DETROIT (Jan 10, 2005) — Michelin North America Inc. executives are touting the firm's “Tweel” non-pneumatic integrated tire/wheel unit as the next revolution in transportation mobility, although the revolution is starting rather modestly—with a fitment on a Segway-inspired stair-climbing wheelchair.
“Major revolutions in mobility may come along only once in a hundred years,” Terry Gettys, president of Michelin Americas Research and Development Center (MARC) told a press conference at the North American International Auto Show in Detroit, “but a new century has dawned, and Tweel has proved its potential to transform mobility.”
“Tweel enables us to reach levels of performance that quite simply aren't possible with today's conventional pneumatic technology,” he said.
The Tweel uses a network of elastomeric polyurethane spokes fused to a wheel hub and a circular outer flat rim to replace the casing, beads and sidewall structures as the load-bearing element. The outer surface of the Tweel rim is covered with a more conventional rubber tread.
Without the air needed by conventional tires, Tweel still delivers pneumatic-like performance in weight-carrying capacity, ride comfort and the ability to “envelope” road hazards, Michelin claims. The design is covered by at least two patents.
The first larger-scale commercial application could be for skid-steer and similar civilian and/or military vehicles, but a first-generation passenger car prototype has showed considerable potential as well, Mr. Gettys said, prompting the firm to go public with it.
The Tweel was designed and developed by engineers at MARC in Greenville, S.C., based on lessons learned from work on the firm's Zero Pressure run-flat pneumatic tires, said Bart Thompson, the lead engineer on the project at MARC.
The fitment unveiled in Detroit was for the iBOT mobility systems invented by Dean Kamen, the inventor of the motorized scooter-like Segway. The six-wheeled iBOT mobility device has the ability to climb stairs and navigate uneven terrain, offering mobility freedom impossible with traditional wheelchairs. The iBot user can even operate the chair balancing on just two wheels, bringing the rider eye-to-eye with other standing pedestrians.
Additionally, Segway L.L.C.'s Concept Centaur, a prototype that applies self-balancing technology to a four-wheel device, also has been equipped with Tweel to increase its performance potential.
The Tweel automotive concept, as demonstrated at MARC on an Audi A4, is a “stretch application with strong future potential,” Mr. Gettys said. “Our concentration is to enter the market with lower-speed, lower-weight Tweel applications. What we learn from our early successes will be applied to Tweel fitments for passenger cars and beyond.”
The company said it also has found that it can tune Tweel performances independently of each other, which is a significant change from conventional tires. This means vertical stiffness—which primarily affects ride comfort—and lateral stiffness—which affects handling and cornering—can both be optimized, pushing the performance envelope in these applications and enabling new performances not possible for current inflated tires.
The Tweel prototype, demonstrated on the Audi A4, is within 5 percent of the rolling resistance and mass levels of current pneumatic tires, Michelin said, translating to within 1 percent of the fuel economy of a conventional pneumatic original equipment fitment.
Additionally, Michelin said it has increased the lateral stiffness by a factor of five, making the prototype “unusually responsive in its handling.”