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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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saftey of acetlene or oxygen in Sch80

Unread postAuthor: bigbob12345 » Sat Dec 01, 2007 10:31 am

Would it be safe to use acetlene or oxygen if I used Sch80 pipe
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Unread postAuthor: Jokke Himself » Sat Dec 01, 2007 10:51 am

you mean acetylene (ethyne)?

now thats a powerfull propellant! (burns at 3000 degrees doesen`t it?)
im sure it could be used but remember it could shrapnalize your chamber completely if the projectile is stuffed to hard in the barrel
:wink:
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Unread postAuthor: From_Hamsterdam » Sat Dec 01, 2007 10:52 am

no. don't mess with acetlene and oxygen unless you like pipe lodged in vital organs.
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Unread postAuthor: Jokke Himself » Sat Dec 01, 2007 10:54 am

it`s NOT safe

unless you got remote controlled ignition and somewhere to take cover :D
(it will give your spudgun a "little extra power" tho)
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Last edited by Jokke Himself on Sat Dec 01, 2007 10:55 am, edited 1 time in total.
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Unread postAuthor: bigbob12345 » Sat Dec 01, 2007 10:55 am

What about metal would that be safe
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Unread postAuthor: Jokke Himself » Sat Dec 01, 2007 10:57 am

bigbob12345 wrote:What about metal would that be safe



i`m sorry bigbob, but i wouldn`t mess with that stuff no matter what the chamber/barrel is made out of unless you willingly risk your life to launch a potato

(sound like it`s worth it, doesen`t it? :D )
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Unread postAuthor: bigbob12345 » Sat Dec 01, 2007 11:03 am

OKay I guess Ill just stick with propane and hairspray
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Unread postAuthor: Jokke Himself » Sat Dec 01, 2007 11:07 am

bigbob12345 wrote:OKay I guess Ill just stick with propane and hairspray



yup, thats the smartest thing to do :wink:
propane, methane and butane works just fine :D

but if you really need more power, the best thing to do is to build a bigger chamber (or spudgun if wou wish) or just get a slightly smaller barrel (with "smaller" i mean the diameter). :wink:
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Unread postAuthor: bigbob12345 » Sat Dec 01, 2007 11:16 am

Okay Ill turn my 3ft 2in barrel into a 1.5in barrel
and turn my 4in by 1ft chamber into a 2ft chamber
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Unread postAuthor: Velocity » Sat Dec 01, 2007 12:11 pm

bigbob12345 wrote:Okay Ill turn my 3ft 2in barrel into a 1.5in barrel
and turn my 4in by 1ft chamber into a 2ft chamber


Ratios FTW.

If you have a 4"x24" chamber, you are going to need a 2"x120" barrel or a 1.5"x213" barrel!

Keep your chamber the same size (4"x12") and use a 2"x60" barrel rather than 2"x36". This will allow the launcher to be extremely efficient, meaning it will take advantage of most of the potential energy stored in the fuel, and basically allow the projectile to travel very far. You will not be wasting propane this way as well.

And if you really wanted to use a 1.5" barrel, it would still need to be about 1.5"x107" to maximize efficiency.
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Unread postAuthor: bigbob12345 » Sat Dec 01, 2007 12:19 pm

Okay I guess Ill Keep my chamber the same size but I would like to have a `1.5in barrel so would it be okay if I made it 90in long
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Unread postAuthor: jimmy101 » Sat Dec 01, 2007 12:27 pm

There is really no advantage to using acetylene in a spud gun. The energy content of acetylene is really not significantly different than propane or butane, roughly 15% more energy in acetylene. See the spudwiki page on fuels or the acetylene page.

Acetylene has several problems that make it unique among spudgun fuels.

1. It can spontaneously detonate, even in the absence of oxygen or air. It is so prone to autodetonation that a cylinder of compressed acetylene has to have several things added to it to keep the tank from detonating all by itself (usually a mixture of acetone and crushed brick IIRC).

2. It is more likely to reach DDT (deflagration to detonation transition) than most other fuels. If the fuel reaches DDT it is possible to get very high pressure spikes that put the gun at risk of exploding.
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Unread postAuthor: bigbob12345 » Sat Dec 01, 2007 12:32 pm

So it just isnt worth the risk but what about oxygen
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Unread postAuthor: potatoflinger » Sat Dec 01, 2007 2:53 pm

I don't think that you should be using anything other than propane or hairspray, given the dangers of the two fuels that you mentioned, and your level of experience.
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Unread postAuthor: jimmy101 » Sat Dec 01, 2007 3:18 pm

bigbob12345 wrote:So it just isnt worth the risk but what about oxygen

Depends on how you use it.

Usually, if somebody goes to the trouble of using pure oxygen then they use 5x as much fuel in the chamber to go with the pure O<sub>2</sub>. According to GGDT, pure O<sub>2</sub>+propane in a closed chamber will hit ~255 PSIG. Should be within the limits of Sch 80 pressure rated PVC. However, I believe the pure O<sub>2</sub>+propane will be much more likely to reach DDT.

On the other hand, if you use 20% oxygen just so you don't have to ventilate the chamber then Sch 40 is fine.
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