PVC Bangsite Cannon
This is a cannon a friend and I made from PVC pipe, loosely based on a cannon first published in Popular Mechanics magazine back in the 70's. The one from PM was a little more elaborate (and expensive) but this one works very well and is very loud (and very safe). It doesn't shoot anything but it does make a hell of a boom! The charge comes from powdered calcium carbide which, when mixed with water, produces acetylene gas. All the parts are available at any plumbing supply or home improvenment store and should cost less than $50.00, and I have included a link below for the calcium carbide.

Parts List

2' x 4" PVC pipe
1' x 3" PVC pipe
1 x 4x3" PVC adapter
1 x 4" PVC Tee
1 x 4" PVC Cleanout Adapter
1 x 4" Threaded Plug
1 x 4" PVC Cap
PVC Solvent Cement (and Primer if you're a plumbing purist)

 

First, cut the 4" PVC into 2 pieces, a 6" piece and a 18" piece. You can see from the photo how the whole thing goes together. The only thing not shown is a 1/4" hole drilled into the top of the 4" Tee. This is where we'll load the calcium carbide and light the cannon off.

Just cement the whole thing together except for the cleanout plug, which just gets screwed into the cleanout adapter. Let it dry for a little while and it's ready to go.

With the cleanout plug in place, pour about 1 cup of water down the muzzle so it settles in the cleanout adapter. Get (or make) a small funnel and pour about 1 teaspoon of powdered calcium carbide into the touchhole. You'll have to play around with the amount of CC to get it just right. Rock the cannon back and forth for a few seconds and light the blowhole! There should be plenty of water inside for more shots so just add more calcium carbide, rock and relight!. The neighbors will be impressed. Fun stuff!!
When you're done playing, unscrew the cleanout plug and hose the whole thing out. That's it!