When I was 18 and just about to graduate from high school, my buddies and I first heard about potato guns and decided we had to build one. This was way before MAKE, Mythbusters, or the modern DIY movement as we know it, and potato guns were, at least on my radar, new and scary. They had just been made illegal in Texas, and so our furtive project to secretly construct one in my bedroom felt comically sinister, in retrospect.
We went to the hardware store and came home with lots of PVC bits that we assembled into a barrel and a chamber. Then we waffled for some time about how to hack together an electric ignition system. Our thoughts went immediately to using an automotive spark-plug, but none of us really understood enough about electricity to know how to separate the spark-plug from the car. We were pretty sure you couldn’t just take a spark-plug and wire it up to a car battery and expect results, but beyond that we were clueless. We ended up using a piezoelectric barbecue grill igniter, which gave satisfactory results but often required several “clicks” to actually fire the thing.
Anyway, what we needed at the time, but did not have, was this tutorial over at Popular Science, which is exactly about how to fire a spark plug without, you know, having to keep a whole car around to do it.
From the pages of MAKE: