0.023
2.82
0.065
1.82
2.00
2.14
1.01
3.09
0.020
1.97
0.070
1.27
0.054
3.24
0.026
2.23
0.64
0.81
0.74
0.87
0.94
1.12
1.07
1.03
1.59
2.13
0.018
0.034
0.076
0.76
0.92
0.88
0.95
1.01
1.18
1.04
1.11
1.14
1.24
0.039
0.151
0.062
178
0.53
0.62
0.66
0.75
0.83
0.90
0.89
0.92
0.88
1.00
0.007
0.015
0.021
1.13
1.37
1.32
1.49
1.61
1.86
1.74
1.78
2.14
2.66
0.027
0.089
0.022
APPENDIX 2.4:
A2.4.1
Agricultural Test Tractor Set-up:- SRI ‘In-Field’
Programme
Unsuspended Tractor (John Deere 7810)
Spraying
(tractor plus front weights)
Implement:-
Hardi 1000 litre 3pt. linkage-mounted, air-assisted sprayer
12 m spray booms
Front
Rear
Total
Axle loadings:Tyres pressures:-
2412 kg
0.6 bar (8.7 lb/in2)
7886 kg
10299 kg
1.6 bar (23.2 lb/in2)
Ploughing / Plough Transport
(tractor plus front weights)
Implement:-
Dowdeswell DP7 5-furrow, fully-mounted reversible plough
Axle loadings:Tyres pressures:-
Front
Rear
Total
1968 kg
0.6 bar (8.7 lb/in2)
7582 kg
9550 kg
1.3 bar (19 lb/in2)
Cultivating
(tractor plus front weights)
Implement:-
Cousins 4 m 3pt.linkage-mounted pigtail cultivator
Axle loadings:Tyres pressures:-
Front
Rear
Total
3115 kg
0.6 bar (8.7 lb/in2)
5889 kg
9004 kg
0.9 bar (13 lb/in2)
Trailer Transport
(tractor less front weights)
Implement:-
Wootton 12 tonne tandem axle tipping trailer
Sprung drawbar, sprung axles
Trailer gross weight:-
17145 kg
Tractor Axle loadings:Tyres pressures:-
Drawbar load:2921 kg
Bogie load:14224 kg
Tyre pressures:- 5.2 bar (76 lb/in2)
Front
Rear
2247 kg
0.6 bar (8.7 lb/in2)
7772 kg
10019 kg
1.6 bar (11.6 lb/in2)
Tractor – Trailer Gross Train Weight:-
10019 + 14224 = 24243 kg
179
Total
A2.4.2
Suspended Cab Tractor (Renault Ares 630 RZ)
Spraying
(tractor plus front weights)
Implement:-
Hardi 1000 litre 3pt. linkage-mounted, air-assisted sprayer
12 m spray booms
Front
Rear
Total
Axle loadings:Tyres pressures:-
1924 kg
0.6 bar (8.7 lb/in2)
6623 kg
8547 kg
1.6 bar (23.2 lb/in2)
Ploughing / Plough Transport
(tractor plus front weights)
Implement:-
Dowdeswell DP7 5-furrow, fully-mounted reversible plough
Axle loadings:Tyres pressures:-
Front
Rear
Total
1352 kg
0.8 bar (11.6 lb/in2)
6344 kg
7696 kg
1.6 bar (23.2 lb/in2)
Cultivating
(tractor plus front weights)
Implement:-
Cousins 4 m 3pt.linkage-mounted pigtail cultivator
Axle loadings:Tyres pressures:-
Front
Rear
Total
2937 kg
0.8 bar (11.6 lb/in2)
3654 kg
6591 kg
0.8 bar (11.6 lb/in2)
Trailer Transport
(tractor less front weights)
Implement:-
Wootton 12 tonne tandem axle tipping trailer
Sprung drawbar, sprung axles
Trailer gross weight:-
17145 kg
Tractor Axle loadings:Tyres pressures:-
Drawbar load:2921 kg
Bogie load:14224 kg
Tyre pressures:- 5.2 bar (76 lb/in2)
Front
Rear
2080 kg
0.6 bar (8.7 lb/in2)
6300 kg
8380 kg
1.6 bar (11.6 lb/in2)
Tractor – Trailer Gross Train Weight:-
8380 + 14224 = 22604 kg
180
Total
A2.4.3
Suspended Front Axle & Cab Tractor (New Holland TM 165)
Spraying
(tractor plus front weights)
Implement:-
Hardi 1000 litre 3pt. linkage-mounted, air-assisted sprayer
12 m spray booms
Front
Rear
Total
Axle loadings:Tyres pressures:-
2235 kg
0.6 bar (8.7 lb/in2)
7138 kg
9373 kg
0.95 bar (13.8 lb/in2)
Ploughing / Plough Transport
(tractor plus front weights)
Implement:-
Dowdeswell DP7 5-furrow, fully-mounted reversible plough
Axle loadings:Tyres pressures:-
Front
Rear
Total
2369 kg
0.6 bar (8.7 lb/in2)
6750 kg
9119 kg
0.8 bar (11.6 lb/in2)
Cultivating
(tractor plus front weights)
Implement:-
Cousins 4 m 3pt.linkage-mounted pigtail cultivator
Axle loadings:Tyres pressures:-
Front
Rear
Total
3479 kg
0.8 bar (11.6 lb/in2)
5042 kg
8521 kg
0.6 bar (8.7 lb/in2)
Trailer Transport
(tractor less front weights)
Implement:-
Wootton 12 tonne tandem axle tipping trailer
Sprung drawbar, sprung axles
Trailer gross weight:-
17145 kg
Tractor Axle loadings:Tyres pressures:-
Drawbar load:2921 kg
Bogie load:14224 kg
Tyre pressures:- 5.2 bar (76 lb/in2)
Front
Rear
2220 kg
0.6 bar (8.7 lb/in2)
7067 kg
9287 kg
1.1 bar (17.6 lb/in2)
Tractor – Trailer Gross Train Weight:-
9287 + 14224 = 23511 kg
181
Total
A2.4.4
Fully Suspended (front & rear axle) Tractor(JCB Fastrac 3185)
Spraying
(tractor less front weights)
Implement:-
Hardi 1000 litre 3pt. linkage-mounted, air-assisted sprayer
12 m spray booms
Front
Rear
Total
Axle loadings:Tyres pressures:-
2577 kg
1.2 bar (17.4 lb/in2)
6813 kg
9390 kg
2.2 bar (32 lb/in2)
Ploughing / Plough Transport
(tractor plus front weights)
Implement:-
Dowdeswell DP7 5-furrow, fully-mounted reversible plough
Axle loadings:Tyres pressures:-
Front
Rear
Total
3038 kg
1.2 bar (17.4 lb/in2)
6350 kg
9388 kg
1.75 bar (25.4 lb/in2)
Cultivating
(tractor less front weights)
Implement:-
Cousins 4 m 3pt.linkage-mounted pigtail cultivator
Axle loadings:Tyres pressures:-
Front
Rear
Total
3073 kg
1.2 bar (17.4 lb/in2)
5047 kg
8120 kg
1.4 bar (20.3 lb/in2)
Trailer Transport
(tractor less front weights)
Implement:-
Wootton 12 tonne tandem axle tipping trailer
Sprung drawbar, sprung axles
Trailer gross weight:-
17145 kg
Tractor Axle loadings:Tyres pressures:-
Drawbar load:2921 kg
Bogie load:14224 kg
Tyre pressures:- 5.2 bar (76 lb/in2)
Front
Rear
3448 kg
1.4 bar (20.3 lb/in2)
6452 kg
9900 kg
2.4 bar (34.8 lb/in2)
Tractor – Trailer Gross Train Weight:-
9900 + 14224 = 24124 kg
182
Total
APPENDIX 2.5:
Task
Agricultural Tractor WBV Emission Data:SRI ‘In-Field’ Programme
Average r.m.s. seat acceleration
2
(1.4 multiplier) (m/s )
Average r.m.s. floor acceleration
2
(1.4 multiplier) (m/s )
Tractor
Speed
(km/h)
X
Y
Z
RSS
X
Y
Z
RSS
Cultivating
A
0.73
0.99
0.57
1.35
0.81
1.20
0.63
1.59
6.71
Cultivating
B
1.00
1.14
0.70
1.67
1.45
1.49
0.79
2.22
6.50
Cultivating
C
0.72
0.90
0.75
1.38
0.89
1.46
0.61
1.82
6.75
Cultivating
D
0.77
0.93
0.48
1.30
1.01
1.28
0.69
1.78
6.84
Plough Transport
A
0.42
0.51
0.49
0.82
0.52
0.58
0.48
0.92
20.72
Plough Transport
B
0.37
0.47
0.47
0.76
0.61
0.60
0.56
1.02
20.77
Plough Transport
C
0.29
0.48
0.46
0.72
0.35
0.65
0.44
0.86
22.54
Plough Transport
D
0.38
0.45
0.39
0.70
0.48
0.59
0.46
0.88
24.12
Ploughing
A
0.53
0.64
0.36
0.90
0.63
0.77
0.36
1.06
5.33
Ploughing
B
0.55
0.65
0.49
0.98
0.74
0.83
0.53
1.24
4.97
Ploughing
C
0.57
0.70
0.41
0.99
0.71
0.89
0.43
1.22
5.18
Ploughing
D
0.46
0.60
0.31
0.81
0.55
0.73
0.36
0.99
5.08
Spraying
A
0.39
0.47
0.40
0.73
0.50
0.56
0.49
0.90
9.67
Spraying
B
0.35
0.44
0.37
0.67
0.57
0.53
0.53
0.94
10.19
Spraying
C
0.30
0.41
0.32
0.60
0.38
0.50
0.36
0.72
9.79
Spraying
D
0.34
0.48
0.37
0.70
0.49
0.74
0.54
1.04
9.94
Trailer Transport
A
0.89
0.78
0.54
1.30
1.32
0.84
0.49
1.64
19.40
Trailer Transport
B
0.81
0.69
0.46
1.16
1.35
0.94
0.53
1.73
18.68
Trailer Transport
C
0.72
0.77
0.53
1.18
1.05
1.09
0.48
1.58
19.71
Trailer Transport
D
0.78
0.59
0.40
1.06
1.32
0.74
0.48
1.58
20.77
Tractor Model Key
•
•
•
•
Tractor ‘A’
Tractor ‘B’
Tractor ‘C’
Tractor ‘D’
=
=
=
=
Unsuspended
Suspended Cab
Suspended Front Axle & Cab
Fully Suspended (Front & Rear Axle)
183
APPENDIX 2.6:
Task
Agricultural Tractor WBV Emission Data:SRI ‘In-Field’ - Trailer Transport
