Michelin Group has its first applications for its new “Tweel” tire and wheel concept, but the innovative device remains 10-15 years from automotive use, executives say.
The non-pneumatic, hub and spoke Tweel, which resembles a bicycle wheel, consists of a polyurethane inner mated to a ring of rubber that contacts the road.
Because it requires no inflation, the Tweel eliminates the need for a tire-pressure monitor or for regular maintenance by vehicle owners, Michelin says.
Three of four vehicles on the road have at least one under-inflated tire, according to data from the National Highway Traffic Safety Admin., which will begin to phase in tire-pressure sensor requirements on new vehicles in September.
Michelin has been experimenting with the Tweel on lower-load, lower-speed applications, such as front-loaders used in construction and wheelchairs, some of which it says are ready for production.
Michelin has been testing the device in automotive applications, as well, but the tire maker was at Detroit's North American International Auto Show in January to drum up more interest from OEMs and open a dialog about the technology.
For now, Michelin says it has its first application for the technology on two new devices from Dean Kamen, inventor of the Segway, an upright, 2-wheeled electric scooter. Tweel will be used on Kamen's stair-climbing iBot wheelchair and Concept Centaur, a prototype 4-wheel electric all-terrain vehicle.
Tweels for those applications will be produced by Michelin in Greenville, SC, where much of the development for the device is taking place. But the company does not say what volume it expects from the specialty applications.
The Tweel's inner ring is made of polyurethane and glass-reinforced plastic and is produced in a 1-step process similar to other plastic injection-molding operations. That is expected to cut manufacturing cost and complexity, but executives say it is too early to quantify the gain.
The construction also allows Michelin to eliminate 85% of the rubber normally used in tire construction. Weight will never be less than a conventional system, but Michelin believes further development will allow Tweel to come close to matching today's tire/wheel assemblies.
There is a 5% rolling-resistance penalty, but Michelin says it expects to trim that margin over time, and executives say in automotive testing the fuel economy penalty amounts to only 1%.
Price is expected to be comparable, says Terry Gettys, president-Michelin Americas Research and Development in Greenville, once the system's advantages are factored in.
In addition to eliminating pressure sensors, the Tweel requires no mounting and balancing. And because the inner wheel flexes over bumps and through turns, the Tweel could have cost-saving implications in suspension-system design.
Unlike conventional tires, Michelin says it can optimize Tweel's vertical and lateral stiffness independently, which could allow for better handling and more comfortable riding tires.
Also, when the tread is worn out, the Tweel can be refitted with new rubber, saving cost over the lifecycle of the vehicle.
Michelin has been testing Tweel in military applications and says the device demonstrates superior resistance to artillery and land mines.
It has completed two rounds of testing on skid-steer front loaders. Michelin says Tweel has resulted in less downtime and less driver fatigue because it provides a smoother ride and better maneuverability.
Gettys says Michelin has had “some inquiries” from OEMs. “We're confident and realistic about the technology, and we want to begin exchanging ideas with key (automotive) players,” he says, adding it probably will be 10 to 15 years before automotive applications surface.
