Originally published: 2002
After building my first combustion cannon I wanted to try a cannon that was slightly different. The pneumatic cannon works on the principal of using compressed air in a sealed chamber to be suddenly released to propel a potato rather than using the combustion of a propellant. This cannon was again build using basic heavy duty plumbing materials and operated up to a pressure of 100psi. The following content is from the original project page.
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
Construction of the cannon
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.
Here is the cannon completed – I do like the double-backed design of this cannon!