After thinking about it, it would be easier to just press the small electric motor's spindle against the rubber wheel. A small spindle against a large wheel will gear it way down. If you use a rear bike tire of a 10/12/18 speek bike you will have the chain sprockets available. You can use a long bike chain (bike chains can be hooked together, one of the links is removable) and run it to another bike chain sprocket (another rear wheel would work).
Speed can be adjusted by picking one of the different sprockets or using more or less voltage on the little dc motor.
If you have two bikes sitting around, all you need is the long chain and the motor. If you have enough space, you don't even need to take the wheels off the bike, just put the two bikes back to back however far apart you need, lift the rear wheel off the ground (or turn bike upside down), and run the chain between the two rear bike sprockets. You will need to build a mounting device for the small electric motor holding it pressed to the tire.
This would be very "Wright Brothers"
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As far as getting the camera to take a picture every x seconds, does your camera have an ir remote? Mine came with one. Anyway, crack it open and solder two leads across the microswitch and hook that to a relay.
Edited by Lou Apo, 02 July 2011 - 09:08 AM.