I built this cannon in late 2010 and early 2011, although I had begun work on it long before that. I started building the basic shell (the copper chamber and barrel and associated fittings) sometime in 2009, and merely finished it in 2011.
- Chamber: 48" of 1" type L copper tubing
- Barrel: 72" of 3/4" type L copper tubing
- Valve: barrel sealing piston valve, check equalization
- Over/under design
I originally built a track pump for use on this cannon... it was pretty fiddly, and I barely managed to get it operating up to 300 PSI, not to mention it took a lot of work to pump the launcher up this way.
So, I eventually ripped an air-conditioning compressor out of an old window unit, and modified it to pump air instead of refrigerant (as simple as connecting a filter to the low pressure side). I frequently used the gun at pressures up to 400 PSI after this.
So anyways, here's some pictures:
To load, the barrel was undone at the union and slid forward in the mounts. The mounts were steel pipe nipples with green velvet glued on the inside. The barrel could then be breech loaded.
The piston and pump were the more challenging things to make. The piston is a floating o-ring design which allows equalization one way, while preventing air from flowing into the pilot volume when exhausting gas behind the piston. The pump went through numerous changes, and eventually was resized very carefully to provide a leak free piston. Two check valves at the bottom controlled inlet and outlet.
The pump usually got me floating around 300 PSI. I eventually replaced it with a refrigerant compressor which could go up to 400 PSI (and more if I were willing).
A short compilation of blasting some household food-stuffs...