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burst disk cartridge idea

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: jackssmirkingrevenge » Mon Sep 24, 2007 11:19 pm

FeLeX wrote:But then again could those brocock (or how ever you spell) air cartridges cycle?


Brocock carts never managed to cycle, even the brocock para made to look like a semi-auto had to be cycled manually by racking the slide. You have to consider though that the design wasn't a very efficient one at all, it achieved its power by using almost 1000 psi of air.
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Unread postAuthor: FeLeX » Mon Oct 01, 2007 2:53 pm

Right well so do you think your cartridges will cycle? Since you carts have higher power spike and bigger air volume.
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 01, 2007 5:40 pm

Bigger volume + infinitely better valve opening time and flow ;) though of course it's all theory for now.
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Unread postAuthor: Antonio » Tue Jan 29, 2008 2:50 pm

I like it! Could be very tidius making lots of ehm though.
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Unread postAuthor: Sticky_Tape » Tue Feb 12, 2008 6:51 am

Sorry to bring this up again JSR but to keep the bb in the shell and out of the chamber right behind the bb you could have 2 wires glued in an x so that the bb can't roll back but the will still be great airflow.
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Unread postAuthor: Sticky_Tape » Tue Feb 12, 2008 8:48 pm

Oh yes what happens to the burst disk well obviously it bursts but what would happen to the pieces will they be so small that they can escape out the barrel or will they clog up the end of the barrel that connects to the shell and restrict the bb from leaving the shell? The edges of the burst disk will be held by the threaded part of the shell but will pieces sort of hinge into the barrel?
These must be factors but maybe they might be solved by using paper burst disks and if that isn't strong enough then you could reinforce it with cheap glue or somthing? Enough ranting it's possible that I already made myself look like an idiot polishing the shoes of my supierior spudders. :cry: .
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 12, 2008 11:57 pm

Any fragments of burst disk that come off are usually blown out of the barrel so that's not much of a worry.

I've been talking to dewey about these cartridges, he suggested something similar to the Saxby & Palmer catridges ( patent ) that preceeded the brocock, basically instead of the bust disk, you'd have a poppet valve that is knocked open by the forward motion of the cartirge against the breech.

This is a workable idea, however my worries would be the greater complexity involved in construction, as well as the reduced flow compared to the instant opening time of a burst disk that might not provide sufficient impulse to reload the cartridge.

I really should give this idea a go, I'll talk to my a friend who works at an engineering firm to see if I can have some threaded heads made :)
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Unread postAuthor: Antonio » Wed Feb 13, 2008 1:13 pm

Hey, I could do some calculations on if the burstdisk catridge would recock the whole system. My theory is that if the point that punctures the disk is sharp enough a weak spring pushing the cartige will do.
I have done calculations on bottle rockets before, involving thrust, time until all water is out of the bottle etc. The problem with this though is that the cartriges dont contain water in them that would shoot out''. Water is 800 times as dense compared to air. Using the Tsiolkovsky formula to calculate the final speed that the catridge gets after all air +ball has been expelled> http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation < I could do figure out the exhaust speed and all when I know the pressure, volume, exhaust diameter. But as you can c on the link the initial/final mass ratio is ganna be reall small in this case. So thats why I have my doubts.
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 13, 2008 3:05 pm

The only way to find out is to make one, which I think I will, it will make a change from fiddling with reciprocating pistons, I need a break from that :)
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Unread postAuthor: Sticky_Tape » Wed Feb 13, 2008 6:07 pm

When you get them made you should post up the dimentions
(as you most likly will :wink: ) Oh yes I was thinking of a single shot pistol I think that you should start small and the acheive semi-auto well of course your Jsr so complexity probable wont be a problem. You little epoxiteer :P .
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 14, 2008 3:56 am

A single shot pistol is hardly worth the effort of making a cartridge, you'll end up with something as useful as this - personally, it's full auto or bust! :D
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Unread postAuthor: Antonio » Thu Feb 14, 2008 7:25 am

jackssmirkingrevenge wrote:The only way to find out is to make one, which I think I will, it will make a change from fiddling with reciprocating pistons, I need a break from that :)


I dont know if you looked at my msg, bc it is possible to calculate if its possible. The only thing u cant calculate is with how much force the disk needs to be punctured. But it as I said it is possible to find the speed that with... the catridge shoots back. Using the kinetic energy of the cartrige and comparing it to the spring energy 0.5kx^2 it is possible to c how much power the spring has left to puncture the disk.
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Unread postAuthor: Ragnarok » Thu Feb 14, 2008 8:05 am

ant wrote:The only thing u cant calculate is with how much force the disk needs to be punctured.

Actually... that is possible to find. However, I'm currently in no such state to do so, I've not been well for several days.

My brain has been slowed so much, I'm now only twice as smart as everyone else. :D

Oh come on, it's a joke... Because I'm still at least five times as... *gets flamed*
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 14, 2008 10:13 am

ant wrote:it is possible to calculate if its possible. The only thing u cant calculate is with how much force the disk needs to be punctured. But it as I said it is possible to find the speed that with... the catridge shoots back. Using the kinetic energy of the cartrige and comparing it to the spring energy 0.5kx^2 it is possible to c how much power the spring has left to puncture the disk.


The stength needed to puncture the disk remains an unknown quantity at this point , there's a lot of pending variables so i'm going for the trial and approach.
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Unread postAuthor: Sticky_Tape » Thu Feb 14, 2008 3:44 pm

I don't know if you can get full auto machinicly but maybe manualy like some bolt on the side that you pull back to load and push forward to fire and then back to load what about a reel on the side of the gun? or is that semi auto?

I forgot the meaning to semi auto for a second :)
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