very nice! nice idea leaving the grearing all intact, you could refine that motor so the motor spins at a high rpm and the geared down portion could spin up a generator at 1800rpms or so. whats the air gap measured between the existing rotor and stator? are you only running at 12v!? considering your existing air gap, resistance in the gear box, and 12v then 100rpm sounds very good!! oh is that 100rpms before of after the gear box? if your circut can handle it, try throwing 2, 3, or 4 12v batts in series (48v total at 4) and see how fast it spins up. you will probably notice different rpm performance levels if you try a batt, cap, light bulb, and or a block resister on the output wires but yes!! be careful to turn the power off!! when changing the output types, lol i have blown plenty of transistors learning the hard way. also i think you mentioned you were using pots instead of fixed resistors for the bridge on the base of the transistor. you should probably try changing those out to a "matched ohms" set of fixed resistors and see if there is an improvment, i have been told that pots are not as accurate.

i am still waiting for my second motor from a local machine shop. its nearly identical to yours in geomitry. just came out of a weed wacker. the shop is making a new rotor for that one with a 5thousands air gap. he is pricing the clean(virgin?) cast iron at about 10$ a pound. does that sound about right anybody? also i would like to post some videos but my camera only outputs quicktime file types. can anyone recomend a utility i can use to shrink the file size and change the format to mpg?

thanks!
Eric