Compared to the catapult, the potato cannon barely seemed like a project! Only took a few hours, in fact my wife completed the assembly while I focused on the beast.
The secret to a good potato cannon is getting a clean insertion that provides an air tight seal. Any air that can sneak by is air not propelling the potato further down the barrel. I tapered the top of the barrel so that the potato will get cut cleanly as its inserted in.
Here’s the full unit with a good proportion of scale.
And a close zoom on the ignition source.
I was thinking about taking the unit apart and wiring the activation switch to a remote box. This would permit me to build a console that had the kids feeling they we launching a ballistic missile. Given time constraints however, that project will have to wait.
Next step is to RTV the electrical components. Then I just need ammo and fuel to do a test firing!