Motors! Motors! Motors!
Those redundant video machines and audio tape recorders are a supply for useful electric motors. You can find them at flea markets, boot fairs, and local authority waste disposal sites (or ‘tips’). The last video machine I found yielded four motors. I’ve paid not more than £1 for a u/s machine.
Arm yourself with assorted screwdrivers and wire cutters and you’re in!
These drive motors are not ‘can’ motors. They are transformed down from mains voltage to, usually 9–12V DC, or battery driven at the same voltage, and they are reversible.
I have found them to be very reliable — they have to be by virtue of their original use! Some have brass or nylon-type armature bearings — the heavier ones have ball bearings — and they are powerful! Two that I have hold a worm on the armature shaft, bracketed to a worm-wheel (as installed) and you just cannot hold the worm-wheel shaft — it will burn!
Mount the motor in your model with ‘Terry’ clips of appropriate size. Primary drive is best by using a belt or band(s) straight off the armature shaft. Avoid gears. They will run, literally, all day without even getting warm, using a suitable controller on 9V DC — I’ve done it. If a motor does go ‘phut’ you can afford to throw it away.
Dimensions vary between 30–40mm in diameter and 15–40mm in length. The machines also yield assorted driving bands and belts.
For obvious reasons, avoid direct mains motors. If in doubt, get the motor checked by a competent TV or Audio repairer, rather than an electrician. Generally, the inscriptions on labels will not give you a clue. Stick to domestic machines — business or commercial outfits, to me, are an unknown quantity.