Step 2: Assembly

-Cut the 3" pipe to about 13" or a size you prefer (the larger the combustion chamber; the more gas; the more boom)
-Make sure the reducer fits over the pipe
-Spread some ABS cement on the inside of the reducer and outside of one end of the pipe, slide the reducer onto the pipe with a twisting method
-Repeat this for the threaded adapter
-Repeat this for the barrel (5' of 1.5" pipe)

Make sure your gluing is done properly, you dont want it to explode.
_Con5 years ago
Just make the combustion chamber galvanized pipe, then use a threaded bell reducer down to sch.80 pvc for the barrel . Will work perfect, not as heavy as a full galvanized pipe gun, but as strong as one.
Turnip1235 years ago
Especially since this instructable has become so popular, I though I might let you know the potential safety problems with ABS.

Unlike PVC, ABS is not rated for any type of pressure, and is actually a more dense version of Styrofoam.

I built a potato cannon like this about 2 years ago, and it was going great until the threaded adapter, shot off, engulfing my friends hand in flame and giving him severe 3rd degree burns.

I love potato cannons, and really wouldn't want to flag this, could you just change the materials to PVC? Those are actually meant for pressure loads.
matt (author)  Turnip1235 years ago
PVC is not good for combustion cannons. It will break.
ABS is fine for combustion.

PVC is good for pneumatic cannons. Make sure you use schedule 40 PVC this is good up to 220psi.
ABS is not strong enough to use for a pneumatic cannon. It will shatter.
Turnip123 matt5 years ago
Pneumatic and combustion both are rated by PSI, a rapidly expanding (combusting) gas, is liable to shatter ABS (due to a less uniform design/brittle material).

Therefore, should the potato get wedged good enough, you could have a similar/worse experience than that of my friends.
mr.break_it5 years ago
12,000 volt ignitor work?
1196626 years ago
will the pvc melt under the explosion?
grim5512216 years ago
the abs sement dried quickly, and getting the gas to axyigen ratio isn't hard, bud if you get it perfict, it shoots far!!!!!!!!!!!!!!!!!!!!!!!!!!!!1 SAWS ARE AWSOME 0)
mavogt7 years ago
also make dang sure you glue dryes fo at least 12 hours or the fumes in the glue can ignite and that is really bad. I also prefer PVC
DR..7 years ago
im scured of saws!!!!:(
you cant put too much gas in, you need the right ratio of gas to oxygen for it to ignite