These are the basic plans for a silencer that can be adapted for any diameter barrel your potato cannon might have.
If you want to read up on the principles behind the design of a silencer, this is a good website to explain.
The quick and dirty of the principle behind this design is to develop a device to allow the pressure generated by the combustion to to be dispersed slowly as it exits the barrel of the canon rather than very quickly, which would create the characteristic loud bang similar to that of a gun.
Step 1: Materials
- 1 pc ABS pipe about 1/4 the length of your barrel & same ID (I used 1-1/2" x ~15")
- 1 pc next size up, 1.5 inches shorter (should slide over 1st pc with a clearance) (I used 2" x ~13.5")
- 2 couplings to adapt above 2 pcs of pipe to each other (I used 2 x 1-1/2" IPEX couplings)
- one can be cut back a 1/2" or so on the 1-1/2" side, but this isn't necessary (see picture of finished asmbly in step 3)
OPTIONAL MATERIALS (see step 4)
- ~2" long pc of abs pipe that is a tight slide fit onto the end of the barrel of your canon.
- 2" hub (see picture) (I used a 2" NO, stainless steel Hub by TYLER CPLG CO. it has 2 x 2" screw clamps, and a piece of rubber to wrap around the two pieces being coupled, and a thin piece of steel to cover the rubber)
Next time I'm at Home Depot or whatever, I'll see if I can get more info on that hub. It was only a few bucks, and I'm sure you can rig something up on your own with similar components.
- screw driver or wrench for hose clamps
- hand drill
- 5/16" & 3/16" drill bits
- ruler (a square would be best)
- scribe or something to mark cuts etc on pipe with
Step 2: Drill the Pressure Release Holes
The shorter piece of large OD pipe will be drilled in the same fashion but with 3/16" holes.
This design is pretty forgiving so do your best to make something that resembles this and I'm sure it will be fine.
Step 3: Glue Inner/outer Pipe to Couplings
Next, apply ABS cement to the end of the large OD pipe and press into coupling. The rows of holes should be offset by 45 degrees between the inner and outer pipes. IMPORTANT! Press all the way into coupling.
Next apply ABS cement to the open ends of both pipes on the OD and press second coupling into place. Note that I cut about a 1/2" from the length of the 1-1/2" end of the coupling to make it look a bit better. Not necessary, but you'll have to adjust the length of the small OD pipe accordingly.
Step 4: Optional: Install Hub to Lengthen
I didn't think this was reliable enough so I added an extension to the silencer which is where the "hub" was used. Basically, a piece of ABS the same diameter (ID & OD) as the small end of the coupling is butted up against the coupling and the hub wraps and clamps around the seam to join them. The rubber piece of the hub should squeeze through the joint as the clamps are tightened and will create a small rubber seal which will grip the barrel of the canon when the silencer is installed. I hope from the photos you can understand what I mean.
With my silencer installed, the canon now sounds more like a loud hand clap than a shotgun when fired.