BrakesystemsWeallknowthatpushingdownonthebrakepedalslowsacartoastop.Buthowdoesthishappen?Howdoesyourcartransmittheforcefromyourlegtoitswheels?Howdoesitmultiplytheforcesothatitisenoughtostopsomethingasbigasacar?BrakeImageGalleryLayoutoftypicalbrakesystem.Seemorebrakeimages.Whenyoudepressyourbrakepedal,yourcartransmitstheforcefromyourfoottoitsbrakesthroughafluid.Sincetheactualbrakesrequireamuchgreaterforcethanyoucouldapplywithyourleg,yourcarmustalsomultiplytheforceofyourfoot.Itdoesthisintwoways:?Mechanicaladvantage(leverage)?HydraulicforcemultiplicationThebrakestransmittheforcetothetiresusingfriction,andthetirestransmitthatforcetotheroadusingfrictionalso.Beforewebeginourdiscussiononthecomponentsofthebrakesystem,we'llcoverthesethreeprinciples:?Leverage?Hydraulics?FrictionLeverageandHydraulicsInthefigurebelow,aforceFisbeingappliedtotheleftendofthelever.Theleftendoftheleveristwiceaslong(2X)astherightend(X).Therefore,ontherightendoftheleveraforceof2Fisavailable,butitactsthroughhalfofthedistance(Y)thattheleftendmoves(2Y).Changingtherelativelengthsoftheleftandrightendsoftheleverchangesthemultipliers.Thepedalisdesignedinsuchawaythatitcanmultiplytheforcefromyourlegseveraltimesbeforeanyforceiseventransmittedtothebrakefluid.Thebasicideabehindanyhydraulicsystemisverysimple:Forceappliedatonepointistransmittedtoanotherpointusinganincompressiblefluid,almostalwaysanoilofsomesort.Mostbrakesystemsalsomultiplytheforceintheprocess.Hereyoucanseethesimplestpossiblehydraulicsystem:YourbrowserdoesnotsupportJavaScriptoritisdisabled.SimplehydraulicsystemInthefigureabove,twopistons(showninred)arefitintotwoglasscylindersfilledwithoil(showninlightblue)andconnectedtooneanotherwithanoil-filledpipe.Ifyouapplyadownwardforcetoonepiston(theleftone,inthisdrawing),thentheforceistransmittedtothesecondpistonthroughtheoilinthepipe.Sinceoilisincompressible,theefficiencyisverygood--almostalloftheappliedforceappearsatthesecondpiston.Thegreatthingabouthydraulicsystemsisthatthepipeconnectingthetwocylinderscanbeanylengthandshape,allowingittosnakethroughallsortsofthingsseparatingthetwopistons.Thepipecanalsofork,sothatonemastercylindercandrivemorethanoneslavecylinderifdesired,asshowninhere:YourbrowserdoesnotsupportJavaScriptoritisdisabled.MastercylinderwithtwoslavesTheotherneatthingaboutahydraulicsystemisthatitmakesforcemultiplication(ordivision)fairlyeasy.IfyouhavereadHowaBlockandTackleWorksorHowGearRatiosWork,thenyouknowthattradingforcefordistanceisverycommoninmechanicalsystems.Inahydraulicsystem,allyouhavetodoischangethesizeofonepistonandcylinderrelativetotheother,asshownhere:YourbrowserdoesnotsupportJavaScriptoritisdisabled.HydraulicmultiplicationTodeterminethemultiplicationfactorinthefigureabove,startbylookingatthesizeofthepistons.Assumethatthepistonontheleftis2inches(5.08cm)indiameter(1-inch/2.54cmradius),whilethepistonontherightis6inches(15.24cm)indiameter(3-inch/7.62cmradius).TheareaofthetwopistonsisPi*r2.Theareaoftheleftpistonistherefore3.14,whiletheareaofthepistonontherightis28.26.Thepistonontherightisninetimeslargerthanthepistonontheleft.Thismeansthatanyforceappliedtotheleft-handpistonwillcomeoutninetimesgreaterontheright-handpiston.So,ifyouapplya100-pounddownwardforcetotheleftpiston,a900-poundupwardforcewillappearontheright.Theonlycatchisthatyouwillhavetodepresstheleftpiston9inches(22.86cm)toraisetherightp...
