UNIVERSITY OF NAIROBI
PROJECT TITLE: DESIGN OF SELF- LUBRICATING KINGPIN
BEARING FOR USE IN HEAVY COMMERCIAL VEHICLES
PROJECT CODE: JMO-06/2014
AUTHORED BY:
KIMBOWA NEUMANN HENRY
F18/29067/2009
ABONGO ALFRED OWI
F18/29958/2009
PROJECT SUPERVISOR: DR. J.M. OGOLA
YEAR: 2013/2014
THIS PROJECT IS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE
AWARD OF THE DEGREE OF BACHELOR OF SCIENCE IN MECHANICAL AND
MANUFACTURING ENGINEERING
DEPARTMENT OF MECHANICAL &
MANUFACTURING ENGINEERING
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
DECLARATION
We hereby declare that this final year project is presented in partial fulfilment of the
requirement for a Bachelor of Science in Mechanical Engineering. It is entirely our own work
and has not been submitted to any other university or higher education institution or for any
other academic award in this university. Where other people’s work has been used it has been
fully acknowledged and fully referenced.
NAME: KIMBOWA NEUMANN HENRY
REG.NO: F18/29067/2009
SIGN: ……………………………..
DATE: ………………………………
NAME: ABONGO ALFRED OWI
REG.NO: F18/29958/2009
SIGN: ……………………………..
DATE………………………………
SUPERVISOR
Dr. J.M OGOLA
SIGN……………………………….
DATE……………………………….
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
DEDICATION
We dedicate this work to our parents our brothers and sisters and to all well-wishers who in
one way or the other facilitated our academic success.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
`ACKNOWLEDGEMENT
We would like to thank Randon East Africa L.T.D for their contribution to our research
regarding failure methods of kingpin bearings. Gateway Bus Transport drivers and
technicians also helped the research by enlightening us on the likely causes of kingpin
bearing failures. We thank Mr F. MuriungiAriaz Auto spares who guided us on principles
ofkingpin bearing measurement. We are also grateful to Professor Rading as regards to his
advice on selection of material for use in self-lubricating bearing We indeed thank our
project supervisor Dr J.M Ogola for his guidance that has made it possible for us to achieve
the objectives of this project. Last but not least we would like to thank all the staff members
of Mechanical and Manufacturing Engineering Department our classmates, friends and our
families for their inspiration and moral support throughout the years the we have been
studying for BSc degree in mechanical engineering.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
ABSTRACT
The aim of this project was to develop a self-lubricating kingpin bearing from an identified
self-lubricating material and to test the developed bearing for its effectiveness for use in
heavy commercial vehicles. Aluminium frelon which is polytetrafluoroethylene (PTFE)
material was identified to have the perfect properties to achieve the objective of this project.
However due to it’s in availability grey cast which is an alloy of iron and carbon but also
contains silicon was instead used in the production of the bearings. Carbon exists as graphite
thus giving grey cast iron its self-lubricating capability.
Simple liner bearings were then machined on a lathe in accordance to the design
specifications. The bearings were made of two rings press fitted onto each other. The outer
ring was of diameter 80mm while the inner ring was of diameter 60mm. A pin was also
machined from mild steel to simulate the working principle of the king pin while in
operation.
Laboratory tests which included stress distribution test across the bearing, hardness and
roundness tests were carried out to check the effectiveness of the produced bearings. It was
found that the maximum allowable stress of this bearings should not exceed 26.66
/
.From the roundness test, a deviation of 0.4 mm was recorded. Rockwell hardness test was
found to be 101.7 as compared with the published value of 100.The developed bearing was
found to be more robust than the current king pin bearings, they can be operated at high speed
and withstand high stress. Furthermore they are cheaper and easily machined.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
NOTATIONS
=
ℎ
= density
= angular velocity
= Poisson’s ratio
E = Young’s Modulus of Elasticity
=
l shift for bearing
= contact pressure
= Inner Radius
= Outer Radius
F= force
= Factor of Safety
= Yield Stress
HCV=Heavy commercial vehicle
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
TABLE OF CONTENTS
DECLARATION……………………………………………………………………………..i
DEDICATION……………………………………………………………………………….ii
ACKNOWLEDGEMENT…………………………………………………………………..iii
ABSTRACT………………………………………………………………………………….iv
NOTATION………………………………………………………………………………….v
CHAPTER ONE………………………………………………………………………….......1
1.0 INTRODUCTION………………………………………………………………………..1
1.1 BACKGROUND…………………………………………………………………………1
1.2 PROBLEM STATEMENT……………………………………………………………….2
1.3 SIGNIFICANCE OF RESEARCH PROJECT…………………………………………...3
1.4 OBJECTIVES…………………………………………………………………………….3
CHAPTER TWO……………………………………………………………………………...4
2.0 LITRATURE REVIEW………………………………………………………………….4
2.1 INTRODUCTION………………………………………………………………………...4
2.2 APPLICABLE CODES AND STANDARDS……………………………………………4
2.3 SCIENCE OF SELF-LUBRICATION……………………………………………………5
2.3.1 DEFINATION OF SELF-LUBRICATION…………………………………………...5
2.3.2 TRANSFER PROCESS………………………………………………………………..5
2.3.3 FACTORS THAT MAKE A SYSTEM SELF-LUBRICATING………………………5
2.4 MATERIAL SELECTION………………………………………………………………..6
2.4.1 FRELON MATERIAL………………………………………………………………….6
2.4.2ADVANTAGES OF BEARINGS MADE OF FRELON………………………………..6
2.4.3 CARBON MATERIALS………………………………………………………………..6
2.4.4 GREY CAST IRON……………………………………………………………………..7
2.4.5 MICROSTRUCTURE OF GREY CAST IRON………………………………………..7
2.4.6 COMPOSITION OF GREY CAST IRON………………………………………………8
2.4.7 CLASSES OF GREY CAST IRON……………………………………………………..8
2.4.8 MECHANICAL PROPERTIES OF GREY CAST IRON………………………………9
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
2.4.9 ADVANTAGES OF GREY CAST IRON………………………………………….11
2.5 BEARING DESIGN…………………………………………………………………..12
2.5.1 DEFINATION OF SIMPLICITY BEARING………………………………………12
2.5.2 STANDARD BEARING NOMENCLATURE……………………………………...12
2.5.3 BEARING PIN DIAMETER………………………………………………………...14
2.5.4 INITIAL INTERFERANCE………………………………………………………....14
2.5.5 FREEING SPEED…………………………………………………………………...15
2.5.6 MAXMUM ALLOWABLE STRESS……………………………………………….15
2.5.7 CIRCUMFERENCIAL STRESS……………………………………………………16
2.5.8 RADIAL STRESS…………………………………………………………………...16
2.5.9 ADVANTAGES OF PLAIN BEARINGS…………………………………………..16
CHAPTER THREE………………………………………………………………………..17
3.0 RESEARCH METHODOLOGY……………………………………………………...17
3.1 INTRODUCTION……………………………………………………………………..17
3.2 PURPOSE OF STUDY………………………………………………………………..17
3.3 RESEARCH QUESTIONS…………………………………………………………....17
3.4 DATA COLLECTION………………………………………………………………...17
3.5 FINDINGS…………………………………………………………………………….18
CHAPTER FOUR…………………………………………………………………………20
4.1 DESIGN OF A KINGPIN BEARING…………………………………………………20
4.1.1 BEARING PIN DIAMETER………………………………………………………...20
4.1.2 INITIAL INTERFERANCE………………………………………………………….21
4.1.3 SHRINKAGE EQUATION…………………………………………………………..22
4.1.4 FREEING SPEED…………………………………………………………………….22
4.1.5 MAXIMUM ALLOWABLE STRESS………………………………………………..24
4.1.6 FACTOR OF SAFETY………………………………………………………………..24
CHAPTER FIVE…………………………………………………………………………….25
5.1 LABORATORY TESTS………………………………………………………………...25
5.1.1 STRESS DISTRIBUTION TEST……………………………………………………..25
5.1.2 ROUNDNESS TEST…………………………………………………………………..29
5.1.3 HARDNESS TEST…………………………………………………………………….30
CHAPTER SIX………………………………………………………………………………31
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
6.1 UNIT COST OF SIMPLICITY LINEAR BEARING…………………………………...31
6.2 LABOUR COST…………………………………………………………………………31
6.3MARKING UP THE UNIT COST……………………………………………………….32
CHAPTER SEVEN…………………………………………………………………………..33
7.1 CONCLUSION AND RECOMMENDATIONS………………………………………...33
CONCLUSION………………………………………………………………………………33
RECOMMENDATIONS…………………………………………………………………….34
REFERENCES……………………………………………………………………………….35
APPENDIX
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
CHAPTER ONE
1.0 INTRODUCTION
1.1. BACKGROUND
Transport is one of the main sectors driving the Kenya’s economy. According to the economy
survey 2013 highlights by the ministry of devolution and planning, Transport and
Communication sector recorded a growth of 4.0 per cent in 2012 compared to 4.7 per cent in
2011.Heavy commercial vehicles play a vital role in this growth, however their contribution
has been hindered by kingpin bearings which requires often lubrication and so the need to
develop a self-lubricating king pin bearing.
Friction and wear are two very critical factors in the design of mechanical systems that
include king pin bearings. While their effects are not always seen immediately and are
typically realized over time, the economic cost associated with friction and wear problems are
significant. Presence of high friction and wear rates creates tremendous energy losses,
material degradation, loss and preventive or reactive maintenance cost. A recent survey
estimated that the total economic impact of friction and wear problems in Kenya equals
approximately 2-3% of the GDP. This cost is likely to reflect both the cost of replacing and
maintaining kingpin bearings and other systems with friction and wear problems.
Of all the failures encountered in HCV,kinpin bearing itself accounts to about 20%.In our
interview with Gateway Transport L.T.D drivers we found out that the often encountered
cases of bearing failure included: bearing rust and corrosion,fracture,cracks in Raceway
Rings and rolling elements, denting or ‘peer skinning’ of bearing and seizure. Bearings fail
for many reasons, but improper lubrication is at the top of the list according to a variety of
studies which is also consistent with Gateway transport L.T.D. Improper lubrication alone is
about 40-50%.As with bearings themselves, there are numerous causes for lubricant failure,
including:







Insufficient lubricant quantity or vi osity
Deterioration due to prolonged service without replenishment
Excessive temperatures
Contamination with foreign matter
Use of grease when conditions dictate the use of static or circulating oil
Incorrect grease base for a particular application
Over-lubricating
This makes lubricating kingpin bearings unreliable, inefficient thus very inappropriate for use
in HCV.It is a global problem encountered not only in HCV but also so many mechanical
systems characterized by the occurrence of power and efficiency sapping friction and
resource consuming wear. From our interview with Randon East Africa L.T.D Engineers it is
evident that self-lubricating bearings have enhanced performance than conventional bearings
that often require lubrication. The lubrication procedures performed both at the factory by the
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
manufacturers and in the field by maintenance personnel may not be optimal under dynamic
conditions and in any case such lubrication cannot remain optimal under all dynamic
conditions such as varying speed loads and surface geometries.
Often specialized bearings have been installed in this friction and wear sensitive locations but
even some of the most established and conventional bearing technologies only slow the effect
of friction and wear. In the latter 21 st century, the introduction of self-lubricating bearing
material with greatly improved friction coefficients and wear rates compared to conventional
metal-to-metal and/or greased bearing interfaces have come to the forefront. Many industries,
Aerospace and Naval in particular have been rapidly adopting self-lubricating bearing
technologies over the last several decades and even at a faster rate in the last two decades.
The increased for new bearing technology for use in products or to replace old or frequently
worn out bearings in old products that are having their operational life extended as resulted in
plethora of self-lubricating bearings such as king pin bearings
1.2. PROBLEM STATEMENT
Most king pin bearing used worldwide today require external lubrication. In order to achieve
this manufactures and maintenance personnel adopted grease and use of other lubricant
products however it is difficult to maintain a satisfactory layer of grease between two bearing
surfaces thus requiring the grease to be often replenished. In addition, grease is
environmentally unfriendly and very messy, attracts dirt and is hazardous to the vehicle.
Further as the grease dissipates the handling and performance characteristic of HCV
deteriorates such that over steer is experienced creating an unsafe condition. Too often grease
is not utilized as required.
To eliminate the need for a layer of grease ball and roller bearing have been utilized to permit
the vehicle bearing surface itself to rotate. However such coupling devices are relatively
complex, expensive, heavy, difficult to maintain and commercially unacceptable. The kingpin
bearing is often difficult to replace because it is typically located in place which is difficult to
reach. Furthermore pulling, turning and changing direction exerts a great deal of force on the
vehicle bearing. Under the forces of the loaded vehicle, bearing surface experiences
premature wear requiring expensive replacement of the bearing surface and so the need to
develop a self-lubricating kingpin bearing.
1.3. SIGNIFICANCE OF RESEARCH PROJECT
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
HCVs play major role in the development of a country’s economy in terms of transportation
of commodities from one location to another. The need to improve their efficiency is also
vital in this regard, a king pin bearing being a major component in steering mechanism of
HCVs need an improvement. In this project we apply a creative engineering solution that will
eliminate the need for external lubricant in the king pin bearing. Self-lubricating bearing offer
excellent performance in application where conventional bearings are subjected to high
failure rates due to high loads, heavy contamination, extreme temperature or whenever
lubrication and regular surface is difficult to maintain.
We apply our engineering knowledge to develop this kind of bearing to provide solutions to
problems associated with none self-lubricating bearings available for use in HCVs.The
bearings have excellent wear resistance resulting in longer service life and improved
mechanical accuracy over time. The maintenance free bearing provide high load capacity,
low wear rates and low friction with excellent corrosion resistance. Therefore our engineering
solutions provides performance enhancement of the kingpin bearing in HCVs through the
reduction or elimination of the effects of friction and wear.
1.4. OBJECTIVES
The broad objective of this study project is to design self-lubricating king pin bearing for use
in heavy commercial vehicle. The specific objectives are as listed below:



