CROSS SEC­TION

Car­bon Rev­o­lu­tion CR9

Automobile - - Progress -

THE AD­VAN­TAGE

Al­though lighter weight is the pri­mary ben­e­fit of a com­pos­ite wheel—par­tic­u­larly a car­bon-fiber one—there are also ad­van­tages to be gained in the noise, vi­bra­tion, and harsh­ness arena. Metal wheels, in­clud­ing steel and alu­minum, trans­mit a great deal of high-fre­quency NVH from the road through the sus­pen­sion and into the car’s struc­ture. Car­bon-fiber wheels damp that en­ergy bet­ter, cut­ting it out of the equa­tion where it be­gins. As a re­sult, car­mak­ers will be able to engi­neer qui­eter cab­ins with­out hav­ing to add pounds and pounds of sound in­su­la­tion.

“Not only the light weight and the stiff­ness, but the damp­ing char­ac­ter­is­tics re­ally just get rid of that high-fre­quency [vi­bra­tion], par­tic­u­larly in the lux­ury elec­tric ve­hi­cle space, where you don’t have pow­er­train and ex­haust noise and all those other things,” Gass ex­plained.

Lighter wheels im­prove ac­cel­er­a­tion and de­cel­er­a­tion, as the engine and brakes no longer need to work against as much ro­tat­ing mass. They also re­duce gy­ro­scopic ef­fects, mak­ing ini­tial turn­ing be­hav­ior more sen­si­tive and con­trolled, and the amount of un­sprung weight at each cor­ner—the byprod­ucts of which are im­proved ride com­fort and more de­sir­able han­dling char­ac­ter­is­tics thanks to a less­en­ing of the sus­pen­sion’s over­all work­load.

Ev­ery as­pect of the car­bon wheel that aids per­for­mance also ben­e­fits ef­fi­ciency for the same rea­son—physics: You’re able to do the same or more with less en­ergy. The only dif­fer­ence is the goal. Rather than chas­ing ter­mi­nal ve­loc­ity and op­ti­mum lap times, lightweight­ing a hy­brid or elec­tric car helps to max­i­mize its range. With less mass in the wheel to be spun up to speed and then dragged back down, there’s less en­ergy go­ing to waste ev­ery time the car speeds up or slows down, which can mean miles (or tens of miles) more to a charge or a tank.

THE “BUT”

So car­bon-fiber wheels can un­lock greater per­for­mance po­ten­tial, im­prove ef­fi­ciency, and en­hance com­fort and quiet­ness. They seem like the per­fect so­lu­tion, so why all the fear, un­cer­tainty, and doubt? Two rea­sons: price and myths.

A set of Car­bon Rev­o­lu­tion’s af­ter­mar­ket wheels will run you about $12,000. Al­though that’s com­pet­i­tive with the very top end of the cus­tom forged al­loy wheel af­ter­mar­ket, there’s no $1,000-a-set op­tion as yet in the car­bon-fiber space. But that will change over time as vol­ume—and even­tu­ally com­pe­ti­tion—in­creases.

“To­day we’re not re­ally a dis­rup­tive tech­nol­ogy,” Gass said. “We’re too ex­pen­sive, too ex­otic. When we get to gen three of the tech­nol­ogy where we’re cost com­pet­i­tive with forg­ings and su­pe­rior in ev­ery prod­uct at­tribute, now you’re dis­rup­tive. Now you’re a real threat to a good chunk of the alu­minum mar­ket. We’re not far off. We’re one gen­er­a­tion of pro­duc­tion away from that, which could show up on the road in the next two to three years.”

What Gass calls the “rarest au­to­mo­tive lightweight­ing tech­nol­ogy in ex­is­tence” to­day (he claims there are more sup­pli­ers for the LaFer­rari KERS hy­brid sys­tem than for one-piece car­bon-fiber wheels) could con­ceiv­ably be­come ubiq­ui­tous within the next decade, wheels that not just su­per­cars but po­ten­tially ev­ery car will roll on. But that will only hap­pen if the myth mon­gers are proven wrong.

CAR­BON FIBER’S ABIL­ITY TO TOL­ER­ATE A WIDE RANGE OF TEM­PER­A­TURES WITH­OUT BE­COM­ING BRIT­TLE OR DEFORMABLE DE­PENDS NOT ON

THE CAR­BON IT­SELF BUT ON THE EPOXY THAT SUR­ROUNDS IT.

