Unit 4 PPT.pdf Suspension steering and brakes

Suspensions

1. Suspension System
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2. AnAutonomousInstitute
AffiliatdToSPPU,Pune
PresentedBy
Dr. GaneshShete
AssistantProfessor
SchoolofMechanicalEngineering
SchoolofMechanicalandCivil
Engineering
APresentationon
UNIT4:Suspension Kinematics
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15. Suspension System Functions
1.Provide vertical compliance so the wheels can follow the uneven road, isolating
the chassis from the roughness of the road.
2.Maintain the wheels in proper steer and camber attitudes to the road surface.
3.React to the control forces produced by the tires-longitudinal (acceleration and
braking) forces, lateral (cornering) forces, and braking & driving torques.
4.Resist roll of the chassis.
5.Keep the tires in contact with the road with minimal load variations.
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16. Suspension System Functions
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17. Suspension System Functions
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18. Suspension System Components
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19. Independent and Dependent Suspensions
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20. Independent and Dependent Suspensions
https://www.youtube.com/watch?v=nJqt14tmrRw4/16/2024 20

21. Four Link Mechanism
•Inresponsetotheshortcomingofleafspringsuspensions,thefourlinkrear
suspensionofchoiceinrecentdecadesforthelargerpassengercarswithsolid
rear-driveaxles.
•Thelowercontrolarmsprovidelongitudinalcontroloftheaxlewhiletheupper
armsabsorbbraking/drivingtorquesandlateralforces.
•Occasionally,thetwoupperarmswillbereplacedbyasingle,triangulararm,
butitremainsfunctionallysimilartofourlink.Theabilitytousecoilsprings(or
airsprings)inlieuofspringsprovidesbetterrideandNVHbyeliminationof
frictioncharacteristicsofleafsprings.
•Althoughmoreexpensivethanleafspring,thegeometricdesignofthefour-link
allowsbettercontrolofrollcenterlocation,anti-squatandantidive
performance,androllsteerproperties.
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22. Wishbone Suspension System
•ThemostcommondesignforthefrontsuspensionofAmericancarsfollowingWorldWarII
usedtwolateralcontrolarmstoholdthewheelasshowninfigure.
•TheupperandlowercontrolarmsareusuallyofunequallengthfromwhichtheacronymSLA
(short-Longarm)getsthename.
•ThearmsareoftencalledA-armsinUSandwishbonesinBritain.
•ThislayoutsometimesappearswiththeupperA-armreplacedbyasimplelaterallink,orthe
lowerarmreplacedbyalaterallinkandangledtensionstrut,butthesuspensionsare
functionallysimilar.
•TheSLAiswelladaptedtofront–engine,rearwheeldrivecarsbecauseofthepackagespace
itprovidedfortheengineorientedinthelongitudinaldirection.
•Additionally,itisbestsuitedtovehicleswithaseparateframeformountingthesuspension
andabsorbingtheloads.
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23. Wishbone Suspension System
https://www.youtube.com/watch?v=93SotyItxUU
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24. MacPherson’s Suspension System
•EarleS.MacPhersondevelopeda
suspensionwithgeometrysimilarto
theunequalarmfrontsuspension
usingastrutconfiguration.
•Thestrutistelescopicmember
incorporatingdampingwiththe
wheelrigidilyattachedatitslower
end,suchthatthestrutmaintains
thewheelinthecamberdirection.
•Theupperendisfixedtothebodyshellorchassis,andthelowerendislocated
bylinkageswhichpickupthelateralandlongitudinalforces.
•TheMacPhersonstrutprovidesmajoradvantagesinpackagespacefortransverse
engines,andthusiswidelyusedforfrontwheeldrivecars.
•Fewerpartandcapabilitytospreadsuspensionoverwidecarbodyarea.
•Installedheightisthedisadvantagehencehoodheightislimit.
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25. MacPherson’s Suspension System
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26. Anti Squat geometry
•Anytypeofanti-geometryisaformofgeometryatthefrontorrear
wheelsthataltersandcontrolstheamountthatacarwillcompressthe
springsduetoacceleration,decelerationorbrakingcondition.
•Anti-squatgeometryisfortherearwheelsunderacceleration
conditions.
•Inordertopreventthisrotationfromhappeningortolimittheamount
ofrotationanopposingforceneedstobeappliedtothecenterof
gravity.Thisopposingforcecomesintheformofantigeometry.
•Anti-squatisasuspensiongeometrythataffectstheamountofrear
suspensiondeflectionwhenthecaraccelerates.
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30. Anti-squat
https://www.crawlpedia.com/4_link_suspensi
on.htm
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31. Anti-squat
https://www.crawlpedia.com/4_link_suspensi
on.htm
Anti-squatinalinkedsuspensionsystemdetermineshowtherearendofavehiclemovesunder
accelerationorupontherearaxlecontactinganobstacleatspeed.Theanti-squatvalueis
determinedbytheverticalangleoftherearlinksastheyrelatetothefrontaxlepositionandthe
centerofgravityofthevehicle.
HowtoCalculateAnti-Squat:
1.Findthehorizontalcenterofgravityheightofthevehicleorusethecrankshaft.(Yellow)
2.Drawalinefromthecenterofthefronttirecontactpointuptothecenterofgravityline.(Dotted
Green)
3.Drawalinefromthatintersectiontothecenterofthereartirescontactpoint.(SolidGreen)
4.Drawlinestoextendtheupperandlowerrearlinksandfindthepointwheretheyintersect.
(InstantCenter)
5.Theverticaldistancefromthegroundtotheinstantcenterprojectedongravitylineistheanti-
squatvalue.
HowAnti-SquatAffectstheVehicle:
•Anti-squatabove100%causestherearendtomoveupandthesuspensiontounloadunder
acceleration.
•Anti-squatunder100%causestherearendtomovedownandthesuspensiontocompressunder
acceleration.
•100%anti-squatresultsinnomovementunderacceleration.
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32. Anti Squat geometry
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33. Anti Dive Geometry
Anti-divegeometryinalinkedsuspensionsystemdetermineshowthefrontendofavehiclemovesunderbrakingandacceleration.
Theanti-divevalueisdeterminedbytheverticalangleofthefrontlinksastheyrelatetotherearaxlepositionandthecenterof
gravityofthevehicle.
HowtoCalculateAnti-Dive:
1.Findthehorizontalcenterofgravityheightofthevehicleorusethecrankshaft.(Yellow)
2.Drawalinefromthecenterofthereartirecontactpointuptothecenterofgravityline.(DottedGreen)
3.Drawalinefromthatintersectiontothecenterofthefronttire'scontactpoint.(SolidGreen)
4.Drawlinestoextendtheupperandlowerfrontlinksandfindthepointwheretheyintersect.(InstantCenter)
5.Theverticaldistancefromthegroundtotheinstantcenterprojectedongravitylineistheanti-divevalue.
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34. Anti Dive Geometry
HowAnti-DiveAffectstheVehicle:
•Anti-diveabove100%willpreventthefrontendfromcompressingunderhardbrakingandstiffensthechassis.
•Anti-diveunder100%causesthesuspensiontocompressunderbraking.
•100%anti-diveresultsinnomovementandtransfersallenergyintothechassis.
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