Lots of people are into mechanical generation of electrical power these days, so here’s a nice tip from the guys at Uncommon Projects: dynohubs. I had a note in my inbox for months that just said “dynohubs, Tarikh.” So I wrote, and he offered a lovely explanation, and a link:
Dynohubs are cool. They are sort of stepper motors in reverse,
actually sealed in a bicycle hub. They generate AC current which can be
easily rectified and smoothed to DC and (mine anyway) generates nearly 400mA
without significant speed. There’s some minor friction from the magnets but
they’re much better than the old style “bottle” hubs (which are
significantly cheaper).
Dynohub in Uncommon Action!
Perhaps you were asking me because I’ve been meaning to make an instructible
for months about how to power or charge your iphone/device from your bike?
They’re not necessarily cheap. A quick google search for the Shimano 3N71 that Tarikh mentions comes up with prices ranging from $99 – $150. 3W at 6V, that’s half an amp. Not a bad start.