Steve Garrison has come up with several innovative ways to cut gears from wood. His technique allows you to use various tools including a router, scroll saw, and table saw. In addition to making standard spur gears, his method allows you to cut helical and herringbone gears from wood. It is wooden herringbone gears that allows this ferocious wood machine to crush cans with ease.
From the YouTube description:
A reduction gear train made of pine plywood sheathing scraps laminated together with screws and powered by a 3/4 h.p. electric motor. Herringbone or Chevron gears are stronger than spur gears and do not have any tendency to move along the axle even under heavy loads. There are no bearings other than the center hole drilled through the plywood turning on half inch diameter smooth steel shafts lubricated with axle grease. The gear ratio is 72:1 not including the belt drive, the belt drive makes the overall ratio around 172:1 (About 10 rpm output with a 1720 rpm input from the motor).
This is an impressive display of power. Garrison's method can also be used to make gears for lighter duty jobs -- like the power train on Dave Johnson's Buckyball Moving Machine.
Visit Steve Garrison's web site to see videos and examples of his wood gear cutting technique. It is available as a 52-page e-book in PDF format.