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20x-30x hybrid gun

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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Is it possible to avoid DDT in this case?

Yes
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Maybe
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Total votes : 6
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20x-30x hybrid gun

Unread postAuthor: Gunner » Fri Aug 08, 2008 1:23 pm

I just finished my hybrid gun and it is not enough for me :D , so my goal is shoot through 6mm steelplate with 10mm bullet and kinetic energy near 1kilojoule so my question is that is it possible to avoid DDT with well designed
chamber with mixture up to 30x? :wink:
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Unread postAuthor: MaxuS the 2nd » Fri Aug 08, 2008 1:35 pm

You know that you should ask Larda.. :wink:
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Unread postAuthor: Gunner » Fri Aug 08, 2008 1:43 pm

Well, if his gun did not DDTd then I have some changes :twisted:
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 2:22 pm

he had a DDT but on that shot there was NOTHING else than oxy/propane in the chamber.
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Unread postAuthor: Gunner » Fri Aug 08, 2008 2:28 pm

OK, but didnt DDT air-propane mixes?
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Unread postAuthor: brplatz » Fri Aug 08, 2008 2:36 pm

correct
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Unread postAuthor: Gunner » Fri Aug 08, 2008 3:42 pm

OK, thanks for information, now, you will see in future my high power hybrid rifle, with 1m barrel and 10mm ID and it will work with 20-30x mixes :wink:
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Unread postAuthor: benstern » Fri Aug 08, 2008 4:09 pm

Correct me if I am wrong, but wouldn't the propane change to an unusable liquid state at the pre-ignition pressures we are talking about here?
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Unread postAuthor: Gunner » Fri Aug 08, 2008 4:16 pm

I dont know but how about Lardas pressures :wink:
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 4:39 pm

a hybrid can use higher mixes untill the pressure gauge stops rising when fueling propane (liquid)..

that would be around 210x to 250x in normal remperature
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Unread postAuthor: benstern » Fri Aug 08, 2008 4:55 pm

No, propane liquefies much lower then around 2000 psi.
Around the 250 psi range is more accurate.
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 4:58 pm

lower than that benny.

and on 100x you would use 60psi of propane.

just multiplie 0.042 on you mix numper and you find your pressure in bars, propan liquifies at around 8bars

(60psi = 4.2 bar)
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Unread postAuthor: benstern » Fri Aug 08, 2008 5:09 pm

Yes but the air pressure + the propane pressure is what matters.
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 5:12 pm

no it does not matter at all, when it is not 100% propane anymore and the "atmospheric" pressure for the propane rises it becomes gas again when ever it was liquid or gas before you put air in..
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Unread postAuthor: psycix » Fri Aug 08, 2008 5:26 pm

Guys, this thread is not about the partial pressure on propane liquefying it, but about DDT.

An important factor of inducing DDT is the chamber size. With a thin, long chamber, DDT is more likely to happen then a spherical one.
Spark gap placement may also play a role.
Its all about the "runup distance" that the flamefront gets.
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