SpudFiles

Now i have been toying with the idea of using hydrogen or O2 in a pneumatic cannon as i heard it is cappable of reaching suppersonic speeds with with different gasses and hydrogen being one of the easyest to make.But storing and using the gas is the problem if i make a galvanised pipe set up i could contain the hydrogen but regulating it out some how is the problem i plan to use it in a copper piston gun so a high pressure isnt a problem but the filling of the cannons chamber is a problem.Any ideas would be a great help.

I will use O2 for my self loading air tank.

i've never heard of using pure oxygen, but i've heard of using H2 or He or heated air to reach supersonic speeds

If you used cold air, it might freeze any rubber seals and make them useless. If you made any spark whatsoever, it would explode, (piston metal striking copper.) Just be careful.

it wouldn't explode because there is no oxidizer in Hydrogen

The molecular weight of O2 is 32 g/mol, whereas the molecular weight of N2 is 28 g/mol. Thus, in accordance to (garham's?) law, the speed of the molecules (and the speed of sound) is higher in nitrogen gas than in oxygen gas - so oxygen gas, besides being a hazard at high pressures (tends to violently react with stuff) is an inferior propellent in a pneumatic.

Hydrogen with a molecular mass of 2g/mol, and helium with a molecular mas of 4g/mol, are significantly better propellents:
Speed of sound in H2: ~3.8 times that of air
Speed of sound in He: ~2.7 times that of air

Well thanks 4 the input the only problem now is the holding chamber(well that is easy galvanised piping)but regulating it out...any ideas because i dont really know what type of pressure it will be making and dont trust air compressor parts if it is higher then 120psi.so any input would be great.And thank you BLB helped there i think i will go for the hyrdogen easily produced.
I'll let you know how progress is going and maybe get my first supersonic marble .

BLB-You must be a math major, you need to add a legend to your post so the rest of us can understand the symbols and abbrevations, i feel kinda dumb trying to understand it. Would a regulator off a big propane tank work? And don't they have perge valves to bleed the air out when filling?

Holy S*^# Its Still Going wrote:it wouldn't explode because there is no oxidizer in Hydrogen

dont start that again.

That's mostly a bit of basic chemistry knolage showing through, but I'll try to translate for someone with no chemistry knolage...

1 unit of oxygen gas weighs 32 grams per 22.4L @ 0*C @ atmopheric pressure, whereas the molecular weight of nitrogen gas is 28 grams for the same valume. Thus, in accordance to (garham's?) law [the ratio of speed 1 to speed 2 = the square root of the ratio of mass 1 to mass 2], the speed of the molecules (and the speed of sound) is higher in nitrogen gas than in oxygen gas - so oxygen gas, besides being a hazard at high pressures (tends to violently react with stuff) is an inferior propellent in a pneumatic.

Hydrogen, at 2 grams per aformentioned volume, and helium at 4 grams, are significantly better propellents:
Speed of sound in hydrogen gas: ~3.8 times that of air
Speed of sound in Helium gas: ~2.7 times that of air

So this means that using CO2 (atomic weight 44) will provide a slower velocity than air or the other less dense gases like H2 (atomic weight 2) and He (atomic weight 4)?

Yes, but the reason we use CO2 is because it's portable, easy to use, fast to fill with, and inexpensive.

I suppose it isn't bad for the environment either. Not exactly good, but not bad...

skrew the inviroment us humans will kill each other befor the world is skrewed by global warming. and john i hope you do make this hydrogen thingy caz i want to se a gun go super sonic (get rid of the mongral cats in my back yard) ( i am too crappy with the throwing knife, i keep hitting it with the handle )

your not allowed to shoot animals.

I wouldn't say that to a guy with a huge hybrid(or at least something big) in front of me.