We build hand generators from DC gear motors which we find on surplus electroncs websites. Look for DC gear motors and order a small selection of different ones to test. These are surplus and always change, so if you find one that you really like, buy a bunch. While you are at the electronics store you may want to pick up a pair of large alligator clips and about 18 inches of lamp cord (Two strand wire) per generator.
We get our crank handles from Reid Supply, 3.5” aluminum cranks, the part number is something like CH-35AL (pretty obvious how they coded that!) These don’t have holes in them so they fit any motor shaft size.
We drill a blind hole (not all the way through) in the handle and fasten it to the motor shaft with epoxy. If we can, we open the motor case and solder the heavier cord directly to the connectors. If we can’t, we will solder the wires together, either way we provide some form of strain relief. we have glued the motors into PVC pipe with the cord knotted and passing through an end cap. Sometimes we have to grind off a metal flange to make a motor more hand-friendly. The alligator clips are soldered to the ends of the wire. We try to keep the wires and the colors of the clips polarized the same way so that saying, “Let’s try connecting all the red clips together” almost has a predictable result. (It depends which way the student turns the crank.)
These generators last a long time, we don’t ever strip the gears in them, and the cost of parts is less than $20. The epoxy joint is typically the failure point and very easily repaired.
We use our generators mostly to turn other generators. Students love it. We have been tempted to make some winches, with pulleys instead of cranks to see if we can lift stuff, and if we can turn the generator with falling weight. Two pulleys on the shaft; a big one and a small one? We have seen a similar device used to split water with electrolysis to make little hydrogen-oxygen explosions. Cool!
We get our crank handles from Reid Supply, 3.5” aluminum cranks, the part number is something like CH-35AL (pretty obvious how they coded that!) These don’t have holes in them so they fit any motor shaft size.
We drill a blind hole (not all the way through) in the handle and fasten it to the motor shaft with epoxy. If we can, we open the motor case and solder the heavier cord directly to the connectors. If we can’t, we will solder the wires together, either way we provide some form of strain relief. we have glued the motors into PVC pipe with the cord knotted and passing through an end cap. Sometimes we have to grind off a metal flange to make a motor more hand-friendly. The alligator clips are soldered to the ends of the wire. We try to keep the wires and the colors of the clips polarized the same way so that saying, “Let’s try connecting all the red clips together” almost has a predictable result. (It depends which way the student turns the crank.)
These generators last a long time, we don’t ever strip the gears in them, and the cost of parts is less than $20. The epoxy joint is typically the failure point and very easily repaired.
We use our generators mostly to turn other generators. Students love it. We have been tempted to make some winches, with pulleys instead of cranks to see if we can lift stuff, and if we can turn the generator with falling weight. Two pulleys on the shaft; a big one and a small one? We have seen a similar device used to split water with electrolysis to make little hydrogen-oxygen explosions. Cool!
