Login    Register
User Information
We are a free and open
community, all are welcome.
Click here to Register
Who is online

In total there are 33 users online :: 2 registered, 0 hidden and 31 guests

Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Google [Bot] based on users active over the past 5 minutes

The Team
Global Moderators
global_moderators.png CS

Is this very safe?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.

How dangerous is this?

Look's safe to me (as long as used correctly)
No votes
ehhh, should be ok?
Total votes : 17
  • Author

Unread postAuthor: DYI » Mon Sep 15, 2008 8:55 pm

I've had experiences with oxy/fuel in plastic pipe and fittings before. Luckily enough for me, I came out of it with only some cuts and bruises, and minor hearing damage. That was in solid wall ABS pipe, which is a damned sight safer than this deathtrap. I shudder at the thought of what you would look like afterward if this failed when you were holding it.

Consider yourself lucky, and either rebuild it with a suitable material (reinforced ABS, aluminum, steel if you don't care about wieldability), or get rid of the oxygen. Chances are that you wouldn't blow the existing chamber without a burst disk and fuel/oxidiser metering, but I wouldn't risk it if I were you.

And grease on/in the chamber isn't anything to worry about here unless you're significantly pressurising the chamber. That reaction won't start at room temperature at anything other than very elevated pressures. Still, I suppose safe is better than mangled... :roll:
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
Lieutenant General
Lieutenant General
Posts: 2862
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 10

Unread postAuthor: jimmy101 » Tue Sep 16, 2008 10:50 am

Paradox: Very nice first gun. Kind of "swung for the fence" with your first gun eh?

Like others have said, pure oxygen in PVC (with a few non-pressure rated parts) is not safe. That theoretical peak pressure is about 18 ATM (265 PSI) which is really pushing it in a gun with non-rated parts. A typical propane + air spudgun rarely exceeds about 60 PSIG (so non-rated parts are generally OK though I would still avoid them).

In normal operation it is very unlikely that the gun will actually reach 265 PSI since the spud will be long gone before the pressure gets that high. I suspect that's why the gun is still in one piece. My personal view is that the gun should be designed for the worst case scenario. For example, what if the round jams in the barrel? A jammed round will send the chamber pressure very near the theoretical maximum pressure and there is a good chance something will fail.

If you put a burst disk on this gun it would almost certainly explode. Perhaps not on the first shots but eventually something bad would happen.

I would retire the gun. You can salvage most of the expensive parts (metal fittings, gauges etc.) and build a very nice pressure rated PVC combustion using air as the oxidant, or an all steel propane + oxygen hybrid type gun.
  • 0


Lieutenant General
Lieutenant General
Posts: 3160
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 14

Unread postAuthor: JDP12 » Tue Sep 16, 2008 2:29 pm

Umm... I'm scared.

But seriously its a nice first build, but you're holding a pipe bomb.
  • 0

User avatar
Major General
Major General
Posts: 1943
Joined: Fri Mar 30, 2007 8:34 pm
Reputation: 0

Unread postAuthor: AgiTator » Wed Sep 17, 2008 1:12 am

I've dreamed about some day building a gun out of steel welded pipe that I could run with oxy/acetylene or oxy/propylene.

I only use propane in pvc gats of mine. If I were you, I'd stop with the oxy right away! that crap can kill you if the gun explodes!

you should just run propane in that scary lookin' thing. Just my opinion.

  • 0

Posts: 18
Joined: Sat Nov 10, 2007 4:25 pm
Reputation: 0


Return to Combustion Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot]

Reputation System ©'