So you have a decent sized vacant lot of land (be it farm country, woods, tundra, ice shelf) and you think to yourself, "Hmm...I wonder just how far I can hurl stuff, maybe even into the next county." Or maybe you just like the idea of kinetic energies ten times that of a 50 cal bullet shot out of a sniper rifle. Or maybe you want to get into Punkin' Chunkin'. Well, my friends, you just might want a piston-valve pneumatic cannon.
It'll sure beat the pants out of your neighbor's ball valve pneumatic or hairspray combustion cannon.
Update 2014 - We were young and stupid when my friend and I first built this cannon. We made a lot of mistakes and a lot of safety oversights. I highly suggest reading up on modern potato cannon theory and design before delving into a project of this magnitude. Use your head!
Videos of the recent 2in valve:
Three test shots at 40psi, two with paper towel, the last one with a whiffle ball bat. We were gonna move on to damage shots, but it got dark. I should have damage vids up today or tomorrow.
Videos of the old Mk IV 3in valve:
Preparing for launch, I couldn't find the rocket. So I put in a can of lemonade instead. "There's the rocket!" refers to my sudden realization that the rocket was in the barrel the whole time. Rocket, lemonade, and wadding all shot out over 120 m.
My cannon has a record distance of 1900 feet (using Google Earth along with terrain mapping - it happened to land right between two distinct knolls that I could see from GE). That was a 70 psi shot with a 2.5in x 20ft barrel that was so long it needed it's own suspension system.
I have a video of that shot somewhere but I have it find it I'll post it as soon as I do. That was also the shot that broke the cleanout cap.
During the testing phases, the cannon was barely charged halfway, so I could get away with plugging my ears. I make sure to grab hearing protection for anything 65+ psi.
For these two shots we had an audience.
They were thoroughly impressed:
This shot, something caused the piston not to actuate, and we had a dud. They weren't as impressed :-P: