Design, Construction, and Evaluation of an Automotive Bridge Jack
By
Thomas Gomes Jr
BioResource and Agriculture Engineering
BioResource and Agriculture Engineering Department
California Polytechnic State University
San Luis Obispo
2011
SIGNATURE PAGE
TITLE
:
Design, Construction and Evaluation of an
Automotive Bridge Jack
AUTHOR
:
Thomas Gomes Jr
DATE SUBMITTED :
June 9th, 2011
Mark A. Zohns
Senior Project Advisor
Signature
Date
Richard A. Caveletto
Department Head
Signature
Date
ii ACKNOWLEDGEMENTS
First, I would like to thank Cal Poly Transportation Services and their employees for sponsoring
this project.
Second, I would like to thank Dr. Mark A Zohns who provided guidance through the challenging
aspects of the project.
Third, I would like to thank Virgil Threlkel who was willing to entertain any question and train
me on any equipment I was unfamiliar with.
Fourth, I would like to thank my parents and family for supporting me throughout my
educational career.
iii ABSTRACT
This Senior Project discusses the design, construction and evaluation of an automotive lift. This
lift will be hydraulically powered with a 6000 lb lifting capacity. The lift constructed in this
project will be installed within a current 4 post drive on vehicle lift and allows the user to lift one
axle of a vehicle a few inches off the ramp of the drive on lift in order to remove the tires.
iv DISCLAIMER STATEMENT
The university makes it clear that the information forwarded herewith is a project resulting from
a class assignment and has been graded and accepted only as a fulfillment of a course
requirement. Acceptance by the university does not imply technical accuracy or reliability. Any
use of the information in this report is made by the user(s) at his/her own risk, which may
include catastrophic failure of the device or infringement of patent or copyright laws.
Therefore, the recipient and/or user of the information contained in this report agrees to
indemnify, defend and save harmless the state, it officers, agents and employees from any and all
claims and losses accruing or resulting to any person, firm, or corporation who may be injured or
damaged as a result of the use of this report.
v TABLE OF CONTENTS
SIGNATURE PAGE .......................................................................................................................................... ii ACKNOWLEDGEMENTS ................................................................................................................................ iii ABSTRACT ..................................................................................................................................................... iv DISCLAIMER STATEMENT .............................................................................................................................. v LIST OF FIGURES .......................................................................................................................................... vii LIST OF TABLES ........................................................................................................................................... viii INTRODUCTION ............................................................................................................................................. 1 LITERATURE REVIEW ..................................................................................................................................... 2 PROCEDURES AND METHODS ....................................................................................................................... 4 Design Procedure ...................................................................................................................................... 4 Construction Procedure ............................................................................................................................ 8 Testing Procedure ................................................................................................................................... 10 RESULTS ...................................................................................................................................................... 12 DISCUSSION ................................................................................................................................................. 14 RECOMMENDATIONS ................................................................................................................................. 15 APPENDICES ................................................................................................................................................ 17 APPENDIX A: HOW PROJECT MEETS REQUIREMENT FOR THE BRAE MAJOR ......................................... 17 APPENDIX B: DESIGN CALCULATIONS ..................................................................................................... 20 APPENDIX C: DEFINITIONS ...................................................................................................................... 29 APPENDIX D: CONSTRUCTION DRAWINGS ............................................................................................. 30 vi LIST OF FIGURES
Figure 1. Leading manufacturer’s Bridge jack (BendPac 2011) .................................................... 2
Figure 2: Bridge Jack Assembly Component Identification ........................................................... 4
Figure 3: Upper center support with enclosure for sleeve bearing ................................................. 5
Figure 4: Upper Sliders shown inserted into Upper Center Support .............................................. 5
Figure 5:Bridge Jack roller assembly set onto BendPak Lift ......................................................... 6
Figure 6: Adapter plate to be welded to end of the smaller tubing. ................................................ 6
Figure 8: Bearing Enclosure and lower pin support ....................................................................... 7
Figure 7: Adapter plates that bolt to the larger tubing sections ...................................................... 7
Figure 9: Tapping 5/16-18 threads into center frame section ......................................................... 8
Figure 10: Sleeve bearing enclosure and fixed pin sleeve tacked in place. .................................... 9
Figure 11: Welding sleeves to support the pin in bending and provide lateral stability ................. 9
Figure 121: Testing the bridge jack using the BRAE hydraulic Test Bench ................................ 10
Figure 13: Proof Load Test setup.................................................................................................. 10
Figure 14: Part drawing of 1 in pin ............................................................................................... 31
Figure 15: Part drawing of tubing flange ...................................................................................... 32
Figure 16: Part drawing of Top Slider .......................................................................................... 33
Figure 17: Part drawing of Roller Assembly ................................................................................ 34
Figure 18: Part drawing of cylinder Sleeve 1 ............................................................................... 35
Figure 19: Part drawing of Cylinder Sleeve 2 .............................................................................. 36
Figure 20: Part drawing of Bottom Frame Extension ................................................................... 37
Figure 21: Part drawing of Adapter Plate Upper .......................................................................... 38
Figure 22: Part drawing of Adapter .............................................................................................. 39
Figure 23: Part drawing of 8 in pin ............................................................................................... 40
Figure 24: Part Drawing of Scissor Lift Arm ............................................................................... 41
Figure 25: Part drawing of Upper Center Section ........................................................................ 42
Figure 26: Part Drawing of Center Frame Section ....................................................................... 43 vii LIST OF TABLES
Table 1. Design parameters of automotive lift components (Automotive Lift Institute 2006) ...... 3
Table 2: Baldwin Test Results when nearly collapsed ................................................................. 13
Table 3: Baldwin Test results when in middle of travel ............................................................... 13
Table 4: Baldwin Test results when fully raised........................................................................... 13
viii 1 INTRODUCTION
Many tools in the automotive industry are designed to help technicians access difficult to reach
places and improve ergonomic comfort. When a technician is working on a vehicle at floor level
they must lean over the vehicle, kneel next to the vehicle or lie under the vehicle to complete the
job. These positions can be awkward and strain the technician’s muscles or joints.
A solution to this problem is lifting the vehicle to a comfortable working height allowing the
technician to work in the fully upright position. There are two styles of lifts that can accomplish
this; the first style lifts the vehicle by the frame allowing the suspension to fully droop and the
tires to be removed. The second style is a drive on lift where the vehicles weight is supported by
its tires while the vehicle is on the lift. Removing the tires on this second style of lift requires the
addition of a bridge jack that spans the area between the lifting ramps.
Cal Poly Transportation Services uses a drive-on lift that works well for routine services and
inspections that do not require removal of the tires. Currently to remove the tires while the
vehicle is on this lift the technician must insert a steel plate and use a bottle jack to lift the
vehicle up to a height where a jack-stand can be placed underneath.
Commercially available bridge jacks are too wide for the narrow wheelbase electric vehicles on
campus meaning the technician would have to remove the bridge jack to drive the electric
vehicle onto the lift.
The objective of this project was the design and construction of a custom bridge jack for Cal
Poly Transportation Services that accommodates vehicles ranging from narrow wheelbase
Electric Vehicles to 1 ton pickups.
2 LITERATURE REV
VIEW
Current Lift
L Design Approaches
A
The Bend
dPak bridge jack (BendP
Pak 2011) is a lift accesssory that alloows technicians to quickkly
lift one axle
a of a vehiicle providin
ng the techniician access to the vehiccles brakes annd suspensioon.
Through visual comp
parisons of companies
c
websites
w
suchh as complettehydraulic.ccom (CLRBJJ8
2011) mo
ost bridge jaacks currently
y on the marrket use a hyydraulically ppowered scissor style lifft
jack (Fig
g 2). Scissor lift style brid
dge jacks haave a small ccollapsed dim
mension provviding clearaance
for the veehicle to driv
ve on the liftt.
Accordin
ng to Cullinss (J Cullins, Personal
P
Communicatioon, 7th Marchh 2011) the bbridge jack fframe
must be adjustable
a
to
o accommod
date differentt vehicle widdths. The BeendPak bridgge jack
incorporaates an adjusstable frame with a pin and
a hole desiign where thhe operator m
manually
removes the pin and aligns the ho
oles correspo
onding to the desired fraame width.
ng manufactturer’s Briddge jack (BeendPac 20111)
Figurre 1. Leadin
Ergonom
mics
Accordin
ng to Gold ett al., the tech
hnician shou
uld be in as nneutral a possture as possiible when
performin
ng repair acttivities and a minimum amount
a
of foorce should bbe required tto gain access to
and maniipulate the part.
p
Accordin
ng to Cullins (J Cullins, Personal Co
ommunicatioon, 7th Marchh 2011) worrking with a
vehicle elevated
e
on a lift providees maximum access for t echnicians w
when compaared to
completin
ng the same job while th
he vehicle is at ground leevel.
3 Industry Standards on Design Parameters
The Automotive Lift Institute along with American National Standards Institute recommends the
following design parameters when designing or selecting components for automotive lifts. These
design parameters provide guidelines on how much component design strength must exceed the
strength required for that component when the jack is at maximum capacity.
For example when selecting flexible hose for the hydraulic system you would select a flexible
hose with a working pressure rating four times the pressure required to raise the maximum
weight the jack is rated for.
Table 1. Design parameters of automotive lift components (Automotive Lift Institute 2006)
Component
Pumps
Rigid Piping
Hydraulic Hose
Valves and Fittings
Cylinders
Bearings
Fasteners
Ductile Metal
Non-ductile Metal
*See Appendix D for definitions
Design Parameters
150% working pressure rating
300% working pressure rating
400% working pressure rating
300% working pressure rating
300% working pressure rating
Strength factor* of 3
Strength factor* of 4
Strength factor* ≥ 3
Strength factor* ≥ 5
4 PROCEDURES AND METHODS
Design Procedure
Design constraints placed on this project came about from discussions with the project sponsor
and project supervisor. Standards set by the American National Standard for Automotive lifts
concerning strength factors were adhered to when designing for the rated load capacity.
