"Pete C" wrote in message
...
On Mon, 14 Nov 2005 13:26:37 -0000, Rob Morley
wrote:

Perpetual motion? I recall hub dynamos which didn't rely on friction
drive.

Unfortunately they didn't put out enough power, especially at low speed.
You could see the lamps flicker as they turned :-)
Bottom-bracket mounted dynamos are pretty good as they don't scrub like
the sidewall-driven ones can, but they can be prone to slipping and/or
rapid wear because the back tyre dumps loads of crap on them. You can
get toothed-belt drive dynamos that are driven by a pulley attached to
the side of the hub. A properly set up high-quality sidewall-driven
dynamo can still work pretty well anyway.

Posted on another group:

http://www.peterwhitecycles.com/Schmidt-Lumotec.asp

cheers,
Pete.

Just a tad expensive though!