design of formula sae suspension components

8/9/2019 Design of Formula SAE Suspension Components

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SAE TECHNICAL

PAPER SERIES 2002-01-3308

Design of Formula SAE

Suspension Components

Badih A. Jawad and Brian D. PolegaLawrence Technological University

Reprinted From: Proceedings of the 2002 SAE MotorsportsEngineering Conference and Exhibition

(P-382)

Motorsports EngineeringConference & Exhibition

Indianapolis, IndianaDecember 2-5, 2002

Downloaded from SAE International by Brunel University, Tuesday, October 21, 2014


2/13

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ISSN 0148-7191Copyright © 2002 SAE International

Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE.The author is solely responsible for the content of the paper. A process is available by which discussions

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ABSTRACT

This paper is an introduction to the design of suspensioncomponents for a Formula SAE car. Formula SAE is astudent competition where college students conceive,design, fabricate, and compete with a small formula-styleopen wheel racing car. The suspension componentscovered in this paper include control arms, uprights,spindles, hubs, pullrods, and rockers. Key parameters

in the design of these suspension components aresafety, durability and weight. The 2001 LawrenceTechnological University Formula SAE car will be usedas an example throughout this paper.

OVERVIEW

In designing suspension components for the2001 Lawrence Technological University Formula SAEvehicle, safety and durability were the top priorities. Inorder to ensure the safety of the suspension system, theloads acting on every component were extensivelystudied by utilizing strength of material calculations and

Finite Element Analysis. Another measure used toensure the safety of the suspension system was thatevery suspension fastener was put into double shearand was either safety wired or secured with a locknut.

Weight was another important consideration while designing and manufacturing the suspensionsystem on the 2001 Lawrence Technological UniversityFormula SAE car. In order to achieve a weight reductionover previous Lawrence Technological UniversityFormula SAE vehicles, Finite Element Analysis wasutilized to remove the maximum amount of material fromevery suspension component while maintaining a critical

safety factor of two. Also, chrome moly or 7075-T6aluminum was used for every suspension componentdepending on which material was more practicalconsidering any compatibility and dimensionalrestrictions. These materials were chosen due to theirsuperior strength to weight ratios. The suspension loadpaths were also extensively studied to ensure that they were fed into the suspension system and frame in arobust manner.

SUSPENSION DESIGN

CONTROL ARMS

The purpose of the control arms is to secure the wheel assembly to the chassis. Coupled with thesuspension geometry, the control arms play a key role indetermining the kinematics of the car such as camberrejection and roll stability. [1] The control arms also

provide a means for tuning the suspension for specificcourses.

Figure 1: Assembled Rear Control Arms

In order to reduce weight, spherical bearings arestaked into the pivot points and ball joints of the lowecontrol arms, along with the rear upper control arm pivotpoints and front upper control arm ball joints instead ofusing traditional heavier rod ends at these locations. Inorder to stake the spherical bearings into the 4130 steetubing, a hollow aluminum insert is pressed into the

tubing. Non-tempered aluminum was used for the inserdue to the fact that tempered aluminum is too hard toflatten, which causes the 4130 steel tubing to crackNext, the end of the tube is crushed flat and a hole ismilled through the flat end of the tubing. The bearing isthen firmly staked into the control arm.

2002-01-3308

Design of Formula SAE Suspension Components

Badih A. Jawad and Brian D. PolegaLawrence Technological University

Copyright © 2002 SAE International



4/13

Figure 2: Inserted Spherical Bearing

Rod ends with 4130 steel threaded inserts areused where suspension adjustment is necessary fortuning. Rod ends are used on the front upper controlarm pivot points to allow for camber and casteradjustments in the front suspension. Also, rod ends areused on the rear upper control arm ball joints to allow forcamber adjustment in the rear.

