jrrdw wrote:water then freeze, sand, plaster, cement, wax. Your imagination is your limit!

Thank you! I'll play around with different weights and materials. I'm trying to stay around 1/2 pound, similar to the tomato paste. We have an industrial printer that just broke down. Permission to destroy!

Hi, folks. I've finally finished my 9' steel cannon, but my ammunition can't handle the pressure. Potatoes turn to shards at anything over 60 PSI, and miniature (2.25" diameter) tomato paste cans also turn to shreds at contact with target (140 PSI). Could I punch a hole in the can, empty the paste o...

I've been trolling Spud Files since high school and have answered a lot of questions by searching through the forum. Good luck with your project! I know this has been dead for nearly a year now, but I've finished it! The cannon is complete and it packs a punch. Test shots have sent mini tomato past...

I machined the piston down a bit. It's still a really tight fit, but air flow past the piston should be sufficient to fill the chamber in good time. I've begun assembly, but am waiting for some stainless steel welding wire to build the flange rear end. Should have this thing wrapped up in a few week...

Yes! The same idea came to me yesterday. Although I hadn't thought of using a high-pressure-cracking check valve. That'd be perfect for seating the piston first. I was thinking of using a small ball valve at first. Thanks! I had to take off a couple mils on the piston. Even though acetal swells less...

I wouldn't drill any holes because it would hurt performance. Let's assume you're filling through a schrader valve, flow restriction in the valve itself is tighter than a gap of a thousandth of an inch between 3" piston and piston housing - so you're not going to help fill rate by drilling any extr...

Thanks for your help! I was considering filling with a 1/4" compressor hose, plumbed with a quick disconnect and a ball valve. My previous guns/cannons were fitted with shrader valves. My only concern is that a shrader valve would be quite slow to fill a 8" by 30" chamber. However, if you suggest th...

Plot twist! I found some flanges to use as an end cap system instead of a threaded cap. This will make for easy servicing of the piston and piston housing. Stoked! Photos will be up on the imgur album soon.

Work has begun! I started with the plasma cutter and bench grinder to make some spacers to hold the barrel centered in the air chamber. I have three questions for you all. 1) The piston (made of delrin, thanks to your suggestions) will be milled down to fit into the piston housing. Since the air cha...

Thanks for the help! I'll get on it.

Hi Folks, The Short: I'd love some help with my plans for an 8ft, 3in. piston, all metal pneumatic cannon. The Long: I've been building guns out of PVC since grade school, mostly sprinkler solenoid or ball valve. One was ten feet long and worked pretty well. Now I'm out of college, and working on a ...