To identify self-lubricating materials suitable for production of king pin bearing.
To design self-lubricating kingpin bearing using identified materials
To test developed kingpin bearings to determine their effectiveness for use in
heavy commercial vehicles
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 INTRODUCTION
To develop an effective self-lubricating bearing it needs to be robust, to not only provide
kingpin bearing but also to provide the most reliable and efficient kingpin bearing that can
make
difference between the current lubricating bearing and self-lubricating
bearing,particulary on the general safety performance and functional aspects of HCVs
operations.
The goal of the bearing design is to provide a bearing that will perform sufficiently without
compromising on the maintenance cost, durability and efficiency. However design of selflubricating bearing varies greatly according to the engine specifications, steering mechanism,
torque exerted and load carrying capacity of the vehicle. The designer should take into
consideration the operational conditions intended for the bearing
2.2 APPLICABLE CODES AND STANDARDS
To facilitate international interchangeability and economic bearing production, the boundary
dimensions of rolling bearings have been internationally standardized by the International
Organization for Standardization (ISO) ISO 15 (radial bearings-except tapered roller
bearings), ISO 355 (tapered roller bearings), and ISO 104 (thrust bearings).
In Japan, standard boundary dimensions for rolling bearings are regulated by Japanese
Industrial Standards (JIS B 1512) in conformity with the ISO standards. Those boundary
dimensions which have been standardized; i.e. bore diameter, outside diameter, width or
height and chamfer dimensions. However, as a general rule, bearing internal construction
dimensions are not covered by these standards. The 90 standardized bore diameters (d) for
rolling bearings under the metric system range from 0.6 mm - 2500 mm.For all types of
standard bearings there has been established a combined series called the dimension series. In
all radial bearings (except tapered roller bearings) there are eight major outside diameters (D)
for each standard bore diameter. This series is called the diameter series and is expressed by
the number sequence (7, 8, 9, 0, 1, 2, 3, 4) in order of ascending magnitude (7 being the
smallest and 4 being the largest).For the same bore and outside diameter combination there
are eight width designations (B ). This series is called the width series and is expressed by the
number sequence (8, 0, 1, 2, 3, 4, 5, 6) in order of ascending size (i.e. 8 narrowest and 6
widest). The combination of these two series, the diameter series and the width series, forms
the dimension series. The international standards organization ISO 4378-1:2009 gives the
most commonly used terms relating to design, bearing materials and their properties of plain
bearings with their definitions and classification. For some terms and word-combinations, the
short forms are given, which can be used where they are unambiguous. Self-explanatory
terms are given without definitions. (ISO) has developed a wide range specification for
bearings. Plain bearings specifications is contained in ISO/TC 123.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
2.3. SCIENCE OF SELF-LUBRICATION
2.3.1 Definition of Self Lubricating
Self‐lubrication is characterized by the bearings ability to transfer microscopic amounts of
material to the mating surface. This transfer process creates a film that provides lubrication
and reduces friction over the length of the rail or shaft.
2.3.2. Transfer Process
The transfer process is an ongoing dynamic function of the self‐lubricating bearing that will
continue throughout its operational life.
The first and most critical step in the process is the break‐in period. This is when the initial
transfer of material to the mating surface takes place. The amount of bearing material
affected during the transfer is dependent upon multiple factors including the speed, load, and
length of stroke, etc. for the application. Typically the initial transfer process will be
accomplished in
50‐100 strokes of continuous operation. The interaction of the Frelon material and the
shafting creates a natural microscopic transfer process of the Frelon to the running surface.
The valleys in the surface finish are filled in with Frelon material during the initial break-in
period. This creates the self-lubricating condition of Frelon riding on Frelon. The break-in
period will depend on several criteria.
1. Preparation of the shafting prior to installation. It is best to clean the shafting with a 3-in-1
type oil before installing the bearings. This ensures that the surface is ready to receive a full
transfer of material.
2. Speed, load, and length of stroke specific to the application. Typically the initial transfer
process will take approximately 50-100 strokes of continuous operation. The running
clearance on the bearing will increase and average of .0002 to .0005in.depending on the
length of the stroke and surface requiring the transfer.
3. How often the shafting is cleaned. If the shafting is cleaned regularly, increased wear will
be seen in the bearings. This due to the transfer process being performed over and over again.
2.3.3. Factors that makes a system self-lubricating
1. The lubrication is an integral component of the bearing material.
2. The oil or grease is NOT added to the original bearing design.
3. The oil or grease will NOT breakdown and be ineffective over time (lubricant ageing or
aging).
4. The oil or grease is consistently applied to the shaft surface.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
5. Additional components do not add cost to the overall system. Shaft or bearing damage and
reduce system life. (Double edge sword of rolling element bearings)
To truly be self-lubricating, a bearing system must do exactly what the name implies. It
must provide its own lubrication throughout the life of the system and not have no external
source facilitating lubrication for a period of time. It must be designed and manufactured into
the bearing material from the beginning.
2.4 MATERIAL SELECTION
2.4.1 Frelon material
The most suitable material for the design of self-lubricating bearing is frelon.Frelon is a
polytetrafluoroethylene (PTFE) based material with other proprietary fillers to increase
bearing characteristics, such as low wear, low friction, and high strength. It is chemically
inert and self-lubricating. It qualifies as a class III plain bearing. The load capacity is four to
eight times that of a ball bearing; for instance, a 0.5 in (13 mm) Frelon bearing can support
the same load as a 1 in (25 mm) ball bearing. Frelon creates a self-lubricating bearing surface
by transferring some of the soft PTFE to the shafting during the run-in process. It is almost
universally chemically inert; the only materials that attack it are molten sodium and fluorine
at elevated temperatures.
It has a plain bearing pressure rating (P) of (10 MPa); dry velocity rating (V) of 140 surface
feet per minute (sfm) (0.71 m/s); and a PV rating of (0.35 MPa m/s).
2.4.2 Advantages of bearings made from frelon material