Average r.m.s. floor acceleration
2
(1.4 multiplier) (m/s )
Tractor
Average r.m.s. seat acceleration
2
(1.4 multiplier) (m/s )
Speed
(km/h)
X
Y
Z
RSS
X
Y
Z
RSS
Field surface
A
1.03
0.94
0.56
1.50
1.43
0.96
0.55
1.81
12.13
Field surface
B
1.14
0.89
0.59
1.56
2.02
1.28
0.67
2.48
11.79
Field surface
C
0.88
0.80
0.58
1.32
1.26
1.23
0.54
1.84
11.20
Field surface
D
1.12
0.81
0.53
1.48
2.03
1.01
0.68
2.37
10.91
Farm track
A
0.98
1.04
0.64
1.57
1.43
1.17
0.52
1.92
12.69
Farm track
B
0.88
0.89
0.47
1.34
1.47
1.18
0.55
1.96
13.07
Farm track
C
0.77
0.97
0.60
1.37
1.10
1.44
0.51
1.88
12.53
Farm track
D
0.85
0.77
0.46
1.24
1.43
1.02
0.61
1.86
16.11
Country road
A
1.02
0.75
0.56
1.38
1.59
0.81
0.57
1.88
28.42
Country road
B
0.83
0.64
0.50
1.17
1.41
0.83
0.55
1.73
30.31
Country road
C
0.88
0.91
0.58
1.39
1.33
1.19
0.53
1.87
32.22
Country road
D
0.78
0.49
0.37
0.99
1.31
0.60
0.38
1.49
36.14
Smooth road
A
0.60
0.44
0.30
0.80
0.94
0.50
0.32
1.11
40.39
Smooth road
B
0.46
0.35
0.28
0.64
0.74
0.42
0.32
0.91
38.84
Smooth road
C
0.40
0.50
0.35
0.73
0.59
0.73
0.36
1.00
40.03
Smooth road
D
0.46
0.42
0.33
0.70
0.74
0.56
0.31
0.97
57.13
Overall
A
0.89
0.78
0.54
1.30
1.32
0.84
0.49
1.64
19.40
Overall
B
0.81
0.69
0.46
1.16
1.35
0.94
0.53
1.73
18.68
Overall
C
0.72
0.77
0.53
1.18
1.05
1.09
0.48
1.58
19.71
Overall
D
0.78
0.59
0.40
1.06
1.32
0.74
0.48
1.58
20.77
Tractor Model Key
•
•
•
•
Tractor ‘A’
Tractor ‘B’
Tractor ‘C’
Tractor ‘D’
=
=
=
=
Unsuspended
Suspended Cab
Suspended Front Axle & Cab
Fully Suspended (Front & Rear Axle)
184
APPENDIX 2.7:
A2.7.1
Tractor
TM 165
A2.7.2
Tractor
JCB
‘On-Farm’ Agricultural Tractor Cab Floor WBV
Emission Data
Suspended Cab & Front Axle Tractor (New Holland TM 165)
Task
Average r.m.s. acceleration (m/s 2 )
Duration
(hr)
RSS
(m/s 2 )
X
Y
Z
Major axis
Ploughing (1)
4.25
0.28
0.44
0.34
Y
0.62
Ploughing (2)
3.25
0.43
0.67
0.52
Y
0.95
Ploughing (3)
4.25
0.38
0.47
0.31
Y
0.68
Cultivating (1)
4.75
0.31
0.39
0.34
Y
0.61
Cultivating (2)
5.25
0.28
0.37
0.28
Y
0.54
Dressing (1)
4.25
0.33
0.45
0.33
Y
0.65
Dressing (2)
4.50
0.35
0.29
0.31
X
0.54
Dressing (3)
4.50
0.30
0.46
0.38
Y
0.67
Trailer Work (1)
3.75
0.37
0.32
0.46
Z
0.67
Trailer Work (2)
4.75
0.37
0.37
0.38
X/Y/Z
0.65
Trailer Work (3)
4.00
0.30
0.30
0.26
X/Y
0.50
Fully Suspended (Front & Rear Axle) Tractor (JCB Fastrac 3185)
Task
Average r.m.s. acceleration (m/s 2 )
Duration
(hr)
RSS
(m/s 2 )
X
Y
Z
Major axis
Ploughing (1)
4.00
0.44
0.57
0.27
Y
0.77
Ploughing (2)
5.75
0.29
0.39
0.30
Y
0.57
Ploughing (3)
4.50
0.48
0.65
0.34
Y
0.87
Cultivating (1)
3.75
0.38
0.61
0.37
Y
0.80
Cultivating (2)
4.50
0.69
0.88
0.64
Y
1.28
Cultivating (3)
4.00
0.67
0.92
0.50
Y
1.24
Dressing (1)
4.75
0.35
0.45
0.31
Y
0.64
Dressing (2)
6.00
0.23
0.29
0.21
Y
0.43
Trailer Work (1)
5.50
0.50
0.44
0.33
X
0.74
Trailer Work (2)
5.00
0.70
0.59
0.39
X
0.99
Trailer Work (3)
4.50
0.39
0.38
0.24
X
0.59
185
APPENDIX 2.8:
Appendix 2.8.1
Agricultural Tractor ‘On-Farm’ WBV Exposure Data:Synopsis of Results
Suspended Cab & Front Axle Tractor (New Holland TM 165)
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: AO51CWC
Ploughing
Task:
Sparrow, Farmers, Soham
Place:
Day
11
1.75
Total VDV (m/s
)
Time
X
6.2
04:15
Month
Jan
Year
2
Start time:
11:17
Z
0.34
Sum
0.62
Z
6.65
Sum
6.77
Month
Jan
Year
2
Start time:
11:17
Z
0.32
Sum
0.78
Z
10.40
Sum
10.40
2
Y
7.3
Z
6.6
Average r.m.s. (Aeq) (m/s )
X
Y
0.28
0.44
Sum
11.6
2
Maximum peak value (m/s )
X
Y
4.21
4.48
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: AO51CWC
Ploughing
Task:
Sparrow, Farmers, Soham
Place:
Day
11
1.75
2
Total VDV (m/s
)
Time
X
7.0
04:15
8-hr est tot
8.2
Y
10.0
11.7
Z
5.7
6.6
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
2.96
>24
r.m.s./A(8)
5.16
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.35
0.62
Sum
13.3
15.6
2
Maximum peak value (m/s )
X
Y
4.23
4.97
Weighted r.m.s. Acceleration (m/s2)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
186
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: AO51HMY
Ploughing
Task:
Edwards, Farmers/Contractors, Mattishall
Place:
1.75
)
Total VDV (m/s
Time
X
6.6
03:15
Day
15
Month
Jan
Year
2
Start time:
13:47
Z
0.52
Sum
0.95
Z
6.08
Sum
6.57
Month
Jan
Year
2
Start time:
13:47
Z
0.47
Sum
1.13
Z
5.06
Sum
6.35
2
Y
9.6
Z
7.9
Average r.m.s. (Aeq) (m/s )
X
Y
0.43
0.67
Sum
14.1
2
Maximum peak value (m/s )
X
Y
4.10
4.20
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: AO51HMY
Ploughing
Task:
Edwards, Farmers/Contractors, Mattishall
Place:
1.75
Day
15
2
Total VDV (m/s
)
Time
X
8.6
03:15
8-hr est tot
10.8
Y
12.3
15.3
Z
6.7
8.4
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.99
>24
r.m.s./A(8)
2.72
14.39
Average r.m.s. (Aeq) (m/s )
X
Y
0.58
0.86
Sum
16.4
20.5
2
Maximum peak value (m/s )
X
Y
5.08
5.56
Weighted r.m.s. Acceleration (m/s2)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
187
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: W823TPW
Ploughing
Task:
Carbrooke Estates, Norfolk
Place:
Total VDV (m/s1.75)
Time
X
Y
Z
Day
22
Month
Jan
Year
2
Start time:
Sum
Average r.m.s. (Aeq) (m/s2)
X
Y
Z
Sum
Maximum peak value (m/s2)
X
Y
Z
Sum
Month
Jan
Year
2
Start time:
11:24
Z
0.26
Sum
0.67
Z
7.63
Sum
7.69
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: W823TPW
Ploughing
Task:
Carbrooke Estates, Norfolk
Place:
Day
22
1.75
2
)
Total VDV (m/s
Time
X
7.5
04:15
8-hr est tot
8.8
Y
8.7
10.2
Z
4.2
4.9
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
5.13
>24
r.m.s./A(8)
8.29
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.39
0.49
Sum
12.2
14.3
2
Maximum peak value (m/s )
X
Y
4.79
4.83
Weighted r.m.s. Acceleration (m/s2)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
188
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: X442NJN
Drilling
Task:
Stevenage
Place:
Day
6
1.75
Month
Mar
Year
2
Start time:
08:06
Z
0.28
Sum
0.54
Z
4.19
Sum
4.45
Month
Mar
Year
2
Start time:
08:06
Z
0.27
Sum
0.69
Z
29.10
Sum
28.90
2
)
Total VDV (m/s
Time
X
6.5
05:15
Y
7.5
Z
5.9
Average r.m.s. (Aeq) (m/s )
X
Y
0.28
0.37
Sum
11.5
2
Maximum peak value (m/s )
X
Y
4.34
3.53
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: X442NJN
Drilling
Task:
Stevenage
Place:
Day
6
1.75
2
)
Total VDV (m/s
Time
X
7.8
05:15
8-hr est tot
8.7
Y
12.0
13.3
Z
10.5
11.7
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
1.74
>24
r.m.s./A(8)
7.04
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.35
0.53
Sum
17.1
19.0
2
Maximum peak value (m/s )
X
Y
5.95
8.18
Weighted r.m.s. Acceleration (m/s2)
2.0
1.6
1.2
0.8
0.4
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
189
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: W823TPW
Cultivating ploughed land
Task:
Carbrooke Estates
Place:
Day
27
1.75
)
Total VDV (m/s
Time
X
7.1
04:45
Month
Mar
Year
2
Start time:
09:26
Z
0.34
Sum
0.61
Maximum peak value (m/s )
X
Y
5.63
6.38
Z
11.20
Sum
11.60
Day
27
Month
Mar
Year
2
Start time:
09:26
Z
0.31
Sum
0.86
Z
15.30
Sum
15.40
2
Y
9.0
Z
8.5
Average r.m.s. (Aeq) (m/s )
X
Y
0.31
0.39
Sum
14.0
2
