1、mmU3. _f“FORAERONAUTICSTECHNICAL NOTE 3604YAWED-ROLLING CHARACTERISTICSANDL_OTHER ELASTICPROPERTIES OF A PAIR OF 26-CH-DIA.METER, 12-PLY-RATG,TYPE Vu AIRCRAFT TIRESBy Walter B. Home, Robert F. Smiley,and Bertrand H. StephensonLangley Aeronautical LaboratoryField, Va.Washingtonmy 1956., . - ,=3,-:_ .
2、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECHLIBRARYKAFBJNM,NATIONALADVISORYCOMITTEEFORAERONAUTICS lullullllHlll#00bb511aTMXNl_CALNO17JZ3604LOW-SPEEDYAWED-ROLLINGCHARACTERISTICSANDOTHERELASTICPROPERTIESOFA PAIROF26-RWH-DIAMEIER,12-PLY-RATING,T
3、YPEVIIAIRCRAFTTIRESByWalterB.Home,RobertF.Smiley,andBertrandH.StephensonEmMARYThelow-speed(upto2milesperhour)corneringcharacteristicsoftwo26x 6.6,ty-peVII,1.2-ply-ratingtiresunderstraight-yawedrollinnweredeterminedoverarangeofinflationpressuresandyawanglesfortwoverticalloads,oneloadapproximatelyequa
4、ltotheratedverticalloadandtheotherloadapproximatelyequaltotwicetheratedverticalloadforthesetires.Thecorneringchsracterin.GTirecircumference9aperipheraldistancemoundtire,in.time,secrollingvelocity,in/see.maxi.mmtirewidth,in.displacementindirectionofmotion,in.verticaltiredeflectionduetocmibinedh.verti
5、caltire*flectionduetoverticalorftin.verticalandyawloadonly,in.,.,!-loads,.vProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN3604 5ener-dissipationparameterforstaticlateral-elasticitytestsreductioninoscillationsmplitudepercycleenergy-dissipationp
6、ersmeterfordynamiclateral-elasticitytests,2(1-qp)(1+ llJlateraldistortionoftireequator,in.lateraldistortionofthe equatoratcenterofcontact,in.maximumdragcoefficientoffriction,Fx,n,?zsliding-dragcoefficientoffriction,Fx,n,s/Fzyawed-rollingcoefficientof.friction,?R,r,e,tizturningradius,fttorsionoryawan
7、gle,degwheelangularvelocity,radians/seeSubscripts:e eqydl.ibriumorsteady-staterollingconditionm msximumn nonrollingconditionr rollgconditions slidingconditionBarsoversymbolsdenotetheaveragevaluesofthequantitiesinvolvedfortiresA andB. .-. ._ ._ _ .-. _ _ .Provided by IHSNot for ResaleNo reproduction
8、or networking permitted without license from IHS-,-,-6AFPARATWTestVehicleNACATN3604Thebasictestvehicleconsistsofthefuselageandwingcentersectionofa cargoairplanewhichwastowedtailfirstbyatractortruckatanattitudesuchthattheoriginalairplaneshockstrutswerenesrlyvertical.Theoriginalyokessadtorquelinksofth
9、elanding-gearstrutsalongwiththewheelassemblieswerereplacedbysteelwheelhousingswhichheldthetiresandwheelstested.Thesesteelwheelhousingswereconnectedtogetherbymeansofaninstrumentedtruss.Holeslocatedinthewheelhousingatregularintervalsof“ permittedthewheelframestoberotatedthroughayaw-anglerangefrom0to24
10、.50toeout. (Itmightbenotedthata smalli.nitialmisaUnementofthewheelsofapproxi-mately0.3,whichwasnotedinref.3,waseliminatedforthepresentinvestigation.)A sketchofthebssictestvehicleisshowninfigure1.AmOredetaileddescriptionofthistestvehicleisgiveninreference3andappliesingeneraltothepresentinvestigation.
11、Theweightofthetestiehicleactingonthetiresforthelight-weightconditiontestedwasapproximately9,000poundsforeachthe. Fortheheavy-weightconditiontested,a concreteweightcan(weighingapproxi-mately8,OOOpounds)wasattachedtoeachwings-bib.(Seefig.2.) Thisweightincreasedtheloadoneachthe toapproximately17,100pmn
12、ds. The “maximumtowingforcerequiredwasapproximately4,000poundsforeachttre.InstrumentationThetestvehiclewasequippedwithinstrumentsformeasuringside force,torsionalnmment(self-aliningtorquefortheyawed-rollingcese),drag,verticaltiredeflection,horizontaltranslation,andwheelrota-tion.Measurementsofthesequ
13、antitieswererecordedsimultaneouslyonalchannelrecordingoscillographmountedinthetestvehicle.ThisoscillographwasequippedwithaO.01-secondtimer.Thisinstrumenta-tionisdiscussedinmoredetailinreference3.TiresGeneraldescription.-Thetirestestedinthisinvestigationwereapatiof26-inch-diameter,26x 6.6, typeVII,U?