No metal‐to‐metal contact
No galling or brinelling
No added lubricants to attract additional contaminants

Actual “maintenance free” operation
2.4.3 Carbon material
Self-lubricating bearings can also be made from materials such carbon, iron, tin and graphite.
However powder of iron, tin and graphite are mixed together to manufacture bearings in a
process known as powder metallurgy.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
Carbon Bearings have been developed over the last 30 years. The generic term “Carbon
Bearings” includes all possible variations of the basic material “Carbon”. Therefore it covers
“carbon-graphite”, “metal-graphite” and “electro graphite”. Carbon is self-lubricating and has
a low coefficient of friction at high and low temperatures. Its use as a bearing material is
extensive when a conventional lubricant is not possible and also where the performance of
other lubrication is poor. There are other properties which give it unique and distinctive
advantages for bearings. These include:

Carbon has a low wear rate.

Is mechanically strong in compression.

Has a high strength-weight ratio.

Has high strength at elevated temperatures.

Has a low modulus of elasticity.

Is electrically conductive.

Has a relatively low density.

Have good hydrodynamic bearing properties.

Has high thermal conductivity.

Has high resistance to thermal shock.

Is chemically inert.
Frelon material is expensive and also not locally available. Design of self-lubricating bearing
using carbon involves powder metallurgy a process that our workshops cannot handle at the
moment. Due to this reasons and upon consultation a material with close to the required
properties for this design was selected to be grey cast iron.
2.4.4 Grey cast iron
Gray iron, or grey iron, is a type of cast iron that has a graphitic microstructure. It is named
after the gray color of the fracture it forms, which is due to the presence of graphite. It is the
most common cast iron and the most widely used cast material based on weight
2.4.5 Micro Structure of grey cast iron
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
A typical chemical composition to obtain a graphitic microstructure is 2.5 to 4.0% carbon and
1 to 3% silicon. Silicon is important to making grey iron as opposed to white cast iron,
because silicon is a graphite stabilizing element in cast iron, which means it helps the alloy
produce graphite instead of iron carbides. The graphite takes on the shape of a three
dimensional flake. In two dimensions, as a polished surface will appear under a microscope,
the graphite flakes appear as fine lines. The graphite has no appreciable strength, so they can
be treated as voids. The tips of the flakes act as pre-existing notches; therefore, it is brittle.
The presence of graphite flakes makes the Grey Iron easily machinable as they tend to crack
easily across the graphite flakes. Grey iron also has very good damping capacity and hence it
is mostly used as the base for machine tool mountings.
Gray Cast Iron
Figure1. A microstructure of grey cast iron as viewed on an electron microscope courtesy
www. Google. Com
The microstructure has two main constituents. The long pale regions are flakes of graphite.
They have a shape similar to the cornflakes the background or matrix of the alloy is pearlite.
This is a fine mixture of ferrite and iron carbide. The graphite also improves the wear
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
resistance of the iron by providing lubrication our design is based on this fact i.e during
sliding graphite is produced and acts as a lubricant for the bearing.
2.4.6 Composition of grey cast iron
The properties of grey iron are primarily dependent on its composition. Lower strength
grades of grey iron can be produced by simply selecting the proper melting stock.
The majority of the carbon in grey iron is present as graphite which has little strength or
hardness. Increasing amounts of graphite result from increasing the total carbon content of
the iron. This decreases the strength and hardness of the iron, but increases other desirable
characteristics listed below
• The ability to produce sound castings economically in complex shapes.
• Good machinability even at wear resisting hardness levels and without burring.
• Dimensional stability under differential heating such as in brake drums and disks.
• High vibration damping as in power transmission cases.
• Borderline lubrication retention as in internal combustion engine cylinders
2.4.7 Classes of grey iron
Grey irons are commonly classified by their minimum tensile strength. A class 30 gray iron
indicates that it has a nominal tensile strength of 30,000 psi. In the International Standard or
Sl System a similar iron would be grade 220 with a tensile strength of 220 MPa (Mpa) or 220
newton per square millimetre. A class designation may be used to indicate a grade of iron
even when tensile strength is not an important consideration and may not be specified or
tested. However, when the class designation is used in conjunction with a standard
specification that requires a minimum tensile strength, then actual tensile tests are made to
determine if the metal meets this requirement. The chemical composition of gray iron is not
commonly specified because it does not assure obtaining specific mechanical properties.
However, for special applications some aspect of chemical composition may be specified to
assure the suitability of the iron for a specific need. For example, an alloy content range may
be specified to assure an adequate response to heat treatment or to provide strength or
oxidization resistance in service at a red heat. A minimum carbon content may be specified to
provide adequate thermal shock resistance or lubrication capability as for this design.
2.4.8 Mechanical properties of grey cast iron
Hardness is a measure of how resistant solidmatter is to various kinds of permanent shape
change when a force is applied. It is the most commonly determined property of metal
because it is a simple test and many of the useful properties of metal are directly related to its
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
hardness. Within a class or type of grey iron, hardness is a good indicator of its engineering
properties, but this relation is not useful between types of grey iron because differences in
graphite structure have more of an effect on tensile properties than on hardness. Specifying
the hardness at a designated place on each casting is an excellent method of establishing
consistency of castings in production quantities where the type of iron being used has been
established as satisfactory for the application. The hardness of cast iron used for this design is
100 on Rockwell test. A conversion chart between Rockwell and Brinell hardness values can
be used accurately for steel but deviations from this relation for steel occur with grey irons.
This deviation increases with high carbon equivalent irons. The amount of flake graphite
present influences the two tests differently. This is evident from a comparison of micro
hardness test results on the matrix of grey irons compared to standard Rockwell C values on
the same irons. The micro hardness impressions do not include the graphite flakes that are
present under the Rockwell C hardness indenter.
For this reason the hardness of grey iron should not be compared directly to the hardness of
other metals for an indication of properties such as machinability or wear resistance.
However, some effective hardness conversions can be made between selective types of
harnesses. The hardness is affected by the processing of the grey iron as well as the
composition because these factors influence the microstructure
FATIGUE Metals which are subjected to repeated or fluctuating loads, such as alternating
between tension and compression like in bearings, can break after a large number of loading
cycles even though the maximum stress was well below the static strength of the metal. This
type of fracture is called a fatigue failure, although the rate of load application or the length
of time over which the cycles occur are not significant. The occurrence of a fatigue crack is
directly influenced by the maximum unit stress and the cumulative number of times it is
applied. Grey cast can withstand relatively withstand fatigue.
DAMPING CAPACITY The relative ability of a material to absorb vibration is evaluated as
its damping capacity. The quelling of vibration by converting the mechanical energy into heat
can be very important in structures and in devices with moving parts. Components made of
materials with a high damping capacity can reduce noise such as chatter, ringing and
squealing, and also minimize the level of applied stresses. Vibration can be critical in
machinery and can cause unsatisfactory operation or even failure.
An accumulation of vibrational energy without adequate dissipation can result in an
increasing amplitude of vibration. Excessive vibration can result in inaccuracy in precision