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: W823TPW
Cultivating ploughed land
Task:
Carbrooke Estates
Place:
1.75
2
Total VDV (m/s
)
Time
X
9.9
04:45
8-hr est tot
11.3
Y
14.8
16.9
Z
8.0
9.1
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.68
19.29
r.m.s./A(8)
4.51
23.84
Average r.m.s. (Aeq) (m/s )
X
Y
0.45
0.67
Sum
19.1
21.8
2
Maximum peak value (m/s )
X
Y
8.76
9.74
Weighted r.m.s. Acceleration (m/s2)
2.0
1.6
1.2
0.8
0.4
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
190
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: W271DNO
Fertiliser spreading
Task:
R Melbourne, Contractor, Stevenage
Place:
1.75
)
Total VDV (m/s
Time
X
6.6
04:30
Day
5
Month
Mar
Year
2
Start time:
08:44
Z
0.33
Sum
0.65
Maximum peak value (m/s )
X
Y
4.77
5.46
Z
10.70
Sum
10.70
Day
5
Month
Mar
Year
2
Start time:
08:45
Z
0.40
Sum
0.92
Z
13.10
Sum
13.30
2
Y
9.4
Z
7.1
Average r.m.s. (Aeq) (m/s )
X
Y
0.33
0.45
Sum
13.3
2
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: W271DNO
Fertiliser spreading
Task:
R Melbourne, Contractor, Stevenage
Place:
1.75
2
Total VDV (m/s
)
Time
X
10.1
04:30
8-hr est tot
11.7
Y
13.8
16.0
Z
9.8
11.3
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.84
23.93
r.m.s./A(8)
4.63
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.50
0.66
Sum
19.3
22.3
2
Maximum peak value (m/s )
X
Y
7.95
10.15
Weighted r.m.s. Acceleration (m/s2)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
191
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM#165
Reg No: X701XVG
Fertiliser Spreader
Task:
G W Harold, Stanhoe
Place:
Day
12
1.75
)
Total VDV (m/s
Time
X
8.6
04:15
Month
Mar
Year
2
Start time:
12:19
Z
0.31
Sum
0.54
Z
3.62
Sum
8.03
Month
Mar
Year
2
Start time:
12:19
Z
0.29
Sum
0.70
Z
14.00
Sum
14.00
2
Y
6.2
Z
5.4
Average r.m.s. (Aeq) (m/s )
X
Y
0.35
0.29
Sum
11.8
2
Maximum peak value (m/s )
X
Y
6.69
4.63
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM#165
Reg No: X701XVG
Fertiliser Spreader
Task:
G W Harold, Stanhoe
Place:
Day
12
1.75
2
Total VDV (m/s
)
Time
X
9.4
04:15
8-hr est tot
11.0
Y
10.3
12.1
Z
7.1
8.3
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
2.55
>24
r.m.s./A(8)
8.39
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.41
0.49
Sum
15.4
18.1
2
Maximum peak value (m/s )
X
Y
9.62
9.83
Weighted r.m.s. Acceleration (m/s2)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
192
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: W241SNH
Fertiliser Spreading
Task:
M Cornwall, Market Harborough
Place:
Day
13
1.75
)
Total VDV (m/s
Time
X
6.4
04:30
Month
Mar
Year
2
Start time:
09:10
Z
0.38
Sum
0.67
Z
8.98
Sum
9.37
Month
Mar
Year
2
Start time:
09:10
Z
0.42
Sum
1.01
Z
23.80
Sum
24.30
2
Y
10.5
Z
9.1
Average r.m.s. (Aeq) (m/s )
X
Y
0.30
0.46
Sum
15.2
2
Maximum peak value (m/s )
X
Y
4.28
6.82
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: W241SNH
Fertiliser Spreading
Task:
M Cornwall, Market Harborough
Place:
Day
13
1.75
2
)
Total VDV (m/s
Time
X
10.1
04:30
8-hr est tot
11.6
Y
17.9
20.7
Z
15.1
17.4
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.30
8.44
r.m.s./A(8)
3.27
17.32
Average r.m.s. (Aeq) (m/s )
X
Y
0.48
0.78
Sum
25.0
28.9
2
Maximum peak value (m/s )
X
Y
7.83
12.50
Weighted r.m.s. Acceleration (m/s2)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
193
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: X839BAW
Grain haulage
Task:
C Mills, Wellingborough
Place:
Day
30
1.75
)
Total VDV (m/s
Time
X
7.1
03:45
Month
Jan
Year
2
Start time:
10:20
Z
0.46
Sum
0.67
Maximum peak value (m/s )
X
Y
4.34
3.68
Z
10.30
Sum
10.60
Day
30
Month
Jan
Year
2
Start time:
10:20
Z
0.34
Sum
0.82
Z
14.30
Sum
14.20
2
Y
5.9
Z
9.6
Average r.m.s. (Aeq) (m/s )
X
Y
0.37
0.32
Sum
13.2
2
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: X839BAW
Grain haulage
Task:
C Mills, Wellingborough
Place:
1.75
2
Total VDV (m/s
)
Time
X
9.9
03:45
8-hr est tot
12.0
Y
9.8
11.8
Z
7.8
9.5
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
2.63
>24
r.m.s./A(8)
6.61
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.55
0.50
Sum
15.7
19.0
2
Maximum peak value (m/s )
X
Y
6.57
6.85
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
Elapsed Time (hrs)
Transverse (X-axis) seat
Aeg
One minute time history of weighted r.m.s. seat accelerations (X-axis) and running average
of r.m.s. acceleration (Aeq) (X-axis)
194
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: AO51HMY
Sugar Beet Haulage
Task:
Edwards, Farmer/Contractor, Mattishall
Place:
1.75
Total VDV (m/s
)
Time
X
7.6
04:45
Day
19
Month
Feb
Year
2
Start time:
07:59
Z
0.38
Sum
0.65
Z
7.99
Sum
7.99
Month
Feb
Year
2
Start time:
08:00
Z
0.37
Sum
0.86
Z
7.90
Sum
11.20
2
Y
8.3
Z
8.9
Average r.m.s. (Aeq) (m/s )
X
Y
0.37
0.37
Sum
14.2
2
Maximum peak value (m/s )
X
Y
5.32
6.24
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: AO51HMY
Sugar Beet Haulage
Task:
Edwards, Farmer/Contractor, Mattishall
Place:
1.75
Day
19
2
Total VDV (m/s
)
Time
X
10.5
04:44
8-hr est tot
12.0
Y
12.6
14.3
Z
7.7
8.8
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
1.31
>24
r.m.s./A(8)
6.00
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.52
0.58
Sum
17.9
20.4
2
Maximum peak value (m/s )
X
Y
6.57
10.92
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (X-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (X-axis) and running average
of r.m.s. acceleration (Aeq) (X-axis)
195
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: TM165
Reg No: W823TPW
Trailer Work (Sugar Beet Haulage)
Task:
Carbrooke Estates, Norfolk
Place:
Day
13
1.75
)
Total VDV (m/s
Time
X
6.2
04:00
Month
Dec
Year
1
Start time:
12:48
Z
0.26
Sum
0.50
Z
0.00
Sum
0.00
Month
Dec
Year
1
Start time:
12:48
Z
0.29
Sum
0.67
Z
0.00
Sum
0.00
2
Y
6.4
Z
6.1
Average r.m.s. (Aeq) (m/s )
X
Y
0.30
0.30
Sum
10.7
2
Maximum peak value (m/s )
X
Y
0.00
0.00
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: TM165
Reg No: W823TPW
Trailer Work (Sugar Beet Haulage)
Task:
Carbrooke Estates, Norfolk
Place:
Day
13
1.75
)
Total VDV (m/s
Time
X
9.8
04:00
8-hr est tot
11.7
Estimated values
Time to EAV (hr):
Time to ELV (hr):
2
Y
8.0
9.5
Z
6.1
7.2
VDV
2.94
>24
r.m.s./A(8)
9.10
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.47
0.38
Sum
14.0
16.6
2
Maximum peak value (m/s )
X
Y
0.00
0.00
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (X-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (X-axis) and running average
of r.m.s. acceleration (Aeq) (X-axis)
196
Appendix 2.8.2
Fully Suspended (Front & Rear Axle) Tractor (JCB Fastrac 3185)
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB
Reg No: Y585APW
Ploughing
Task:
John Orford (Contractor) Diss
Place:
Day
22
1.75
)
Total VDV (m/s
Time
X
7.1
04:00
Month
Feb
Year
2
Start time:
11:27
Z
0.27
Sum
0.77
Z
2.79
Sum
4.24
Month
Feb
Year
2
Start time:
11:27
Z
0.33
Sum
1.12
Z
8.05
Sum
9.58
2
Y
9.3
Z
4.5
Average r.m.s. (Aeq) (m/s )
X
Y
0.44
0.57
Sum
12.5
2
Maximum peak value (m/s )
X
Y
3.54
3.95
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB
Reg No: Y585APW