14、-ply-ratingribtreadtireswhichweremadebythesanemsmfacturer.Thespecificationsfor 1thesettiesgivenintableIwereeitherobtainedfromreference4 orbydirectmeasurements.Figure3 showsWlated auddeflatedhalfcrosssectionsforthetwotesttties.Thesecrosssectionswereobtainedfrom “Provided by IHSNot for ResaleNo reprod
15、uction or networking permitted without license from IHS-,-,-NACATN3604plastercaststakenwhenthethebeginningofthetests.betweentheprofilesforthe7ttieswereinanewandunusedconditionatThereappearstobenoappreciable.differencetwotires.Tirewear.-Duringthecourseofthepresentinvestigation,therewasanappreciablepr
16、ogressivechangeinthecross-sectionalshapeofthetiresduetoskiddingandworkingofthetires.Therefore,thechrono-logicalorderinwhichthetestdatawerecollectedmaybeofsomeimpor-tanceintheinterpretationofthedata.Thischronologicalorderisindicatedinthispaperbya seriesletterwhichisassignedtoalltestdata.Specifically,
17、thetestsinchronologicalorderareA,B,C,andD.Thechangeintire-treadpatternduetotirewesrthroughoutthetestisillustratedinfigure4.Atthebeginningofthetestsbothtireshadarectangularcross-sectionaltreadpattern(fig.4(a)andthispat-ternwassubstantiallypreservedthroughoutseriesA (fig.4(b).DuringtetseriesB thesides
18、ofthetreadstidirectcontactwiththewoundbegantowearawayad thiswesringawayproducedthetreadshapeshowninfigure4(c),whichwastakenatthebeginningoftestsertesC. DuringtestseriesCthiswearincreasedsubstantiallyasisshowntifigure4(d)fortireB attheendoftestseriesC. FortestseriesD,forwhichonlytireAwastested,thesma
19、llprojectingedgesremainingonthetreadattheconclusionoftestseriesC (showninfig.4(d)werecutoffbeforebeghninnthetests.(Seefig.4(e).)Itshouldbenotedthat,whenthetireswereremovedfromthetestvehicleattheconclusionofthetests,tireBwasfoundtohavesufferedseverslapparentlydeepcutsarounditsoutboardsidewallinthepro
20、xim-ityofthewheelrhn.ThesecutswereevidentlymadebytheoutboardsideofthewheelrimcuttingintothetireduringoneoftherunsoftestseriesC atthelargeryawanglewherelargeverticalandlateraltiredeflectionswereexperienced.Inordertoinvestigatetheimportanceofthesecuts,thesectionofthetirehavingthedeepestcutwasremovedan
21、dinspected.A photographofthissectionispresentedasfigure4(f).l?romthiscrosssectionitappearedthatthiscutpenetratedcompletelythroughonlyoneplyofthecasingandthereforeprobablydidnotappre-ciablyaffectthetirecharacteristics.Itwasfoundaftercloseexam-inationthattireA hadnotexperiencedthistypeofdamage.Itceeth
22、e radius.-Radius-pressurehysteresisloopsassociatedwithincreasingsmddecreasingpressuresreshowninfigure5 fortiresAandB. Theelapsedtimefromthestat isshownfora fewofthemeamre-mentspresented.Thevariationinthe radiusduetohysteresisforagivenpressureisseentobepracticallynegligible(lessthan0.1inch)intheopera
23、tingpressurerangeforthesetiresforthisrelativelyslowrateofchangeofpressure(roughly,3hoursformostofthecycle).Alsoshowninthisfigureareseveralradiusmeasurementswhichweremadeafterthetireshadbeenleftunloadedatconstantpressureforatleast24hoursinordertoreachanequibriumcondition. . ._ _. _ _ . _Provided by I
24、HSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- . . -8TestSurfaceNACATN3604I.Allyawed-straight-rollinganddragtestswereconductedbytowingthetestvehiclealongthecenterofa 9-inch-thickreinforced-concretetaxistrip.Thistsxistriphada slightcrownsothatthetiresonthetestve
25、hicleweresubjecttoa slighttiltrelativetothesurface.How-ever,thistiltwaslessthan1. Thetextureofthetaxistrip,abosmiedconcretesurface,asdeterminedfromplastercasts,isshowninfigure6 forthreerandompositionsonthestrip.AILothertests,withtheexceptionofthestatictorsional-elasticityandtheyawed-curvilinear-roll
