Christmas fun !

[areofall]

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!

[jonnyboy]

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.

[areofall]

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?

[LCTChamp]

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.

[areofall]

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

[SP00K]

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.

[Lentamentalisk]

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.