Ploughing
Task:
John Orford (Contractor) Diss
Place:
Day
22
1.75
2
)
Total VDV (m/s
Time
X
8.8
04:00
8-hr est tot
10.5
Y
16.8
19.9
Z
6.3
7.5
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.35
9.85
r.m.s./A(8)
2.31
12.24
Average r.m.s. (Aeq) (m/s )
X
Y
0.54
0.93
Sum
19.8
23.5
2
Maximum peak value (m/s )
X
Y
4.89
9.56
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
197
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac 3185
Reg No: Y624WER
Ploughing
Task:
Fen Farming Co, Thorney, Cambs
Place:
Day
19
1.75
)
Total VDV (m/s
Time
X
6.8
05:45
Month
Dec
Year
1
Start time:
09:58
Z
0.30
Sum
0.57
Z
0.00
Sum
0.00
Month
Dec
Year
1
Start time:
09:57
Z
0.30
Sum
0.93
Z
0.00
Sum
0.00
2
Y
8.5
Z
5.9
Average r.m.s. (Aeq) (m/s )
X
Y
0.29
0.39
Sum
12.4
2
Maximum peak value (m/s )
X
Y
0.00
0.00
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3185
Reg No: Y624WER
Ploughing
Task:
Fen Farming Co, Thorney, Cambs
Place:
Day
19
1.75
2
Total VDV (m/s
)
Time
X
7.7
05:45
8-hr est tot
8.3
Y
20.2
21.9
Z
9.1
9.8
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.24
6.74
r.m.s./A(8)
3.06
16.18
Average r.m.s. (Aeq) (m/s )
X
Y
0.34
0.81
Sum
22.9
24.9
2
Maximum peak value (m/s )
X
Y
0.00
0.00
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
198
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac 3185
Reg No: T933NEG
Ploughing
Task:
Russell, Contractor, Downham Market
Place:
1.75
)
Total VDV (m/s
Time
X
9.5
04:30
Day
13
Month
Feb
Year
2
Start time:
09:59
Z
0.34
Sum
0.87
Z
6.49
Sum
7.78
Month
Feb
Year
2
Start time:
09:59
Z
0.39
Sum
1.03
Z
17.70
Sum
17.80
2
Y
11.9
Z
6.1
Average r.m.s. (Aeq) (m/s )
X
Y
0.48
0.65
Sum
16.3
2
Maximum peak value (m/s )
X
Y
6.27
5.74
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3185
Reg No: T933NEG
Ploughing
Task:
Russell, Contractor, Downham Market
Place:
1.75
Day
13
2
Total VDV (m/s
)
Time
X
11.7
04:30
8-hr est tot
13.5
Y
14.2
16.4
Z
10.0
11.6
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.76
21.52
r.m.s./A(8)
3.47
18.37
Average r.m.s. (Aeq) (m/s )
X
Y
0.59
0.76
Sum
20.4
23.6
2
Maximum peak value (m/s )
X
Y
7.34
6.94
Weighted r.m.s. Acceleration (m/s2)
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
199
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac 3185
Reg No: W193BAV
Cultivating
Task:
Russell Contractors, Downham Market
Place:
1.75
)
Total VDV (m/s
Time
X
7.2
03:45
Day
26
Month
Mar
Year
2
Start time:
09:18
Z
0.37
Sum
0.80
Z
3.87
Sum
6.98
Month
Mar
Year
2
Start time:
09:19
Z
0.46
Sum
1.11
Z
13.70
Sum
13.60
2
Y
11.2
Z
6.7
Average r.m.s. (Aeq) (m/s )
X
Y
0.38
0.61
Sum
14.8
2
Maximum peak value (m/s )
X
Y
4.27
6.01
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3185
Reg No: W193BAV
Cultivating
Task:
Russell Contractors, Downham Market
Place:
1.75
Day
26
2
Total VDV (m/s
)
Time
X
10.6
03:45
8-hr est tot
12.8
Y
18.0
21.7
Z
9.5
11.5
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.25
7.01
r.m.s./A(8)
2.79
14.75
Average r.m.s. (Aeq) (m/s )
X
Y
0.54
0.85
Sum
22.4
27.1
2
Maximum peak value (m/s )
X
Y
7.34
11.21
Weighted r.m.s. Acceleration (m/s2)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
200
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac 3185
Reg No: Y585APW
Dutch Harrow
Task:
John Orford, Contractor, Diss
Place:
Day
3
1.75
)
Total VDV (m/s
Time
X
11.9
04:30
Month
Apr
Year
2
Start time:
08:12
Z
0.64
Sum
1.28
Maximum peak value (m/s )
X
Y
7.97
9.93
Z
11.00
Sum
12.20
Day
3
Month
Apr
Year
2
Start time:
08:12
Z
0.65
Sum
1.73
2
Y
15.2
Z
11.1
Average r.m.s. (Aeq) (m/s )
X
Y
0.69
0.88
Sum
22.2
2
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3185
Reg No: Y585APW
Dutch Harrow
Task:
John Orford, Contractor, Diss
Place:
1.75
2
Total VDV (m/s
)
Time
X
19.2
04:30
8-hr est tot
22.1
Y
25.5
29.4
Z
13.4
15.5
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.07
2.08
r.m.s./A(8)
1.09
5.76
Average r.m.s. (Aeq) (m/s )
X
Y
0.86
1.36
Sum
34.1
39.3
2
Maximum peak value (m/s )
X
Y
15.4
16.80
Z
15.80
Sum
21.80
Weighted r.m.s. Acceleration (m/s2)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
201
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac 3155
Reg No: W378YGS
Drag Harrow
Task:
Hayhill Farming, Haynes
Place:
Day
5
1.75
)
Total VDV (m/s
Time
X
10.6
04:00
Month
Apr
Year
2
Start time:
07:02
Z
0.50
Sum
1.24
Z
6.18
Sum
6.50
Month
Apr
Year
2
Start time:
07:03
Z
0.63
Sum
1.76
Z
26.90
Sum
27.00
2
Y
14.2
Z
7.6
Average r.m.s. (Aeq) (m/s )
X
Y
0.67
0.92
Sum
19.3
2
Maximum peak value (m/s )
X
Y
4.82
5.94
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3155
Reg No: W378YGS
Drag Harrow
Task:
Hayhill Farming, Haynes
Place:
Day
5
1.75
2
)
Total VDV (m/s
Time
X
14.2
04:00
8-hr est tot
16.9
Y
22.0
26.2
Z
12.1
14.4
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.12
3.32
r.m.s./A(8)
1.04
5.51
Average r.m.s. (Aeq) (m/s )
X
Y
0.89
1.39
Sum
28.5
33.9
2
Maximum peak value (m/s )
X
Y
6.87
10.21
Weighted r.m.s. Acceleration (m/s2)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
202
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac 3155
Reg No: W378YGS
Spreading fertiliser
Task:
Hayhill Farming, Haynes
Place:
Day
4
1.75
)
Total VDV (m/s
Time
X
7.3
04:45
Month
Apr
Year
2
Start time:
06:28
Z
0.31
Sum
0.64
Maximum peak value (m/s )
X
Y
5.25
5.68
Z
10.40
Sum
10.80
Day
4
Month
Apr
Year
2
Start time:
06:28
Z
0.41
Sum
0.86
Z
27.50
Sum
27.40
2
Y
9.6
Z
6.7
Average r.m.s. (Aeq) (m/s )
X
Y
0.35
0.45
Sum
13.7
2
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3155
Reg No: W378YGS
Spreading fertiliser
Task:
Hayhill Farming, Haynes
Place:
1.75
2
)
Total VDV (m/s
Time
X
10.3
04:45
8-hr est tot
11.7
Y
12.8
14.6
Z
12.7
14.4
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
1.20
>24
r.m.s./A(8)
5.86
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.48
0.58
Sum
20.4
23.3
2
Maximum peak value (m/s )
X
Y
7.91
7.97
Weighted r.m.s. Acceleration (m/s2)
2.0
1.8
1.5
1.3
1.0
0.8
0.5
0.3
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
203
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac 3155
Reg No: W133TRP
Spreading fertiliser
Task:
Barnes contractor, Marston
Place:
Day
8
1.75
)
Total VDV (m/s
Time
X
5.7
06:00
Month
Apr
Year
2
Start time:
09:31
Z
0.21
Sum
0.43
Z
3.69
Sum
3.97
Month
Apr
Year
2
Start time:
09:16
Z
0.26
Sum
0.52
Z
17.90
Sum
17.80
2
Y
6.1
Z
4.4
Average r.m.s. (Aeq) (m/s )
X
Y
0.23
0.29
Sum
9.3
2
Maximum peak value (m/s )
X
Y
3.88
3.42
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3155
Reg No: W133TRP
Spreading fertiliser
Task:
Barnes contractor, Marston
Place:
Day
8
1.75
Total VDV (m/s
)
Time
X
6.4
06:00
8-hr est tot
6.9
Estimated values
Time to EAV (hr):
Time to ELV (hr):
2
Y
7.8
8.4
Z
7.9
8.5
VDV
10.72
>24
r.m.s./A(8)
15.32
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.27
0.36
Sum
12.4
13.4
2
Maximum peak value (m/s )
X
Y
3.96
7.66
Weighted r.m.s. Acceleration (m/s2)
2.0
1.8
1.5
1.3
1.0
0.8
0.5
0.3
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
Elapsed Time (hrs)
