Also, it is really cheap; it only cost me about $13
It really is a very simple, small scale pneumatic cannon. Overall length is about 18 inches, height is 4 inches. The barrel and air chamber are both removeable, which makes it easy to modify.
Step 1: Get parts
These materials I got at Lowes Hardware:
One 12-inch long 1/2-inch nipple (pictures 3 and 4)
One 1/2-inch ball valve with threaded ends (picture 6)
Two 1/2-inch close nipples
Two 1/2 inch elbows that are threaded (screw on) on one end and need to be glued on the other
One 2-inch to 1/2-inch threaded reducer
One 2-inch coupler
One 2-inch cap
These I got at Ace Hardwate:
One PVC Purple Primer (trust me, you need this if you don't want it to leak)
One PVC Cement
One roll Teflon (Plumbers) Tape
2 inches of 1/2 inch PVC pipe
8 inches of 2 inch PVC pipe
MAKE SURE YOUR PIPE IS PRESSURE RATED!
These I got at Schucks Auto Supply:
One pack (icludes two) tire replacement valves for a .453 rim hole (picture 2)
Step 2: Get Taping and then Screw!
Do the same thing to get other bend connected to the 2-inch to 1/2-inch bushing. Again, you should not be able to see the nipple once they're screwed together.
Step 3: Get the Valve on!
Step 4: Prime and Cement
Primer and cement the coupler to the bushing, then the pipe to the bushing and the cap (which has the valve on it) onto the pipe.
Yes, I used the photo twice ;)
Step 5: Ammo Preperation
Step 6: Pump it UP
Check for leaks.
Step 7: FIRE!
Until you have fired it and seen what it can do, please don't fire it within 200 yards of anything of value.
Aim, and flip the ball valve open as fast as you can.
Those movies are two shots I did. Sorry for the crappy video quality.
Step 8: Different cannon, same ammo
It is made entirely from 1/2 inch pipe.
If enough people can't figure out how to build it, I'll do another unstructable
Step 9: Conclusion
Remember to use LOTS of primer and cement. A little overflow is a good thing.
NEVER shoot anyone with a AA battery (some animals are acceptable, such as opossums). Marshmallows are okay.
I know you can use a modified sprinkler valve, but I wanted a cheap, compact, fun little cannon.
I Love friendly comments. Please, no comments about this being dangerous or me being crazy, I already know these things.