My friend Pete shared the animated GIF attatched to this thing and said "this has RepRap written all over it", so I decided I had to model it and print it.

This is a model of a Geneva Drive, which converts continuous rotational motion to intermittent continuous motion.. (think of the seconds hand on a clock which "ticks" rather than moving smoothly).

http://youtu.be/HCnYnhws_cA

Print the base and then one of each wheel (either printing each wheel independently or use the bothwheels file). The wheel with the finger-hole (wheel one) goes finger-hole side up, The other wheel (with the spikes) goes upside down.

Turn the small wheel with your finger, and it will turn the large wheel in steps.