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Mixes

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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Mixes

Unread postAuthor: noname » Sun Sep 03, 2006 12:38 pm

So with a hybrid, the fuel/air mix (according to boogieman) is
1x = 0 psi
2x = 14.7 psi
3x = 29.4 psi
and 4x should never be tried, right?
2x and 3x just mean you inject the same amount of propane 2 or 3 times, correct? I'm pretty sure about this stuff, but I just need to be confirmed on all of it. Don't worry everyone, I'm not going to be stupid, if I make a hybrid it's going to be a small, all metal (maybe coaxial) one.
The only thing about making a metal one is how would it spark? The electric charge would just go into the pipe around to the other screw, or am I wrong?
One last question, How does injecting propane 3 times and pressurizing to 29.4 psi create up to like 250?!?!?!?

And no, right after firing I'm not going to unscew it and take apart the union to replace the disk. I'll wait at least 5 minutes or wear heavy gloves.
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Unread postAuthor: mark.f » Sun Sep 03, 2006 10:12 pm

I don't get why everybody considers hydrids such a no-no. If you're gonna build one just build the damn thing. If you "know what you're doing" you shouldn't need other peoples opinions except for new or trivial aspects.

A 4x mix can be tried, all right. Especially if you're using metal pipe. People have done 4x mixes with plastic launchers.
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Unread postAuthor: noname » Mon Sep 04, 2006 11:09 am

Ooooo, maybe I'll go to 5 or 6x. Since the biggest metal pipe I can get around here is 2", The barrel will have to be 5/16" or 3/8" for the union to fit inside. I making a diagram that I'll post in a little while.
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Unread postAuthor: Jolly Roger » Tue Sep 19, 2006 8:13 am

No dude thats what he just said. You can make a hyrbid but if you don't even know how the whole mixes thing works, don't go trying 5x and 6x mixes, because for starters you don't even know what they are or what pressures they create, and even the pro's aren't keen on using them... And a 1x mix or a normal combustion mix "technically" should be 0psi but because it is 0 before you add the fuel from the meter, the pressure rises slightly relative to the fure:air ratio when you charge it. And for the ignition, the current will follow the path of least resistance, so just make it easier to jump the spark gap than rather follow the chamber. Thats why spark plugs have a ceramic outer, it is resistant to heat and it offers a solution to the problem you outlined. Actually multiple spark plug ignition points would be feasible although you would have to custom make their inlets. Also just remeber the bursting pressures of pipe is reduced when a sudden pressure is applied such as an explosion or rapid pressure spike. Thats why it is sometimes safer to fire a pneumatic cannon at 300psi rather than a combustion or hybrid which makes 300psi.
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