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Hybrid Question

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Hybrid Question

Unread postAuthor: Rambo » Mon Feb 13, 2006 3:53 pm

Why the rapid rise of the presure can breake a chamber made for much more preshure?A cola bottle can withstand 120 psi but it can't withstand the presure of O2 and propane wich don't make more then 120psi?they tell that it is very dangerous to fire a hibrid with more then 4 atmnosferrs.Are there anything with the cenetic energy of the gases?A detonation can be avoid by not using twin spark and puting the spark in the end of the chamber.
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Unread postAuthor: nabu92 » Mon Feb 13, 2006 5:07 pm

think about it, if i punch u, it will hurt much more than me pushing u with my fist...same thing inside a chamber........correct me if im wrong
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Unread postAuthor: boilingleadbath » Mon Feb 13, 2006 5:44 pm

I'm not sure of this, but I beleive that O2-propane would generate roughly 2.3 times as much pressure as air-propane, which takes it up to about... 120-140 psi, nevermind the very short-lived increase in pressure from the "shockwave".

I think that a 4 atmophere ignition generates ~230 psi. Most sch 80 PVC unions are only rated to about that pressure, so that's where the restriction comes from. With a steel union, higher mixes could be done, although you start to get close to the rating on the PVC chamber by then... high mix hybrids should be done in small-diameter steel.

And I'm thinking that a single ignition in the back would tend to promote the transition to detonation... I'd have to search to find it, but I saw a page that had data on this - with smaller diameter pipes, it took less distance to transition to detonation than with large diameter pipes; that is, the transition would occur after a certain distance - multiple ignition points would give the flame front less time to "run up" and get to detonation velocity. (tests where done with air/propane, I think)
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Unread postAuthor: crazy jap » Mon Feb 13, 2006 8:49 pm

id say its mostly a shockwave that is the culprit here. thinking about it since my dads an engineer i asked him about it . he says the most probable cause is the shockwave. since most hybrids have ignition towards the rear of the gun it causes a very strong shockwave to hit the union all at once. but if you were to use. ignition near the union the shockwave coming from both sides the one towards the union will start bursting the disk. and the other going down the rest of the length of the chamber bounces off like radar and is about the same but more focused this finishes bursting the disk and reduces in less broken unions. as far as i know it works but who am i to say. so im gonna try it. but he also said if one were to have a concave endcap on the chamber that helps to funnel the shockwave better as well instead of the flat threaded plugs
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Unread postAuthor: Atlantis » Mon Feb 13, 2006 10:39 pm

I think I saw this some where on this site. If you surround the firing chamber with an outer, pressurized chamber, the relative firing chamber pressure will be drastically reduced therefore reinforcing the chamber.
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Unread postAuthor: Rambo » Tue Feb 14, 2006 2:47 am

This is the strongest pipe i have.It can withstand much more then any hibrid.
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Unread postAuthor: nicholai » Tue Feb 14, 2006 8:21 am

i got an idea... what if you used 4" sch 80 pipe and made your chamber out of 4" sch 80 couplings and short cuts of 4" pipe? cut the small pieces of pipe so that the couplings would butt end to end. this would make a chamber of double walled sch 80. i suppose this would be great if the glued joints could be prepared well. It would also allow you to mount your electrodes on any spot of the chamber since its all double thick instead of just at the ends of the pipe.

or this could fail miserably where the chamber couplings are solvent welded together. what do u guys think?
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Unread postAuthor: Rambo » Tue Feb 14, 2006 1:42 pm

I don't understand all these termins but even if I do, I don't have enough money to buy all these expensive pipes.In bulgaria I have never seen the end caps of the clasical spud gun and the pipes.... :(
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Unread postAuthor: CS » Tue Feb 14, 2006 9:07 pm

nicholai-Its already been done. Its called sleeving your chamber in couplings. I sleeved my soon-to-be hybrid with sch40 couplings. If you were to go about cutting the pipe, you would create weak spots were the cuts were made. The way to get around this is to grind out the ring stop on the inside of the coupling, and sleeve it that way.

Man, spudding and living in another country has to suck!
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Unread postAuthor: nicholai » Wed Feb 15, 2006 6:18 am

yeah i dunno why i didnt think of that. i sleeved my 1.5" barrel with 2" sch 80 cause i thought id bust such a long barrel. and i ground out the male adapter so i could breech load spuds.

im still toying with my hybrid, i scrapped the endcap idea i knew it would blow out. been messing with my propane launcher recently, i added a chamber fan and something new to the ignition, ill post it after i get outta work today.
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Unread postAuthor: jrrdw » Wed Feb 15, 2006 9:12 am

I agree with Pimpmann, way to many weak spots! You should be thinking 1 piece chamber for strenth. I've seen threads that tell about lineing the inside of thier barrel, by sliceing a same sized pvc pipe leanth wise, to make it fit just snuggly inside your barrel. Doubleing the wall thickness.

Question to any one who has done it this way.

Did you solvent weld the slice before inserting the liner?

Can't the chamber be done the same way?
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Unread postAuthor: PCGUY » Wed Feb 15, 2006 11:22 am

Next time please spell "Hybrid" correct in your post and put it in the correct section. I moved it for you.

Thanks.
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