The appropriate size of 4130 steel tubing wasdetermined to be 19.05 mm OD x 0.71 mm wallthickness from performing buckling and bending stresscalculations. (See Appendix) This size of tubing isequivalent to 0.75 inch x 0.028 inch wall thickness, which is a common size of tubing in the United States.Using this size of tubing with a cornering load of 1.3 gand a braking force of 1.4 g, which were determinedfrom equipping previous Lawrence TechnologicalUniversity Formula SAE vehicles with data acquisition,the minimum safety factor in any of the control armssubjected to simultaneous braking and cornering wascalculated to be 1.7. [2] The cornering and brakingforces were calculated using a vehicle and driver weightof 2935.8 N. (See Appendix) These calculations werealso verified by performing Finite Element Analysis using

COSMOS software.

Figure 3: Control Arm FEA Results

Also, an extensive load study performed on thecontrol arms resulted in the arms of the control armsbeing directly in line with chassis nodes, minimizing anybending moments acting on the frame. All of the controlarm fasteners are put into double shear and meet ANspecifications. Therefore, the control arms weredesigned to be lightweight, reliable, and safe.

UPRIGHTS

The main function of the uprights is to providean interface to connect the upper and lower ball joints

with the spindle. It is crucial to minimize the weight othe uprights because they are unsprung mass, and theshocks have to control this weight in bump. [3]

The uprights were manufactured from 7075-T6aluminum instead of 4130 steel, which is common onmany Formula SAE vehicles, as a weight reduction Also, the 2001 Lawrence Technological UniversityFormula SAE uprights were manufactured using CNCprocesses instead of cutting and welding tubing in orderto increase their strength.

For safety purposes, the ball joint fasteners were put intodouble shear by passing them through the top web othe ball joint pocket and threading them into the lowe web of the ball joint pocket.

Front Uprights

To maximize the strength and minimize thedeflection of the front uprights, many design iterationsconsisting of various shapes were performed. FiniteElement Analysis was executed on each iteration incornering, braking, and a combination of cornering andbraking situations as a worse case scenario. Thesesituations are seen while performing typical maneuverson a Formula SAE course. To simulate a corneringforce of 1.3 g, the spindle hole was rigidly constrained while a load of 895.0 N was applied to the upper bal joint and a load of 2304.7 N was applied to the lower bal joint in the opposite direction. (See Appendix) Braking was simulated in Finite Element Analysis by rigidly

constraining the spindle hole and applying a force o1121.1 N at each of the brake caliper mountinglocations.

Preliminary Finite Element Analysis resultsshowed that a wide upright with pockets in it wasstronger than a traditional narrow upright without anypockets. It was also discovered through Finite Elemen Analysis that triangular pockets provided the greatesstrength with the least amount of deflection. FurtheFinite Element Analysis iterations resulted in an uprigh with optimized triangular pockets with the majority of themass centered around the spindle hole. The safety

factor of the final front upright was 4.0 in cornering, 2.8in braking, and 2.5 for combined cornering and braking.

Front Lower Control Arm

Maximum Stress=817.43 MPa

SF=1.68



5/13

Figure 4: Final Front Upright FEA Results

Rear Uprights

Many design iterations were performed on therear uprights to maximize their strength while minimizingtheir weight. Finite Element Analysis was performed onthe rear uprights in cornering, braking, and acombination of both of these situations. To simulatecornering on the rear uprights, the center hole wasrigidly constrained, while forces of 781.3 N were appliedto the upper ball joint and toe bar mounting location anda force of 2227.0 N was applied to the lower ball joint inthe opposite direction of the upper ball joint force. (See Appendix) To simulate braking, a force of 2224.1 N wasapplied to the upper and lower ball joints in thelongitudinal direction, while the center hole was fixed.

Finite Element Analysis results showed thattriangular pockets proved to be the most effective meansto reduce the weight of the rear uprights without

compromising strength. The resulting safety factors ofthe rear upright were 4.3 in cornering, 3.3 in braking, and3.1 in combined cornering and braking.