Transverse (Y-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (Y-axis) and running average
of r.m.s. acceleration (Aeq) (Y-axis)
204
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac
Reg No: W193BAV
Trailer Work (Sugar Beet Haulage)
Task:
David Russell Contractor (Downham Market)
Place:
1.75
Day
17
Month
Jan
Year
2
Start time:
11:47
Z
0.33
Sum
0.74
Z
8.55
Sum
9.40
Month
Jan
Year
2
Start time:
11:47
Z
0.38
Sum
1.03
Z
18.10
Sum
18.10
2
)
Total VDV (m/s
Time
X
11.5
05:30
Y
9.3
Z
8.8
Average r.m.s. (Aeq) (m/s )
X
Y
0.50
0.44
Sum
17.1
2
Maximum peak value (m/s )
X
Y
7.25
4.27
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac
Reg No: W193BAV
Trailer Work (Sugar Beet Haulage)
Task:
David Russell Contractor (Downham Market)
Place:
1.75
Day
17
2
)
Total VDV (m/s
Time
X
16.3
05:30
8-hr est tot
17.9
Y
16.6
18.2
Z
9.6
10.6
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.50
14.06
r.m.s./A(8)
3.93
20.79
Average r.m.s. (Aeq) (m/s )
X
Y
0.71
0.65
Sum
24.4
26.8
2
Maximum peak value (m/s )
X
Y
11.09
9.84
Weighted r.m.s. Acceleration (m/s2)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
Elapsed Time (hrs)
Transverse (X-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (X-axis) and running average
of r.m.s. acceleration (Aeq) (X-axis)
205
6:0
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac
Reg No: V535SVV
Trailer Work (Sugar Beet Haulage)
Task:
David Russell Contractor, Swaffham
Place:
Day
8
1.75
)
Total VDV (m/s
Time
X
16.0
05:00
Month
Jan
Year
2
Start time:
11:58
Z
0.39
Sum
0.99
Z
0.00
Sum
0.00
Month
Jan
Year
2
Start time:
11:43
Z
0.48
Sum
1.48
Z
0.00
Sum
0.00
4:30
5:00
2
Y
13.6
Z
9.3
Average r.m.s. (Aeq) (m/s )
X
Y
0.70
0.59
Sum
22.9
2
Maximum peak value (m/s )
X
Y
0.00
0.00
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac
Reg No: V535SVV
Trailer Work (Sugar Beet Haulage)
Task:
David Russell Contractor, Swaffham
Place:
Day
8
1.75
2
)
Total VDV (m/s
Time
X
25.7
05:00
8-hr est tot
28.9
Y
20.2
22.8
Z
12.0
13.4
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.08
2.22
r.m.s./A(8)
1.60
8.49
Average r.m.s. (Aeq) (m/s )
X
Y
1.12
0.85
Sum
34.7
39.0
2
Maximum peak value (m/s )
X
Y
0.00
0.00
Weighted r.m.s. Acceleration (m/s2)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (X-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (X-axis) and running average
of r.m.s. acceleration (Aeq) (X-axis)
206
Larson Davis HVM100
SN:00272
Floor
Location:
Machine: JCB Fastrac 3185
Reg No: Y585APW
Beet haulage
Task:
John Orford, Contractor, Diss
Place:
Day
21
1.75
)
Total VDV (m/s
Time
X
9.6
04:30
Month
Feb
Year
2
Start time:
11:10
Z
0.24
Sum
0.59
Z
8.69
Sum
9.53
Month
Feb
Year
2
Start time:
11:10
Z
0.33
Sum
0.90
Z
18.70
Sum
18.70
2
Y
10.4
Z
6.1
Average r.m.s. (Aeq) (m/s )
X
Y
0.39
0.38
Sum
15.1
2
Maximum peak value (m/s )
X
Y
6.69
6.12
Larson Davis HVM100
SN:00215
Seat
Location:
Machine: JCB Fastrac 3185
Reg No: Y585APW
Beet haulage
Task:
John Orford, Contractor, Diss
Place:
Day
21
1.75
2
Total VDV (m/s
)
Time
X
13.2
04:30
8-hr est tot
15.3
Y
21.9
25.3
Z
10.6
12.2
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.13
3.81
r.m.s./A(8)
4.94
>24
Average r.m.s. (Aeq) (m/s )
X
Y
0.54
0.64
Sum
26.4
30.5
2
Maximum peak value (m/s )
X
Y
11.21
17.36
Weighted r.m.s. Acceleration (m/s2)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
Elapsed Time (hrs)
Transverse (X-axis) seat
Aeq
One minute time history of weighted r.m.s. seat accelerations (X-axis) and running average
of r.m.s. acceleration (Aeq) (X-axis)
207
208
APPENDIX 3.1:
A3.1.1
ATV WBV & HAV Emission Data:- ISO Test Track
Programme
Machine A
Average r.m.s. seat acceleration (1.4 multiplier) (m/s 2 )
Y
Z
0.96
1.06
0.98
1.21
1.02
1.33
1.07
1.44
1.14
1.51
1.13
1.57
Actual
Speed (km/h)
9.3
11.4
13.0
14.6
16.7
18.5
X
0.82
0.96
0.97
1.03
1.07
1.14
Actual
Speed (km/h)
9.3
11.4
13.0
14.6
16.7
18.5
Average r.m.s. footrest acceleration (1.4 multiplier) (m/s 2 )
X
Y
Z
RSS
0.51
0.75
2.36
2.53
0.59
0.79
2.87
3.03
0.58
0.86
3.08
3.25
0.53
0.86
3.30
3.45
0.48
0.87
3.46
3.60
0.48
0.81
3.48
3.61
Surface
ISO
100m
Track
Smooth
Concrete
Overall
Field
Speed
(km/h)
8.7
12.4
13.9
15.3
16.4
19.0
4.3
8.1
11.4
14.3
16.4
Average
-
X
2.81
3.81
4.19
4.65
4.77
5.06
1.04
1.37
0.95
0.81
0.87
Y
2.09
3.08
2.97
2.86
2.95
3.66
0.70
1.31
1.20
0.88
1.11
1.87
2.13
RSS
1.65
1.82
1.94
2.07
2.18
2.25
Average r.m.s. hand-arm vibration (m/s2)
Left
Right
Z
RSS
X
Y
Z
3.71
5.10
2.82
2.05
3.38
5.47
7.34
3.87
3.15
4.89
6.04
7.93
4.40
2.69
4.92
6.29
8.33
4.95
2.74
5.25
6.72
8.75
4.74
2.78
5.33
7.12
9.47
5.51
3.31
6.13
1.17
1.71
1.00
1.34
1.33
3.02
3.57
1.26
1.49
1.95
1.74
2.32
0.71
1.74
1.20
1.60
2.00
0.65
1.25
1.36
1.84
2.32
0.77
1.51
1.46
2.38
2.88
209
4.04
1.89
1.93
2.98
RSS
4.86
6.99
7.13
7.72
7.66
8.88
2.14
2.76
2.23
1.96
2.24
2.26
4.02
A3.1.2
Machine B
Average r.m.s. seat acceleration (1.4 multiplier) (m/s 2 )
Y
Z
1.05
1.38
1.16
1.51
1.26
1.74
1.36
1.86
1.42
1.89
1.50
1.84
Actual
Speed (km/h)
9.4
11.4
13.3
14.9
17.7
19.5
X
0.66
0.73
0.76
0.81
0.84
0.88
Actual
Speed (km/h)
9.4
11.4
13.3
14.9
17.7
19.5
Average r.m.s. footrest acceleration (1.4 multiplier) (m/s 2 )
X
Y
Z
RSS
0.56
0.59
1.86
2.03
0.58
0.64
2.13
2.30
0.52
0.64
2.32
2.46
0.53
0.66
2.55
2.68
0.57
0.70
2.87
3.01
0.72
0.77
2.98
3.16
RSS
1.86
2.04
2.27
2.44
2.52
2.53
2
Surface
Speed
(km/h)
ISO 100m
Track
8.4
11.6
13.3
16.0
18.0
20.6
Smooth
Concrete
-
Overall
Field
Circuit
-
X
1.29
1.99
2.30
2.55
3.01
3.11
0.54
0.73
0.72
0.74
1.09
1.97
1.21
1.23
Average r.m.s. hand-arm vibration (m/s )
Left
Right Hand
Y
Z
RSS
X
Y
1.53
2.24
3.00
1.39
1.46
2.07
3.37
4.43
2.35
2.29
2.61
3.80
5.15
2.57
2.46
3.25
4.33
5.98
2.89
2.85
3.50
5.20
6.95
3.55
3.02
3.90
5.60
7.50
3.67
3.39
0.76
0.77
1.21
0.42
0.73
1.11
1.66
2.13
1.09
1.24
1.08
2.48
2.80
1.26
1.25
1.07
2.11
2.48
1.00
1.09
2.51
3.10
4.13
2.38
2.55
1.76
6.17
6.71
2.31
3.16
Average:
Average:
3.24
1.65
2.42
3.17
1.65
2.18
1.70
2.43
3.21
1.58
2.03
Average:
Average:
3.19
210
Z
1.97
3.11
3.42
3.89
4.77
5.11
1.06
1.37
1.49
1.08
1.15
2.37
2.35
2.37
RSS
2.82
4.52
4.93
5.62
6.67
7.15
1.35
2.15
2.32
1.83
3.67
4.58
2.65
3.61
3.50
3.55
A3.1.3
Machine C
Average r.m.s. seat acceleration (1.4 multiplier) (m/s 2 )
Y
Z
1.54
2.29
1.64
2.94
1.65
3.16
1.56
3.32
1.62
3.15
1.65
3.11
Actual
Speed (km/h)
9.3
11.7
13.6
15.7
18.0
18.6
X
0.77
0.81
0.83
0.91
0.92
0.96
Actual
Speed (km/h)
9.3
11.7
13.6
15.7
18.0
18.6
Average r.m.s. footrest acceleration (1.4 multiplier) (m/s 2 )
X
Y
Z
RSS
0.74
0.73
3.40
3.56
0.79
0.81
3.03
3.24
0.83
0.83
2.71
2.95
0.72
0.80
3.59
3.75
0.69
0.86
3.43
3.60
0.76
0.88
3.35
3.54
RSS
2.86
3.46
3.66
3.78
3.66
3.65
2
Surface
Speed
(km/h)
ISO 100m
Track
9.6
11.8
13.8
16.4
20.0
20.9
Smooth
Concrete
-
Overall
Field
Circuit
-
X
1.87
2.84
3.36
3.46
3.71
3.63
1.71
1.16
0.91
0.70
0.73
0.47
1.50
1.51
Average r.m.s. hand-arm vibration (m/s )
Left
Right
Y
Z
RSS
X
Y
Z
2.21
3.68
4.68
2.28
2.31
3.88
1.97
4.92
6.01
3.28
2.84
4.77
2.29
5.72
7.02
3.86
3.19
5.56
2.64
5.81
7.26
4.09
3.38
5.72
3.00
5.91
7.60
4.35
3.42
6.14
3.58
5.77
7.70
4.44
3.90
6.43
0.97
5.62
