SpudFiles

Hi, total new to this but seen a guy making a cannon on another forum and though this would be a bit of fun over the hoildays. Just really copying his simple design but now I'm wondering have a made a error at the start.

Sorry no pics but here is the basic idea. I made a metal tank today with a internal dia of 100mm and a length of 200mm (0.0016m3 I think) with a standard quick release fitting for an air compressor The tank will be welded up and was going to fit a 3/4" ball valve about to the centre of the opposite tank face and fit about a 36" barrel to suit by threading the barrel into the ball valve. The welds are of a high quality, tank is pre heated and mig welded and 100% leak free and the metal is about 5mm wall thickness, just wondering is 80-90psi safe for this and would it be powerful enough to fire a potatoe slug? Also I was thinking about spraying WD40 oil into the barrel to reduce slug friction? Is this a good idea?

If you think this is un safe I will destroy this as it's only for a little family fun, safety is the most important factor!

what are you asking?

The big thing I see is that hes using 5mm metal for a cannon that uses about 100 psi. You can use pvc for pressure like this. He also states using a ball valve... I would upgrade to a sprinkler valve for better performance.

The ball valve is just what I have about but I can increase the siz of the valve and barrel or decease the size to help performance?

Metal can usually take pressures up to 300psi unless it is cracked or thin. The WD-40 really isn't necessary as the water in the spud works as a lube. For your first gun a ball valve will be alright, but if you want a really powerful gun I would suggest a QEV.

Forgive me whats a QEV? It's probably getting late to have parts delivered befor Christmas but can I get any thing similar?

Burst disk valve to the rescue!! Jk. But if you don't have much time on your hands, you can shoot it with a burst disk and later whehn you do have the time. it would be pssible to weld on your other components.

Well if you really trust that the welder is a top notch one, then go ahead. Usually welders will need a license in order to be allowed to make pressure vessels. Why not just use standard malleable iron pipe and fittings? It is a ton faster, safer, and probably will end up being cheaper for you, because you can just unscrew them to mod your cannon.