The bridge jack shown in figure 2 operates as a scissor lift with the hydraulic cylinder located
horizontally between the lower pins. The adjustable frame and upper sliders accommodate
different wheelbase vehicles ranging from electric vehicles to full size pickups. The roller
assembly on the end of the frame extensions shown allows the technician to move the bridge jack
to lift either the front or the rear axle of the vehicle.
1. 2. 5. 6. 3. 4. Figure 2: Bridge Jack Assembly Component Identification
1. Upper Center Support
2. Upper Sliders
3. Center Frame Section
4. Frame Extensions
5. Scissor Lift Arms
6. Roller Assembly
Due to the geometry of the scissor lift the hydraulic cylinder must exert the most force to
counteract the vehicle weight when the bridge jack is in its lowest position. When fully collapsed
the hydraulic cylinder must exert a theoretical force of 8700 lbs to raise a 6000 load. As the
scissor lift arms extend the hydraulic cylinder has greater leverage against the vertical force
applied by the vehicle being lifted. To lift the same 6000 lb load when the jack is fully extended
requires a theoretical force of 3500 lbs (see Appendix B for further information).
Design began by working with a SolidWorks model to pinpoint weak spots in the design.
Components of the bridge jack requiring special attention were the top sliders and the pins the
hydraulic cylinder acts on. Design methodology of the main components of the bridge jack is
explained below.
Upper Center Support. The Upper Center Support section was decided upon based on the need to
have other tubes inserted into the Upper Center Support. This tubing size was driven through
selection of the upper slider dimensions.
5 The sleev
ve bearing th
hat slides on
n the upper ceenter supporrt is fully encclosed to preevent the uppper
center su
upport from tipping
t
in thee case uneveen loading. T
The box encllosing the sleeve bearingg is
designed
d to be a posiitive stop wh
hen the lift reeaches max llifting heighht. The box is gusseted too
support the
t box when
n the sleeve bearing reacches the end of travel.
Figuree 3: Upper center
c
suppo
ort with encclosure for ssleeve bearinng
Upper Slliders. Thesee sections off tubing weree sized basedd on the maxx stress due tto the bendinng
moment when they are
a fully exteended. A sim
mple bendingg stress calcuulation comppleted with thhe
ders fully ex
xtended show
wed this porttion of the ddesign to be tthe limiting factor when
upper slid
selecting
g a load capacity.
Center
C
Framee Section. Thhe center fraame section is
th
he same matterial used foor the upper center support.
This
T allowedd the materiaal to be cut frrom the sam
me
leength of recttangular tubing.
Frame
F
Extennsions. The fr
frame extensions are the
same rectanggular tubing used for the upper sliderrs.
These
T
extenssions allow tthe operator to select 4 fr
frame
widths
w
basedd on the vehiicle wheelbaase they are
working
w
on.
Scissor
S
Lift A
Arms. The liift arm lengtth was limiteed by
Figure 4:: Upper Slid
ders shown inserted
i
th
he minimum
m overall widdth we were trying to
intto Upper Ceenter Supporrt
acchieve. The length of eaach section w
was based uppon
th
he ratios requuired betweeen pins to m
meet lift traveel
reequirements .
Roller Assembly. Th
he roller asseembly was deesigned to seet into a secttion of the B
Bendpak
automotive lift the brridge jack reests in (Figurre 4). By inccorporating rrollers into thhe design thee
jack can roll forward
d and back within
w
the liftt. This allow
ws the techniccian to lift eiither the fronnt or
o the vehicle.
the rear of
6 BenddPak Lift
Bridgee Jack
Fig
gure 5:Bridg
ge Jack rolleer assembly set onto BeendPak Lift
Adapter platees. The tubin
ng inserted in
nto the centeer frame secttion will havve a sloppy ffit if
ock dimensio
ons. Adapterr plates weree designed thhat weld to th
the end of the sliding tubbing.
dapter plates fit snugly in
nto the corneers of the largger tubing an
and have a gaap to providee
e for the welld seam in th
he larger tubiing.
Figuree 6: Adapterr plate to be welded to eend of the sm
maller tubinng.
plates were also
a cut with
h an inside dimension
d
sliightly largerr than that off the smallerr
nd an outsidee dimension that fit the outside
o
of thhe larger tubiing (see figuure 6). Steel
ns were weld
ded to this ad
dapter allow
wing them to be bolted too the larger ooutside tubinng.
eel extension
ns not only allow
a
the brid
dge jack to bbe disassembbled for insppection and
ment of the slleeve bearing
g when neceessary but alsso decrease tthe bearing stress on thee
plates.
7 Lift Cy
ylinder Sele ction. The llift cylinderr travel was
selecteed based on the minimuum lifting heeight
requireements. A 110 in Travell cylinder reests at full
extensiion while thhe jack is coollapsed andd retracts 8 iin for
the Briidge jack to reach full hheight. The cylinder boore
was sellected basedd on the am
mount of forcce we needeed to
exert on
o the pins t o lift the 60000 lb load ((see Appenddix
B).
