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saftey of acetlene or oxygen in Sch80

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: octane89 » Sun Dec 02, 2007 12:31 pm

I would think so since you would be adding more pressure into the chamber, and then needing a burst disc or some other self venting valve.
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Unread postAuthor: bigbob12345 » Sun Dec 02, 2007 12:37 pm

Yea it would turn it into a hybrid Ill do so experimenting with this on my other gun which is smaller but is pressure rated I wont go past a 2x mix for saftey reasons because it is only sch40
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Unread postAuthor: jimmy101 » Mon Dec 03, 2007 11:04 am

bigbob12345 wrote:So I will be able to put alot more in the chamber and still have it ignite if I put oxygen in with it which would boost performance but is it safe to do this


Yes. For example, flush the chamber with pure oxygen, then add 20% propane, that gives you a stoichiometric mix. You end up with 5 times as much energy in the chamber. You will get much higher chamber pressures and you may exceed what you gun can safely handle.

Or, add 8% propane to an air filled chamber then add 20% pure oxygen. That gives you twice the fuel load, still a stoichiometric mix, and roughly twice the energy in the chamber.

Or, 6% propane to an air filled chamber then add 10% pure oxygen, ...

Obviosuly, there is an infinite range of fueling options, you just need to end up with 1 part propane to every 5 parts oxygen and stay within the pressure limits of the gun.
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Unread postAuthor: bigbob12345 » Mon Dec 03, 2007 5:37 pm

So how much pressure does a normal combustion get to
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Unread postAuthor: psycix » Tue Dec 04, 2007 5:50 am

bigbob12345 wrote:So how much pressure does a normal combustion get to

Not more then 60-70PSI on a well-made propane injection.
40-50 psi on a hairspray cannon.

Note when using acytelyne and pure oxygen this speeds up the combustion SO FAST this creates not only more pressure because of the more powerful fueling but also the SHOCKWAVE is much (REALLY MUCH) stronger.
And this shockwave is a pressure spike that wont accelerate the projectile much but it DOES make shrapnel out ofyour chamber.
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Unread postAuthor: MikeNice » Tue Dec 04, 2007 9:26 am

My brother told me about a dude he knew a while ago that powered his PVC gun with acetylene. First shot it blew up. He of didn't get hurt bad, a few minor cuts, which seems to usually be the case with combustion cannon failure. But the cannon was completely destroyed. So if you want to invest in an all pressure rated cannon just to blow it up with acetylene, go for it. Wear something to protect for from the fire and shrapnel. Eye protection is a good idea too. Have fun.
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Unread postAuthor: Fnord » Tue Dec 04, 2007 9:50 am

PVC= not shock resistant.
Acetylene= produces shock loads.

I can see a sch80 acetylene gun surviving for a time, but as micro-fractures develop you risk destroying the gun. That's the same reason PVC hybrids have blown up in the past.
It's just not designed for what we're using it for.

Now, if you want to remote-trigger the thing, go for it.


But then is it considered a hybrid?

No, it isn't.
Look up what the word "hybrid" means. It's a combination of two different things working together, i.e. gas-electric cars.

A hybrid gun uses a combination of pneumatic and combustion principles (or others).
An oxygen-enhanced combustion is just that.
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Unread postAuthor: xXunderXcoverXx » Mon Dec 10, 2007 2:06 am

no. don't mess with acetlene and oxygen unless you like pipe lodged in vital organs


I like the way From_Hamsterdam put it. Its defiantly not an option in my book.
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Unread postAuthor: shiftyguy » Tue Dec 11, 2007 11:28 am

I think you guys are nuts for trying ace/o2 in any pvc or abs, i have mixed acedeline and ocygen in a baloon the size of a tennis ball, placed it in a cylender 4" x 14" (metal) and ignited it placing only cardboard on top.... It nealy bloew out my eardrums, and the cardboard had a perfect circle where it sat on top of the metal cylender.

Think twice.... or be cautions...
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Unread postAuthor: octane89 » Thu Dec 13, 2007 4:56 pm

Most of us have said not to use acytelene and possible outcomes if it was used.
Please use spell check too next time-Unless you don't speak english then you get a "pass" card.
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Unread postAuthor: JDP12 » Thu Dec 13, 2007 6:41 pm

Umm don't even think about it. My cousins friend injected pure acetylene into his gun one day and it blew up in his shop. I fortunately wasn't there and no one was hurt, but it just goes to show never mess with acetylene.

I believe it instantly detonates instead of deflagration?
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Unread postAuthor: DYI » Thu Dec 13, 2007 6:49 pm

C2H2 won't "instantly" detonate, but it has a very short DDT run-up distance (shorter than hydrogen I believe), and it really shouldn't be used as a fuel in a chamber that isn't built to withstand DDT. Considering that it is very difficult to pressurise it over 15 psig without it decomposing rather violently, it's slight combustion pressure advantage over propane isn't even really an advantage, since propane can be used at much higher hybrid mixes without fears of autoignition. If you are actually trying to achieve DDT, I would recommend hydrogen, due to its decreased cost, and greatly increased (relatively speaking of course :roll: ) safety.
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Unread postAuthor: JDP12 » Thu Dec 13, 2007 7:22 pm

ah okay.. then thats what happens.. but it pretty much detonates very quickly, thanks for clarifyin that DYI.


haha... i just had a chemistry test today that had C2H2 on it lol
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