hybrid idea

[cardinals08]

The teacher did a demo in chem class today. she put little zinc pebbles in Hydrochloric acid. It made a reaction producing zinc chloride and hydrogen gas. then she covered the test tube with her thumb, lit a toothpick, removed her thumb and put the toothpick there, it made a pretty big flame that looked like it would be good for a combustion, and the hydrogen would also build up pressure in the chamber. Im not sure how high the pressure would get. Probably not enough to be considered a hybrid
If nothing else, you could do this for a semi auto combustion because it will continue to give off hydrogen so you could keep clicking and it would keep firing. You wouldnt be able to use copper tubing for the chamber though, because the HCl would react with it and begin to eat away at it. It probably would with PVC to though, so you would need to find something that wouldnt react with HCl.
just an idea

[drac]

We've been over this numerous times that hydrogen or H2 is just too dangerous to use in a cannon. I recently spoke with a member who blew his trash can to pieces with H2, I believe it's on the spudtech forums. If that is the power of hydrogen, then I wouldn't even touch it with a cannon.

[cardinals08]

ok, it did seem pretty powerful, good thing i didnt try using it before I posted
thanks

[boilingleadbath]

Drac, did you acctualy just compare a thinwalled, large diameter, container (with a flat end) that isn't designed for pressure (the metal ones not even being welded if I remember) to sch 40 PVC pipe?

... I mean, that'd be like saying that hairspray was able to blow up a toilet paper tube, so we shouldn't us hairspray in cannons.

calculations:
plastic can:
.1" walls
24"diameter
24"*pi/2/.1"*50psi = ~20,000psi hoop stress in material (plastics typicaly have a tensile strength of about 7,000psi)

metal can:
.05" walls
24" diameter
24"*pi/2/.05"*50psi = 40,000psi hoop stress (mild steel has a tensile strength of about 30,000psi)

[NeoSpud]

Regardless, using hydrogen in a cannon is a very bad idea in my opinion.

That H2 creation system would be messy and dangerous, too.

It wouldn't have any real use for semi-automatic because you still have to exhaust the chamber and bring in oxygen. If you were to have that running the whole time, perhaps it would work but it would be horribly inefficient. I wouldn't do that anymore than I'd have a 1psi constant flow of propane into a cannon. Its just wasteful.

[nicholai]

kinda like tossing some oxygen/acetylene into plastic pipe, not a very good idea.

take for example propane, roughly a 4% fuel to 96% air ratio is optimum. However this is considering that the air we breathe is around 20% oxygen (higher elevations are even less). I found out one day that oxygen from the tank is pure 100% hardcore oxygen, the shit is flammable in its own state. and therefore you can add a lot more fuel into the chamber by using 100% oxygen. well i wouldnt reccomend this because it will definatly blow up on you. we were lucky it had a 20 foot cord for the remote switch.

[boilingleadbath]

The mentioned reaction produces H2... there is no O2 produced, so you can't change your chamber with an enormous amount of H2.

It's been stated before: H2/air has the same energy/volume as C3H8/air. You won't get any more pressure from it (which is the best answear [IMO] to these questions anyway - just tell them it's not any better than C3H8), although I'd have to check the burn-front velocity... it'll almost certainly be subsonic so you almost certainly won't cause a chamber failure.

Cardinals08, you havn't gotten to the activity series yet, have you? HCl won't react with Cu, although I can't garantee it won't react with other things they alloy with the Cu to make copper pipe.

People have acctualy done C2H2/O2 mixtures. In one case, an ABS threaded fitting cracked after a dozen shots or so. In the other, the ABS barrel fell off after several shots.

[nicholai]

i ripped a 4" long hole in an abs chamber one time with oxygen/acetylene. on a seperate occasion i shot a 4' long sch 40 barrel about 30 yards while the bouncy balls wrapped in packing tape went another 100 yards. thats why i dont like using abs for big guns and i dont like all purpose or one step cement.

[regre7]

Has anyone here ever heard of the Hindenburg?

[boilingleadbath]

And you think it wouldn't have gone up in flames if it was filled with propane?
(ignoring that it would have never been set on fire, because propane doesn't float very well, so it would have never have left the ground and gotten the electrostatic change required to ignight it)