machinery and in excessive wear on gear teeth and bearings. Mating surfaces normally
considered in steady contact can be caused to fret by vibration.
The exceptionally high damping capacity of grey cast iron is one of the most valuable
qualities of this material. For this reason it is ideally suited for machine bases and supports,
engine cylinder blocks and brake components. The damping capacity of gray iron is
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
considerably greater than that of steel or other kinds of iron. This behaviour is attributed to
the flake graphite structure of the gray iron, along with its unique stress-strain characteristics.
Damping capacity decreases with increasing strength since the larger amount of graphite
present in the lower strength irons increases the energy absorbed. Larger cast section
thicknesses increase damping capacity and inoculation usually decreases it. Heat treating can
also have an appreciable effect on damping capacity.
Table 1.0 mechanical properties of grey cast iron
Selected Properties of Gray Cast Iron
ASTM
Numbe
r
Tensile
Strengt
h (Kpsi)
Compressiv
e Strength
(Kpsi
Shear
Modulu
s of
Rupture
(Kpsi
Modulus of
Elasticity (Mpsi)
Enduranc
e Limit
(Kpsi
Brinell
Hardnes
s H_b
20
22
83
26
tensio
n
9.6-14
25
26
97
32
11.5-14.8
4.6-6.0
11.5
174
30
31
109
40
13.0-16.4
5.6-6.6
14
201
35
36.5
124
48.5
14.5-17.5
5.8-6.9
16
212
40
42.5
140
57
16.0-20
6.4-7.8
18.5
235
50
52.5
164
73
18.8-22.8
7.2-8.0
21.5
262
62.5
187.5
88.5
20.4-23.5
7.8-8.5
24.5
302
60
torsio
n
3.9-5.6
10
156
2.4.9 Advantages of grey cast iron design
Grey iron is a common engineering alloy because of its relatively low cost and good
machinability, which results from the graphite lubricating the cut and breaking up the chips.
It also has good galling andwear resistance because the graphite flakes self-lubricate. The
graphite also gives grey iron an excellentdamping capacity because it absorbs the energy.
Grey iron also experiences less solidification shrinkage than other cast irons that do not form
a graphite microstructure. The silicon promotes good corrosion resistance and increase
fluiditywhen casting. Grey iron is generally considered easy to weld. Compared to the more
modern iron.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
2.5 BEARING DESIGN
2.5.1 Definition of simplicity bearings
Simplicity bearings are in a class of bearings known as plane bearings, which means that they
have no rolling elements.
There are three classes of plane bearings:
Class I - Require an outside source of lubrication (oil, grease, etc.).
Class II - Lubrication is impregnated within the walls of the bearing. (Bronze, powder metal,
etc.) Typically these bearings require an added lubricant also.
Class III - Self-lubricating bearings, which do not require added lubricants.
Simplicity bearings are Class III plane bearings and are self-lubricating.
This design entails the design of class III type of bearing.
Figure 2. Oblique view of simplicity bearing
2.5.2 Standard bearing nomenclature
The following terminologies as defined are used in the design of bearings
i.
Axial Clearance: The total amount of free axial movement between the inner and outer
race of a bearing. Bearings with internal clearance will contain both axial and radial
clearance.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
ii.
Axial load: Load applied to the bearing parallel with the bearing axis of rotation — also
known as thrust load.
iii.
Capacity: Dynamic capacity is the basic “C” rating which represents a load that the
bearing can theoretically endure for 1 million revolutions. Static capacity is the
approximate load the bearing can endure before permanent deformation occurs on the
ball or raceway.
iv.
Deflection:The amount of movement associated with compression or stretching of
bearing components when placed under load.
v.
Diametric Clearance: The total free movement of the inner race relative to the outer
race in a radial plane, also referred to as radial clearance. “X” and “C” type bearings are
made with some internal clearance as a standard factory internal fit before mounting.
vi.
L10 life: The theoretical life span of a bearing under a specific set of dynamic operating
conditions associated with 90% reliability.
vii.
Moment load: Load such that when applied to a bearing system, tends to overturn or
bend the axis of rotation in an angular direction.
viii.
Pitch Diameter: The theoretical median diameter of a bearing, which passes through
the centre of the rolling elements.
ix.
Preload: The amount of load placed on the rolling elements before the application of
any external loads. Preload can be created in “X” and “C” type bearings by controlling
internal fits of the ball and the raceway at the factory. Preload in angular contact
bearings is controlled by a “preload gap” between the duplexed races. Tight mounting
conditions will increase the final bearing preload. Preload stiffens the bearing and
eliminates axial and radial play, but the load on the balls increases friction and shortens
L10 life.
x.
Radial load: Load applied perpendicular to the bearing axis of rotation.
xi.
Run out: The maximum axial or radial race wall thickness variation of an inner or outer
bearing race. Run out influences the repeatable location variation of rotating
components.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
The maximum allowable load capacity for the knuckle in the steering mechanism of an
ISUZU DI TX was found to be 203.2 KN with a design safety factor of 1.31.
2.5.3 Bearing Pin Diameter
The bearing pin diameter is evaluated from the maximum allowable load capacity of the
ISUZU DI TX taking into consideration the factor of safety of 1.31.
The diameter is evaluated from the equation below:
.√
.
d=
.
Where d = pin diameter
F = Force
= Factor of Safety
= Yield Stress
The operational load capacity value, F
=
.
2.5.4 Initial Interference
The initial interference between the pin and bearing was found to be 0.1 mm from the
research findings.
The radial shift for the bearing at standstill considering the inner ring is evaluated from:
=
Where
.
.
[(1- )+(1+ )
=bearing radial shift
= contact pressure
E = Young’s Modulus of Elasticity
= Inner Radius
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
= Outer Radius
= Poisson’s ratio
Similarly,
The radial shift for the pin at standstill is calculated from:
=- (1- )
Where
= pin radial shift
2.5.5 Freeing Speed
Bearing radial shift at a rotating speed,
=
Where
[2(3+ )
is given by:
+ 2(1 − )
]
= radial shift
= density
= angular velocity
= Poisson’s ratio
E = Young’s Modulus of Elasticity
Radial shift for the pin is given by,
=
Where
{2(1- )}
= pin radial shift
At freeing speed,
Separation
=
-
= Initial interference
2.5.6 Maximum allowable stress
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
The maximum allowable operating stress for a condition of no yielding anywhere in the
bearing as per Tresca’s yield criterion is given by:
=
Where
= freeing speed
= density
= Poisson’s ratio
2.5.7 Circumferential stress
Circumferential stress distribution across the bearing is evaluated by:
=
Where
[
+
.
+
-
]
= circumferential stress
2.5.8 Radial stress
Similarly radial stress distribution across the bearing is evaluated by;
=
Where
[
+
−
.
−
]
= Radial stress
2.7.9 Advantages of plain bearings
• Initial cost is lower in most cases.
• Less radial space required than for rolling contact bearings.
• Better suited to overload or shock conditions.
• Quieter operation than rolling contact bearings (more noticeable after wear has taken place).
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
• Less difficulty with fatigue related issues.
• Less easily damaged by foreign matter e.g. grime, dirt etc.
CHAPTER THREE
3.0 RESEARCH METHODOLOGY
3.1 INTRODUCTION
The purpose of this study was to examine the impact of self-lubricated king pin bearings in
place for externally lubricated bearing for heavy commercial vehicles.A survey was
administered together with assessment of various transport and automotive industries in the
country. The research begun on 10th of November 2013 to 5th January 2014.the research was
carried out in Nairobi the information required was gathered mostly through interviews and
questionnaires.
3.2 purpose of study
This study developed and implemented an automotive industry survey and a transport sector
assessment.
The purpose of the automotive industry survey was to determine major challenges of using an
externally lubricated kingpin bearings and the purpose assessing transport was to evaluate the
losses and damages that could be caused by failure of externally lubricated king pin bearings.
This phase of the study examined the data collected from this two sectors. Data collection and
analysis assisted in determining whether the design of self-lubricating bearing would have a
positive impact to the society in regard to use of heavy commercial vehicles for transport.
3.3 Research Questions





