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Ford’s first mass-produced carbon fiber wheels

12 July 2015

To source the new lightweight track-capable carbon fiber wheels that are standard on the new Shelby GT350R Mustang, Ford partnered with Australia-based Carbon Revolution. Carbon Revolution first began delivering composite wheels in 2004 for Formula SAE campaigns. The company now is producing its “CR-9” wheel series in limited numbers for Porsche, BMW M3, Audi R8, Lamborghini and McLaren MP4-12C within Europe, Japan and North America. Ford, however, wanted more of a mass-production solution.

The one-piece carbon fiber wheels for the Mustang weigh nearly half that of an equivalent aluminum wheel (18 pounds versus 33 pounds), and handling and acceleration performance see serious benefits. The wheels also provide a reduction in rotational inertia of more than 40%, which positively impacts acceleration and braking performance. The wheels are so light, the springs and MagneRide dampers had to be recalibrated because the suspension can respond considerably faster to road inputs.

GT350R-wheel-1372

In early testing with benchmark vehicles, prototype wheels showed significant potential—improving suspension response times, chassis dynamics, steering feel and ride quality. When the decision was made to pursue this technology for use in a production vehicle, the engineering team was challenged to develop a wheel that met Ford’s standards for durability, quality, craftsmanship and premium finish.

Lowering overall curb weight in general is beneficial to a car’s dynamics, but a reduction in unsprung weight (those components not supported by the suspension) can have a significant impact on handling and performance. Less unsprung weight helps vehicles start, stop and turn faster by reducing wheel rotational inertia, significantly improving response time to driver input. Lower unsprung weight also results in suspension components not having to work so hard to keep the tires in contact with the road over undulating or broken surfaces.

Although Carbon Revolution has been the leading manufacturer of carbon fiber wheels, both Ford and the supplier recognized significant innovation was needed to meet Shelby GT350R program needs.

Ford wheels must endure tests that include curb strikes, UV and chemical exposure, and extreme heat durability testing. The GT350R wheels would need to fulfill all of these demands in order to proceed to production.

A common misconception of carbon fiber is that while it’s strong, it’s also a brittle material. Some formulations may have this characteristic, but carbon fiber’s durability is a feature of the type of resin and design intent of the part. The wheels of Shelby GT350R are designed to be stiff, light and resilient.

One of the most severe tests for wheels in the Ford development process involves striking a curb at speed— a test that, without proper design, can cause serious wheel and tire damage. Because of the light weight, advanced construction methods and resins in the wheels, along with the highly-developed MagneRide dampers, the suspension was able to react so fast that the driver wasn’t sure the test had been carried out correctly and ran it twice to be sure. The suspension response was fast enough to greatly diminish the severity of the impact.

During track testing the extreme performance capabilities of the braking system developed heat which required the maximum technology available from Carbon Revolution. Shelby GT350R’s ultra-powerful brakes were creating rotor temperatures in excess of 900 degrees Celsius. As a result, the wheel design was elevated from a road car specification to a thermal standard more suitable for motorsports.

For decades aerospace companies have treated turbine blade materials subject to extreme heat with ceramic coatings to help improve durability. The technology is also used in top-tier open-wheel racing environments. A thermal barrier coating system developed by Carbon Revolution uses this same technology.

Created specifically for motorsport and aerospace applications where extreme temperature conditions are encountered, Carbon Revolution’s thermal barrier coating system uses a multistage, multimaterial coating formulation that provides an excellent thermal barrier. Using a plasma arc gun to liquefy a ceramic material, the wheels are coated at critical points around the inner wheel “barrel” and on the back of the spokes. The result is a thin, nearly diamond-hard coating that reliably shields the resin from heat—reducing maximum wheel temperatures and allowing continuous track use by even the most aggressive drivers.

Upon extreme exposure to harsh UV environments, corrosive salts and road chemicals, it became apparent that to achieve the durability required by Ford, a special coating would need to be developed to protect the resin from the environment.

Carbon fiber parts are challenging when it comes to delivering a flawlessly smooth painted surface. Several proprietary new processes were developed that resulted in a robust, high-gloss black finish that not only looks good, but ensures a long life for the wheels.

