Selection, Modification And Analysis Of Suspension System .

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Selection, Modification and Analysis of SuspensionSystem for an All-Terrain VehicleEshaan Ayyar, Isaac de Souza, Aditya Pravin, Sanket Tambe, Aqleem Siddiqui & Nitin GuravE-mail :,,, sank 200956@yahoo.comThe following types of suspension systems aregenerally available in the market:Abstract - The real pleasure of driving for an off-roadenthusiast can be described as the thrill of the terraincoupled with a capable machine to handle the terrain.However, this pleasure can be derived only when thecomfort level of the driver is maintained. Thus, it isconcluded that the suspension system (which is responsiblefor providing a comfortable ride quality to the driver) isone of the most important sub-systems to be designed. Thispaper aims at selecting, modifying, analyzing andfabricating a suspension system capable of handling roughterrains while maintaining the ride quality.1. Mechanical Suspension System:i) Independent Suspension Leaf Spring Suspension MacPherson Suspension Wishbone Suspensionii) Dependent SuspensionI. INTRODUCTIONRigid Axle SuspensionSuspension system is the term given to the systemof springs, shock absorbers and linkages that connect avehicle to its wheels.When a tire hits an obstruction,there is a reaction force and the suspension system triesto reduce this force. The size of this reaction forcedepends on the unsprung mass at each wheel assembly.In general, the larger the ratio of sprung weight tounsprung weight, the less the body and vehicleoccupants are affected by bumps, dips, and other surfaceimperfections such as small bridges. A large sprungweight to unsprung weight ratio can also impact vehiclecontrol.2. Electric Suspension SystemThe main role of suspension system is as follows:1.Load bearing capacity It supports the weight of the vehicle2.Flexibility Provides a smoother ride for the passengers3.Cost Protects the vehicle from damage4.Technical aspects: Camber, Stiffness, Rolling Keeps the wheels firmly pressed to the ground forbetter traction5.Availability of parts and components It isolates the vehicle from road shocks3. Magnetic Suspension SystemII.The selection of the suspension system which willbest satisfy the requirements of an ATV was carried out.Out of the many available suspension systems in themarket, the Double Wishbone Suspension System wasselected for the ATV. This selection was done based onthe following basic parameters:III. DESIGNThe design procedure for the chosen suspensionsystem is divided into two stages:There are three basic components in any suspensionsystem: Springs Dampers Anti-sway barsSELECTION OF SUITABLE SUSPENSIONSYSTEM1.Primary design: Basic design and development of SuspensionSystem componentsISSN : 2319 – 3182, Volume-2, Issue-4, 201362

International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME) Modifieddesignparametersbasedapproximation of Dynamic Conditions According to the mass distribution of 60:40 (Rear:Front) Static testing and analysis Mass per wheel (Front) 50 kg2.Secondary design: Mass per wheel (Rear) 80 kg Mathematical modeling of finalized concept ATV1) Front spring Dynamic testing and analysisAngle of inclination of the strut 60 (from horizontal) Modification of Design Parameters based onDynamic Testing resultsPoint of attachment of strut 10” (254 cm) from chassisend .(from suspension geometry)onReaction force acting from the ground on the wheel (Mass per wheel * 9.81) NThe following components are to be designed: Suspension Spring Wishbones Knuckle (50 kg * 9.81) N 490.5 NDesign procedure for the components of Suspensionsystem is dependent on the suspension geometry (asshown in Fig.1 and Fig.2); found out by taking intoconsiderations the design constraints.Fig.3. Forces on front wishboneConsidering the wishbone hinges as the point aboutwhich moment is taken;Horizontal distance of reaction force from hinge pointFig.1 Front suspension geometry 17.36” (44.09 cm)geometry .from suspensionHorizontal distance of strut attachment point from hingepoint 8.2” (20.828 cm)By taking moment about hinge points :490.5 * 17.36 Spring Force * 8.23 Spring Force 1034.6 NConsidering the dynamic factor,Dynamic force acting on the spring 2586.59 NFig.2 Rear suspension geometryAccording to the ride conditions and road quality for anATV, it is concluded that the optimum spring travelshould be approx. 4” (10.16 cm)Design of suspension springAssumptions made: Sprung mass 260 kg(approx.) Factor for static to dynamic conditions : 2.5Hence, Required Spring Stiffness Dynamic Spring ForceSpring Deflection 2586 .59101 .6 25.46 N /mmISSN : 2319 – 3182, Volume-2, Issue-4, 201363

