The Steam Punk outhouse light idea intrigued me too, today I think I found the gear drives, just got done opening one up, I think it will take 2 of these to get input rpm down slow enough to last 5 or more minutes, hmm, maybe try 3. They were from some type of rolling door brake, the faster door tryed to roll the faster final drive spun causing shoes on the final drive to fling out and rub housing. For the initial drive I was thinking of using the crank hub from a bicycle (just center hub), that way it would freewheel as you pulled free side of the chain, then the weight on other end of chain could drive gears, hmm, kinda hard to explain, hope one of you understood that.
Kristi