26、ingtests,wereconductedonamuchsmoother,level,reinforced-concretesurface.Thetestsurfacesfortheexceptionsweresmoothsteelplates.TESTPROCEDUREANDAL REsuLTsThepresentinvestigationoftirecharacteristicsisdividedintothefollowingparts:yawed-straight-rollingtests,yawedcurvilinesr-rollingtests,relaxation-length
27、tests,locked-wheeldragtests,staticvertical-elasticitytests,staticlateral-elasticitytests,dynsmiclateral-elasticitytests,statictorsional-elasticitytests,andsupple-mentarymeasurements.Yawed-Straight-RollingTestsForeachrunoftheyawed-straight-roltigtests,thetestvehiclewasmovedintotowingpositiononthedry,
28、clean,concretetaxistripandthewheelhousingswererotatedandlockedattheparticularyawangledesired.Thetireswereadjustedtothetestinflationpressureandwerethenjackedclearofthegroundtoremoveanyresidualstressesremainingfromthepreviousrunsorresultingfromthechangingoftheyawanglesofthewheels.Thejackswerethenremov
29、edandtheinitialverticaltiredeflectionsnoted.Formmt oftheruns,thevehiclewasthentowedstraightaheadfromthisinitialessentiallyunstressedconditionforadistanceofapproximately40feetatanapproximatelyconstantspeed.Althoughthespeedremainedapproximatelyconstantthroughoutanypartic-ulsxrun,itvariedfromruntorunwi
30、thina speedrangefromapproxi-mately0.7to2milesperhour.Figure7 showsoneofthetiresdurarunat24.5yaw. Forseveralruns,whicharenotedintableII,thevehiclewasbackedupbeforestartingthestraiglrt-aheadrollingportionoftheruninordertoputaninitialfiegativelateralstressinthetires.Thisinitialstressingwasap.iedbefores
31、tartingtheseparti- cularrunsforthepurposeofobtainingsufficientlylargechangesinlateralforceduringtheearlystagesoftheserunstoenabledetermina-tionoftheyawed-rolgrelaxationlength.(Ifthevehiclewasnotthtibackedup,itusuallyturnedoutthatthelateral-forcetestdata.,.v“ - .- -. .-. - -.- .Provided by IHSNot for
32、 ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN3604 9obtainedduringtheearlystagesoftheyawedrunswerenotsufficientlyaccurateforthisrelaxation-lengthdetermination.) A comparisnofthevariationoflateralforcewithdistanceroldedforthesetwotypesoftowingconditionsisshowninfig
33、ure8forthelight-weighttowingcondi-tionforayawangleof3.5andatireinflationpressureofapproxi-mately163poundspersqusreinch.Alltestrunsat0,3.5,70,10.7,14, 17.50, 21, and 2+.50weremadewithbothwheelssymmetricallyyawedwithrespecttothelongi-tudinalaxisofthetestvehicle.Althoughtheseparticularyawanglesweretheo
34、nlyangleseasilyattainableonthetestvehicle,sometestrunsat1.75 weremadebysettthe wheelsunsymmetricallyyawedwithrespecttothelongitudinalsxisofthetestvehicle(thatis,onewheelwassetat0andtheotherat3.5 yaw).Whentowedaheadintldsunsym-metricaU_yyawedcondition,thetestvehiclefirstveersofftothesidebecauseoftheu
35、nsymmetricalforces.Aftera shortrun,howver,theVemclerunssmoothlywiththelongitudinalaxisofthetestvehicleyawedwithrespecttothedirectionofmotionsuchthatbothwheelshavethessmefinalintermediateyawangleof1.75with”respecttothedirectionofmotion.Thefollowingmeasurementswererecordedcontinuouslyfromthestartofthe
36、run: sideforce,topnal momentorself-aliningtorque,dragforce,verticaltire$ikflection,wheelrotation,andvehicletranslationtithedirectionofmotion.TableIIcontainsaU testdataobtaineddurithefinalsteady-statestageofeachyawed-roilingrun. (Itshouldbenotedthattherunnumberslistedinthistablesmdinallothertablessmd
37、figuresdonotindicatethechronologicalorderinwhichtherespectiverunsweremade.Theserunnumbersme listedonlyforconvenienceinreferringtothetestdata.)Dataarepresentedforthreedifferenttestseries(AtoC)whichrepresenteitherdifferenverticalloadingsordiffernttirewear.Thevmiationofnormalforce*,r,eYself-aliningtorq
