saej684v004

SAETechnicalStandardsBoardRulesprovidethat:“ThisreportispublishedbySAEtoadvancethestateoftechnicalandengineeringsciences.Theuseofthisreportisentirelyvoluntary,anditsapplicabilityandsuitabilityforanyparticularuse,includinganypatentinfringementarisingtherefrom,isthesoleresponsibilityoftheuser.”SAEreviewseachtechnicalreportatleasteveryfiveyearsatwhichtimeitmaybereaffirmed,revised,orcancelled.SAEinvitesyourwrittencommentsandsuggestions.Copyright©2005SAEInternationalAllrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystemortransmitted,inanyformorbyanymeans,electronic,mechanical,photocopying,recording,orotherwise,withoutthepriorwrittenpermissionofSAE.TOPLACEADOCUMENTORDER:Tel:877-606-7323(insideUSAandCanada)Tel:724-776-4970(outsideUSA)Fax:724-776-0790Email:custsvc@sae.orgSAEWEBADDRESS:http://www.sae.orgSURFACEVEHICLESTANDARDJ684REV.JUL2005Issued1938-01Revised2005-07SupersedingJ684JUN2004TrailerCouplings,Hitches,andSafetyChains—AutomotiveType1.Scope—ThisSAEStandardincludescouplings,hitches,andsafetychainsusedinconjunctionwithalltypesoftrailersortowedvehicleswhoseGrossVehicleWeightRating(GVWR)doesnotexceed4540kg(10000lb).Thisincludessuchtypesasutility,boat,camping,travel,andspecialpurposetrailerswhicharenormallytowedbyconventionalpassengercars,light-dutycommercialvehicles,lighttrucks,andmultipurposepassengervehicles.Thisdocumentisintendedprimarilyforball-and-sockettypeofcouplingsandhitches.Itshouldnotbeconstruedasalimitationtothistypealonebutshouldapplywhereappropriatetoring-and-pintle,clevis-and-pin,oranyotherdraftmeansdesignedtoservethispurpose.1.1Rationale—ThisdocumentwasrevisedtocorrectmetricversionofformulasfoundinTable3.2.References2.1ApplicablePublications—Therearenoreferencedpublicationsspecifiedherein.3.Definitions—CouplingandHitchNomenclature—Thefollowingnomenclaturehasbeenadoptedforuniformityinthetermsusedforthecomponentpartsofthetrailer-couplingmechanism:3.1Hitch—Thatpartoftheconnectingmechanismincludingtheballsupportplatformandballandthosecomponentsthatextendandareattachedtothetowingvehicle,includingbumpersintendedtoserveashitches.3.1.1WEIGHTDISTRIBUTINGHITCH(OREQUALIZINGHITCH)—Amechanicaldevicethatconnectsthetrailertothetowingvehicleandbymeansofleverageappliedonbothtrailerandtowingvehiclestructures,whenproperlyadjusted,distributestheimposedverticalloadatthehitchandcouplingconnectionbetweenstructuresoftowingvehicleandtrailer.3.1.2WEIGHTCARRYINGHITCH—Amechanicaland/orstructuraldevicethatconnectsthetrailertothetowingvehicle,andthatdoesnotemployfeaturesdesignedtoredistributetheloadimposedatthehitchandcouplingconnection.3.2Coupling—Thatpartofthetrailerconnectingmechanismbywhichtheconnectionisactuallymadetothetrailerhitch.Thisdoesnotincludeanystructuralmember,extensionofthetrailerframe,orbrakeactuator.SAEJ684RevisedJUL2005-2-4.TrailerClassification4.1Class1—AlltypesoftrailerswithatrailerGrossVehicleWeightRating(GVWR)(trailerweightincludingitsload)nottoexceed910kg(2000lb).4.2Class2—AlltypesoftrailerswithatrailerGVWRofover910kg(2000lb)andnottoexceed1590kg(3500lb)GVWR.4.3Class3—AlltypesoftrailerswithatrailerGVWRofover1590kg(3500lb)andnottoexceed2270kg(5000lb)GVWR.4.4Class4—AlltypesoftrailerswithatrailerGVWRofover2270kg(5000lb)andnottoexceed4540kg(10000lb)GVWR.5.Couplings5.1CouplingClassification—Thereshallbefourdesignationsofcouplingstocoveralltrailersupto4540kg(10000lb)GVWR.ThedesignatedclassificationofthecouplingshallbebasedontheGVWRofthetrailerratherthantheweightimposedverticallydownontheballbythecoupling.TheClass1couplingshallbeusedonClass1trailers;theClass2coupling,onClass2trailers;theClass3coupling,onClass3trailers;andtheClass4coupling,onClass4trailers.Thisisnotintendedtolimitthenumberorvarietyofcouplingsinagivenclassortorestricttheuseofaheavier-dutycouplingorhitchballbeingusedonalighterclassoftrailer.5.2AttachmentofCouplings—Allcouplingsaretobeattachedtothetrailer'sstructuralattachingmemberbybolting,welding,orrivetinginsuchamannerthattheloadsindicatedinTable1maybeappliedwithoutincurringlossofattachmentordistortionorfailurewhichwouldaffectthesafetowingoftrailers.5.2.1Manufacturersoftrailercouplingsshallprovideinstructionsfortheattachmentofcouplinghousingstotrailers.5.3ProvisionforSafety—Couplingsinallclassesshallbeequippedwithamanuallyoperatedmechanismsoadaptedastopreventdisengagementoftheunitwhileinoperation.5.4Identification—TrailercouplingswhichmeettheminimumstandardssetforthinTable2shallbepermanentlymarkedwiththefollowinginformation:5.4.1Couplingmanufacturer'sname,initials,ortrademark.5.4.2Part,style,ormodelnumber.5.4.3SAEcouplingclassificationandmaximumtrailerGVWR.5.4.4Balldiametersforwhichcouplingisdesigned.TABLE1—STRENGTHTESTLOADSFORCOUPLINGATTACHMENTSModeMinimumStaticTestLoadLongitudinalTensionandCompression1.5xMaximumTrailerGVWRTransverseThrust0.5xMaximumTrailerGVWRVerticalTensionandCompression0.5xMaximumTrailerGVWRSAEJ684RevisedJUL2005-3-5.5CouplingRatings—ThereshallbeaminimumstrengthtestforcouplingsbyclassasindicatedinTable2.5.6TestFixture—Basicdrawingsoftypicaltestfixtures(Figure1)foruseindeterminingconformanceofcouplingstotheminimumstrengthtestloadrequirementsofTable2areincludedinthisdocumenttopromoteuniformityintestresultsbyvarioustestinglaboratories.TABLE2—STRENGTHTESTLOADSFORBALLSANDTRAILERCOUPLINGS(1)(2)1.VerticalTensionLoadRequirement—Theverticaltensionloadrequirementisextremelyimportantbecauseofthemechan-icsofholdingtheballinthesocket.Onvertical-tension(orpullout)testing,themajorportionofthetensileloadistransferredfromthelipofthecouplingtotheballclampanditssupportingbolt,rivet,orinclinedplane.Whilerelativelylittledistortionoccursinthecouplinghousing,theballclampisforcedbackanddownwarduntilthefinalrestrictingforceretainingtheballislostandpulloutoccurs.Theloadatwhichretentionismaintainedishighlycriticalandlossofpurchaseontheballoccurssuddenly,goingfromsaferetentiontocompleteseparation.2.CouplingversusHitchStaticBenchTestLoadRequirements—Couplingstrengthdesigncriteriaarenecessarilydifferentthanthoseforhitchesandwillbegreaterbecauseofthestressestowhicheachissubjected.Couplingsareweldedorboltedtotrailertongueswithonlythesocketandlatchingmechanismexposed.Thecouplingsocketmusttaketheconcen-trateddynamicshockloadaswellasthevaryingstressesinducedfromnormaltrailering,andisthepointofhigheststress.Thehitchloadisdistributedthroughthehitchcomponents,springdeflectionsinthetowingvehicle,shockabsorbers,andthevehiclestructure,andisaffectedbyentirelydifferentforcedistributionthanthecoupling.Hitchesareactuallysubjectedtomuchlowerunitforcesthanarethecouplingandtheball.TrailerClassificationTrailerCouplingDesignationTypicalBallDiameter,mm(in)(whereball-typehitchisused)MinimumTestLoadRequirements,kN(lb)Class1Class147.6(1-7/8)LongitudinalTension:26.7(6000)LongitudinalCompression:26.7(6000)TransverseThrust:8.9(2000)VerticalTension:11.1(2500)VerticalCompression:11.1(2500)Class2Class250.8(2)LongitudinalTension:46.7(10500)LongitudinalCompression:46.7(10500)TransverseThrust:13.3(3000)VerticalTension:20.0(4500)VerticalCompression:20.0(4500)Class3Class350.8(2)LongitudinalTension:66.7(15000)LongitudinalCompression:66.7(15000)TransverseThrust:17.8(4000)VerticalTension:31.1(7000)VerticalCompression:31.1(7000)Class4Class4BallandboltshallbeofsuchsizeandstrengthastoconformtotheminimumbreakingstrengthrequirementsofthematingcouplingrequiredforthespecificloadofClass4trailerLongitudinalTension:GrosstrailerWeight,N(lb)x3LongitudinalCompression:Grosstrailerweight,N(lb)x3TransverseThrust:Grosstrailerweight,N(lb)x1VerticalTension:Grosstrailerweight,N(lb)x1.3VerticalCompression:Grosstrailerweight,N(lb)x1.3SAEJ684RevisedJUL2005-4-FIGURE1—TYPICALTRAILERCOUPLINGTESTFIXTUREARRANGEMENT5.7CouplingTestProcedure—AcouplingorballshallwithstandthetestloadsindicatedinTable2withoutincurringfailure.Forthepurposeofthissection,failureisdefinedasthepointatwhichthecouplingorballwillacceptnoadditionaltestloadwithoutseparationoftheballfromthecouplingballsocket,ortheoccurrenceofametalfractureofeithercouplingballorcouplingassemblywhichresultsinseparationoftheballfromthecouplingballsocket.DistortionorbendingoftheballorofacouplingassemblycomponentoccurringduringtestingdoesnotconstituteafailureasdefinedhereinunlessactualseparationoftheballfromthecouplingsocketoccurspriortothedesignatedtestloadsindicatedinTable2.Whenconductingtests,anewcouplingorballshallbeusedforeachmodeofloadapplication.6.Hitches6.1HitchStrengthRequirements—ThehitchshallmeetthetestloadrequirementsindicatedinTable3ofthisdocument.SAEJ684RevisedJUL2005-5-TABLE3—HITCHTESTLOADS(1)(2)1.V=VerticalForce(kN[lb])L=LongitudinalForce(kN[lb])T=TransverseForce(kN[lb])M=SpringBarMoment(kN·m[in-lb])(LevelingForceCouple)R=HitchRatingintermsoftrailerGVWR(kN[lb])(GrossVehicleWeightRating)X=HitchRatingforMaximumVerticalLoadonHitch(kN[lb])(TongueWeight)2.Notes—HitchTestForceApplications—(SeeTable3andFigure2)Applytheforcesinanysequenceasfollows:a.Applythespecifieddownwardverticalforceconcurrentlywiththespecifiedcompressivelongitudinalforceorspringbarmoment.b&c.Applythespecifiedtensileorcompressivelongitudinalforceconcurrentlywiththespecifieddownwardverticalforce.d&e.Applythespecifiedtransverseforce.f.Forhitcheswithweightdistributingcapability,applythespecifiedspringbarorlevelingmoment(levelingforcecouple)concurrentlywiththespecifieddownwardverticalforce.Allforcesinsteps(a)through(e)aretobeappliedalonganaxiswhichintersectsthecenteroftheball.Allforcesaretobeappliedwithanonsetrateofnotmorethan0.667kN/s(150lb/s),andmaintainedatthemaximumspec-ifiedforcelevelforatleast5s.StepWeightCarryingHitchForce,kN(lb)WeightCarryingHitchDirectionWeightDistributingHitchForce,kN(lb)WeightDistributingHitchDirectionaV=0.47R+2.135(480)L=0.47R+2.135(480)DownwardCompressiveV=0.045R+7.339(1650)M=5.762(51000)DownwardSeeFigure2bL=0.23R+6.805(1530)V=0.15RTensileDownwardL=0.067R+9.207(2070)V=0.15RTensileDownwardcL=0.23R+6.805(1530)V=0.15RCompressiveDownwardL=0.067R+9.207(2070)V=0.15RCompressiveDownwarddT=0.20R+2.224(500)LeftwardT=0.20R+2.224(500)LeftwardeT=0.20R+2.224(500)RightwardT=0.20R+2.224(500)RightwardfNotapplicableNotapplicableM=2.367X+2.372(93.2X+21000)V=0.15RSeeFigure2DownwardSAEJ684RevisedJUL2005-6-FIGURE2—HITCHTESTFORCESAPPLICATION6.2AttachmentofHitch—Thehitchshallbeattachedbyboltingorothermeanstothetowingvehicleframe,body,bumperstructure,ortoacombinationoftheseorotherpointsinsuchamannerthattheloadsindicatedinTable3aretransferredtothetowingvehiclewithoutincurringlossofattachment.Thissectionisnotintendedtorequirethatspecifichitchesshallbetestedontheactualvehiclesforwhichtheyweredesigned.(See6.3.1.)6.3HitchTestProcedure6.3.1ASSEMBLYANDINSTALLATION—Thehitchshallbeassembledandinstalledonthevehicle,vehiclesimulatingfixture,orothernon-yieldingfixtureaccordingtothehitchmanufacturer'sinstallationinstructions.6.3.2ThehitchshallwithstandtheappliedforcesindicatedinTable3withoutincurringpermanentdeformationsuchthatthepositionoftheballaxis,atthecompletionofeachteststep,shallnotdepartmorethan5degreesfromtheoriginal,nominallyvertical,position.6.4HitchIdentification—Thehitchshallbepermanentlymarkedbythemanufacturertoshowthefollowing:6.4.1Hitchmanufacturer'sname,initials,ortrademark.6.4.2Part,style,ormodelnumber.6.4.3MaximumtrailerGVWRtobedrawn.6.4.4Maximumverticaltongueweighttobeimposedontheballorotherpointofconnection.6.5HitchBalls6.5.1DIMENSIONALTOLERANCEONBALLDIAMETERS—TheallowablefinisheddimensionaltoleranceonallballdiametersshowninTable2shallbe+0.000mm(0.000in)and–0.76mm(0.030in).By“diameter”ismeantthethroughdimensiontakenonanyplanepassingthroughthecenteroftheballonitssphericalsurface.SAEJ684RevisedJUL2005-7-6.5.2BALLSTRENGTHREQUIREMENTS—ThereshallbeaminimumstrengthtestforballsbyclassasindicatedinTable2.6.5.3BALLIDENTIFICATION—ThenominaldiameteroftheballandthemaximumtrailerGVWRforwhichtheballisdesignedshallbepermanentlymarkedontheball.Themarkingsshallbeclearlyvisiblewhentheballisattachedtothehitch.7.SafetyChains7.1DefinitionsandPurpose—“SafetyChain”isdefinedasanassemblywhichprovidesasecondarymeansofconnectionbetweentherearofthetowingvehicleandthefrontofthetrailer(ortowedvehicle);itincludeslinkchainandallattachingmeans,oranalternativesystem(see7.6).ThepurposeofSafetyChainistoretainconnectionbetweenthetowingvehicleandtrailerintheeventofseparationofthetrailercouplingfromtheballortheballfromthehitch,longenoughtobringthevehiclestoastop.Itshouldnotbeconstruedthatsafetychainscanensurethatvehiclecontrolorconnectionwillbemaintainedintheeventofvehicleincidentssuchaslossofcontrol,rollover,jackknife,collision,etc.Forthepurposeofthissection:a.The“hitch”assembly(includingballandballsupportplatform)isconsideredpartofthetowingvehicle.b.The“safetychain”isconsideredpartofthetrailer.c.