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Power loss and operating temperature of tires

1960; The National Institute of Standards and Technology; Volume: 64C; Issue: 1 Linguagem: Inglês

10.6028/jres.064c.002

2376-5720

Robert D. Stiehler, Maurice Steel, G.G. Richey, Joel Mandel, R.H. Hobbs,

Vehicle Dynamics and Control Systems

The p O\\'e r loss of pn cumat ic t ires wa s m eas ur'ed under stead y-state condi t io ns b y m eans of t wo d y nam om eter s, o ne of whi ch m ea sured t hc total p o\\' er inpu t a nd th e ot her power ouL pu t.A steel wheel wa s uscd to m easure t he po\\'c r' loss in t he equipme nt a nd in windag;e.T he power req uired to flex Lhe t ire (inpu t p ower m inus ou t put ])o \\'er min u s equipmen t a nd wi nd a!\e losses) , wa s not a ff ected by t he tmcti ve effor t (a u t pu t po we r) , The coeffi cient of rolling resist a nce, a dimen sio nl ess qu a nt ity, was calcul ated b.v m eans of t he equ at ion: R = (P I SL), whe re P is po we r loss of t ire, S is speed, a nd L is load .This coe ffi cie nt in creased a t a n increasing ra te wit h t h e slip a ng le (a ngle betwee n pl a ne of t irc a nd dircctio n of t ra ve l) a nd was ap prox imate ly d o ubled a t a n a ngle of 2 d egr ees .The ch ange in R wi t h s peed va ri ed a nd appea red t o de pend o n const ru ction of t he t ir e.Both nylon and steel wirc t ru ck t ires cxhibi ted a d ecrease in R wi t h s peed , rayo n t nr ck t ircs showed eit he r no chamro or a linear in creasc i n R wi th s peed, a nd fo r p assen ,e r ca l' t ires R incr eased at a n in crcas in g ratc wi t h sp ced, p a r t icul a rl y for a rayo n t ir'e .R in crea scd wit h load fo r all bu t t he steel wire t ire.The cha nge in R wi t h infla t io n p ress ure was st udi ed o nl y fo r rayon t ru ck t ires.R in creased lin earl y wi t ll t he reciprocal of t he p ress ure b ut th e rate wa s de pe ndent o n Lhe s peed a nd load condi t ion s.T he typ e of ru bber had a pro no un ced effect o n R a nd co m bin at io ns of nat ura l a nd sl y re ncbutadi ene ru bbe r ca used R to be la rge r tha n expected fr o m t hc valu es o f R fo r t ires m ad e fro m a sin gle r ubber, Vary ing t he t yp e of car bo n bla ck in ti'J' t reads of t ru ck t ires h ad no effect o n it, bu t SAl" blae k in p a sse nge r car t ires ca used R to be la rge r tha n tha t wh en H Al" blac k was used .Because of co nst ru cti ona l differc nces, no co nclusio ns o n effecl of co rd co uld be d rawn .H owever, R fo r a s teel wire t ru ck t ire was the lowes t obse rved , a nd the va lu es for rayon t ires were lower t lut n t hose for ny lo n t ires excep t a t high s peed s.The temperat lll'e ri se of t he air in t he inner tub e was fou nd to be r elated to t h e power loss by t h e relation: !J. TI P = G+ TfI (SL )o .8wher e G a nd IT a re pa ra meters d epend e nt o n t he thermal resistance of the ru bber co mpo un ds a nd of t he in te rface be twee n t ire a nd air or roadway, r espectively.The ratio /1 7'1 P re ma ined esse nt ia ll y un cha nged by ch a nges i n in fla ti on pr essure a nd did no t appear to be a ffec ted by t he ty pe of cord ,