Figurre 7: Adapteer plates thaat
bolt to the larg
ger tubing
section
ns
Pin Sizzing. Static aanalysis was completed sstarting withh the
upper pins
p and worrking througgh a free boddy diagram too
determiine the maxiimum shear on each pin. The pins
supportting the uppeer center suppport have a theoretical m
max
shear sttress of 3.8 K
KSI. The pinns the hydrauulic cylinderr act
on weree found to hhave a shear sstress of 14.1 KSI. Thesse
pins weere also anallyzed for maax normal strress due to
bending
g from the fo
force appliedd by the hydrraulic cylindder. It
was fou
und that the pins the hyddraulic cylindder acts on
required sleeves to support the pin in bendiing.
Bearing Enclosure.
E
The
T lower beearing enclossure allows tthe bearing tto move horiizontally butt
supports it from mov
ving in the veertical directtion. The topp section is bbolted on to allow for briidge
jack disassembly. Th
he bearing en
nclosure asseembly is wellded to the ccenter frame section. Thee ¼”
plate the bearing ridees on is weld
ded fully acro
oss the bottoom to keep thhe plate from
m bending uunder
load.
Lower Piin Support. The
T lower fix
xed pin in th
he scissor lifft arms has a removable cover that alllows
for disasssembly but fully
f
supportts the pin in the horizonttal direction.. This Pin suupport will bbe
welded to
o the center frame sectio
on.
Figure 8: Bearing
B
Encclosure and lower pin ssupport
8 Construction Procedure
Rectangular Tubing. All rectangular tubing used in the construction of the bridge jack was cut
with the Marvel 8 band saw in shop 6. After cutting the tubing sections to final dimensions holes
were located and center drilled using one of the knee and column mills located in shop 7. Due to
the large pin diameter these holes were finished using the large drill press in shop 7.
The 5/16” holes that allow the adapter plates to be bolted on were drilled using one of the smaller
drill presses in shop 7.
Scissor Lift Arms. The scissor lift arms were burned out on the CNC plasma and de-burred after
cutting. The plates were welded together before drilling to ensure all holes are in the same
location. Initial holes were cut out on the plasma and then drilled to 1” hole diameter using the
large drill press located in shop 7. After drilling the pins were a tight fit in the holes and required
reinstallation in the drill press in order to bore out the holes using a 1” reamer.
Roller Assembly. Material for the roller assembly was cut using the Marvel 8 bandsaw. The
material was then de-burred and welded using the Airco MIG welder in shop 7.
Adapter Plates Welded to Smaller Tubing. These plates were drafted in AutoCad and burned out
using the CNC plasma located in shop 6. After being cut out on the plasma theses plates were
sanded to a smooth finish and welded to the ends of the upper sliders and frame extensions.
Adapter Plates Bolted to Larger Tubing. These
plates were also cut on the CNC Plasma. The steel
extensions that the bolts thread into were cut out on
the Marvel 8 Band saw, de-burred and welded to
the sections that were cut out on the plasma. These
plates were inserted into the ends of the larger
tubing sections and clamped in place to transfer
punch the bolt holes from tubing to the steel
extensions on the adapter plate. After drilling the
holes to the correct size the holes were tapped to
allow the 5/16 button head allen bolts to thread into
them.
Figure 9: Tapping 5/16-18 threads into
center frame section
Enclosures on Upper Center Support. The material
for the sleeve bearing enclosure was cut using the
band saw and welded using a MIG welder. After
tacking the sleeve bearing enclosure on the Upper
Center Support gussets were fabricated from ¼”
plate and welded in place for support in the
horizontal direction.
9 The fixed
d sleeve wass cut from 1.5” stock and
d bored out tto 1” using thhe lathes in shop 7. Afteer
tacking th
he sleeve on
n the Upper Center
C
Support and checcking alignm
ment gussets were fabricaated
from ¼” plate and weelded in placce for horizo
ontal supportt.
Figure 10:: Sleeve beaaring enclossure and fixeed pin sleevve tacked in place.
Bearing Enclosure.
E
Material
M
for the
t bearing enclosure
e
waas cut using the band saw
w and put
together as a subasseembly beforee welding to the center frrame sectionns. After the assembly w
was
completeed it was tack
ked onto thee lower framee sections annd welded using the Aircco MIG welder
in shop 7.
7
To minimizee warping off the
Welding Procedure. T
parts beinng welded toogether partss were weldeed in
short welld sections annd allowed tto cool beforre
continuinng with the w
welding proccess.
Welding sleeeves to sup
pport the pin
n
ing and prov
vide lateral stability
Installatioon of sleevess to prevent lateral
movemennt. Sleeves w
were installeed on the scissor
lift arms tto prevent thhe scissor lifft arms from
twisting oon the pins. T
The sleeve sstock was plaaced
in the lathhe and drilleed to the desiired inside
dimension. After drillling the sleeeves were cuut
from the sleeve stockk to the desirred final lenggth
These sleevees were weldded to
using the band saw. T
the scissoor lift arms uusing one of the MIG weelders
located inn shop 6.
