[BRENT in 10-uh-C]

Originally Posted by Tom Wesenberg

Brent, an old exercise treadmill would have a variable speed motor, but if you want a reversible variable speed motor, you'll have to find an old 1/2" electric drill.

Yep drill motors have been used too... This Youtube vid covers it pretty nicely;
https://www.youtube.com/watch?v=YqErTwU1rSE



...along with winch motors;