SpudFiles

Would it be safe to use acetlene or oxygen if I used Sch80 pipe

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

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

it`s NOT safe

unless you got remote controlled ignition and somewhere to take cover
(it will give your spudgun a "little extra power" tho)

What about metal would that be safe

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? )

OKay I guess Ill just stick with propane and hairspray

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

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

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).

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

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.

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

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.

So it just isnt worth the risk but what about oxygen

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.

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 O₂. According to GGDT, pure O₂+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 O₂+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.