There's nothing wrong with potato guns... we love sparking up Right Guard as much as the next geek. But compressed air, now that makes for a seriously fun cannon.
We've been asked several times about building spud guns on Systm. Whether you call 'em spud guns, potato cannons, combustible (or pneumatic) potato launchers... and whether you're shooting tubers, tennis balls or random bits and pieces found around the garage, they're fun. And easy to build.
We built a compressed air (or CO2!) powered cannon on this week's episode of Systm.
We chose pneumatic 'cause they're easier to load, faster to shoot, don't require an ignition systm (tho you can get into some serious mods for the sprinkler valves most folks use to control a cannon) and, frankly, figured building a tennis ball launcher would go over better with the wife than a Potato Mortar of Doom.
Plus, frankly, we're inspired by the cannons Joel Surprise has built at spudtech.com
BTW, if you're looking for a new career, is for sale, along with the spudtech.com URL, the tools to build rifled PVC spudgun barrels, and who knows what all else. The current owner, Joel Surprise, can no longer operate the Spudtech out of his home shop, and he's ready to move on. Bummer, since he's built some amazing cannons.
The heart of our tennis ball cannon is a 1 inch inline sprinkler valve that controls the air flow.
The barrel is 121 inches of 2.5 inch Schedule 40 PVC and the air tank is 6 inches of 3 inch Schedule 40 PVC... we had a second 24 x 2.5 inch barrel ready to go, along with a 12 inch x 3 inch tank, but operator error at the drill press (It rolled off) cracked it beyond repair.)
Using Schedule 40 or 80 PVC is critical. These types of pipe are pressure rated. If you don't see Schedule 40 or 80 and a pressure rating on a piece of pipe and the fittings you use to join them, -don't!!!- use it for this project. It could blow up! That would be bad.
Also, not waiting 24 hours after you glue the parts together is bad... the cement needs that long to set. (Did we mention don't blow stuff up?)
The C02 regulator we used to connect to our tank came from Lowes, it's their Kobalt Portable Compressed CO2 Regulator... it uses regular paintball tanks, and you'll want to buy a few on the cheap to take with you. Or an air compressor. Our 20 oz tank ran out in less than 20 shots! (Fortunately, we had an air compressor we could use, to a 20oz tank is a -lot- more portable!)
If you're thinking you'd rather build a combustible potato cannon, head straight to Build Your Own Launcher at the Joel Surprise's most excellent Spudgun Technology Center. It's the best set of directions we've seen anywhere on building a basic potato gun.
Got any links you think we should add in here? Email 'em to us: firstname.lastname@example.org