What are some of the reported cases of kingpin bearing failure
How often do you encounter such reported cases of failure?
Do you import kingpin bearings? If yes what are the material specifications of the
manufacturer?
Do these bearings come with their technical drawings and assembly procedure?
Do you think a kingpin bearing manufactured locally would have an impact on the
country’s economy?
3.4 Data collection
The study employed an automotive industry survey and transport assessment as its data
source. Survey research design was applied to investigate the research questions
formulated.an assessment for methods of kingpin bearing failure was carried out.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
We selected a range of relevant automotive and transport companies to approach and request
information from. To gain as wide a viewpoint as possible we did not restrict our information
requests to the management of the companies alone but also to other junior staff like drivers’
technicians and transport mechanics. The organisations and individuals we requested
information from are:





Randon east Africa L.T.D
General motors L.T.D
Roy parcels L.T.D
Gateway Bus Transport L.T.D
MR F MuriungiAriaz auto spares
3.5 Findings
Three responses were received with regards to our information request.
Randon East Africa: Most kingpin bearings that use external lubrication failed because of:
i.
Corrosion damage is due to chemical attack on metal surfaces by reactive agents. The
damage can be to both the bearings and the shaft. This damage results from chemical
attack on some bearing constituent by a substance originating in the lubricant or the
environment. Corrosion may produce either removal of bearing material or build-up
of a deposit on the bearing surface.
ii.
OVERHEATING: Overheating includes both damage caused to bearings by
exposure to temperatures above the softening point of one of the Babbitt constituents
and damage due to excessive thermal gradients causing the Babbitt to crack this
mainly occursdue to friction by improper lubrication.
iii.
ABRASION
Abrasion is a mode of bearing failure due to the erosive action of a large number of
solid particles that are harder than the bearing surface. Under certain conditions both
the bearing and the shaft may be damaged by the abrasive action of the particles this
particles mostly originated from dirty lubricant
iv.
According to Randon east Africa L.T.D Engineers this failure can be eliminated if
self-lubricating bearings could be employed if only the self-lubricating bearings are
locally available at affordable cost. The kingpin bearings were imported alongside
their installation manuals but no design manual.
v.
Mr MuriungiAriaz Auto Spares according to him the purchase of kingpin bearings
that are lubricated externally was high implying that if better bearing was design
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
could help to a much extent. He also stated that it was almost impossible to replace
the bearing alone in case of a failure because of its location and thus there was a need
to employ a more robust bearing for the king pin.
vi.
Gateway bus Transport drivers and mechanics: often encountered cases of
bearing failure included: bearing rust and corrosion,fracture,cracks in Raceway Rings
and rolling elements, denting or ‘peer skinning’ of bearing and seizure. Bearings fail
for many reasons, but improper lubrication is at the top of the list. They also stated
that it was hard to detect the bearing failure at an early stage .The drivers reported that
failure of kingpin bearings had led to loss of control of the vehicle, delay of journey
and to a great extent losses because of delays as they repaired the kingpin bearings.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
CHAPTER FOUR
4.1. DESIGN OF A KING PIN BEARING
The following parameters are considered in this design:
1.
2.
3.
4.
5.
6.
Maximum allowable load capacity = 203.2 KN
Design factor of safety = 1.31
Poisson’s ratio = 0.26
Young’s modulus of elasticity = 150 GN/
Density = 7100 Kg/
Yield stress = 140 MN/
4.1.1. Bearing pin diameter
The operational load capacity value, F
For ,
=
.
= 203.2 KN and S.F =1.31,
.
Then, F =
.
= 155.073 KN,
The diameter is evaluated from the equation below:
d=
.√
.
.
Where d = pin diameter
F = Force
= Factor of Safety
= Yield Stress
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
= 1.31,
For F = 155.073 KN,
Then d
√ ∗
=
.
∗
∗
∗
,
∗ .
= 40 mm
4.1.2. Initial Interference
The radial shift for the bearing at standstill considering the inner ring is evaluated
from
:
=
Where
.
.
[(1- )+(1+ )
=bearing radial shift
= contact pressure
E = Young’s Modulus of Elasticity
= Inner Radius
= Outer Radius
= Poisson’s ratio
=
.
.
∗
.
.
.
[(1-0.26) +(1+0.26)
.
.
=3.8133*10
Similarly,
The radial shift for the pin at standstill is calculated from:
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
=- (1- )
Where
= pin radial shift
=- (1-0.3)
.
=6.667*10
∗
= 6.6667 ∗ 10
4.1.3. Shrinkage equation
=
Where
=
+
=
l shift for bearing
ℎ
For the initial interference of 0.1 mm, then
0.1*10
=
(3.8133 ∗ 10
+ 6.6667 ∗ 10
)
= 4.48*10
=
0.1 ∗ 10
4.48 ∗ 10
= 223.214
/
4.1.4. Freeing Speed
Bearing radial shift at a rotating speed
=
[2(3+ )
is given by:
+ 2(1 − )
]
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
Where
= radial shift
= density
= angular velocity
= Poisson’s ratio
E = Young’s Modulus of Elasticity
. ∗
=
∗
∗
∗ .
∗
{2(3+0.26)0.03 + 2(1 − 0.26)0.02 }
= 6.9508*10
Radial shift for the pin
=
=
.
{2(1- )}
∗
∗
∗
∗ .
∗
[2(1-0.26)]0.02
=5.53238*10
At the fleeing speed
Separation
=
−
=
=interference for this case interference is 0.1mm
(6.9508 ∗ 10
= 6.9452676*10
− 5.53238 ∗ 10
)
=0.1*10
= 1.439829 ∗ 10
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
= 1199.9
/
4.1.5. Maximum allowable stress
=
Where
= freeing speed
= density
= Poisson’s ratio
.
=
*7100 * 1199.9 ∗ 0.08
= 26.66 * 10 N/
= 26.66 MN/
4.1.6. Factor of safety
For a condition of no yielding according to Tresca’s yield criterion the factor of safety is
calculated as shown below:
=
But
.
∗ . .
= 4*26.66 = 106.64 MN/
=
=
.
for all the front wheels and
= 0, then
= 1.31
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
CHAPTER FIVE
5.1. LABORATORY TESTS
The following tests were carried out on the bearing:
1. Stress distribution test
2. Hardness test
3. Roundness test
5.1.1. Stress distribution test
Laboratory procedure
1. The bearing was firmly fixed on a lathe machine.
2. The lathe was then rotated at a speed of 3000 rpm. This speed was then used to
compute the stresses at various radius across the bearing.
3. The above procedures was repeated for revolution speeds of 4000 rpm and 5000 rpm
respectively.
The equations below were used to compute both radial and circumferential stresses across the
bearing.
For the case of circumferential,
=
+
[
+
.
−
]
For a revolution speed of 3000 RPM and at a radius of 40 mm, the circumferential stress is
analyzed as shown below.
=
.
*7100*314.159 [ 0.08 + 0.04 +0.08 - 0.546*0.04 ]
= 3.82 MN/
Similarly radial stress is analyzed by,
[
=
=
.
+
−
.
−
]
*7100*314.159 [ 0.08 + 0.04 − 0.08 − 0.04 ]
=0
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
Other values for both radial and circumferential stresses at same rotational speed but various
radiuses were computed in a similar manner. The same was done for revolution speeds of
4000 RPM and 5000 RPM and the tables below generated.
RESULTS
TABLE NO.2: Stress distribution at a speed of 3000 RPM
Radius, r (mm)
40
50
60
70
80
Circumferential
stress, (MN/ )
3.82
3.06