10 Testing Procedure
P
No Load Testing. Th
he lift was cy
ycled from co
ollapsed to ffull extensioon with no looad to ensuree
correct operation of the
t Bridge jaack. No load
d cycling testted the bridgge jack for innternal bindiing
and allow
wed the operrator to check
k for stabilitty at differennt lift heightss during opeeration.
Figure 121
1: Testing th
he bridge jacck using thee BRAE hyddraulic Testt Bench
The follo
owing test prrocedures aree outlined by
y the Autom
motive Lift Innstitute (2006).
Proof Lo
oad Test. Opeerate the lift through its full cycle tw
wo times whiile loading too 150% of thhe
maximum
m rated load capacity. Fo
or a successfful test to takke place no vvisually apparent
deformattion of any liift structurall elements caan occur.
Figure 13: Prroof Load T
Test setup
11 To mimic lifting the chassis of a vehicle the jack applied the vertical force developed through the
upper slider extensions as shown in figure 13. During the proof load test no visual deformation
of any components occurred when 8550 lbs (142% of capacity) of vertical force was applied.
Operation Test. Operate the lift through its full cycle 5 times while loaded to the maximum rated
load capacity. During this test the function of the load holding devices and the operating control
system should be observed. During one of the tests the operator should release the control
mechanism when the lift is nearly collapsed to see make sure the load does not free fall. On
hydraulically operated lifts the oil level should be checked while the lift is fully extended and
pressure gauges should be placed in line to record operating pressures.
Lowering Speed Test. The lowering speed should be recorded from full extension to the nearly
collapsed dimension. A successful test is determined by the ability to maintain the lowering
speed below 20 ft/min
Load Holding Device Test. While the lift is loaded at 150% of rated capacity the load shall be
supported by the load holding device in the position that induces the most stress on the load
holding device. During the test the load holding device should experience no visual deformation
and exhibit no impaired function after the test.
The operation test and lowering speed test are not applicable to the scope of this senior project
and will be performed when the permanent hydraulic system is installed. The load holding
device test was not performed since the jack has no load holding device in current form meaning
technicians will use this bridge jack as a lifting apparatus only and provide mechanical support
for the vehicle while servicing using jack stands to support the weight of the vehicle.
12 RESULTS
R
General Observation
O
s. Under no load conditiions the briddge jack cyclled with no iinternal bindding
and traveeled from collapsed to fu
ully extended
d with no intterference isssues. The addapter platess
used on the
t upper sliders and low
wer frame ex
xtensions proovide a snugg fit for the adjustable
portions of the framee with a smooth sliding action
a
when adjusting thhe frame widdth.
M
off the lift. Du
uring initial testing the brridge jack haad more lateral movement
Lateral Movement
than desiired. This latteral movem
ment may resu
ult in seriouss operator innjury if the vvehicle were to
begin sw
waying and tip the bridge jack over. Sleeves
S
weree welded to tthe scissor liift arms that
prevent them from piivoting on th
he pins. Thesse sleeves cuured the laterral movemennt problem
found du
uring initial testing.
t
Lateral M
Movement Figure 13: Side view
w of lift with
h arrows shoowing directtion of movement
Lift Operration. The lift does nott incorporatee a mechaniccal stop at thiis time. Duriing use the
techniciaan must treatt this bridge jack
j
as a liftting device aand put jack stands undeer the vehiclee
frame as mechanical supports on
nce the vehiccle is at the ddesired heighht.
oad Test Resu
ults. During the proof lo
oad test the B
Bridge Jack w
was placed iin the Baldw
win
Proof Lo
Hydrauliic Test Bench
h with a hyd
draulic poweer supply pluumbed to thee hydraulic ccylinder. Thiis
hydraulicc power supp
ply is capablle of produciing a maxim
mum pressuree of 2000 psi resulting inn a
maximum
m cylinder fo
orce of 10,50
00 lbs (see Appendix
A
B)). The jack w
was tested foor maximum
vertical force
f
develop
ped at three lifting heigh
hts 1” above fully collappsed, 6.5” above fully
collapsed
d, and 10” ab
bove fully co
ollapsed. Resulting vertiical forces arre listed in thhe tables bellow.
13 Table 2: Baldwin Test Results when nearly collapsed
1” into travel
Fluid Pressure in Cylinder (PSI)
600
1000
1400
2000
Resulting Vertical Force (LBS)
975
1890
2780
4100
Table 3: Baldwin Test results when in middle of travel
6.5” into travel
Fluid Pressure in Cylinder (PSI)
600
1000
1500
2000
Resulting Vertical Force(LBS)
1734
3000
4800
6600
Table 4: Baldwin Test results when fully raised
10” into travel
Fluid Pressure in Cylinder (PSI)
600
1000
1500
2000
Resulting Vertical Force (LBS)
2600
4100
6350
8550
14 DISCUSSION
Construction phase took longer than anticipated. This was due in part to incorrectly estimating
required shop time and to changes made to the design during the construction phase. Examples
are the need for brackets between the center frame sections that keep the two pieces locked in
position relative to each other and boxing in the ends of the upper sliders to support the section
when vertical loads are applied.