5.95
1.38
2.41
2.62
0.87
2.53
2.92
1.13
1.06
2.43
0.53
1.62
1.93
0.61
1.14
1.50
0.65
2.54
2.71
0.45
1.30
1.14
0.88
3.21
3.41
0.58
1.28
1.86
0.64
2.10
2.25
0.58
0.83
1.09
Average:
Average:
3.19
1.74
2.99
3.77
1.55
1.93
3.14
1.56
2.99
3.70
1.59
2.02
2.89
Average:
Average:
3.73
211
RSS
5.06
6.45
7.48
7.80
8.27
8.73
3.82
2.88
1.98
1.79
2.33
1.49
2.38
4.00
3.87
3.93
A3.1.4
Machine D
Average r.m.s. seat acceleration (1.4 multiplier) (m/s 2 )
Y
Z
1.08
1.08
1.16
1.24
1.24
1.26
1.34
1.28
1.51
1.37
1.67
1.41
Actual
Speed (km/h)
9.9
11.9
13.5
15.5
18.0
20.0
X
0.78
0.83
0.84
0.87
0.89
0.83
Actual
Speed (km/h)
9.9
11.9
13.5
15.5
18.0
20.0
Average r.m.s. footrest acceleration (1.4 multiplier) (m/s 2 )
X
Y
Z
RSS
0.57
0.53
1.83
1.99
0.58
0.57
2.17
2.32
0.58
0.59
2.48
2.62
0.58
0.56
2.47
2.60
0.60
0.63
2.77
2.90
0.66
0.70
3.09
3.24
RSS
1.71
1.89
1.96
2.05
2.23
2.34
2
Surface
Speed
(km/h)
ISO 100m
Track
10.3
12.0
13.3
17.1
18.5
21.2
Smooth
Concrete
-
Overall
Field
Circuit
-
X
2.38
2.52
2.89
3.18
3.54
3.82
0.87
1.78
2.02
1.65
1.83
3.34
1.82
Average r.m.s. hand-arm vibration (m/s )
Left
Right
Y
Z
RSS
X
Y
Z
2.39
3.56
4.90
2.84
3.27
3.88
2.94
3.84
5.45
3.03
3.93
3.98
2.92
4.02
5.75
3.30
3.80
3.94
2.96
4.38
6.17
3.45
3.67
4.12
3.54
4.97
7.05
3.87
4.34
4.62
3.55
5.18
7.35
4.44
4.57
5.05
0.97
1.63
2.09
1.13
1.30
1.57
1.60
2.62
3.55
1.72
1.57
2.47
1.79
2.33
3.57
2.09
1.12
2.73
2.32
1.63
3.28
1.57
1.39
2.18
1.69
2.03
3.21
1.55
1.32
1.52
1.79
2.49
4.53
3.25
2.30
2.52
Average:
Average:
3.37
1.89
2.55
212
3.66
2.01
2.62
2.46
RSS
5.81
6.36
6.39
6.51
7.43
8.13
2.33
3.39
3.62
3.02
2.54
4.71
3.27
4.12
APPENDIX 3.2:
A3.2.1
ATV WBV & HAV Emission Data:- SRI ‘In-Field’
Programme
Machine A
Surface
Road
Track
Field
Overall
Surface
Road
Track
Field
Overall
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
X
0.30
0.87
0.95
0.88
Y
0.31
0.98
0.87
0.83
Z
0.52
1.21
1.97
1.60
RSS
0.67
1.78
2.36
2.01
Average r.m.s. footrest acceleration (1.4 multiplier) (m/s2)
X
0.27
0.39
0.45
0.44
Y
0.35
0.59
0.51
0.53
Z
1.88
2.38
2.56
2.37
RSS
1.93
2.48
2.65
2.46
NB:- For ‘in-field’ hand-arm vibration data see Appendix A3.1.1.
A3.2.2
Machine B
Surface
Road
Track
Field
Overall
Surface
Road
Track
Field
Overall
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
X
0.26
0.88
0.93
0.86
Y
0.26
0.78
0.84
0.75
Z
0.34
1.13
1.80
1.46
RSS
0.50
1.63
2.20
1.85
Average r.m.s. footrest acceleration (1.4 multiplier) (m/s2)
X
0.47
0.44
0.47
0.47
Y
0.34
0.52
0.42
0.43
Z
1.62
1.73
1.93
1.77
NB:- For ‘in-field’ hand-arm vibration data see Appendix A3.1.2.
213
RSS
1.73
1.86
2.03
1.88
A3.2.3
Machine C
Surface
Road
Track
Field
Overall
Surface
Road
Track
Field
Overall
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
X
0.21
0.77
0.87
0.81
Y
0.29
0.80
0.95
0.83
Z
0.27
1.30
2.26
1.80
RSS
0.45
1.71
2.60
2.14
Average r.m.s. footrest acceleration (1.4 multiplier) (m/s2)
X
0.72
0.54
0.66
0.64
Y
0.23
0.52
0.44
0.43
Z
1.50
2.28
2.63
2.38
RSS
1.68
2.40
2.74
2.50
NB:- For ‘in-field’ hand-arm vibration data see Appendix A3.1.3.
A3.2.4
Machine D
Surface
Road
Track
Field
Overall
Surface
Road
Track
Field
Overall
Average r.m.s. seat acceleration (1.4 multiplier) (m/s2)
X
0.19
0.64
0.79
0.73
Y
0.27
1.04
0.87
0.84
Z
0.37
0.93
1.41
1.19
RSS
0.50
1.53
1.84
1.63
Average r.m.s. footrest acceleration (1.4 multiplier) (m/s2)
X
0.50
0.54
0.47
0.50
Y
0.46
0.59
0.46
0.48
Z
1.80
2.00
2.05
1.90
NB:- For ‘in-field’ hand-arm vibration data see Appendix A3.1.4.
214
RSS
1.93
2.15
2.15
2.02
APPENDIX 3.3:
ATV ‘On-Farm’ WBV & HAV Exposure Data:Synopsis of Results
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Total VDV
Time
00:45
8-hr est tot
SN:00215
Seat
ATV
Month
Sep
Year
2
Start time:
07:55
Z
1.39
Sum
2.20
Z
22.10
Sum
22.10
Stock tour
Hill Farm #1 (1)
X
12.6
22.8
Y
16.1
29.1
Z
17.0
30.7
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.06
1.75
r.m.s./A(8)
1.03
5.46
Average rms (Leq)
X
1.06
Sum
26.5
48.0
Y
1.39
2
Maximum peak value (m/s )
X
Y
8.53
12.84
3.0
2
Weight ed r.m.s. Acceleration (m/s )
Day
24
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:15
0:30
0:45
1:00
Elapsed Time (hrs)
Vertical (Z-axis) seat
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Total VDV
Time
00:45
X
9.3
Aeq
SN:00272
Footrest
ATV
Day
24
Month
Sep
Year
2
Start time:
07:55
Stock tour
Hill Farm #1 (1)
Y
8.9
Z
38.7
Sum
40.8
Average rms (Leq)
X
0.71
Y
0.76
Z
3.62
Sum
3.69
Maximum peak value
X
7.84
Y
5.56
Z
26.80
Sum
26.80
2
Weighted r.m.s. Acceleration (m/s )
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0:00
0:15
0:30
0:45
1:00
Elapsed Time (hrs)
Vertical (Z-axis) footrest
One-minute time history of weighted r.m.s. seat & footrest accelerations (Z-axis) and running
average of seat r.m.s. acceleration (Aeq) (Z-axis)
215
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Total VDV
Time
01:15
8-hr est tot
SN:00215
Seat
ATV
Month
Sep
Year
2
Start time:
07:45
Z
1.21
Sum
1.98
Z
31.70
Sum
32.00
Stock tour
Hill Farm #1 (2)
X
12.4
19.8
Y
17.5
27.8
Z
18.4
29.2
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.08
2.14
r.m.s./A(8)
1.21
6.40
Weighted r.m.s. Acceleration (m/s2)
Day
25
Average rms (Leq)
X
0.90
Sum
28.1
44.7
Y
1.29
2
Maximum peak value (m/s )
X
Y
9.83
14.42
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:15
0:30
0:45
1:00
1:15
Elapsed Time (hrs)
Vertical (Y-axis) seat
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Weighted r.m.s. Acceleration (m/s2)
Total VDV
Time
01:15
X
9.6
Aeq
SN:00272
Footrest
ATV
Day
25
Month
Sep
Year
2
Start time:
07:45
Stock tour
Hill Farm #1 (2)
Y
9.8
Z
37.8
Sum
40.2
Average rms (Leq)
X
0.64
Y
0.74
Z
3.05
Sum
3.19
Maximum peak value
X
7.06
Y
5.84
Z
27.60
Sum
27.80
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0:00
0:15
0:30
0:45
1:00
Elapsed Time (hrs)
Vertical (Z-axis) footrest
One minute time history of weighted r.m.s. seat and footrest accelerations (Z-axis)
and running average of r.m.s. acceleration (Aeq) (Z-axis)
216
1:15
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Total VDV
Time
00:45
8-hr est tot
SN:00215
Seat/Saddle
ATV
Month
Dec
Year
2
Start time:
09:59
Z
0.87
Sum
1.31
Z
11.40
Sum
12.90
Shepherding
Hill Farm #2
X
10.0
18.0
Y
8.1
14.6
Z
10.9
19.7
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.36
10.27
r.m.s./A(8)
2.62
13.84
Weighted r.m.s. Acceleration (m/s2)
Day
12
Average rms (Leq)
X
0.72
Sum
16.8
30.4
Y
0.65
2
Maximum peak value (m/s )
X
Y
8.62
6.43
2.0
1.6
1.2
0.8
0.4
0.0
0:00
0:15
0:30
0:45
1:00
Elapsed Time (hrs)
Vertical (Z-axis) seat
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Weighted r.m.s. Acceleration (m/s2)
Total VDV
Time
00:45
X
7.7
Aeq
SN:00272
Footrest
ATV
Day
12
Month
Dec
Year
2
Start time:
09:58
Shepherding
Hill Farm #2
Y
5.2
Z
23.5
Sum
25.2
Average rms (Leq)
X
0.47
Y
0.43
Z
2.07
Sum
2.16
Maximum peak value
X
10.77
Y
3.63
Z
18.50
Sum
18.50
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0:00
0:15
0:30
0:45
1:00
Elapsed Time (hrs)
Vertical (Z-axis) footrest
One minute time history of weighted r.m.s. seat and footrest accelerations (Z-axis)
