Mark 1 Potato Cannon

Search youtube for potato cannon and you’ll find loads of examples. My son was keen to try building one so we came up with a plan to build this one from bits of pipe we had lying about. It didn’t really need much. The “combustion chamber” is a 100mm waste water rodding fitting. One end is completely closed off with a blanking plate and the other with a reducer down to 2″. The entire thing is mounted on a wooden carriage. That’s pretty much it:

We put a couple of bolts through the blanking plate on the end and wired each one to the wires of the spark generator from a barbeque lighter. The button for the spark generator was just glued to the blanking plate using Araldite. I also wired the blanking plate in place as unlike the reducer which was a solvent-weld fitting, it was just a push fit piece:

On the inside a couple of bare copper wires are fixed on the bolts and bent so they produce a nice fat spark when the button is pressed. They’re just visible at the bottom of the rodding eye here:

To fire the cannon, a potato is rammed down the barrel to the end. A quick burst of hairspray is squirted into the chamber through the rodding eye and the cover is screwed on. Push the spark generator button and away you go. Or the potato does, at least.

The first test firing wasn’t entirely successful. The potato did shoot out, but the rodding eye cover also blew off. There was clearly also a lot of stress on the barrel.

We shortened the barrel by about 30cm and fitted a retaining chain to the cover to keep it in place.

The second test was far more successful. The potato cleared some well-grown sycamore trees about 60m away and was still travelling upwards when we lost sight of it.

Next we should make a video of it in operation.

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