Originally Posted by
geo8rge
If you are looking for an electronics project go for it, but if you want more watts for less effort a hub generator is probably the way to go.
FWIW I was thinking of rigging a plastic gear to my spokes and connecting that via chain drive to an electric model airplane engine running it as a generator. I figure a model airplane engine must be extremely efficient and outdoor friendly. Maybe a model boat engine. Never did it. Mounting is the biggest obstacle. You might try to upgrade a cheapy bottle generator with a better engine. Gearing is also a problem as to get the volts you need 1000s of RPMs, check specs before waiting your time.
Hmm, I'm at work, but I think that bottle generator wheel is about 2cm diameter. I'd guess it would sit about 1cm down on the tire; or at about the 33.3cm mark on my 27" tire (as from the center). This would give it a step up of about 33.3:1.
6mph is about 10km/hr; I get about 77.5rpm. That translates into about 2,600rpm on the bottle generator. Give or take a bit, given that the numbers are fudged.