38、ueMz,r,e,andpneumaticcaster withyawangleme showninfigures9 and10forallverticalloadssmdinflationpressures.Ssmplerolling-radiusdataareplottedinfigureU asfunctionsofyawangle,tireinflationpressure,andverticaltiredeflection.Thebuildupofcorneringforcewithhorizontaldistancerolledduringtheinitialstagesofthe
39、yarned-straight-rollingrunsisillustratedinfigure12forseveraltestiuflationpressuresforthevertical-loadcon-ditionsinvestigated.Inasmuchasfornmstrunstherewasa slightinitialresidualforceorpreloadinthetires,theoriginaltestcurvestidnotpassexactlythroughtheorigin.Inordertotakethisfactintocon-sideration,the
40、testcurvesshowninthisfigurehavebeenhorizontallyshifted(ifnecessary)sothattheextrapolationofeachcurveismadetopassthroughtheorigin. -. _-_ _ _ _ -.- -._ _ _.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-10 NACATN3604Yawed-CurvZMnear-RollingTestsInthe
41、Yawed-;umilinear-rollingtests,therightwheelfrsmeofthetestvehiclewasanchoredtothefloorbytie-downfittingsinordertomakeitasbmovableaspossible.(Seefig.13(a).) A steelplate,approxhnatel.y5feetwide,weldedtoa steel1-beam,wasplacedunder 8Pthetire(tireA)intheleftwheelframe.(Seefig.13(b).) Thissteelplatewaspu
42、lledoutfromunderthetire,bymeansofhydraulicrams,alongcirculsr-arcpathswhoseradiiweredet-erminedbythepivot-petitlocationonthesteelI-beam.(Seefig.13(b).) Thus,thistestsetupsimulatestherollingofthetireh a circulsrpathona steelsurface.Thetestvehiclewasrestrainedfromrotatingabouttherightwheelfrsmeasthepla
43、tewaspulledoutfromunderthetirebymeansofthetie-downfittingsconnectedtotheleftwheelframewhichareshowninfigure13(b).Figure13(c)showsanoveraUviewofthetestsetup.Alltestrunsatnominalyawanglesof0,“, and70weremadebyP= thefitnted trusstotheleftwheelframeaswasdonefortheyawed-straight-rollgtests.Intermediateno
44、minalyawanglesof1.75and5.25wereobtainedbyclang thetrusstotheleftwheelfrsmewiththeaidofheavy-dtiyclsmps.Theactualyawanglesdifferedslightlyfromthenominalanglesbecauseofmisalinementofthetestvehiclewithrespecttothepivotpoint.Beforeeachruntheleftwheelhousimgwasrotatedandpinnedor Qclampedattheparticularno
45、minalyawangledesired.Thelefttire(tireA)wasthenadjusted%othetestinflationpressureandjacked .,clew ofthegroundtoremoveanyresidualstressesremainingfromthe upreviousrunsorfromthechangingofthewheelyawangle.Thejackwasthenremovedandtheactualyawangleandverticalthe deflectionweremeasured.Then,theplatewasp-d
46、outfromunderthetirethroughadistanceofapproxtitely4 feet.Measurementsofsideforceandself-alfigtorquewererecordedcontinuouxilyduringtherun. Therollingspeedwasapproximately6 inchesperminute(0.006mileperhour).ThedataobtainedfromtheYawed-curvilinear-rollingtestssrepre-sentedinfigure14.Thisfigureshowstheva
47、riationofcorneringforceandseH-afin torquewithyawangleandturningradiusfortireA atthetestcontitionof Fz= 9,000poundsand p= 1* poundspersquaretich.Relaxation-LengthTestsa71Twotypesofrelaxationlengthsweredeterminedinthisinvestiga-tion,nsmely,staticrelaxationlengthLs andyawed-roUingrelaxation. Provided b
48、y IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN3604lenh . Thedefinitionsfortheserelaxation!. reference3. Themethodsusedtodeterminetheseasfollows:ILlengthsaregivenhrelaxationleqgthsare-StaticrelaxationlengthLs.-Thestandingttiesweregiveninitial.lateraldeflectionsbypullingoutward,bymeausofhydraulicrams,platesplacedunderneaththetires.Thelateraldistortionofeachtiretreadnearestthecenterofthetirerelativetothewheelcenterplanewasthenmeasuredforseveralpointsarou
