Copper Pneumatic Air Cannon

How to create a powerful air cannon from copper pipe and fittings, for very little in the way of cash.

Step 1: Materials

Materials
1.5m (5ft) of copper pipe
One 22mm elbow
Two 22mm endcaps
Two 22mm elbows
One 22mm Ballvalve
One tire valve
Solder
Flux
Ammunition

All pipe in this project can be any diameter, however, as the pipe size increases, so does the bill .
A good chamber:barrel ratio by volume 1:2, however you can change this to suit your needs. A gun with a barrel which is either too long or too short will not be more powerful, but rather less. You can use the Gas Gun Design Tool Tool to find out this length. The ".GDT" file is the saved data for my gun.

As a UK based user getting copper is simple. Many plumbing and hardware stores stock it. I highly reccomend BES Gas and plumbing supplies. I suspect the situation is similar in the US. Ballvalves are very common, and can be bought from most plumbing stores.
Flux and solder will more than likely be available in the same store.
A tire valve can be got from any auto store, or ebay. I got 10 snap in tire valves off ebay for �3 posted. nd they are perfect for this project.

Comments

[struckbyanarrow]

did you sweat the pipe together?

[Biopyro]

I believe they're the same thing under a different name.

[Biopyro]

If by sweat you mean solder, then yes.

[struckbyanarrow]

i didn't know soldering or sweating would hold pressure. will try in the future!

[Biopyro]

It certainly does. At higher diameters, the pipe itself will burst before the solder joint does.

[struckbyanarrow]

wow, thanks! i am looking forward to building my next cannon!

[flashanimator]

If i were to make something like this, i've made pvc air cannons before, could you take a 1/2" piece of copper pipe about 1 or 2 feet long, put an end cap with the tire valve on it, and on the open end just use either A) a ball valve and another piece of pipe for the barrel, or B) use a coupler and reducer to make the barrel even smaller, or bigger.
So the design would like -----------OOOOO-    with the dashes being the barrel abd the zeros being the air chamber and last dash being the valve. Also could you use pvc cement to join the pipe together or do you have to solder it.

[Biopyro]

Yes you could do it in that layout, but to connect copper to PVC you would have to use a threaded joint.
Something like a 22mm x 3/4" M adapter (soldered to the copper) would allow the copper to screw into a 3/4" threaded ball valve.
If you want to use PVC for the barrel you may as well use it for the whole cannon. There's not much point using both because then you just have the price and heaviness of copper AND the fragility of PVC.

[deNZil90]

Would Mild steel work or is it best to use copper piping?

[Biopyro]

mild steel would work, but the ends need to be threaded or you have to weld it. I chose copper because it's available, and lighter (not as thick)

[deNZil90]

welding is not going to be a problem just wanted to make sure that its going to be safe thanks

[skimboarder33]

is coppper safer than abs?

[Biopyro]

22mm copper has a safe working pressure of 51 bar. Even if you did take it high enough to cause damage (60-70 bar), it would swell, then split. At lower pressure ABS splits without swelling, and at 60 bar, if you got it that high, it might split catastrophically. TL;DR yes, but ABS is still very safe IF IT HAS A PRESURE RATING ON THE SIDE

[MJRSnyder]

how do u attach the valve at the back?

[Biopyro]

What do you mean "at the back"? You can buy "snap-in" tire valves off ebay or from an auto parts store. You drill a hole a little larger than the stem, then pulle the tire valve through with pliers. It should seal perfectly above 1 bar.

[LED master22]

i ment PVC ball valve and not OVC

[Bugman9]

iounce shot my airgun at my bike 50 feet away and it came back at my head and got me.

[i wanna do that]

ermm i have a question, i live in the uk and i cant find pvc ball valves at all, firstly can a metal ball valve be used on pvc piping and what glue did you use to stick the bike valve to the end cap? Because i am thinking of jus making a simple staright cannon(chamber with end cap woth the bike valve on it,which leds to ball valve which leds to the barrel) thank you and write back please

[Biopyro]

I used a metal ball valve, what's the problem? I used only a little epoxy glue. If the hole is a good fit then the force of the air against the rubber around the base of the valve will push it against the rest of the endcap. Hope this helps :)

[i wanna do that]

yup helped a lot....so it is possible to use a metal ball valve on pvc piping then

[Biopyro]

Yes, they have the same threads, so the just screw onto each other.

[afrodude99]

good work keep it up

do you like mine my copper cannon

[ryanohal]

isn't it awkward to fire

[Biopyro]

If you want to fire it by holding it then yes, but you can get much better performance by having it on a flat surface because you can hit the valve open faster.

[binnie]

how about joining them via sweat welding?

[Biopyro]

I can't say i know what that is, but if it can stick copper, it'll work.

[binnie]

uh plumbers sweat weld the joins they do heat it all up then little 'solder' and a capillary action sucks it all in or sumfin like that

[n0ukf]

It's just a difference in terminology for the same thing. Though "welding" is the wrong term in this case since you're using a different metal (alloy) to join the copper. For welding, you'd need to melt copper to join the copper pieces together.

[Biopyro]

thats what soldering is

[monkeybiker24]

thank you, my cousin also made one, but better. You can see it at
http://www.youtube.com/watch?v=N8L4iVazozs

and him shooting it at

http://www.youtube.com/watch?v=A0pX_-v_Jbs

[monkeybiker24]

i didn't use this DIY, but i did make this air cannon, it's the exacte same idea, just remodeled different. Take a look, you can swap barrels for different diameter sizes, i used a bit of ABS for more air room.

[Biopyro]

That's a nice cannon, I like the Idea of addidng some ABS to increase the chamber size, make sure it's pressure rated though!

[dogfighter 45]

do you think a wider berrel would make it work as a paintball mortar

[Biopyro]

Definately, but you'll want a bigger chamber and valve too. You might also want to change the structure.

[uvalacrosse]

do you have to use a blowtorch or can you use cement or superglue?

[Biopyro]

If you can solder it do, it is definately the easiest and imo best way to do it. Otherwise you can use compression fittings, which screw on and are re-useable.
There is a copper glue product a available, for more info check out Just for copper
This glue was used for the winning design in the UKSGC competition.

[lemonie]

What are you pumping this up with, and roughly how much pressure do you achieve? Your reservoir is small, any thoughts on adding a tank to this?

[Biopyro]

Adding a tank would do next to nothing, because the barrel is very small. The gun will take up to 300psi, but using the bike pump i have gets around 150psi

[iamcroweman]

What would happen if you shot flour like that over a campfire. something maybe best done remotely

[irwinner]

ball valves open really slow, make it a piston valve, or atleast make the ball valve spring loaded, i t will GRAETLY improve preformance