Figure 5: Final Rear Upright FEA Results

SPINDLES

The spindles provide a base at which the wheeassembly rotates about. Its outer diameter is critical toprevent slop in the bearings, resulting in premature wear. Also, as learned from previous LawrenceTechnological University Formula SAE cars, thissuspension component is greatly prone to fatigue loadsthat originate from abnormalities in the road surface andfrom weight transfer due to lateral and longitudina

accelerations. [4]

The spindles were manufactured from 4340steel due to its excellent fatigue-resistant properties andstrength. Key dimensional considerations for thespindles included bearing and upright dimensionsbecause the spindle is pressed into the upright. In ordeto prevent the hub from sliding into the upright, a step was designed into the spindle 5.08 mm from the uprightThe step is the same thickness as the bearings’ width inthe hub so that the slight impact load caused bymovements of the hub and bearings would be distributedthrough the entire bearing. Another step was added to

the free end of the spindle so that a washer and castlenut could be used to secure the hub to the spindle.

Figure 6: Final Spindle Design

An analysis of the spindle was performed usingmaximum braking and vertical forces. The maximumbraking force experienced by the 2001 LawrenceTechnological University Formula SAE car was found tobe 1.4 g, and the maximum cornering force on a tire wasfound to be 1.3 g. Using these forces and FiniteElement Analysis, the spindle's safety factor wasrevealed to be 25.8 in braking and 2.8 during corneringThe spindle's safety factor was determined to be 2.6 when braking and cornering loads were applied to thespindle simultaneously.

Front Upright FEA Results

Loading Case Max Stress

(MPa)

Deflection

(mm)

Safety Factor

Cor ner ing 1 23. 35 .363 4

Braking 179.66 .044 2.8

Cornering and

Braking

205.10 .409 2.45

Deflection

Combined Cornering

and Braking Stress

CorneringStress



6/13

Figure 7: Spindle FEA Results

For safety purposes, a backplate was welded tothe back of the spindle so that it could be bolted onto theback of the front uprights after it was pressed into theupright.

HUBS

The purpose of the hubs is to rotate the wheels

and tires. It is critical to minimize the weight of the hubsbecause they are rotating and unsprung mass. [5] Also,to reduce friction due to the rotational motion of thehubs, the 2001 Lawrence Technological UniversityFormula SAE car utilizes bearings in the hubs.

Front Hubs

The front hubs are manufactured from 7075-T6aluminum due to its superior strength to weight ratio. Also, in order to minimize weight without compromising

strength, the front hub utilizes a four-leaf clover patternto hold the lugs and brake rotor fasteners. The brakerotor and lug four-leaf clover patterns are offset 45

0 from

each other to allow for ease of pressing lugs into the huband installation of brake rotors. Also, a 10.16 mm highstep that is 19.69 mm wide is designed into the insidecenter of the front hub to keep the bearings apart fromeach other and to dissipate heat from the bearings.

Another key function of the front hubs is to allowthe brake rotors to float freely. This is accommodatedthrough a slot in the brake rotor fingers. Floating rotorsprovide maximum stopping force by allowing both brake

pads on the caliper to grip the rotor evenly. Also, theslot in the brake rotor fingers allow the brake rotorfasteners to be put into double shear as a safetyfeature. [6]

Figure 8: Final Front Hub

Finite Element Analysis was performed on thefront hubs to validate their design. A braking force of 1.4g applied to the brake rotor fastener holes resulted in asafety factor of 5.0. Also, a cornering force of 1.3 g wassimulated by applying a force of 4469.9 N on the bottomlug hole and 3024.2 N on the top lug hole in oppositedirections while constraining the brake rotor fingers from

translating. (See Appendix) This loading resulted in asafety factor of 2.8. A safety factor of 2.7 was obtained when combining braking and cornering.

Figure 9: Front Hub FEA Results

Rear Hubs

The main function of the rear hubs is to connecthe driveline to the wheels through the halfshafts andconstant velocity (CV) joints. The rear hubs aremanufactured from 4340 steel because they must becompatible with the outer CV joints that are splined toaccept a hub.

