Hydrogen powered spud gun - now with a video
 

I was wondering if anybody has already done this...?

Right now I am setting up to make a hydrogen powered spud gun. My hydrogen/oxygen production unit is nearing completion, loosely based off of this site:
http://www.fortunecity.com/greenfiel...6/hydrogen.htm

Using my cosmic power of solving PV=nRT and the specific heat/heat of formation of water, I have determined that the heat generated would handily melt PVC, and that output pressure should be about 8.35 times the input pressure of H2 + O2 mix. It goes without question that there is a good chance this gun will blow up.

In order to simulate the various conditions of a gun of this type, I plan on writing a java program that takes all sorts of things into account.

These things should be important:
Volume of chamber and barrel
C/W of PVC pipe
Wall thickness
Ambient temperature
Ammunition displacement versus time (implicit differentiation to come up with related rates of pressure vs temperature vs ammo position)
Mass, size, shape of ammunition
Air drag information on ammunition
Spark location
Flame front speed, temperature, and location

The idea here is to calculate peak pressure and temperature that the gun will be exposed to, and to calculate if the pipe will hold or explode.

Any thoughts? I'll be posting back here as I make progress.

EDIT:
Video of an exploding balloon using fuel made from my completed electrolysis unit. here

Just use 4% propane. It's a lot easier and a lot less likely to kill you.

Also, use ABS, not PVC. It'll crack instead of shattering and you'll be kicking yourself instead of riding in an ambulance.

And, no matter what you use, put some sort of scatterblanket on it. It's a lot easier to open it and shake pieces out than to open you and pull them out.

I was definitely planning on using PVC for this because of its cheapness and availability. I also have a large steel tube that the whole thing is going to slip inside of just in case of explosion. I also plan to have a wireless detonator so I can be way far away from the thing when it fires.

Safety first!

I used propane for a while, and while nicer than hairspray, it just doesn't have as much bang as I would've hoped. This hydrogen combustion/compression hybrid should be quite a bit of fun.

Also, progress on the electrolysis rig is good, I have acquired the mesh from a friend. :)

Here are the endcaps I have made thus far. This constitutes most of the work on the electrolysis setup.

http://img94.exs.cx/img94/1345/hoh-caps-barbed.jpg

looks cool... sounds like youve got things under control with the remote trigger and the metal shrapnel casing.... should take video of firing it for us...

Unfortunately, for video I only have a crappy old Intel webcam. It'll work, it just won't be very impressive, or have sound. :(

I'll definitely see if I can get my paws on a real camera. A friend of mine is a cameraman at one of the local TV stations, perhaps he can use his uber camera to film this.

Well, the H2 O2 rig is almost done.... it works too, but I have a small leak in one chamber that I need to fix.

Also, a car battery charger is an excellent power supply for this purpose.

Fixed one leak, now I found one more that only manifests itself at high pressure. It is between a fitting and a valve. More teflon is required.

Anyway, here's a test of a water balloon filled with hydrogen and oxygen:
http://home.insightbb.com/~kleptophobiac/H2.avi

Has anyone else told you that you're fucking insane? :)

Yes. Many times... but I'm still here, right?

How's the rig coming?

I've had a setback with the hydrogen generator. I'm engineering a better solution now.

I forgot about the (aluminum shroud + steel eye) rivets in my setup, and I managed to destroy my anode (accelerated by the presence of an electric field) and turned it into a combination of aluminum chloride and aluminum powder. Whoopsie.

My next unit will be 100% copper/brass and should not corrode anywhere near as fast as my aluminum setup did.

As for the gun itself, I have procured a source of solenoids and fatter pipe. The gun won't be completed for at least a month or two due to time constraints. The hydrogen generator must also be in good working order before I can build a gun to use the fuel it makes.

Finally, I found my camcorder (from 1987) but it does not power on. I'll see if I can't breathe some life into it during my spare time.