THE MYTHS

Car­bon is frag­ile! Car­bon shat­ters! You can’t re­pair it! Car­bon wheels will melt when they’re hot! They’ll crack when they’re cold! They leak air!

The litany of fake news fa­tal flaws of the car­bon­fiber wheel is not quite end­less, but it’s cer­tainly ex­ten­sive. And none of it is true—at least if the wheel is made cor­rectly. The seed of the myths was planted by a hand­ful of af­ter­mar­ket wheels, most of them two- or three-piece “hy­brids” (car­bon bar­rels with al­loy hubs and spokes), none of them tested to OEM stan­dards for road use. They’re very dif­fer­ent cre­ations from the fully tested one-piece wheels from Porsche, Koenigsegg, and Car­bon Rev­o­lu­tion.

The mul­ti­p­iece, mul­ti­ma­te­rial na­ture of hy­brid car­bon/al­loy wheels presents ad­di­tional points of fail­ure com­pared to a tra­di­tional one-piece wheel, re­gard­less of the ma­te­rial. The al­loy cen­ter sec­tion has to be mated to the car­bon-fiber bar­rel, typ­i­cally by bolts, and each presents an op­por­tu­nity for shear and strain to cause fail­ure of the joint. Worse, when you bolt the alu­minum cen­ter sec­tion to the car­bon bar­rel, there’s likely to be some twist­ing that adds in­ter­nal stresses and pulls the wheel out of true.

That’s not to say that all hy­brid wheels are bad or in­her­ently flawed. In fact, some hy­brid wheels, in­clud­ing those pro­duced by Carbo Tech (sup­plier of hy­brid car­bon wheels to BMW and Rolls-Royce as well as some of McLaren’s road-go­ing car­bon mono­co­ques) and Geric, are built to meet or ex­ceed the pa­ram­e­ters of stan­dard al­loy wheels, not just in terms of stiff­ness but also of dura­bil­ity and tough­ness. Hy­brid wheels are a fac­tory op­tion on the ex­cel­lent BMW M4 GTS, a car vaunted for its han­dling and per­for­mance.

As for re­pair, car­bon-fiber wheels—whether one­piece or hy­brid—can be pol­ished and resur­faced pro­vided any scratch­ing (hello, curb!) is lim­ited to the sur­face epoxy layer and doesn’t dis­turb the car­bon fiber below. That’s not too dif­fer­ent from fix­ing an al­loy wheel; no mat­ter the ma­te­rial, you take a big enough chunk out of one or bend one too far, and there’s no re­pair­ing it back to its orig­i­nal strength and stiff­ness.

Al­though con­cerns about car­bon fiber’s abil­ity to han­dle ex­treme tem­per­a­tures are le­git­i­mate, they’re mis­placed. Car­bon fiber’s abil­ity to tol­er­ate a wide range of tem­per­a­tures with­out be­com­ing brit­tle or deformable de­pends not on the car­bon it­self but on the epoxy that sur­rounds it—and wheel mak­ers like Car­bon Rev­o­lu­tion have put a lot of sci­ence into their se­cret sauce, in­clud­ing the plasma coat­ing in­side the wheel to pro­tect the epoxy from brake heat. The re­sult is a wheel that’s as strong and as safe to use in the Arc­tic as it is at a mid­sum­mer Ari­zona track day—oth­er­wise that wheel never would have ended up on a car like the Ford GT.

PRESENT AND FU­TURE

Porsche’s up­com­ing op­tional wheel for the 911 Turbo S Ex­clu­sive Series is a one-piece braided-car­bon unit that’s so tricky to cre­ate that Porsche de­cided it had to build a spe­cial cir­cu­lar loom (the world’s largest) just to weave the car­bon into the wheel form. Ford’s de­ci­sion to go with Car­bon Rev­o­lu­tion for its Mus­tang GT350R and GT su­per­car wheels also lends sup­port to the idea that one-piece car­bon-fiber wheels might be some­thing worth spend­ing for—even when you nor­mally de­sign your own.

A one-piece car­bon-fiber de­sign also opens the mar­ket to a wealth of fu­ture pos­si­bil­i­ties, in­clud­ing the ad­vent of the smart wheel.

“There’s all kinds of stuff go­ing on as far as the car­bon wheels them­selves and the man­u­fac­tur­ing process,” Gass said. “I can em­bed wires and sen­sors in­side of a wheel, so there’s a whole range of op­tions and tech­nol­ogy there to in­te­grate into the ve­hi­cles.” In fact, ev­ery Car­bon Rev­o­lu­tion wheel is al­ready em­bed­ded with an RFID chip that’s used for track­ing and qual­ity con­trol through­out the man­u­fac­tur­ing process.

Be­yond in­te­grat­ing pres­sure, tem­per­a­ture, and other sen­sors di­rectly into car­bon wheels, there are also new de­signs and ge­ome­tries that can be re­al­ized thanks to their unique method of con­struc­tion.

“The par­al­lel I’d draw is the bike in­dus­try, where the early car­bon-fiber road bike and moun­tain bike frames were butt joints,” Gass said. “Once it was painted, you couldn’t tell if it was a metal bike or a car­bon bike. As the tech­nol­ogy evolved from man­u­fac­tur­ing to the stu­dio and the in­dus­trial de­sign side, you’d know it was painted car­bon just be­cause of the struc­ture and its shape. … Wheels haven’t got­ten there yet. The [de­sign] stu­dios, they’re just not ma­ture enough. They haven’t learned enough about the tech­nol­ogy.”

As they be­come more fa­mil­iar with the process of cre­at­ing car­bon-based wheels, de­sign­ers will be able to stretch be­yond de­vel­op­ing them for aes­thetic ben­e­fits alone. Once the com­pu­ta­tional fluid dy­nam­i­cists get in­volved, for ex­am­ple, we might all have a dash of For­mula 1-level tech at each cor­ner of our car. “One of the things that’ll be neat is when you think about ef­fi­ciency on fu­ture ve­hi­cles, aero­dy­nam­ics will play a big role,” Gass said.

As the world grap­ples with how to re­duce car­bon in the at­mos­phere (or at least how to re­duce the amount we pump into it), it’s a bit ironic that one of the things that will help achieve that goal could be car­bon it­self. But it’s be­com­ing in­creas­ingly hard to deny that’ll be the case and that the next fron­tier of the Car­bon Age is upon us. AM

CAR­BON REV­O­LU­TION HAS PUT A LOT OF SCI­ENCE INTO ITS SE­CRET SAUCE, IN­CLUD­ING ITS PLASMA COAT­ING IN­SIDE THE WHEEL TO PRO­TECT THE EPOXY FROM BRAKE HEAT.

There’s no part of a wheel that isn’t es­sen­tial, but the strength and dura­bil­ity of the hub por­tion is cen­tral to trans­fer­ring the torque of ac­cel­er­a­tion and brak­ing from engine to road and back to the brakes.

The cen­tral por­tion uses an al­loy struc­ture to mate the wheel to lugs and hub face.

All metal hard­ware is pressed in after the mold­ing process and can be ser­viced with sim­ple hand tools. Each por­tion of the wheel is made of many lay­ers of car­bon fiber, each with dif­fer­ent weave di­rec­tions and ma­te­rial prop­er­ties to max­i­mize strength. This odd cross sec­tion with cop­per in­serts is an in­te­rior view of the RFID chip Car­bon Rev­o­lu­tion uses to track each wheel through­out the man­u­fac­tur­ing and qual­ity as­sur­ance pro­cesses. A rigid, light­weight foam is in­jected into the in­te­rior cav­ity of the wheel dur­ing man­u­fac­ture to en­sure the in­ner sur­face of the car­bon main­tains shape and po­si­tion dur­ing mold­ing. The foam it­self pro­vides no struc­tural strength to the fin­ished wheel. The ex­te­rior of each wheel is cov­ered in a purely aes­thetic top layer of car­bon fiber and

a glossy epoxy fin­ish. The ap­pear­ance-fo­cused na­ture of that top layer leaves a lot of room for

tai­lored looks.

The Ford GT’s use of car­bon fiber isn’t about style. It’s about speed. There’s zero chance the GT, bred for the track and loosed on the street, would be shod in car­bon if the ma­te­rial weren’t up to the task.

The ce­ram­icmetal­lic coat­ing on the in­side of Car­bon Rev­o­lu­tion wheels can vary widely or get skipped

al­to­gether de­pend­ing on the car the wheel was de­signed for.

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