I had seen a number of potato cannons before with slight variations, but we based our design on one in Make Magazine. There were two differences in ours: we didn't use clear plastic and we didn't use a stun gun for the ignition. For the body, we used schedule 40 PVC, but we made the entire thing black.

Build Log

For the ignition, Make used a stun gun. However, we didn't have one lying around, so we were having a hard time figuring out how to do it on the cheap. We tried a variety of different electrical sources, but they all seemed to be putting through too much current and actually left residue on the electrodes. Finally, we went to the hardware store and splurged on a gas grill sparker (the manual, push-button kind). It was just the ticket, and ignited the fuel with pretty good consistency.