If You Have Found it Hard To Find Variable Speed , This is The Place For You!
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Debunk variable speed transmission invention?
A friend describes his invention for a variable speed tranmission for bicycles, which involves a novel design for a sprocket wheel. This sprocket wheel has a flexible system of spring-like spokes so that it can have an eccentric axle, i.e. the axle is off center with the sprocket wheel. The theory is that the "effective lever arm length" is continuously adjustable. What's the best way to explain why this idea won't work?
Continuously variable transmissions almost always rely on static friction instead of intermeshing teeth since, obviously, you can't change the number of teeth on a gear or sprocket. (although people have tried......) Modern CVT's either use friction rollers or adjustable pulleys.
Having an eccentric axle wouldn't work, because at the end of the day, the chain still has to travel the *same distance* around the shaft, per rotation, in order to transmit work. Hence the location of the axle doesn't matter, only the size and/or the number of teeth in the sprocket.
Interestingly, Ellsworth Bicycles out of California make a bicycle with a CVT, if you are willing to shell out $3,000..
http://www.gizmag.com/go/6132/
http://www.ellsworthride.com/