The original design called for strips of steel to be inserted into the outer frame tubing. These
strips of steel would reduce the inside dimension of the outer tubing to provide a snug fit for the
smaller tubing that slides in and out of the center frame section. Through further observation of
current lifting devices the new design of welding an adapter plate to the end of the sliding tubing
and have a removable adapter that bolts to the larger fixed portion of the tubing was
implemented. This design allows full disassembly of the bridge jack for inspection and
replacement of wear items.
Disassembly of the bridge jack is simple, fast and requires only two hand tools. One 3/16 allen
wrench and a sturdy pair of external snap ring pliers can take the bridge jack from fully
assembled to individual components in about 15 minutes.
15 RECOMMENDATIONS
There is potential for roller bearing and sleeve damage if the jack is operated while against the
positive stops. The roller bearings are rated at 2970 lbs max radial load each the hydraulic
cylinder can apply up to 10,600 lbs of force, much greater than the dynamic load capacity of the
roller bearings.
Incorporating a mechanical stop would be beneficial to the customer and would eliminate the
requirement to use jack stands after lifting the vehicle. In the case of having a mechanical stop
the technician could apply the stop and lower the bridge jack until the positive stop is fully
supporting the load relieving pressure on the hydraulic system. A positive stop could be in the
form of a steel block placed against one end of the hydraulic cylinder or through the use a
locking pin that would lock the scissor lift arms in position.
16 REFERENCES
Automotive Lift institute. 2006. Safety Requirements for Construction, Testing and Validation.
Automotive Lift Institute, Inc. Cortlan, NY.
Bendpac RJ-9 Rolling Bridge Jack Specifications. Available at: http://www.bendpak.com/carlifts/4-post-bridge-jacks/RJ-9.aspx. Accessed March 10th 2011.
Budynas R.G. and Nisbett K.J. 2011. Mechanical Engineering Design. McGraw-Hill Companies
Inc. New York, NY
CLRBJ8 Rolling Bridge Jack Product Overview. Available at
http://www.completehydraulic.com/lifts-bridge-jacks-clrbj8.html Accessed 1st March 2011.
Eaton Corporation. 2008. Industrial Hydraulics Manual. Eaton Fluid Power Training
Maumee,OH
Gold, J.E., Fulmer, S., Tak, S., Yuan, L. Ergonomic hazards in automotive service technicians.
Department of public health, Temple University, Philadelphia, PA.
J Cullins, Personal Communication, 7th March 2011
17 APPENDICES
APPENDIX A: HOW PROJECT MEETS REQUIREMENT FOR THE BRAE MAJOR
18 How Project Meets Requirements for the BRAE Major
Major Design Experience - The project must incorporate a major design experience. Design is
the process of devising a system, component, or process to meet specific needs. The design
process typically includes the following fundamental elements. Explain how this project will
address these issues. (Insert N/A for any item not applicable to this project.)
Establishment of
objectives and criteria
To meet the lift requirements of the transportation shop. Please see
“parameters and constraints” section below for specific objectives
and criteria for the project.
Synthesis and analysis
The project will require structural analysis of the steel frame and
scissor lift components.
Construction, testing
and evaluation
The bridge jack will be designed, constructed, tested, modified (if
needed) and evaluated.
Incorporation of
applicable engineering
standards
This project will utilize AISC standards and ISO standards for
hydraulic circuits.
Capstone Design Experience - The engineering design project must be based on the knowledge
and skills acquired in earlier coursework (Major, Support and/or GE courses).
Incorporates
knowledge/skills from
earlier coursework
129 Lab Skills/Safety, BRAE 152 3D solids modeling, 421/422
Equipment Engineering, Engineering Statics, BRAE 234 Intro to
Mechanical Systems in Ag, Strengths of Materials, Technical Writing
Design Parameters and Constraints - The project should address a significant number of the
categories of constraints listed below. (Insert N/A for any area not applicable to this project.)
Physical
The bridge jack will be designed to have a minimum width of 42
inches and a max width of 61 inches. Fully collapsed the desired
height is 11 in
Economic
The bridge jack will save labor time for shop customers.
Health and Safety
Warning: This is a lifting device should never be used as a load
holding device during vehicle service. Placement of jack stands under
19 the vehicle or other means of mechanical support is necessary.
Aesthetic
The finished bridge jack will display the max lifting capacity of the
system.
Versatility
The bridge jack will be adjustable from the max desired width to the
minimum desired width in 6 in increments.
