SpudFiles

Got a little problem here (well little, prity big actualy). I want to build a spud gun and i was looking around in the shops here for parts. I found PVC-pipes, but non of them had a pressure rating on them.

The pipes have a thicknes of 3.2 mm. Will that do the job? Or are they not strong enough. I want to use a pressure of approximately 7 to 8 bar (100 to 120 psi) I also found PVC pipes, only 2". Bigger pipes are just plastic.

Those pressure resistant PVC pipes, what are they used for in real life ? Also the sprinkler valves, are they used in gardening or in fire prevention. Can't find those eighter.

I was very hapy to find a cupper pipe of 16 mm inside, so I can shoot marbles

Don't trust non-pressure rated pipe with pressure, if it ruptures you could be killed. Just get pressure rated pipe, if you can't then use metal.
Pvc pipe is used mainly for transpotation of water. Sprinkler valves are for controling the flow of pressurized water and are used in irrigation.

If you have found copper pipe why don't you just make a cannon completly out of metal, it has advantages, like being able to re-use fittings and pipe.

yes, that's true, but the biggest pipes i found, were 22 mm on the outside. I guess i could go to a metal shop where they weld things of all sort on demand. Could ask them to make me a nice big container to use as a chamber. OR i could look for a fire destinguisher of 3K or something.

You are talking about copper pipes right? Generally, anywhere you can obtain metal fittings you can obtian metal pipe. You can use comression fittings as an adapter for the copper to the metal fitting(usually galvanized). You can make your own chamber with metal fittings alone if they don't have large diameter pipe. You could use a fire extinguisher but you would still need metal fittings.

yes, i'm aware of that. Metal fittings are no problem. Worked those on my water rocket launcher.

If you can find a machiene shop then you must definately get a custom made chamber. Ask them to weld bolts to the chamber so you can attach various things and make body parts for it. You can't just weld nickle based metals. You need to silver solder them together. This can be done with a propane tourch. Silver solder is more expensive then normal welding sticks though.

I can also simply screw them in a hole with teflon, can't I ?

Yes you can.
You can also order pressure rated PVC from Holland at "www.bouwplastics.nl"

THey are the best of only three shops in Holland who sell pressure rated PVC in Holland, and they are around the corner to my house.
I've been searching for stuff like that for years, and only a month or four ago I found out I live near them.
If you live close to Baarle-Nassau/Hertog I can even buy it for you and meet you there...But I warn you..I aint pretty hahahaha!!

Copper pipes are commonly found no bigger than 22mm, if you go to proffesional fitting suppliers, you can find 28,35,42,and 54 mm.
They cost a fortune.
Galvanised pipes and fittings have even higher pressure ratings, but are rougher on the inside ( seam from welding) and the T's I have found do not lend themself to building piston valves with them too well.Sizes are most commonly 3/4 inch, or 1inch ( duims noemen wij dat)
1 1/4, 2 and 2,5 inch are again only availible through pipe wholesalers, who normally only sell to proffesionals.

Ya, but I am talking about soldering stuff to the outside. Although I will be silver soldering the chamber on my shotgun together to form one piece. It should look sweet. You need to apply sh!t loads of teflon tape to threads to seal them on metal fittings, an experience that has set me back many times.

*Brian beat me *

I could use galvanised pipes for the chamer, get a real high pressure. T-parts to make valves are no problem, I work two copper pipes inside a T-part, like on this topic

The barrel should be copper then, cause of the smood inner side. Right outside the T-part, the barrel could be made stronger for the high pressure in the beginning, when the ammo passes true

An intresting way to make a barrel stronger, is to surround it with a much bigger pipe, for instance the barrel is a 18 mm copper pipe, the second pipe is a 40 mm pipe. The space in between you fill up with melted lead. When this sets, you get a realy strong barrel. These concept is also used in home made cannons with black powder or any other explosive.

Anyone got any idea how much pressure a galanised pipe can stand ? I mean, 250 psi (18 bar), should not be a problem ?

No that's no problem at all
It is rated for 25 Bar ( working pressure) but can take 40 according to Killah gorrilla.
BLB has even claimed it can hold unregulated CO2 at 60 bar.
It's busting pressure is really really high!


Copper can take 22 bar at least.I've done it without a problem.
The topic you linked me to, I know very well.

BTW Brain ... Where do you get the sprinkler valves ? Or don't you use any ?

Don't use 'em.Not easy to find.

Well .. www. tuinberegening.nl has some, but they are ridiculously expensive

I'll see about that

You could order a quick exhaust valve from overseas. They arn't that expensive and you can get them in small sizes. I haven't seen any here but I am sure they are around somewhere. If you surround the barrel with lead you will have a very heavy barrel. Another approch is to surrond it with a bigger pipe screwed directly into the tee, this will make it a co-axial but very strong. Becuase the main chamber is at the bottom of the tee you don't need to worry about resticting flow in the co-axial part of the cannon. So you put something around the barrel to stabilize it in the bigger pipe. You join the barrel to the larger pipe with a link on the compression fitting, with the compression fitting you reverse the direction the barrel sticks out.