The rear hubs also utilize a four-leaf clovedesign to minimize their weight. To reduce friction fromthe rotating hub, bearings are placed in between theupright and the shaft on the hub. As a safety feature, aspindle lock nut is applied on the end of the CV joint toprevent the hub from becoming disengaged from thedriveline.

Finite Element Analysis proved that the reahub’s design was adequate for its application. A safetyfactor of 4.9 was obtained when a torque of 697.0 N-m

Spindle FEA Results

Lo ad ing Ca se Ma x S tre ss

(psi)

Def lec tio n

(in)

Sa fet y F act or

Cornering 324.05 .150 2.8

Braking 35.21 4.32 x 10 -4 25.8

Cornering and

Braking

343.90 .155 2.63

Cornering

Deflection

CorneringStress

CorneringStress



7/13

originating from the driveline was applied to the hubshaft while restraining the hub from rotating. When acornering force of 1.3 g was simulated on the hub byplacing a load of 3024.2 N on the top lug hole and4469.9 N on the bottom lug hole in the opposite direction while preventing the shaft from rotating, the resultantsafety factor was 4.2. (See Appendix) When combininga cornering situation with the torque acting on the hub,the resultant safety factor was 3.8.

Figure 10: Rear Hub FEA Results

ENERGY MANAGEMENT MECHANISMS

The energy management system consists of thepullrods, rockers, and shocks. The system’s purpose isto activate the inboard shocks, which greatly improvesthe handling qualities of the car. The geometry of thesuspension mechanism is critical because it determinesthe motion ratio, which is the ratio of vertical wheelmovement to shock displacement. This ratio is used todetermine the car’s natural frequency, which significantlyaffects the car’s handling qualities. Friction is kept to anabsolute minimum in the dampening system to allow formaximum efficiency of the shocks. [7] It is also critical

that the pullrod, suspension mechanism, and shock arelocated in the same plane to eliminate bending momentson these suspension components.

Figure 11: Placement of Pullrod and SuspensionMechanism

Pullrods

Pullrods are utilized on the 2001 LawrenceTechnological University Formula SAE car instead ofpushrods, which are typically used on Formula SAE

vehicles, for a weight reduction. Smaller diameter tubingcan be used for pullrods because when the car hits abump, the pullrod pulls the suspension mechanism which puts it in tension. During rebound the pullrods aresubjected to an insignificant buckling load equivalent tothe weight of the wheel assembly. Therefore, bucklingdoes not have to be considered in the design of pullrodsfor a Formula SAE vehicle. However, a pushrod issubjected to a buckling load whenever the car goes intorebound, so buckling must be considered in the designof pushrods. Also, pullrods allow the rockers and shocksto be packaged towards the bottom of the car resulting ina lower center of gravity.

A stress analysis of the pullrods using a 1.4 gtensile force resulted in a maximum stress of 118.89MPa. A safety factor of 2.6 is obtained from this stressFinite Element Analysis was also performed on thepullrods to verify the stress calculations and resulted in asafety factor of 2.5.

Rockers

Rockers, commonly called bellcranks, wereplaced on the 2001 Lawrence Technological UniversityFormula SAE car so that the shocks could be packagedinboard. This packaging scheme significantly reducesunsprung mass. Also, rockers allow the pullrod andshock displacements to be in different directions, whichaids tremendously in the packaging of suspensioncomponents. The rockers were designed to have a oneto one motion ratio, which means that the shocks travelsthe same amount that the wheel moves in the verticadirection. A one to one motion ratio was selectedbecause it allows the total range of shock displacemento be used, which improves the sensitivity of the

suspension system.

The rockers were manufactured from 7075-T6aluminum due to its superior weight to strength ratio. Toreduce friction in the energy management system, rollebearings were placed in between the two rocker platesand thrust bearings were incorporated into the bellcrankplates at the pivot points.