20 APPENDIX B: DESIGN CALCULATIONS
21 Allowable stress as defined by the Automotive Lift Institute
1018 CD Steel: Sut/3= 63.8 KSI/3= 21.3 KSI
Welded Seam Tubing (A36 Mild Steel): Sut/3= 58 KSI/3= 19.3 KSI
Free body diagram of Scissor Lift Arm while jack is collapsed
3000 Lbs Y=3160lbs X=Fcyl=8300 lbs Fcyl=8300 lbs 22 Free body diagram of Scissor Lift Arm while jack is extended
3000 Lbs Y=3437 lbs X= Fcyl=3220 lbs F cyl= 3220 lbs 23 Required Cylinder Force to Counteract the vehicle weight Cylinder Force Vehicle Force(VF) [lbs] X Distance [in] Y Distance [in] [lbs] 3000 10.6
9.9
3215.4 3000 10.70
9.7
3301.7 3000 10.81
9.6
3391.0 3000 10.91
9.4
3483.4 3000 11.01
9.2
3579.2 3000 11.12
9.1
3678.4 3000 11.22
8.9
3781.3 3000 11.32
8.7
3888.2 3000 11.42
8.6
3999.1 3000 11.53
8.4
4114.3 3000 11.63
8.2
4234.2 3000 11.73
8.1
4359.0 3000 11.84
7.9
4489.0 3000 11.94
7.7
4624.5 3000 12.04
7.6
4766.0 3000 12.15
7.4
4913.7 3000 12.25
7.3
5068.1 3000 12.35
7.1
5229.8 3000 12.45
6.9
5399.1 3000 12.56
6.8
5576.8 3000 12.66
6.6
5763.3 3000 12.76
6.4
5959.4 3000 12.87
6.3
6165.8 3000 12.97
6.1
6383.4 3000 13.07
5.9
6613.2 3000 13.17
5.8
6854.5 3000 13.28
5.6
7111.6 3000 13.38
5.4
7382.7 3000 13.48
5.3
7670.8 3000 13.58
5.1
7977.5 3000 13.65
4.9
8288.3 24 Bending stress on upper sliders 9.5 in 3000 lbs3000 lbs
3000
∗ 9.5 = 28500 in-lbs
1
1.48
∗ .
19.3 KSI
25 Bending Stress on Bearing Support
1500 lbs Assuming 5” of material is supporting in bending the theoretical stresses are as follows:
1500
∗ .5 = 750 in-lbs
.125
5
. 25
12
12
∗.
.
.00651
14.4 KSI
26 Roller Assembly
`
Centroid location of material resisting bending 1.35 in 1500 lbs Top View showing cross‐section used in calculations Side View 1500
∗ 1.35 = 2025 in-lbs
.7083
.0840
via AutoCAD section drawing
∗.
.
17.1 KSI
27 Force on upper pins
6000 lbs total
2 pins‐5 in long
1018 ultimate Strength=63.8 KSI
allowable normal stress=Sut/3=21.3 KSI
allowable shear stress=.4Sy=21.3 KSI
Force on the Pins(lbs)
3000
3000
3000
3000
3000
3000
3000
Diameter (in)
0.5
0.625
0.75
0.875
1
1.125
1.25
Shear stress
15287
9783
6794
4992
3822
3020
2446
Max cylinder force developed
Max Pressure(PSI)
Cylinder Bore(in) rod diameter
2000
1.5
1
2000
2
1.25
2000
2.5
1.5
2000
3
1.5
2000
3.5
1.75
2000
4
2
Bending Moment With Sleeves and Bracing Installed
Max Cylinder Force [lbs] Moment [in‐lbs]
C[in]
10597.5
10597.5
0.75
Safety Factor shear
1.39
2.18
3.14
4.27
5.57
7.05
8.71
Rod Area (sq in)
0.785
1.2265625
1.76625
1.76625
2.4040625
3.14
I [in^4]
0.519178906
Usable Area of piston (sq in) developed Force (lbs)
0.98125
1963
1.9134375
3827
3.14
6280
5.29875
10598
7.2121875
14424
9.42
18840
Bending Stress [PSI]
15309.0
Area (sq in)
0.785
1.2265625
1.76625
1.76625
2.4040625
3.14
Shear stress (PSI)
8535
5462
3793
3793
2787
2134
Bending Moment in Upper Sliders
Force(lbs)
M (in‐Lbs)
3000
27000
C(in)
1
I (in^4)
1.6823
Allowable Bending Stress=Sut/3=21.3 KSI
Bending Stress(lbs/sq in)
Safety Factor
16050
1.3271
Bending Moment on Lower frame Extensions
Force (lbs)
m(in‐lbs)
1500
15000
C(in)
2
I(in^4)
5.3073
Allowable Bending Stress=Sut/3=21.3 KSI
Bending Stress(lbs/Sq in)
Safety Factor
5653
3.77
Pin Diameter (in)
1
1.25
1.5
1.5
1.75
2
Bending moment on ball bearing support
Force (lbs)
Moment(in‐lbs) c(in)
1500
750
Bending Moment on Roller Assembly
Force (lbs)
Moment (in‐lbs) C(in)
3000
4500
I (in^4)
0.125
I(in^4)
0.125
Safety Factor
2.5
4.0
5.7
5.7
7.8
10.1
