This is my largest pneumatic cannon which can fire potatoes and other projectiles through ply wood board at close range. I usually pressurize the cannon to about 100psi. I think that this cannon is ideal for an amature to build, as long as they know how to solvent weld and select appropriate materials correctly. It can fire a potato about 200 meters when using a high pressure and fired at 45 degrees.

I did not base the cannon dimensions on a specific chamber to barrel ratio - I made an educated guess from comparing existing cannons. A cool effect is after firing, a white mist of steam exits the barrel giving the classic just fired look of a gun.

All piping/plumbing components are made from pressure rated ABS - 120psi.

• Two 50mm Ø, 90°, bend
• 50mm Ø, 1200mm long pipe
• 40mm Ø, 1200mm long pipe
• Two 50mm Ø, double socket
• 50mm Ø, access plug
• 50mm Ø, 60mm long pipe
• Two 50mm Ø to 22mm Ø tundish
• Two 22mm Ø, 80mm long pipe
• 50mm Ø to 40mm Ø reducer
• 50mm Ø, 190mm long pipe
• 50mm Ø, 220mm long pipe
• 22mm Ø, levered ball valve
• A car tire valve
• 50mm Ø, 10mm long pipe (or ring)
• 50mm x 50mm sheet of 5mm squared wire mesh
• Solvent weld cement

Note: Method for preparing surfaces that need to be solvent welded are as follows:
Prepare the two surfaces that are to be joined by lightly sanding them to roughen the surfaces and clean with methelated sprits or some other cleaner, then apply the solvent weld generously to one face of the material and then promptly push them together firmly.

I solvent welded the two 50mm Ø, 90°, bends; the 50mm Ø, 1200mm long pipe (chamber pipe); and a tundish together as shown.
I then solvent welded a double socket and access plug to the other end of the chamber pipe, also shown in photo.
To add the car tire valve to the access plug I simply drilled a tight fitting hole in the centre of the access plug 'cap' and inserted the valve.



I then made the valve fixings. Using a 50mm Ø, 60mm long pipe and the ball valve fittings, as shown in the first picture, I solvent welded the pipe into the tundish and screwed the parts together attaching the ball valve (making sure that the ball valve was in the correct position for firing) using pluming wrench to make sure they were tight. I did this for other tundish to complete the valve section.





To stop potatoes from getting stuck in the tundish/reducer section, I used some wire mesh and a ring cut from an ABS pipe. I solvent welded the mesh to the inner face of the reducer and then welded the ring inside to hold the mesh securely in place. See photos. The barrel can now be solvent welded into the tundish.


To make the cannon structurally strong, I made two separator supports to fit between the barrel and the chamber. The support nearest the valve is positioned between the chamber and the tundish attached to the barrel. I did this by cutting the pattern shown in the photo to a short length of pipe, which fit flush with the walls of the tundish/chamber. This was then solvent welded into position. The second support fits flush with the end of the chamber and slots over the barrel (the barrel passes through a hole in the support at 90°). This is then also welded into place.




This is the finished cannon:

This is just a small guideline to operating the cannon - to get best results you will need to practice and develop you own methods of operation.



• Unscrew the access plug to allow air to freely pass through the cannon before loading a potato/projectile.
• Load a potato (or other projectile) into the barrel and ram it down to the other end.
• Screw the access plug back onto the chamber tightly and connect an air compressor or foot pump to the tire valve and pump to desired pressure.
• Aim well and sharply release the ball valve.