Sway_bar_Calculations

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1、EffectiveSpringRateinSwayBars:IamsurethatmanyofyouhaveseentheEquationbelowfromFredPuhn’sbookHowtoMakeYourCarHandle.Thefollowingpagesofdiagramsandequationsaremyattempttoexplainwhythisequationgivesyoutheeffectivespringrateattheendofthearmwheretheendlinkattachestotheswaybar.

2、lbfTheequationfromPuhn’sbookisonlygoodforspringratein,anditassumesingenericpropertiesforsteel.Ifthatisgoodenoughforyou,usehisequation;Itworks.Ifyouwouldliketoknowmoreaboutwhythatequationwillgiveyouagoodnumberfortheeffectivespringrateofaswaybar,keepreading.Figure1:basicswa

3、ybardimensionsSolveforspringrateasForceperdeflection:Wecansolvefortheeffectivespringratebyusingtheindividualspringratesforeachsegmentofthebarandcombiningtheminseries,orwecanaddthedeflectionduetobendingoftheendstothedeflectionattheendsduetotorsioninthebarandsolvefortheeffe

4、ctivespringrate.Combinethedeflectionsforeachsegmentandsolvethespringrate:Thetotaldisplacementis:*Weuse2x’sthedeflectionforbendingbecausetheswaybarhas2segmentsinbending(eacharm)Bysubstitutingcommonvaluesforsteelinpsiandassumingthatthebarissolid(i.e.d=0)wegetthefollowing:Fi

5、nallyifwedivideeachtermby141.37154(equivalenttomultiplyingby1…sorryifthatisobvious)wegettheequationusedinPuhn’sbook.IreallyhavenoideawhyCombinethespringrateofeachsegmentinseriesandcalculatetheeffectivespringrate*Weuse2x’sthedeflectionforbendingbecausetheswaybarhas2segment

6、sinbending(eacharm)Bysubstitutingcommonvaluesforsteelinpsiandassumingthatthebarissolid(i.e.d=0)wegetthefollowing:Finallyifwedivideeachtermby141.37154(equivalenttomultiplyingby1…sorryifthatisobvious)wegettheequationusedinPuhn’sbook.IreallyhavenoideawhyUsingEitherMethodwege

7、tthesameanswer.Thegeneralequationsthathavenotassumedmaterialpropertiescanbeusedforanysystemofconsistentunits.•TypicalvaluesfortheElasticModulusofsteel(E)canrangesteelfrom27,000,000–30,000,000psi(190-210MPa)•TypicalvaluesfortheShearModulusofsteel(G)canrangesteelfrom10,400,

8、000-12,000,000psi(75000-80000MPa)Obviouslyusingdifferentnumberwillchangethecalculatedvaluessligh