Allowable Bending Stress=Sut/3=21.3 KSI
Bending Stress(lbs/sq in)
Safety Factor
0.013020833
7200
2.96
Allowable Bending Stress=Sut/3=21.3 KSI
Bending Stress(lbs/sq in)
Safety Factor
0.100585938
5592
3.81
Shear Stress [PSI]) safety factor bending
3397.0
1.39134
1018 Sut=63.8 KSI
allowable bending stress=Sut/3=21.3 KSI
allowable shear stress=Sut/3=21.3 KSI
Force on pivoting pin
force (lbs)
6700
6700
6700
6700
6700
6700
shear on pin
6000.0
28 Stress on pins to hydraulic cylinder
Cylinder Force [lbs]
Moment [in‐lbs] C[in]
3215.4
3215.4
3301.7
3301.7
3391.0
3391.0
3483.4
3483.4
3579.2
3579.2
3678.4
3678.4
3781.3
3781.3
3888.2
3888.2
3999.1
3999.1
4114.3
4114.3
4234.2
4234.2
4359.0
4359.0
4489.0
4489.0
4624.5
4624.5
4766.0
4766.0
4913.7
4913.7
5068.1
5068.1
5229.8
5229.8
5399.1
5399.1
5576.8
5576.8
5763.3
5763.3
5959.4
5959.4
6165.8
6165.8
6383.4
6383.4
6613.2
6613.2
6854.5
6854.5
7111.6
7111.6
7382.7
7382.7
7670.8
7670.8
7977.5
7977.5
8288.3
8288.3
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
I [in^4]
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
0.0490625
4096.0
4206.0
4319.8
4437.5
4559.5
4685.9
4817.0
4953.1
5094.4
5241.2
5393.9
5552.9
5718.5
5891.1
6071.3
6259.5
6456.2
6662.1
6877.9
7104.2
7341.8
7591.6
7854.5
8131.8
8424.4
8731.8
9059.4
9404.7
9771.7
10162.4
10558.3
Shear Stress [PSI]) safety factor bending safety factor shear
5217.8
0.98877
8.16
5357.9
0.96291
7.95
5502.9
0.93755
7.74
5652.9
0.91267
7.54
5808.3
0.88826
7.33
5969.3
0.86429
7.14
6136.3
0.84077
6.94
6309.6
0.81768
6.75
6489.6
0.79500
6.56
6676.7
0.77272
6.38
6871.2
0.75085
6.20
7073.7
0.72935
6.02
7284.7
0.70823
5.85
7504.6
0.68747
5.68
7734.1
0.66707
5.51
7973.9
0.64702
5.34
8224.5
0.62730
5.18
8486.8
0.60791
5.02
8761.6
0.58884
4.86
9049.9
0.57009
4.71
9352.6
0.55164
4.55
9670.8
0.53349
4.41
10005.8
0.51563
4.26
10358.9
0.49805
4.11
10731.7
0.48075
3.97
11123.3
0.46382
3.83
11540.6
0.44705
3.69
11980.5
0.43063
3.56
12448.0
0.41446
3.42
12945.7
0.39853
3.29
13450.1
0.38358
3.17
1018 Sut=63.8 KSI
allowable bending stress=Sut/3=21.3 KSI
allowable shear stress=Sut/3=21.3 KSI
Bending Stress [PSI]
shear on pin
32768.1
33647.9
34558.0
35500.1
36475.9
37487.2
38536.0
39624.5
40754.8
41929.5
43151.3
44423.0
45747.8
47129.0
48570.3
50075.8
51649.8
53297.1
55023.0
56833.2
58734.0
60732.5
62836.3
65054.1
67395.2
69854.4
72475.0
75237.8
78173.5
81299.1
84466.3
29 APPENDIX C: DEFINITIONS
Strength Factor: is defined as the ratio of the ultimate strength of the material to the design stress at
rated load capacity (ALI 2006)
Ductile Metal: describes metal capable of sustaining not less than 5% elongation before fracture (ALI
2006)
Non-Ductile Metal: Describes metal not capable of sustaining 5% elongation before fracture (ALI 2006)
30 APPENDIX D: CONSTRUCTION DRAWINGS
31 Figure 14: Part drawing o f 1 in pin
32 Figurre 15: Part drawing
d
of t ubing flangge
33 Figu
ure 16: Partt drawing off Top Sliderr
34 Figure 17: Part draawing of Rooller Assem
mbly
35 Figure 18: Part draawing of cyllinder Sleevve 1
36 Figure 19: Part draawing of Cyylinder Sleevve 2
37 Figure 20: Part drawin
ng of Bottom
m Frame Exxtension
38 Figure 21: Part draw
wing of Adaapter Plate U pper
39 Fig
gure 22: Parrt drawing o f Adapter
40 Figure 23: Part drawing o f 8 in pin
41 Figure 24: Part Drawing of Sccissor Lift A rm
42 Figure 25
5: Part draw
wing of Uppeer Center Seection
43 Figure 26
6: Part Draw
wing of Centter Frame Section