Sunday, January 25, 2009

Reinventing the Wheel

I'm fascinated when someone takes something so familiar to us (like a car tire) and rethinks it in a dramatically new configuration.

The Tweel (a combination of tire and wheel) is a rethinking of the automobile tire by Michelin that rides on rubber permanently attached to flexible spokes fused with a flexible wheel that deforms to absorb shock. Checking tire pressure, fixing flats, highway blowouts and balancing between traction and comfort could all fade into memory if the Tweel catches on.

Over a hundred years ago, in the 1890s, the Michelin brothers were the first to use air-filled tires on a racecar. Almost 60 years ago, the company introduced the radial tire.

At the Detroit Auto Show, Michelin showed a video with an Audi A4 running on concept auto Tweels. The Tweel doesn't look like a conventional tire, you can see through it, but it has some unconventional aspects that are drawing attention from the U.S. military. Stopping to repair flats can be dangerous for soldiers, making them vulnerable to ambushes. Landmines and other explosives can disable trucks. Preliminary tests by Michelin show that the Tweel can run over explosives and keep on rolling even if some of the spokes are broken and some tread ripped off. It also directs the blast energy of land mines and other explosives outward rather than up and into the vehicle like traditional tires.

Michelin can tune Tweels so vertical stiffness (which primarily affects ride comfort) and lateral stiffness (which affects handling and cornering) can both be optimized, and enable performance not possible for current inflated tires. The Tweel prototype, demonstrated on the Audi A4, is within one percent of the fuel economy of current tires. Michelin has also increased the lateral stiffness by a factor of five, making the prototype unusually responsive.

The Tweel probably won't be in the showroom for a least a decade. If all goes well in the lab, Tweels could replace radials, but that is a long-term prediction. It took radials 30 years to replace bias tires and become the universal tire standard.

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