2.54
2.12
1.74
Radial stress, (MN/
)
0
0.4
0.44
0.29
0
TABLE NO.3: Stress distribution at a speed of 4000 RPM
Radius, r (mm)
Circumferential
stress, (MN/ )
Radial stress, (MN/
40
6.87
0
50
5.45
0.71
60
4.51
0.79
70
3.76
0.51
80
3.10
0
)
TABLE NO.4: Stress distribution at a speed of 5000 RPM
Radius, r (mm)
Circumferential
stress, (MN/ )
Radial stress, (MN/
40
10.73
0
50
8.51
1.11
60
7.04
1.23
)
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
70
5.88
0.80
80
4.84
0
The data in the above tables were used draw the graphs below.
A GRAPH OF STRESS(MN/m2) ANGAINST
RADIUS(mm)
4.5
4
3.82
3.06
3.5
2.54
3
2.12
2.5
1.74
2
Radial
1.5
1
0.5
Circum.
0.4
0.44
0
0.29
0
0
40
50
60
70
80
Radius (mm)
FIGURE NO. 3. Stresses distribution at 3000 RPM,
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
A GRAPH OF STRESS(MN/m2) ANGAINST
RADIUS (mm)
8
7
6
5
4
Circum
3
Radial
2
1
0
40
50
60
70
80
r
Radius r (mm)
FIGURE NO. 4. Stresses distribution at 4000 RPM
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
A GRAPH OR STRESS(MN/m2) ANGAINST
RADIUS(mm)
12
10
8
6
Circum.
Radial
4
2
0
40
50
60
70
80
Radius r (mm)
FIGURE NO.5 Stresses distribution at 5000RPM
5.1.2 Roundness test
Roundnessis the measure of how closely the shape of an object approaches that of a
circle.Roundness is dominated by the shape's large-scale features rather than the sharpness of
its edges and corners, or the surface roughness of a manufactured object. A smooth ellipse
can have low roundness, if its eccentricity is large. Regular polygons increase their roundness
with increasing numbers of sides, even though they are still sharp-edged.
Procedure
The machined bearing was placed over a flat plate and the point of contact was taken as the
datum point. Again a dial gauge was placed over the bearing and the bearing was rotated on
a lathe machine while keeping the datum at constant position. Thus the error in roundness
was directly determined by comparing the peak height as measured by the dial gauges
The deviation was calculated as shown below
Δ= -R
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
From test ∑
= 0.98
=20mm
Δ=20-0.98(20)=0.4mm
5.1.3 HARDNESS TEST
Hardness is the property of a material that enables it to resist plastic deformation, usually by
penetration. However, the term hardness may also refer to resistance to bending, scratching,
abrasion or cutting.
Procedure
The type of metal in each sample is given in Table 1. Each sample was tested three separate
times using the Rockwell B scale.
This scale employs a 0.1875 mm (1/16”) steel ball with a load of 100 kg. Care was taken to
insure that each test was conducted sufficiently far from indentations left by precious tests.
Once the hardness values were gathered they were analyzed. The results are shown. The
gathered hardness values were compared to published values.
This comparison is shown. The results of the comparison were used to infer their processing
conditions and rank them according to their ductility
Results
Statistical results for grey cast iron
TABLE 5. Hardness RB
Test 1
101.7
Test 2
102.5
Test 3
101.0
average
101.7
Published value grey cast iron hardness RB is 100
Deviation from published value = 101.7-100 = 1.7
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
CHAPTER SIX
6.0 PRODUCTION COST
6.1 UNIT COST OF SIMPLICITY LINEAR BEARING
The production cost for a unit simplicity bearing comprises cost of material used for the
design.
The material which is grey cast iron was bought at basis of a unit mass.
Mild steel and wood which were not part of the actual design but for demonstration of the
king pin and steering knuckle respectively mild steel was also bought on the basis mass. The
miscellaneous cost include the cost of the labour cost for machining and cost of the screws
for locking included.
Breakdown of the cost of production is as follows.
TABLE 6. PRODUCTION COST BREAK DOWN
Material/component Type
Quantity
Price/quantity
Iron
Pin/shaft
Wood
Screws
Labour
Miscellaneous
TOTAL
7
7
1
4
195
250
200
25
700
400
Grey cast iron
Mild steel
Soft wood
1/16’
Total
(Ksh
0
1365
1750
200
100
1000
585
5000
price
6.2 LABOUR COST
To determine the value of labour, the cost of the actual hired labour is portioned according to
the time in hours spent in producing the self-lubricating king pin bearing.
Taking a labour cost Kshs 200 as the actual hired cost for four hours daily,
Kshs 200/4hrs=ksh 50/hour
Production schedule being set as 5 days the cost of labour then becomes:
Ksh 200*5days=ksh 1000
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
6.3 MARKING UP THE UNIT COST
From cost analysis it is found that it cost Ksh5000 to manufacture a self-lubricating kingpin
bearing in 5 days.
Putting into consideration the maximum profit and the affordability to the customer it is
advised that the manufacture marks the production cost by 30% to come up with the selling
price.
100% + 30% =130%
(130/100)*5000=6500
It is seen that the customer can purchase the self-lubricating bearing at an average cost of ksh
6500.If this price is compared to the market price which ranges from ksh 9000-ksh 12000
depending on the manufacturer of an ordinary bearing for an Isuzu TX direct injection, it is
found that the self-lubricating bearing is cheaper in addition to its enhanced properties
compared to the ordinary bearing.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
CHAPTER SEVEN
7.0 CONCLUSION AND RECOMMENDATIONS
7.1 CONCLUSION
Friction and wear are two critical factors in mechanical systems design. Kingpin bearings are
not exception to friction and wear. The aim of this project was to identify self-lubricating
materials, to produce a self-lubricating kingpin bearing from the selected material and to test
the bearing for its effectiveness for use in heavy commercial vehicles
According to the research findings current kingpin bearings are mainly roller bearing that
require frequent lubrication. This bearings to a large extent fail due to lack of lubrication or
improper lubrication which occurs because they cannot be accessed easily in the vehicle and
dismantling the whole assembly is the solution of their access. A self-lubricating king pin
bearing can be manufactured locally from Grey cast iron as a simplicity bearing to replace the
roller bearings.
From improvised in the laboratory test to predicate operating stresses of the developed
bearings the bearings were found to have high freeing speed of 1199.9 rad/sec while
withstanding maximum circumferential and radial stresses of about 27Mpa.Roundness test
indicated a deviation of 0.4 mm from that of a perfect circle also a Rockwell hardness test of
100 was recorded from hardness test.The developed self-lubricating kingpin bearings are
more robust and of low cost while other self-lubricating bearings have been made before this
remains the only design that provides a self - lubricating kingpin bearing for use in heavy
commercial vehicles.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
7.2 Recommendation
The developed kingpin bearing performance can be improved by a few changes in design
however some of this the ways of improving the bearing are not feasible unless the selflubricating kingpin bearings are produced on mass production.
The main improvement would be to create double groove on the inner surface of the outer
bush to restrain the inner bush. This will result to improved alignment which in turn reduce
vibration thus increasing bearing operating cycles.
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
APPENDIX
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)