Extensive Finite Element Analysis wasperformed on the rockers to minimize their weight. Asafety factor of 4.9 was obtained for the final design ofthe front rockers when a force of 1.3 g was applied to

them at the pullrod attachment point while restraining itfrom translating. A safety factor of 4.5 was obtained fothe rear rocker when it was loaded in a similar manner.

CorneringStress



8/13

Figure 12: Rocker FEA Results

CONCLUSION

This paper addressed essential designconsiderations for a small formula-style open wheelracing car. These considerations were addressedproperly because none of the suspension componentson the 2001 Lawrence Technological University FormulaSAE car failed during intensive driver’s training or at the2001 Formula SAE competition.

ACKNOWLEDGMENTS

The authors would like to thank the 2001 LawrenceTechnological University Formula SAE team for all oftheir hard work and effort put into the project.

REFERENCES

1. Smith, Carroll. Tune to Win. Fallbrock, CA: AeroPublishers, 1978.

2. Hibbeler, R.C. Mechanics of Materials. 3rd ed. UpperSaddle River, NJ: Prentice Hall, 1994.

3. David E. Woods and Badih A. Jawad. “Numerical Designof Racecar Suspension Parameters”, Wahington, D.C.:SAE International, 1999.

4. 2000 LTU FSAE Team, “2000 Formula SAE Final Report”,Southfield, Michigan: Lawrence Technological University,2000.

5. Puhn, Fred. How to Make your Car Handle. Los Angeles,CA: HPBooks, 1981.

6. Smith, Carroll. Engineer to Win. Osceola, WI:Motorbooks International, 1984.7. William F. Milliken and Douglas L. Miliken. Race Car

Vehicle Dynamics. Warrendale, PA: SAE International.

Suspension Mechanism FEA Results

Stress Displacement

Rocker FEA Results



9/13

APPENDIX

SAMPLE CALCULATIONS

TOTAL WEIGHT

Target Vehicle Weight = 2224.11 N Average Driver Weight = 711.72 N

Total Weight = 2224.11 + 711.72 = 2935.83 N

CONTROL ARMS

FRONT CONTROL ARM AXIAL FORCES

1445.7 N 4.40o 28.06

o

15.45o FUCA

FPR

FLCA

556.0 N

N F

N F

N F

F

F M

F F

F F

F F

F F

PR

UCA

LCA

o LCA

o LCA

o LCA

o PR

oUCA y

o LCA

o PR

o

UCA z

0.233,2

6.208,17.259,2

)1.4)(40.4sin()8.21)(0.556(

)8.238)(40.4cos()381)(7.1445(0

40.4cos06.28cos

45.15cos7.14450

40.4sin06.28sin

45.15sin0.5560

−=

−=−=

+−

+==+

+−

+==→+

−+

−==↑+

∑

∑

∑

)

REAR CONTROL ARM AXIAL FORCES

1445.7 N 4.13o 28.03

o

14.30o R UCA

R PR

R LCA

556.0 N

N R

N R

N R

R

R M

R R

R F

R R

R F

PR

UCA

LCA

o LCA

o LCA

o LCA

o PR

oUCA y

o LCA

o PR

oUCA z

0.088,2

5.060,1

3.267,2

)29.2)(13.4sin()64.8)(0.556(

)3.241)(13.4cos()381)(7.1445(0

13.4cos03.28cos

30.14cos7.14450

13.4sin03.28sin

30.14sin0.5560

−=

−=

−=

+−

+==+

+−

+==→+

−+

−==↑+

∑

∑

∑

)

BUCKLING CALCULATIONS

2

2

L

EI P

cr

Π=

4121020.1723

84.206

m I

GPa E

−

×=

=

( ) ( )

N P

P

MAX

MAX

90.167,52

0176.00191.04

1058.1206 226

=

−

Π×=

y

z

y

z



10/13

Front Upper Control Arm Front Arm

( (( )

