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Sorry, i'm a noob here, and most suitable fuel for me is hydrogen + oxygen. Is it possible? Or gun would be blown up? I can't get propane or right hair spray. But water and electrolysis system. P.S. Sorry for my bad english.

It wil be hard to get enough hydrogen and oxygen. You can get hairspray or propane almost anywhere. have you made any guns yet?
Welcome to spudfiles!

Hydrogen has a very high burn rate

Metered Propane =;)

Hydrogen and Oxy are extremely easy to obtain in bottled form. and nearly free!

Thanks. And how about ignition? I've made some tests. In a bottle it's burning pretty good. But in closed chamber?
*** I've made two guns. One mini, my first, than bigger. I used hair spray. Now i'm thinking about using something like this http://www.spudfiles.com/forums/advance ... 13053.html to get hydrogen because i'll use my gun at my cottage, far from places where i can buy something. So i'll try to make another mini with hydrogen fueling. If it will work, i'll make full size cannon.

of course it would work. it would not blow up with the right chamber. you obviously couldn't use pvc or abs. if i were you i would find a 2 or 3 inch diameter steel pipe that was probably 1/4 to 1/2 inch thick, then there would be no problem with it blowing up. anything is possible with the right tools.

you nailed it hi...

Hydrogen and Oxy are extremely easy to obtain

I've Never seen bottle hydrogen....

You would have to make sure your fittings are extremely well sealed. Hydrogen has a nasty tendency to leak even when its in a "leek proof" container.
Perhaps try MAPP gas is probably much easier to obtain. I don't know how it holds up to propane but I've been told its got a bit more of a kick...

mapp gas is just a mixture of propane and acetylene. its only slightly more powerful. its gives about an extra 10-15% power, but i costs 3x as much as propane. i use it sometimes, but the only thing i really use it for is soldering copper pipe, its not even a noticeable difference in a launcher. if you were using a small cannon, they i would recommend using mapp, but in a large cannon its almost pointless.

but i agree, mapp is easier to get than hydrogen. you can get mapp and oxygen in throw away bottles.

Jared Haehnel wrote:

Hydrogen and Oxy are extremely easy to obtain

I've Never seen bottle hydrogen....

Niether have I but I bet we've both seen water backing soda some sort of wall charger 2 nails, too plastic bottles and something to hold water in

bobrofilin wrote:I can't get propane or right hair spray.

I think the first order of business is to establish why you can't get propane (or other common fuel).

walmart sells propane for $2.50 a bottle

If you were to use hydrogen and oxygen I think you'd be an idiot, mainly for the reason Jared said that hydrogen has that tendencey to leak from leak proof containers. If you were to do something with oxygen i'd use oxygen and acetelyne, but that would only be with a sch40 steel chamber and everything done right.

Jared Haehnel wrote:I've Never seen bottle hydrogen....

You just need to get out more. Hydrogen is indeed sold by the bottle.

I can get bottled hydrogen, but I'd have to drive 2 hours to get the bottles. It is quite easily available, as are regulators, just not at your local WalMart or Home Depot.

I ask the same question as D_Hall: Why can't you get propane? It is sold at all camping supplies, hardware stores, and WalMarts that I've ever been to.

Hydrogen has more applications in the field of pneumatic launchers than combustions (unless you intend on building hybrids operating at over 204x), although you run into embrittlement problems then, which aren't very easy to circumvent.