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Hydrogen Hybrid?

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: Moonbogg » Fri Jun 03, 2011 7:36 pm

air and propane is already so damn powerful, i'm not sure if the effort for hydrogen would be worth it. I know for me it wouldn't be.
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Unread postAuthor: DYI » Fri Jun 03, 2011 9:47 pm

Alster, these mixes aren't worth the trouble unless you're approaching the SOS in the combustion gases from air/propane mixes. Anything under 30X or so, minimum, you'll not see any difference at all, and it won't be apparent for relatively heavy projectiles until much higher mixes than that.
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Unread postAuthor: Alster370 » Sat Jun 04, 2011 5:53 am

I assume it would also be pretty much identical in terms of combustion pressure compared to But/Pro when using in a regular combustion too? Its more convenient for me as I can produce a healthy amount of the stuff and its free. I couldn't afford to buy butane/propane all the time on a budget as tight as mine :/

Perhaps I shouldn't focus on the ratio of Hydrogen/Oxygen as It would be too much of a fuss. Given that Hydrogen will combust in a wide hyd/oxy ratio, If I just fill the chamber for 10-15s using my electrolysis cell, I would no doubt get ignition every time? The different concentrations of Oxygen in the chamber would affect the pressure of the resulting combustion, but as I shoot in a range of only 16 yards, I don't think it would affect performance much.
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Unread postAuthor: ramses » Sat Jun 04, 2011 12:19 pm

There is no point in using hydrogen in your setup. Propane costs around $3.00/ pound where I live in those little 1 lb bottles. Harbor Freight carries ball valves for maybe $3.00 each. A propane torch to adapt is $10.00. Pipe to go in between maybe $5.00. Regulator/gauge was on clearance at Harbor Freight for $5.00. (I should have bought more than two).

So you total about $25.00 for metered propane. Each tank will probably give you well over 500 shots, many more in a smaller launcher. For paintball gun type performance, tippmann claims over 50,000 shots. It is also portable, and with the addition of a $10.00 three way ball valve and a $3.00 computer fan, can be made to cycle very quickly. 10 shots per minute should be do-able.

Hydrogen is only really beneficial when you're approaching the SoS in conventional propellant gas, which is around mach 3.
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Unread postAuthor: SpudBlaster15 » Sat Jun 04, 2011 2:43 pm

Alster370 wrote:I assume it would also be pretty much identical in terms of combustion pressure compared to But/Pro when using in a regular combustion too?


No, it will actually perform significantly worse.

Hydrogen/oxygen and hydrogen/air mixtures suffer from very low molar energy density, meaning each atmosphere will produce less pressure than a propane/air mixture. You're looking at about 136PSI adiabatic combustion pressure for stoichiometric propane/air, and about 117PSI for stoichiometric hydrogen/air.

Hydrogen also suffers from a severe lack of gas production, which is evidenced when you remove the buffer gas from the mixture. Stoichiometric propane/oxygen produces nearly double the adiabatic pressure of stoichiometric hydrogen/oxygen.

In reality, H<sub>2</sub> only becomes advantageous to use when the projectile velocity begins to approach the SOS in the gas, or the partial pressure of the fuel gas approaches its vapour pressure. These only come into play when you're working with very high hybrid mixes.
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Unread postAuthor: Alster370 » Sat Jun 04, 2011 3:07 pm

Well that has opened my eyes :shock:. I guess Il use Propane for my upcoming combustion then, Im going to base it on SpudaMines cannon as I really like the design, and the use of copper :P . I think il try to put it into a stock though, so that means a scale down of bore size and such. I do however have one more idea :idea:. I could make this combustion use a piston valve, like on a hybrid. Obviously it would do pretty much nothing except prevent the gases from leaving the chamber before ignition, but If I decide somewhere down the line, that I want to make a hybrid, I wouldn't have to build another gun as this one would be capable of more than x1 mixes. Smart idea? or just pointless work?
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Unread postAuthor: ramses » Sat Jun 04, 2011 7:51 pm

It's do-able, except you would have a hard time making it seal initially. It would basically act like a burst disk (which are sometimes used on combustion launchers to increase performance).

You may have to make the pilot area completely air-tight from the chamber, and pre-fill it with low pressure air. Or you could use a huge spring, or make a hybrid QEV with a weaker spring and a bumper.
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Unread postAuthor: Moonbogg » Sat Jun 04, 2011 9:29 pm

If you use a camlock on your cannon, you just instantly created a hybrid. If you're interested, look at my venom cannon as it is both a combustion and low mix hybrid. All I did was add a camlock and a schrader valve and it goes from combustion to hybrid.
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Unread postAuthor: Alster370 » Sun Jun 05, 2011 3:43 am

I would use a spring for the piston, to keep things simple. There was a diagram of one I wanted to use as a reference, but I cant find it. :oops:. Interesting idea Moonbogg, although im not sure if you can get cam locks that fit onto copper pipe. Im thinking that I don't want to go over a 4x mix when using a copper chamber. Im using a steel barrel to fire 10mm steel balls( I would use a bigger calibre , but I cant find any) at 900fps at a 4x mix.
Any higher mixes don't really improve fps.
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Unread postAuthor: ramses » Sun Jun 05, 2011 10:43 am

The working pressure of most copper pipe (in affordable diameters) is around 3000 psi. The failure pressure is somewhere around 9000 psi (don't even :roll: ). So you should be safe with 30x. If higher mixes don't help, you need to use hydrogen, a longer barrel, and/or a stronger burst disk. A heavier projectile would also yield more muzzle energy, but not muzzle velocity

If you can't find cam locks, you could solder on threaded adapters and use threaded cam locks. You could also just use a union, but it takes longer to reload.


If you use a spring, it will need to be really stiff. If you have a 1" barrel port and a 1.5" piston, your spring will need to exert around 100 pounds to open at 100 psi. If you used an air spring, you would simply fill the pilot to 55% of the pressure you want the valve to open at.
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Unread postAuthor: RJB INDUSTRIES » Sun Sep 11, 2011 5:00 pm

If you want the plans to do a H2 Reactor i can help you...







RJB INDUSTRIES
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Unread postAuthor: Crna Legija » Mon Sep 12, 2011 1:21 am

RJB INDUSTRIES wrote:If you want the plans to do a H2 Reactor i can help you...


if you wanna stop kicking up dead topics, i can help you.
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Unread postAuthor: wyz2285 » Mon Sep 12, 2011 3:56 am

well, at least not a really old one, 4 month :roll:
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