Manufacturing carbon fiber wheels begins with the creation of the preformed internal carbon structure, composed of precisely manufactured carbon strands arrayed into woven fabrics. The elements are then placed into a mold using advanced manufacturing techniques.

An RFID chip with a unique tracking number is embedded in this structure, and each wheel is individually entered into a quality assurance system. Once this structure is assembled, it’s infused with resin and cured at high temperatures.

This process results in a one-piece wheel that ensures maximum strength—eliminating the need to bond or glue the wheel’s spokes and barrel components together.

As the wheel cures, 61 individual checks and more than 246,000 data points are logged before it’s released from the machine. To guarantee quality parts, the cured wheels are analyzed using a 3D computerized tomography (CT) imaging process in which more than 18,000 X-ray images are taken.

If the wheel passes inspection, it undergoes machining for the valve stem and mounting hardware holes before it gets painted, coated, assembled, dimensionally checked and shipped to Flat Rock Assembly Plant for installation on a new Shelby GT350R Mustang.

July 12, 2015 in Fuel Efficiency, Materials, Weight reduction | Permalink | Comments (15)

Comments

Good news for future in-wheel e-Motors?

Harvey, not sure, I bet these babies cost a 1000$ each...if not more

I see a very, very expensive experimental racing wheel, nothing more at this point.

Hub-motors have been a dream since Porsche worked with them in the early 1900s; still a dream because of unsolved reliability problems.

@Lad:

Hub motors are what BYD use in their admittedly very different electric bus, so they are not a dead loss in all applications.

My God, all of that is impressive, but it must be terribly expensive. But I must admit I'd probably spring for some as long as it's not more than a few thousand dollars for a set so maybe they'll have plenty of suckers like me.

DM:
Would love to see hub motors perfected; with the batteries in the floor, smaller control electronics using graphene and hub motors, think of all the space in a family sedan, etc.

Half weight 16-22-inch wheels and tires would allow hub e-motors on all four wheels without significant increased in unsprung weight?

Mass produced at lower cost (in China?) it could become one of the worldwide solution for future AWD more efficient EVs.

I'm just not a big fan of hub motors. They've always had real world problems that just don't seem to be overcome very easily and they will add unsprung weight so they're not going to be great for performance. And if you're not going for performance then why not one simple motor with drive on one axle?

So the question is this: What problem do they solve that can't be solved more easily by another solution?

DaveD:
4WD without differentials?

No, I was talking about the low end where performance doesn't matter so you don't need 4WD. Just drive the back wheels or the front wheels with a single differential...probably the front for better regen braking.

Early flat LCD panel TVs were so expensive that only people with very deep pockets could buy them. Ten years latter, they were so cheap that everybody could afford to buy 3 or 4.

The same thing will happen with (carbon) fiber ultra light wheels and CF car bodies and components.

There's at least one study that finds in-hub motors and their unsprung weight not a problem.

There's also the solution of using separate motors for each wheel, mounting the motors on the frame and connecting to the wheels with half axles. This would allow high quality computer controlled 4WD.

"Less unsprung weight helps vehicles start, stop and turn faster by reducing wheel rotational inertia, significantly improving response time to driver input." Surely you must mean less rotational weight, not less unsprung weight, right?

There are lots of ways to reduce unsprung weight that don't reduce rotational inertia, just as there are many ways increase unsprung weight without increasing rotational inertia.

In this case we have a reduction in unsprung weight and a reduction in rotational weight which are both good things, but let us not confuse the two subjects.

"Less unsprung weight helps vehicles start, stop and turn faster by reducing wheel rotational inertia, significantly improving response time to driver input." Surely you must mean less rotational weight, not less unsprung weight, right?

There are lots of ways to reduce unsprung weight that don't reduce rotational inertia, just as there are many ways increase unsprung weight without increasing rotational inertia.

In this case we have a reduction in unsprung weight and a reduction in rotational weight which are both good things, but let us not confuse the two subjects.

Hybrid (aluminum + CF) wheels are about 40% lighter than aluminum units and cheaper to make.

That may be an acceptable short term compromise?

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