International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)Table 1. Spring dimensions25 N/mm2) Rear springSr.No.oAngle of inclination of the strut 80 (from horizontal)Point of attachment of strut 6.5” (16.51 cm) fromchassis end (from suspension geometry)12Reaction force acting from the ground on the wheel (Mass per wheel * 9.81) N3 (80 kg * 9.81) N456789Fig.4. Forces on rear rialWire diameterInnercoildiameterOutercoildiameterTotal numberof turnsFree length ofstrutPitchofsuspensionspringEye-to-eyelength of strut(unloaded)StiffnessGrade 4 oil hardened spring steel11 mm11 mm55 mm55 mmMaximumdynamic springtravel66 mm66 mm2214365 mm292 mm18 mm27 mm456 mm484 mm25 N/mm40 N/mm101.12 mm100.88 mmConsidering the wishbone hinges as the point aboutwhich moment is taken;B. Design of wishbonesHorizontal distance of reaction force from hinge point 14” (35.56 cm) .(from suspension geometry)The design parameters that govern the dimensions of thewishbone are :i) Available length for wishbones: 32 inchesHorizontal distance of strut attachment point from hingepoint 6.38” (16.02 cm)ii) Available width for wishbones: 20 inchesBy taking moment about hinge points :1) Front wishbone784.8 * 14 Spring Force * 6.38The front wishbones are standard A-arms and thedimensions are decided on the basis of the length andwidth constrains (as shown in Fig.5). The wishboneshave unequal length.The upper wishbone is shorter thanthe lower wishbone.The advantage of having differentlengths is that when the car takes a turn a negativecamber is induced which increases the stability.Theunequal lengths also result in a positive camber of1.5⁰.The strut is mounted on the lower wishbone and theknuckle is attched to the wishbone by a ball joint. Thewishbone is then tested using Autodesk Inventor. Spring Force 1722.13 NConsidering the dynamic factor,Dynamic force acting on the spring 4305.325 NAccording to the ride conditions and road quality for anATV, it is concluded that the optimum spring travelshould be approx. 4” (10.16 cm)Hence, Required Spring Stiffness 42.375 N40 N/mmISSN : 2319 – 3182, Volume-2, Issue-4, 201364

International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)Fig.7.Front KnuckleFig.5.Front WishboneDue to lack of funds the above design could not bemanufactured.The knuckle of a maruti 800 wasmodified so that it could accmmodate the designedwishbones.The modified design is shown below.2) Rear wishboneInitially, the A-arm was considered for the rearsuspension. However, while the vehicle takes a turn, dueto the horizontal forces acting on the attachments of thewishbones and the knuckle and due to lack of steeringon the rear wheels, there may be toe-in or toe-out of thewheels. This may lead to improper steering and mayresult in unbalance. Excess toe-in may cause oversteerwhile turning leading to loss of control. Excess toe-outmay cause understeering while turning.To avoid anytoeing, the A-arm is converted into H-arm (as shown inFig.6). Thus the vertical pin knuckle-wishboneattachment is converted into horizontal pin attachment.This prevents formation of an axis and hence thepossibility of toeing of the wheels. This ensures properalignment and steering. It also increases the ride stabilityand linear travel.Fig.8.Modified Front Knuckle2) Rear knuckleThe rear knuckle was designed to accommodate thedesigned H-arms (Fig.9)Fig.6.Rear WishboneC. Design of knuckleA knuckle is used to connect the wishbones to thewheel hub.1) Front knuckleThe first step in the design was market research. Astandard knuckle of MARUTI SUZUKI ESTEEM wasselected from the market and studied. The suspensionsystem of the Esteem is MacPherson type, hence theknuckle had to be modified. The designed knuckle isshown. (Fig.7)Fig.9.Rear KnuckleISSN : 2319 – 3182, Volume-2, Issue-4, 201365

