20x-30x hybrid gun

[SpudMonster]

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?

No, propane liquefies much lower then around 2000 psi.
Around the 250 psi range is more accurate.

Yes but the air pressure + the propane pressure is what matters.

Dude, you've been corrected. Accept it.

Also

[DYI]

Yeah, pure propane liquefies at around 120psi at room temperature. We're talking about 4.2% propane, which means the propane portion will liquefy at around 2900 psi.

As long as you have a decent percentage of buffer gas left in the chamber, no high energy ignition, and no absurdly long runup distances, you really don't need to worry too much about DDT in propane/air mixes no matter how highly pressurised they are prior to ignition. Larda's 200x hybrid is living proof of those guidelines.

[SpudFarm]

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.

if he is worried he can just inject some inert gas like argon, Co2, nitrogen or helium..

DDT just wont happend here

[Gunner]

I am not worried about it anymore, BTW I have designed my next weapon very much and I think that I will starting to construct it someday and it will be MUCH more powerful than the old one

[SpudFarm]

sounds good

[Gunner]

Spudfarm: I have added you on msn but there is something error? I cant write to you?

[SpudFarm]

hmm, people have the same problem on my msn..:S

[Gunner]

Hmm...what do you think that can I use square chamber, does it make DDT easier?

[Gunner]

I mean this kind of chamber:


Comments please!

[Sticky_Tape]

It makes the chamber more likely to exsplode most pressure vessels are cylindrical so there is less surface area for pressure to work on. Circles have less circumference than a square with the same diameter.

[Gunner]

OK, but How about if thickness is enough much so there shouldnt be then any problems?

[Pilgrimman]

I wouldn't trust it. It's weaker by far than cylindrical pipe because of the shape, and it appears welded together. The wall thickness looks very low, too.

[SpudFarm]

you can try to find something to sleeve it in, to make it thicker.

also, this insane finnish dude did charge copper pipe to 16x so that shows that things DO take more then you think.

[Gunner]

Spudfarm, I am sorry but I did read wrong the pressure,it was 13bar and it means 14X but today I did really to put in it 15bars=16X and it was mistake, when I fired it, solder joint cracked well, that was this guns story, but next will be much better

[SpudFarm]

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