65.226.660,19

90.167,52

26.660,19

423.0

1020.17231084.206

2

1292

==

=

××Π=

−

SF

N P

P

cr

cr

Rear Arm

( )

90.234.006,18

90.167,52

34.006,18

442.0

1020.17231084.206

2

1292

==

=

××Π=

−

SF

N P

P

cr

cr

Front Lower Control Arm Front Arm

( )

01.458.009,13

90.167,52

58.009,13520.0

1020.17231084.206

2

1292

==

=

××Π=

−

SF

N P

P

cr

cr

Rear Arm

( )

49.406.629,11

90.167,52

06.629,11

550.0

1020.17231084.206

2

1292

==

=

××Π=

−

SF

N P

P

cr

cr

Rear Upper Control Arm Front Arm

( )

15.367.552,16

90.167,52

67.552,16

461.0

1020.17231084.206

2

1292

==

=

××Π=

−

SF

N P

P

cr

cr

Rear Arm

( )

66.355.241,14

90.167,52

55.241,14

497.0

1020.17231084.206

2

1292

==

=

××Π=

−

SF

N P

P

cr

cr

Rear Lower Control Arm

Front Arm

( )

21.471.382,12

90.167,52

71.382,12

533.0

1020.17231084.206

2

1292

==

=

××Π=

−

SF

N P

P

cr

cr

Rear Arm

( )

37.482.930,11

90.167,52

82.930,11

543.0

1020.17231084.206

2

1292

==

=

××Π=

−

SF

N P

P

cr

cr

MOMENT CALCULATIONS

M=Fd

Bending Moment due to Vertical Force Front Upper Control Arm

m N M

d VF M

−=

==

61.93

45.25cos413.045.25cos0.278))(( 00


( (m N M

d VF M

−=

==

45.131

40.14cos504.040.14cos0.278))(( 00

Rear Upper Control Arm

m N M

d VF M

−=

==

14.101

30.24cos438.030.24cos0.278))(( 00


m N M

d VF M

−=

==

97.107

13.14cos413.013.14cos0.278))(( 00

Bending Moment due to Cornering Force Front Upper Control Arm

( m N d CF M −=== 86.94)117.0(45.15cos16.841))(( 0


( m N d CF M −=== 37.92)041.0(40.4cos70.2259))(( 0


( N d CF M −=== 29.117)114.0(30.14cos79.1061))(( 0


m N d CF M −=== 92.85)038.0(13.4cos81.2266))(( 0



11/13

Shearing Moment due to Braking Force Front Upper Control Arm

m N d BF M −=== 39.90)127.0)(72.711())((


m N d BF M −=== 39.90)127.0)(72.711())((


m N d BF M −=== 39.90)127.0)(72.711())((


m N d BF M −=== 39.90)127.0)(72.711())((

STRESS CALCULATIONS

I

MyS =

m y

m I

3

412

10525.9

1020.1723

−

−

×=

×=

Bending Stress due to Vertical Force Front Upper Control Arm

( )(

33.243.517

58.1206

43.517

1020.1723

10525.961.93

12

3

==

=

×

×

=−

−

SF

MPaS


( )(

66.159.726

58.1206

59.726

1020.1723

10525.945.131

12

3

==

=

×

×

=−

−

SF

MPaS


( )(

16.205.559

58.1206

05.559

1020.1723

10525.914.101

12

3

==

=

×

×

=−

−

SF

MPaS


( )(

02.280.59658.1206

80.596

1020.1723

10525.997.107

12

3

==

=

×

×

=−

−

SF

MPaS

Bending Stress due to Cornering Force

Front Upper Control Arm

( )

30.234.524

58.1206

34.524

1020.1723

10525.986.94

12

3

==

=

×

×

=−

−

SF

MPaS


( )(

36.258.510

58.1206

58.510

1020.1723

10525.937.92

12

3

==

=

×

×

=−

−

SF

MPaS


( )(

86.132.648

58.1206

32.648

1020.1723

10525.921.117

12

3

==

=

×

×

=−

−

SF

MPaS


( )(

54.292.474

58.1206

92.474

1020.1723

10525.992.85

12

3

==

=

×

×

=−

−

SF

MPaS

Shearing Stress due to Braking Force

Front Upper Control Arm( )

