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H2 and O2 cannon?

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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H2 and O2 cannon?

Unread postAuthor: Deli » Sun Apr 27, 2008 2:54 pm

Has anyone ever made a cannon using H2 and O2 as fuel?

If you don't know, you run electricity (I think it has to be DC, but I may be wrong) through water to separate the molecules which turn into gas. You then put those 2 gases together, introduce a spark and they recombine and unleash massive amounts of energy. Technically you are losing energy because your electricity doesn't get 100% used up (it's more like 40%, the ceiling is 90%). They use liquid and solid H2 and O2 for rocket fuel.

So has anyone ever seen this work? I know this is one of the more dangerous ways of doing things, but it's cheap and easy. I wonder if it'd be worth it to try making a cannon or rocket.
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Unread postAuthor: DYI » Sun Apr 27, 2008 4:27 pm

You could make a fun cannon with it, just make sure to not give it too much runup distance. There should be a lot of sparks spaced evenly along the chamber to avoid DDT. Oxy/propane would be more powerful for propelling a projectile though.
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Unread postAuthor: MaxuS the 2nd » Sun Apr 27, 2008 4:35 pm

Never heard of solid O2 and H2.. :?:
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Unread postAuthor: Deli » Sun Apr 27, 2008 4:45 pm

Maxus, you will probably never get the chance to use it. It's really cold, and really dangerous. Thats why you always see ice on the sides of rockets on the launch pad, the fuel is frozen. I'm not sure they ever use solid stuff (I think there are better fuels) but it's possible.

I want to hear if anyone has tried it first, just so I can talk to them about materials. I don't know what temperature the gases burn at, and I'd be worried not only about blowing my cannon up, but melting it if I didn't blow it up. Plus I wouldn't get within 20 feet of it while it's ready to fire, even if I had parts I thought were safe.
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Unread postAuthor: D_Hall » Sun Apr 27, 2008 4:51 pm

:roll:

Deli,

Liquid oxygen can be had for less money than soda costs. It's dirt cheap and anybody who wants to use it can if they're willing hold that particular tiger by it's tail.

However.... Solid O2 and H2? Yes, both exist in theory, but they are never used as fuel.

Seriously.... Between your misconceptions about thermite and now this, may I make the suggestion that you get out of the hobby? Your understanding of energetic materials and their applications is stunningly incomplete. Playing with such materials with such an understanding is a good way to get yourself hurt.
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Unread postAuthor: Ragnarok » Sun Apr 27, 2008 4:58 pm

I've done similar things a few times, but never in a cannon. I used to blow up 2 litre coke bottles pressurized with H2/O2 mixtures to somewhere between 60 to 100 psi.
I just put two screws through the harder parts of the base, tipped in an inch or two of water, glued on the lid, connected a few in series to a DC power supply and left them until the sides were firm to the touch.

I then tossed them onto fires (Warning: NOT a safe thing to do). Often the resulting explosion would blow the fire out - or it would send flaming debris over a wide area at some speed.

MaxuS the 2nd wrote:Never heard of solid O2 and H2.

Oh, it's entirely possible, just ridiculously impractical for fuel systems - only liquefied gases are used there.
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Unread postAuthor: rp181 » Sun Apr 27, 2008 5:07 pm

you pressurised h2 and o2 to 60 PSI? ide think it would auto ignite from the heat created by the electrolysis and the pressureized fuel.
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Unread postAuthor: Deli » Sun Apr 27, 2008 5:23 pm

Ragnarok, I wouldn't touch that with a 20 foot pole. Maybe using pressure, but never throwing them at fires. If I got the pressure up to 100psi, I'd be scared to set it off unless I had a blast shield.

I might have to try a cannon, but it'd be weird to construct. I think I'd need to have one long barrel with a plunger (lack of better word, airtight ammo) stuffed halfway down and locked in place, then I would unlock, ignite and watch the plunger fly. Would I need metal (steel, Al, etc) though, or would PVC do?
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Unread postAuthor: Ragnarok » Sun Apr 27, 2008 5:39 pm

rp181 wrote:you pressurised h2 and o2 to 60 PSI? ide think it would auto ignite from the heat created by the electrolysis and the pressurized fuel.

Not at the rate I was pressurizing it at. It could take days to reach that point. Current was very low, so there was no noticeable temperature build up.

I don't know for certain it was 60 psi, but based on how firm the bottles became, and my later experiences with similar bottles being pressurized to known pressures tells me it must have been around 60 to 100 psi.

@Deli: I wouldn't even think of doing that these days, because I have the scars for the stupidity.

Let's just say that petrol, half a dozen pressurized bottles of hydrogen and fire do not mix.
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Unread postAuthor: Deli » Sun Apr 27, 2008 6:24 pm

SO do you think this would work?

Anything I'm missing?

Materials?
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Oh, wire lengths would all be the same.

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Unread postAuthor: rp181 » Sun Apr 27, 2008 6:43 pm

your spark gap system wont work. only one gap will fire, put them in series.
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Unread postAuthor: Deli » Sun Apr 27, 2008 6:52 pm

so I should evenly space all my wires, not put them in pairs? (I'm not so sure I need more than one sparker on the scale I would build anyway)

And I'd love to know what materials I should have to use. I don't want to build it out of PVC to find out that it's too weak. I should probably build it on a really small scale (like 1" PVC) to test.
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Unread postAuthor: THUNDERLORD » Sun Apr 27, 2008 7:11 pm

Quote:Ragnarok: Fine print: This post's side effects may include insanity, wild ideas or immorality.
Dosage: Do not read more often than every three hours, and not more than 4 times in a 24 hour period.

Good reading material (in this entire post)!!! :wink:
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Unread postAuthor: Ragnarok » Sun Apr 27, 2008 7:30 pm

THUNDERLORD wrote:Good reading material (in this entire post)!!!

Oh dear lord, he's OD'd on my posting. Someone get me a really big mallet, we need to induce amnesia as quickly as possible.

Seriously, DO NOT follow my example on that one, unless permanent scarring is your kind of thing.
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Unread postAuthor: starman » Sun Apr 27, 2008 7:53 pm

Truthfully, if you just want to watch and hear H2 and O2 go boom, slip a small plastic bag (1 quart) over your electrolysis beaker and seal it with a rubber band around the beaker. Wait until the bag loosely fills with gas and just light the plastic bag with a match... BOOM.. ok you're done... :roll:

Then proceed straightway to design yourself a proper propane cannon...
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