and running average of r.m.s. acceleration (Aeq) (Z-axis)
217
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Total VDV
Time
02:15
8-hr est tot
SN:00215
Seat/Saddle
ATV
Month
Dec
Year
2
Start time:
07:06
Z
0.85
Sum
1.25
Z
18.20
Sum
18.40
Feeding Game
Gamekeeper
X
11.3
15.5
Y
11.9
16.4
Z
15.6
21.4
Estimated values
Time to EAV (hr):
Time to ELV (hr):
VDV
0.26
7.47
r.m.s./A(8)
2.77
14.63
Weighted r.m.s. Acceleration (m/s2)
Day
10
Average rms (Leq)
X
0.55
Sum
22.2
30.4
Y
0.76
2
Maximum peak value (m/s )
X
Y
8.19
9.48
2.0
1.6
1.2
0.8
0.4
0.0
0:00
0:30
1:00
1:30
2:00
Elapsed Time (hrs)
Vertical (Z-axis) seat
Larson Davis HVM100
Location:
Machine:
Reg No:
Task:
Place:
Weighted r.m.s. Acceleration (m/s2)
Total VDV
Time
02:15
X
10.1
Aeq
SN:00272
Footrest
ATV
Day
10
Month
Dec
Year
2
Start time:
07:05
Feeding Game
Gamekeeper
Y
9.0
Z
45.6
Sum
47.5
Average rms (Leq)
X
0.57
Y
0.53
Z
3.30
Sum
3.38
Maximum peak value
X
8.23
Y
7.70
Z
25.10
Sum
25.00
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0:00
0:30
1:00
1:30
2:00
Elapsed Time (hrs)
Vertical (Z-axis) footrest
One minute time history of weighted r.m.s. seat and footrest accelerations (Z-axis)
and running average of r.m.s. acceleration (Aeq) (Z-axis)
218
APPENDIX 3.4:
ATV ‘On-Farm’ WBV Programme:Forward Speed & Operator Seat Presence Details
A3.4.1 Hill Farm #1
Whole-body vibration, first day
ATV Record of speed, Hill Farm#1 WBV(1)
60
50
Speed km/h
40
30
20
10
0
0
10
20
30
40
50
60
50
60
Elapsed time, minutes
ATV Record of driver presence, Hill Farm#1 WBV(1)
1.0
Seat switch, volts
0.8
0.6
0.4
0.2
0.0
0
10
20
30
40
Elapsed time, minutes
Hill Farm #1 was a 230 hectacre upland holding operated by the farmer with one stockman. It
was the stockman who drove the ATV on his morning round. On the first morning this took
very nearly an hour, and the machine was out of sight for all but the first half minute and the last
few seconds. The machine did not carry any load. The stockman was estimated to weigh
approx. 70 kg.
219
Whole-body vibration, second day
ATV Record of speed, Hill Farm#1 WBV(2)
60
50
Speed km/h
40
30
20
10
0
0
10
20
30
40
50
60
70
50
60
70
Elapsed time, minutes
ATV Record of driver presence, Hill Farm#1 WBV(2)
1.0
Seat switch, volts
0.8
0.6
0.4
0.2
0.0
0
10
20
30
40
Elapsed time, minutes
The second morning was a close repeat of the previous day, taking about 10 minutes longer.
This was probably accounted for by a stop at 16-22 minutes for reasons not explained.
Hand-arm vibration
No recording is available. The driver was away from the farmstead for only 35 minutes. I am
not sure whether this was because it came on to rain, or because there were other pressing jobs
(lambs to be loaded for market). It would seem reasonable to assume that daily use of the ATV
varies between ½ - 1 hour.
220
A3.4.2
Hill Farm #2
Whole-body vibration
ATV Record of speed, Hill Farm#2 WBV
60
50
Speed km/h
40
30
20
10
0
0
5
10
15
20
25
30
35
40
45
35
40
45
Elapsed time minutes
ATV Record of driver presence, Hill Farm#2 WBV
1.0
Seat switch, volts
0.8
0.6
0.4
0.2
0.0
0
5
10
15
20
25
30
Elapsed time minutes
Hill Farm #2 was a smaller farm run by a young farmer and his mother. It was the mother
(estimated weight approx. 70 kg) who rode the ATV. The overall operating time of about
35 minutes was probably typical of daily use, there being no very distant grazing areas. The
time was split into two sections. That between 5 - 25 minutes (see above) was spent fetching a
group of lambs into the yard, to be prepared for auction, with the aid of several dogs. After that,
she went out alone, and at higher speed to check on the rest of the stock.
221
A3.4.3
Gamekeeper
Whole-body vibration
ATV Record of speed, Gamekeeper#1 WBV
60
50
Speed km/h
40
30
20
10
0
0
15
30
45
60
75
90
105
120
135
150
120
135
150
Elapsed time, minutes
ATV Record of driver presence, Gamekeeper#1 WBV
1.0
Switch voltage
0.8
0.6
0.4
0.2
0.0
0
15
30
45
60
75
90
105
Elapsed time, minutes
This “farm” was bought about 12 years ago by a wealthy businessman, who lets out some of the
grazing and has built-up a series of shooting plantations. The whole covers about 200 hectares
on a shoulder of ground above the river Wye. There are tracks between and within the
plantations which are in places only passable on foot or on the ATV.
The work was split into two types of operation. For the first part (80 min) a feed hopper /
dispenser was mounted on the rear rack. The machine was driven out to a plantation, and then
driven more slowly for spreading feed, before returning for a refill. There were 5 such runs, but
the Keeper admitted to holding some work back from the previous day “to give me a good
stretch to measure”. After a 20-minute break, in which the feed hopper was removed, sacks of
222
feed were transported out to top up standing hoppers in the plantations. This gave shorter, faster
runs, with more time off the machine.
Separate calculations for the two types of operation do not show a very great difference. The
estimated weight of the gamekeeper was 90 kg. The ATV was a 2001-manufactured machine,
and may have been a more modern design than the other ‘on-farm’ ATVs tested. It had
puncture-resistant filling in the tyres, which were set to 5 psi.
Hand-arm vibration
ATV Record of speed, Gamekeeper#1 HAV
60
50
Speed km/h
40
30
20
10
0
0
5
10
15
20
25
30
35
40
45
Elapsed time minutes
As a result of the extra use of the machine on the previous day, there were only 4 runs with the
feed dispenser on this visit, totalling about one hour. Note that the TEAC recording stopped
after the third run. It is reasonable to assume that an average day’s use of the ATV is between
1 - 1½ hours.
223
224
APPENDIX 4:
Estimating WBV Exposure from Measured Data:Particular Issues
There are two features of the data reported here from commercial ‘on-farm’ work that are
worthy of discussion. These are first the fact that, except in the case of ATVs, the vibration
measurements did not cover the whole working day, and second the nature of the data itself.
In particular, it is the non-stationary nature of the data, in a statistical sense, which is of
concern.
2.5
20.0
2
16.0
1.5
12.0
1
8.0
0.5
4.0
0
0:00
VDV (m/s1.75)
Weighted r.m.s. Acceleration (m/s2)
The ‘on farm’ vibration exposure data obtained in this study is based on some of the longest
recording durations to be found in the literature. Nevertheless, it was restricted to
approximately 4 hours for each machine / location, this being the time for half a shift, and
allowing instruments to be mounted and removed before or after work or during a normal
break. In practice the sampling period varied between 3 ¼ hours and 6 hours. For stationary
data (i.e. limited variation of r.m.s. acceleration level and other statistical parameters with
time), such as that shown in Figure 5.29 (and reproduced in Figure A4.1 below), estimation of
daily exposure does not present any serious difficulties.
