It's built completly out of Sch 40 PVC, save for the Sch 20 barrel (wrapped in duct tape) that I use to launch tennis balls and cans of spray paint. Both barrels are a 2.5 inch outside diameter, but the tank is a 3 inch outside diameter.
I didn't expect it to as a powerful as it really is, but it's got some pretty serious kick behind it. My theories are that I used a large steel ball valve, and a long barrel to allow more time for the projectile to accelerate with the expanding air behind it. I also think that it was because the tank was built large enough to supply air for the projectile's entire trip through the barrel (to not experience a vacuum effect towards the end), so it can really send something flying. Shot at 90 degrees relative to the ground it can, with about 80 or so PSI in the tank, launch a tennis ball into the air for around ten seconds, which is ROUGHLY (without figuring in air resistance.. a rather large factor..) 125 meters. The cannon design was loosely based off of the design of "Pnewton's Petard" from the book "Backyard Ballistics" (An AWESOME book if you like this kind of stuff)
Any Questions or comments?
-Vice