“Attachingmeans”aredefinedasthehooks,bolts,anchorages,orotherdevicesusedtofastenorconnectlinkchain,oritsequivalent,tothetrailertongueandtotherearofthetowingvehicleincludinghitchassemblydevicesprovidedforsuchconnection.7.2StrengthRequirements—Eachindividualsafetychain,andallattachingmeans,shallmeettheminimumbreakingforcetensileloadasindicatedinTable4,andwhereapplicablesuchloadshallbeappliedinadirectionparalleltothetrailer’sortowingvehicle’slongitudinalaxis.AnyoperationperformedonsafetychainsubsequenttoitsmanufactureshallnotreduceitsstrengthbelowtherequirementsofTable4.7.3WireRopeThimbles—Whenwireropeisusedassafetychain,thestrandsoftheropeshallbeprotectedfromdamagebyuseofawireropethimbleintheareasofitsattachingmeans.TABLE4—STRENGTHREQUIREMENTSFORSAFETYCHAINANDATTACHINGMEANS(1)1.Whenconductingatensilestrengthtestofalengthofchainorequivalentanditsattachingmeans,whentheminimumloadspecifiedinTable4isapplied,suchloadshallbemaintainedforaminimumof1min.SafetyChainorTrailerClassificationBreakingForce—MinimumClass18.9kN(2000lb)Class215.6kN(3500lb)Class322.2kN(5000lb)Class4ThestrengthratingofeachlengthofsafetychainoritsequivalentanditsattachmentsshallbeequaltoorexceedinminimumbreakingforcetheGVWRofthetrailer.SAEJ684RevisedJUL2005-8-7.4ChainApplicationandIdentification—SafetychainassembliesshallbeclassifiedandappliedtotrailersasshowninTable4.SafetychainassembliesforindividualsaleshallbeidentifiedwiththeapplicabletrailerclassificationandGVWRonthespecifications,packaging,orthesafetychainassembyitself;alternativelythisinformationmaybeincorporatedincataloguesorotherspecificationswheresafetychainsareselectedbyservicepersonnel.7.5Installation7.5.1Twosafetychainsshallbepermanentlyfastened(i.e.,bolted,anchored)tothetrailertongue,oneoneachside.Thesafetychainsshallbeconnectedfromthetrailertonguetothehitchassemblyortoothertowingvehiclemembersmeetingthestrengthrequirementsof7.2.7.5.2Safetychainshallbeconnectedtothetowingvehicleandtrailersothattheslackforeachlengthofchainisapproximatelythesamewhenthevehiclesarealignedonacommonfronttorearcenterline.Thereshallbenomoreslackthannecessarytopermitproperturningofthevehicles.Thesafetychainsshallbecrossedunderthetrailertongueandconnectedtothehitchassemblyortoothertowingvehiclemembers.NOTE—Crossingthechainsunderthetonguetypicallyreducestheprobabilityofstressingorbreakingthechainswhenturning.SeeFigure3.FIGURE3—TYPICALSAFETYCHAININSTALLATION7.5.3Safetychainsshallnotbeattachedtothetowingvehiclebyuseofthefastenersthatsecuretheballtoitssupportinghitchmember,norshalltheybeconnecteddirectlytoanypartoftheball.7.6Equivalency7.6.1NothinginSection7shallprecludetheuseofanalternativeconnectingarrangementwhichwilleffectivelymaintainconnectionbetweentowingvehicleandtrailerintheeventofseparationofthecouplingfromtheballortheballfromthehitch.7.6.2Asinglesafetychainmaybeusedprovideditispermanentlyfastenedtoeachsideofthetrailertonguesoastofunctionastwoseparatechains,andmeetsallotherrequirementsofthisdocument.SAEJ684RevisedJUL2005-9-8.Notes8.1MarginalIndicia—Thechangebar(l)locatedintheleftmarginisfortheconvenienceoftheuserinlocatingareaswheretechnicalrevisionshavebeenmadetothepreviousissueofthereport.An(R)symboltotheleftofthedocumenttitleindicatesacompleterevisionofthereport.PREPAREDBYTHESAETRAILERCOMMITTEE