Electric Wheelchair Future Technology

First automobiles to use air-filled tires appeared in the early 1890's. A century later, the French company Michelin, begun work on an innovation that could render the pneumatic tire obsolete. Michelin's american technology center envisioned a future in which vehicles ride on what they call the Tweel - a combined tire and wheel that could never go flat because it contains no air.

The first commercial use of the integrated tire and wheel assembly will be on the stair-climbing iBOT wheelchair. iBOT product s are developed by Dean Kamen, more widely known as the Segway's inventor. The Tweel offers a number of benefits beyond the obvious attraction of being impervious to nails in the road. The tread will last three times as long as today's radial tires, Michelin says, and when it does wear thin it can be retreaded.

In recent years, manufacturers have devoted an increasing amount of attention to tires that let motorists continue driving after a puncture. Mounted on a car, the Tweel is a single unit, though it actually begins as an assembly of four pieces bonded together: the hub, a polyurethane spoke section, a "shear band" surrounding the spokes, and the tread band - the rubber layer that wraps around the circumference and touches the pavement.The Tweel's hub functions as it would in a normal wheel - a rigid attachment point to the axle - the polyurethane spokes are flexible to help absorb road impacts. The shear band surrounding the spokes effectively takes the place of the air pressure, distributing the load. The tread is similar in appearance to a conventional tire. Steering response as the driver begins a turn is excellent, and large bumps are swallowed up easily by the Tweels.

Tweel can give up to five times as much lateral stiffness as current pneumatic tires without any loss of ride comfort. Tweels currently transmit more of the feel of a coarse road surface than customers would tolerate in a production tire, but the level is understandable considering the early stage of development. There are other negatives: the flexibility, at this stage, contributes to greater friction, though it is within 5 percent of that generated by a conventional radial tire. And so far, the Tweel is no lighter than the tire and wheel it replaces.