A while back I had a simple dynamo crank flashlight (and I suppose it is very possible it was intended to mount into a holster on a bike as a bike light). I thought about taking it and trying to make the rotation of the back tire/chain/whatever attach to the dynamo so that riding a bike would charge the light. The resistance is not very much so it would no burden the rider.
But then I figured I'd be out of a dynamo flashlight. One day I went to RadioShack and found a like flashlight on sale, but this one seemed even more cool. It was the crank, light, radio, siren, and USB-power out, so not only did it not need batteries, it could charge cellphones (and perhaps anything taking USB power!) It can also take a 9v battery if desired. It was on clearance for 6.97.
The first one I got seemed to be broken, which I estimated because there was hardly any resistance at all during cranking, and the light would never produce energy I had expected would be stored, although I could run the light immediately while cranking. I presumed that the dynamo was not connected with the charging mechanism correctly, since the creation of power in a motor is what causes the resistance. I fear this model may be somewhat fragile, but hope it is just an manufacturing error. I returned that one for another one.
This one seems to work (although I can't recall if I ever tested charging a phone.) One weird thing about the product is RadioShack refuses to recognize it exists on their website, even in the legacy support section (catalog num. 61-131). Just because I like the light, some pictures will follow in my next post.
