|The Wheel’s basic design.|
RevoPower, a Denver-based company, is developing a 2-stroke engine-powered replacement front wheel for bicycles. The 25cc hub engine in the Wheel delivers 1hp (0.8 kW) peak power at 7,500 rpm and supports a top speed of 20 mph. Fuel economy is an estimated 200 mpg.
The Wheel meets CARB/EPA standards for small off-road engines, and features an idle-stop function that cuts off the engine at speeds below 5 mph. (Conversely, the rider needs to hit 5 mph before the engine will engage.) By stoping the engine at low speed or rest, RevoPower avoids the issue of idling emissions, as well as the problem of cooling the engine when the wheel is not rotating.
The company has developed seven prototype engines, two hand-built and five from Komatsu. RevoPower is working with another manufacturer on a stratified charge two-stroke engine with port geometry that will meet the emissions requirements.
The Wheel itself weighs less than 15 pounds (5 kg), and uses a standard one-quart fuel tank (although other designs are possible). Noise emitted by the engine is less than 65 dB at a distance of 7.5 m.
Swapping out a conventional bike wheel with the powered Wheel takes about 30 minutes. The Wheel will be available in 2007, and will cost about $400.
RevoPower has put about $1M into the development of the Wheel so far, and is raising an additional $3-7 million.
US Patent # 6,971,467: Hub Motor Formed in a Wheel and a Method Associated Therewith