International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)The rear knuckle too could not be manufactured due tolack of funds.the knuckle of an esteem was modified asshown in the figureThe rear upper wishbone was tested as the strutattachment point was on the upper wishbone. The hingeswere considered as fixed points and a load of 4305.325N was applied at the strut attachment point.Fig.10.Modified Rear KnuckleFig.12.Rear WishboneTESTING OF DESIGNED COMPONENTSLoad applied: 4305.325 NAnalysis of all the parts was done using Autodeskinventor.Factor of safety: 1.5WishbonesB. KnucklesThe front lower wishbone was tested as the strut isattached on the lower wishbone due to which most ofthe load acts on the lower wishbone. The wishbone wastested on Autodesk inventor. The two hinge points andball joint were considered as fixed points and a load of2586.59 N(load on spring) was applied at the strutattchment point.The hub end of the knuckle was considered fixedand a load of 2586.95 N was applied at the lower part ofthe knuckle as shown in fig.13.Result: Design is safeFig.13.Testing of front knuckleLoad applied: 2586.59 NFactor of safety 3.5Fig.11.Front WishboneResult: Design is safeLoad applied: 2586.59 NThe attchment for the front knuckle was tested and theresult (Fig 14).Factor of safety: 1.5Result: Design is safeISSN : 2319 – 3182, Volume-2, Issue-4, 201366

International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)Load applied: 2586.59 NFactor of safety 3.5Result: Design is safeIV. FABRICATIONThe fabrication of all the parts was done in theworkshop.The final fabricated parts are shown below.Material used for wishbones: AISI 1026Dimensions of pipe: 19 mm ID, 3 mm thicknessMaterial usedmodifications:Fig.14.Testing of front knuckle attchmentThe rear knuckle was tested in a similar way.theresults are shown belowforallotherfabricationsandMild Steel plates of thickness 4 mm and 8 mmFig.15.Testing of rear knuckleFig.17.Fabricated front wishboneLoad applied: 4305.325 NResult: Design is safe (Factor of safety 4)Fig.18.Fabricated rear wishboneFig.16 Testing of modified rear knuckleISSN : 2319 – 3182, Volume-2, Issue-4, 201367

International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME)V. REFERENCESFig.19 Front knuckle with attachment[1]Christina Elena Popa, ‘Steering System andSuspensionSystem’, University Of SouthQueensland[2 ]Edmund F. Gaffney and Anthony R. Salinas,‘Introduction to Formula SAE Suspension’,University Of Missouri[3]Mitchell W., ‘Force based roll centres andkinematic roll centres’, SAE-India[4]Gertz L., L. Laranja, ‘An off-road suspensionsystem’, University Of Brazil[5]Gerrard M., ‘Roll centres and jacking forces’,Engineering Solutions[6]NK Giri, ‘Automobile Mechanics’, KhannaPublications, 1996[7]Kirpal Singh, ‘Automobile Engineering’,Standard Publishers Distributors, 2008[8]Thomas D.Gillespie, ‘Fundamentals of VehicleDynamics’[9]T.K. Garrett, K. Newton, W. Steeds, ‘The MotorVehicle’, Butterworth-Heinemann, 2000[10]Design Data Book, PSG Technology Institute Fig.20 Rear SuspensionFig 20. Final AssemblyISSN : 2319 – 3182, Volume-2, Issue-4, 201368

Design procedure for the components of Suspension system is dependent on the suspension geometry (as shown in Fig.1 and Fig.2); found out by taking into considerations the design constraints. Fig.1 Front suspension geometry Dynamic force acting on the spring 2586.59 N Fig.2 Rear suspension geometry

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