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Hybrid Confusion

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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Hybrid Confusion

Unread postAuthor: judgment_arms » Fri Jan 05, 2007 1:49 pm

After consulting the Wiki I have bean left with even more questions.
First off and the biggest question: will this work? If I take a pressure chamber fill it with enough propane for combustion and the pressurize it to 100psi and touch off the propane will it go off or not??? The reason I ask this is because in the Wiki it says
“A hybrid is first injected with fuel, then with pressurized air. The amount of air depends on how much fuel was added, and is calculated to achieve a stoichiometric fuel/air ratio in the chamber. A hybrid using twice as much fuel and air as a comparable combustion gun is said to be using a 2X mix, higher mixtures can be used and will produce even higher pressures. The fuel and air needs to be measured and matched carefully to ensure reliable operation, pressure gauges and fuel meters are used for this.”.
So now I’m utterly confused… I thought I understood it but now I don’t know…
Great…after typing all this, except the quote which I copied, I have forgotten my other questions…. I’ll ask them later this one is the most Important…
Forgive me if I sound like a newb, I just don’t want a pipe bomb, or a big waste of money.

Edit:
In a hybrid do you measure stuff by pressure? i.e. 100psi of propane to 100psi of air??? Or is there some other ratio??
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Unread postAuthor: benstern » Fri Jan 05, 2007 2:14 pm

no.
4.19851% is the amount of propane to air.
(yes I memorized that number)
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Unread postAuthor: judgment_arms » Fri Jan 05, 2007 2:20 pm

Can I get a little more information on that?
Allow me to rephrase my first question: lets say I have a burst disk cannon, the burst disk bursts at 150psi, and I fill it too 100psi and add propane, the exact amount of which I’m not sure at this point, and attempted to touch it off. Will it go off? Will if generate enough pressure to burst the burst disk? Yes I know I’d need to put the propane in first it was just easier to say/type/understand this way.
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Unread postAuthor: benstern » Fri Jan 05, 2007 2:45 pm

Yes it will go off easily at that mix. which would actually be a 7.8x mix
at that mix the burst disk should be around 250 psi
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Unread postAuthor: judgment_arms » Fri Jan 05, 2007 7:20 pm

Well I was planning on using coke bottle disks as my burst disk, so that’s why I said 150, and I was also planning on using 11/4inch SCH40 PVC…I’m guessing that I should try something else…
Next question:
If the burst disk goes at 150psi and the pipe’s rated to 300psi would the afore mentioned mix be safe??? Since the burst disk goes at 150psi the pressure should never exceed that or at least not for a long amount of time…
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Unread postAuthor: frankrede » Fri Jan 05, 2007 8:17 pm

Hold on I'm confused, filling it to 100psi?
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Unread postAuthor: judgment_arms » Fri Jan 05, 2007 8:35 pm

Basically what I want is a burst disk gun trigged by a pressure spike generated by the combustion of propane. This whole thread is a result of me doing research for a proposed automatic cannon as read about here: no burst disk hybrid
Since I don’t need that much pressure I’ll just reduce the mix…which means math, YEA
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Unread postAuthor: benstern » Fri Jan 05, 2007 9:30 pm

a 7.8x mix has never been done.
it is way too powerful for plastic pipe.
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Unread postAuthor: judgment_arms » Fri Jan 05, 2007 10:06 pm

Figures… so anybody want to recommend a mix, please? Sorry I’m lazy… 2x, 2.5x, 3x, 1.495x?
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Unread postAuthor: benstern » Fri Jan 05, 2007 11:19 pm

2x to 2.5x would be sufficient

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Unread postAuthor: Killjoy » Fri Jan 05, 2007 11:34 pm

Ive got a question thats kinda related to this. Ive been desighing an all steel hybrid (everything rated to 3000 psi or more), and i am planning to use oxygen and acetylene, but im not exactly sure how to meter the oxygen. How exactly would i do that?
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Unread postAuthor: judgment_arms » Sat Jan 06, 2007 12:19 am

From what I’ve read you can’t use oxyacetylene for fuel it’s considered an H.E. I think…
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Unread postAuthor: frankrede » Sat Jan 06, 2007 12:57 am

No its not.
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Unread postAuthor: sergeantspud2 » Sat Jan 06, 2007 1:01 am

What is the top/maximum pressure that a hybrid can reach with the most combustible fuel (Im guess acetylene) and air (not oxygen) and a 2x mix?
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Unread postAuthor: judgment_arms » Sat Jan 06, 2007 1:20 am

[quote=frankrede] Hold on I'm confused, filling it to 100psi? [/quote]
[quote=frankrede] No its not. [/quote]

Are you sure???
And I meant it’s like H.E. in the fact that it burns VERY rapidly and that blast is hard to contain. Plus somebody else said it’s like H.E. in another thread.
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