0.0
0:30
1:00
1:30
2:00
2:30
3:00
Elapsed Time (hrs)
Transverse (Y)
Figure A4.1
Aeq
VDV
Time history of weighted 1-minute r.m.s. accelerations (Y-axis, TM 165
seat – ploughing) plus development of equivalent continuous r.m.s.
acceleration (Aeq) & 15-minute record of Vibration Dose Value (VDV)
Using the r.m.s. approach, it can be seen that a level of equivalent continuous acceleration
(Aeq) (cumulative energy-equivalent, frequency-weighted r.m.s. acceleration) is reached after about
30 minutes, and does not change significantly throughout the remaining period of work. This
is explored further in Figure A4.2, where the time-base has been extended to 10 hours, and
the Aeq has been extended using the assumption that the vibration magnitude on the vehicle
continues as it was for the first 3¼ hours. The added curve shows the build-up of daily
exposure, measured as A(8) and, if 8 hours were worked, the value would be the same as the
Aeq, in this case 0.86 m/s2. If 10 hours were worked, the A(8) exposure would rise to
225
0.96 m/s2, whereas if the operator had finished ploughing when the recording finished, his
A(8) exposure would have been only 0.55 m/s2, assuming no other work involving exposure
to WBV had been undertaken. Because of the stationary nature of the data, very similar
values would have been estimated had the original vibration measurement been stopped after
1 hour, or even after only 30 minutes.
Weighted r.m.s. Acceleration (m/s2)
1.5
1.25
1
0.75
0.5
0.25
0
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:0
Elapsed Time (hrs)
1-min r.m.s. (Y)
Figure A4.2
Aeq (Y)
A(8)
Predicted development of equivalent continuous r.m.s. acceleration
(Aeq) and daily vibration exposure level (A(8)) if machine / operation
depicted in Figure A4.1 were to continue for 10 hours
Using the VDV approach, an exposure of 12.3 ms-1.75 was measured at the end of
3¼ hours (see Figure A4.1). This could be extended to a longer working day by applying the
simple formula:-
T2
VDV2 = VDV1 ⎡⎢ ⎤⎥
⎣T1 ⎦
1
4
(1)
where:-
VDV1
T2
=
the VDV measured (in a given axis) over measurement duration T1
=
the actual duration of exposure (machine operation) for which an
(estimated) VDV is required
This is illustrated in Figure A4.3, and is the method by which the “8-hour estimated total”
values, as presented in the results tables within this report, were obtained. As can be seen in
Figure A4.3, the estimated curve for growth of VDV approximates closely to the measured
curve. This means that estimated curves that could be used for projecting VDV growth for
longer periods could be based on measurements of only ½ to 1 hour, as shown in Figure A4.4.
226
2.5
16
2
12
10
1.5
8
1
6
VDV (m/s1.75)
Weighted r.m.s. Acceleration (m/s2)
14
4
0.5
2
0
0:00
0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
Elapsed Time (hrs)
1-min r.m.s. (Y)
Figure A4.3
Measured VDV
Estimated VDV
Estimated development of VDV over an extended (theoretical) period
of machine operation (i.e. beyond 3¼ hours actually measured)
16
2.5
2
10
1.75
1.5
)
12
8
1
6
VDV (m/s
2
Weighted r.m.s. Acceleration (m/s )
14
4
0.5
2
0
0:00
0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
Elapsed Time (hrs)
1-min r.m.s. (Y)
Figure A4.4
Measured VDV
VDV Est 3.25hr
VDV Est 1hr
VDV Est 30 min
Development of VDV: measured directly or estimated from alternative
durations of recorded (stationary) WBV data
However, in farm work, stationary data is the exception rather than the rule. A typical
example is the WBV measurement made upon a self-propelled sprayer (see Figure 4.20),
reproduced here as Figure A4.5. In this case, after a short delay, there are breaks for refilling
the tank, and several short periods of higher acceleration, two of which, occurring after
227
2.5
15.00
2
12.00
1.5
9.00
1
6.00
0.5
3.00
0
0:00
VDV (m/s1.75)
2
Weighted r.m.s. Acceleration (m/s )
3 hours, have a strong effect on the VDV measurement. In this case, using the r.m.s.
approach, the Aeq measured after 30 minutes is only about 50% of the value measured after
4¼ hours. However, the Aeq value after 1 hour operation is about 0.5 m/s2, which may be
close enough to the value of 0.6 m/s2 measured at 4¼ hours for practical purposes.
0.00
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y)
Aeq
VDV
Figure A4.5 Time history of weighted 1-minute r.m.s. accelerations (seat, Y-axis,
Air Spring Suspension Sprayer) plus development of equivalent
continuous r.m.s. acceleration (Aeq) & 15-minute record of Vibration
Dose Value (VDV)
Using this data to evaluate exposure according to the VDV method, leads to rather more
anomalies. The estimated (extrapolated) VDV curve, based on the entire dataset captured
over 4¼ hours of machine operation (see Figure A4.6), produces a VDV of 15.8 ms-1.75 at
8 hours (see Figure 4.20 & Table 4.5). However, it deviates by a considerable margin from
the measured VDV growth curve during the first 3 hours. This leads to the effect that the
estimated time to reach the EAV, of just under an hour, coincides with a measured exposure
that is considerably below the EAV. It also means that estimates of exposure at 8 hours from
the first 30 minutes or 1-hour of field data, at 6.8 ms-1.75 and 12.3 ms-1.75 respectively
(see Figure A4.7) are lower than the measured VDV after 4¼ hours (13.7 ms-1.75) and
considerably lower than the prediction for 8 hours of nearly 16 ms-1.75 estimated from the
entire dataset (4¼ hours). If WBV data acquisition had not continued for the whole 4¼ hours,
but had stopped before 3 hours, estimates of the driver’s WBV exposure would have been
25% lower. In this case that would not have been enough to take an 8-hour day below the
EAV, but in other cases it might well be. Whatever the reason for the high accelerations after
3 hours of sprayer operation, the longer measurement time must give a closer approximation
to the overall condition from which it is only a sample. It can be seen that the 30-minute
estimate of 8-hour VDV exposure is less than half the more accurate estimate, and does take
the exposure below the EAV.
228
2.5
16
2
12
10
1.5
8
1
VDV (m/s1.75)
Weighted r.m.s. Acceleration (m/s2)
14
6
4
0.5
2
0
0:00
0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
Elapsed Time (hrs)
1-min r.m.s. (Y)
Figure A4.6
Measured VDV
Estimated VDV
Estimated development of VDV over an extended (theoretical) period
of machine operation (i.e. beyond 4¼ hours actually measured)
2.5
16
2
12
10
1.5
8
1
6
4
0.5
2
0
0:00
0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
Elapsed Time (hrs)
1-min r.m.s. (Y)
Figure A4.7
Measured VDV
VDV Est 4.25hr
VDV Est 1hr
VDV Est 30min
Development of VDV: measured directly or estimated from alternative
durations of recorded (non-stationary) WBV data
229
VDV (m/s1.75)
Weighted r.m.s. Acceleration (m/s2)
14
2.0
16.0
1.5
12.0
1.0
8.0
0.5
4.0
0.0
0:00
)
20.0
1.75
2.5
VDV (m/s
Weighted r.m.s. Acceleration (m/s2)
Another example of a non-stationary WBV dataset, on this occasion for a fully suspended
tractor undertaking cultivating work, can be seen in Figure 5.32 and is reproduced below in
Figure A4.8. In this case, a particularly rough section occurred early in the recording period.
In fact, the Aeq level at 1 hour approaches the Exposure Limit Value, although by the end of
3¾ hours the Aeq has reduced to 0.85 m/s2, well within the ELV, although still well above the
EAV.
0.0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
Elapsed Time (hrs)
Transverse (Y)
Figure A4.8
Aeq
VDV
Time-history of weighted 1-minute r.m.s. accelerations (seat, Y-axis,
JCB 3185 – cultivating) plus development of equivalent continuous
r.m.s. acceleration (Aeq) & 15 minute record of Vibration Dose
Value (VDV)
In this case the VDV exposure at 8 hours (21.7 ms-1.75) just exceeds the ELV, when estimated
from the entire acceleration dataset recorded during machine operation (see Figure A4.9), but
VDV estimates based upon the first hour of recorded data are significantly higher.
Conversely, the estimates of VDV based upon acceleration data recorded during the first
30 minutes are very low, because of the delay between starting the recording and the machine
moving off, probably as a result of additional implement preparation. If this first 30 minutes
of data is excluded (see Figure A4.10) then both the 30-minute and the 1-hour estimates of
VDV growth are very much higher than the estimate based on the entire dataset and, in this
case, are seriously above the ELV.
It can be concluded that relatively long overall sampling durations are necessary for collection
of representative WBV data in conditions similar to those found in agricultural vehicle
operations. There are some relatively unusual conditions in which 30 minute samples would
be sufficient. However, in cases where there are breaks and changes in travel speed or
surface roughness, even a sampling duration of one hour is frequently not long enough for
precision better than ±25% in the VDV measure of vibration exposure.
It can also be concluded that, given 1-hour of machine operation / data acquisition, the r.m.s.
measure of vibration exposure is less susceptible to change than is the VDV method.
230
30
25
2.0
20
1.5
15
1.0
VDV (m/s1.75)
Weighted r.m.s. Acceleration (m/s2)
2.5
10
0.5
0.0
0:00
5
0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
Elapsed Time (hrs)
1-min r.m.s. (Y)
Figure A4.9
Measured VDV
VDV Est 3.75hr
VDV Est 1hr
VDV Est 30 min
Development of VDV: measured directly or estimated from alternative
durations of recorded (non-stationary) WBV data
35
2.5
25
1.5
20
15
1.0
10
0.5
5
0.0
0:00
0
0:30
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
Elapsed Time (hrs)
1-min r.m.s. (Y)
Measured VDV
VDV Est 3.25hr
VDV Est 1hr
VDV Est 30 min
Figure A4.10 Development of VDV: measured directly or estimated from alternative
durations of recorded (non-stationary) WBV data (excluding first
30 minutes of dataset)
231
VDV (m/s1.75)
Weighted r.m.s. Acceleration (m/s2)
30
2.0
Printed and published by the Health and Safety Executive
C30 1/98
Printed and published by the Health and Safety Executive
C1.10
02/05
ISBN 0-7176-2970-8
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Whole-body vibration on agricultural vehicles: evaluation of emission and estimated exposure levels
HSE BOOKS