42.263.499

58.1206

63.499

1020.1723

10525.939.90

12

3

==

=

×

×

=−

−

SF

MPaS


( )

42.263.499

58.1206

63.499

1020.1723

10525.939.90

12

3

==

=

×

×

=−

−

SF

MPaS


( )(

42.263.499

58.1206

63.499

1020.1723

10525.939.90

12

3

==

=

×

×

=−

−

SF

MPaS


( )(

42.263.499

58.1206

63.499

1020.1723

10525.939.90

12

3

==

=

×

×

=−

−

SF

MPaS

SPINDLES

FATIGUE ANALYSIS

Maximum Vertical Force = 2891.2 NMinimum Vertical Force = 0 N



12/13

Maximum Bending Moment = (2891.2)(0.082)= 237.08 N-m

Minimum Bending Moment = (0)(0.082)=0 N-m

( ) 4844 1022.7014.0019.04

m I −

×=−Π

=

Maximum Stress

( )( ) MPa

I

MyS 39.62

1022.7

019.008.237

8max =

×

==−

Minimum Stress

( )( ) MPa

I

MyS 0

1022.7

019.00

8min =

×

==−

Mean Stress

MPaS S

S m

20.312

039.62

2

minmax=

+=

+

=

Average Stress

MPaS S

S a

20.312

039.62

2

minmax=

−

=

−

=

MPaS

MPaS

MPaS

MPaS

e

YT

UT

5.412

5.742

25.701

825

1000

=

=

=

=

Soderberg Approach

( ) be

b

c

e

e

e

a

YT

m

S N

MPaS

S

S

S

S

S

/110

65.32

120.31

25.701

20.31

1

−

=

=

=+

=+

( ) ( )

126.35.412

5.742loglog

085.0

5.412

5.742log

3

1log

3

1

22

1000

1000

=

==

−=

−=

−=

c

S

S c

b

S

S b

e

e

( ) 085.0/1085.0126.3

65.3210 −

−

−

= N

N=1.39X1019 cycles

UPRIGHTS

FRONT UPRIGHT CORNERING FORCE

1445.7 N

FUBJ

FLBJ

y

z

∑

∑=+==+

−−==+

0)239.0()142.0)(7.1445(0

7.14450

UBJ

LBJ UBJ y

F M

F F F

)

r

N F

N F

LBJ

UBJ

65.2304

95.859

=

−=

REAR UPRIGHT CORNERING FORCE

1445.7 N

FUBJ

FLBJ

y

z

∑

∑=+==+

−−==+

0)272.0()147.0)(7.1445(0

7.14450

UBJ

LBJ UBJ y

F M

F F F

)

r

N F

N F

LBJ

UBJ

02.2227

32.781

=

−=



13/13

HUBS

FRONT HUB CORNERING FORCE

1445.7 N

FUL

FLL

y

z

∑

∑+==+

−−==+

)0.98()0.205)(7.1445(0

7.14450

UL

UL LL y

F M

F F F

)

r

N F

N F

LL

UL

87.4469

17.3024

=

−=

REAR HUB CORNERING FORCE

1445.7 N

R UL

R LL

y

z

∑∑ +==+

−−==+

)0.98()0.205)(7.1445(0

7.14450

UL

UL LL y

R M

R R F

)

r

N R

N R

LL

UL

87.4469

17.3024

=

−=

PULLRODS

TENSILE STRESS

A

P=σ

( ) 2522 10432.20077.00095.04

m A −

×=−Π

=

( )

61.289.118

26.310

89.118

10432.2

7.14452

5

==

=

×

=−

SF

MPaσ


design of formula sae suspension components

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