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The Tweel (a portmanteau of tire and wheel) is an experimental tire design developed by the French tire company Michelin. Its significant advantage over pneumatic tires is that the Tweel does not use a bladder full of compressed air, and therefore it cannot burst nor become flat. Instead, the Tweel's hub connects to flexible polyurethane spokes which are used to support an outer rim and assume the shock-absorbing role of the compressed air in a traditional tire.
The Tweel consists of a cable-reinforced band of conventional tire rubber with molded tread, a shear band just below the tread that creates a compliant contact patch, and a series of energy-absorbing polyurethane spokes. The rectangular spokes can be designed to have a range of stiffnesses, so engineers can control how the Tweel handles loads. The inner hub contains a matrix of deformable plastic structures that flex under load and return to their original shape. By varying the thickness and size of the spokes, Michelin can generate a wide array of ride and handling qualities. The tread can be as specialised as any of today's tires and is replaceable when worn.
Benefits and drawbacks
Potential benefits of the Tweel include the obvious safety and convenience of never having flat tires. Eventually, it may be able to outperform a pneumatic tire since it can be designed to have high lateral strength for better handling without a loss in comfort since the design of the spokes allows the vertical and lateral stiffness to be tuned independently. The tread patterns may incorporate holes in the design thus eliminating or significantly reducing aquaplaning. Michelin expects the tread to last two to three times as long as a conventional tire. Because only the tread around the circumference would be disposed of when worn as opposed to a whole tire, the environmental impact should be less.
The Tweel does have several flaws, however, the worst being vibration. Above 50 mph (80 km/h), the Tweel vibrates considerably, which in itself is a problem that also gives rise to undesired noise and heat. A fast-moving Tweel is unpleasantly loud and produces 5 percent more friction compared to a radial tire.
Given the high speed problems with the Tweel, the first commercial applications will be in lower-speed, lower-weight vehicles such as wheelchairs, scooters, and other such devices. The iBOT mobility device and Segway's Concept Centaur were both introduced with Tweels. Michelin also has additional projects for Tweel on small construction equipment, such as skid steer loaders, for which it seems well-suited.
The first large-scale applications may be in the military where a flat-proof tire would be advantageous. Military testing has indicated that the Tweel deflects mine blasts away from the vehicle better than standard tires and that the Tweel remains mobile even with some of the spokes damaged or missing.
In October 2012, Michelin North America Inc. began commercial sales of the 12N16.5 X-Tweel for skid-steer loaders used in landscaping, construction, contracting, refuse/recycling and agricultural industries.
- HowStuffWorks "How the Tweel Airless Tire Works"
- MAYERSOHN, NORMAN (3 January 2005). "Reinventing the Wheel (and the Tire, Too)". New York Times. Retrieved 15 January 2012.
- "Airless Tires? Consider The Tweel". CBS News.
- Nasa’s Rover Vehicle equipped with Michelin tires
- LRI AB Scarab wheels
- Michelin X-Tweel>
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