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11x burst disk

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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11x burst disk

Unread postAuthor: SpudFarm » Sat May 17, 2008 9:52 am

i got a problem. in my hybrid (has arrived but can't pick it up untill next week) i will run 11x on a 2" burst disk housed in a union. the problem is that i have troubles figure out disks that will burst on that pressure.

anyone has some experience with 2" disk at 1000psi?

any suggestion? i think of duck tape over aluminium sheet. or i can get some 0.000984251969" brass sheet of Larda if i am allowed to buy. he used two disks in it and it bursed at around 70PSI.
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Unread postAuthor: mark.f » Sat May 17, 2008 9:54 am

Layered. Aluminum. Foil.

Customizable. Cheap. Reliable.

That's really all I can think off. You may have to modify your union to have it seal well, but in the long run the Al foil would be a better choice.
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Unread postAuthor: STHORNE » Sat May 17, 2008 9:57 am

Being serious now....

I have heard a lot of good reviews on using layered Condoms as burst disks. I guess like 3 is equivalent to 20 aluminum disks?? I'm not quite sure, it was something like that. I will have to find the link again, I'll post if I find it.
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Unread postAuthor: SpudFarm » Sat May 17, 2008 9:58 am

the alu disk will have to be so thick it can't be clamped. and i am going to grind away the sealing face in the union if it don't seal. a thing you can do to alu disks that don't seal is to put one layer of duck tape on the chamber side..

mabe one layer aluminium foil and something else and a layer of foil. repeat
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Unread postAuthor: mark.f » Sat May 17, 2008 10:40 am

DYI has successfully used 64 layer aluminum foil burst disks in his hybrids, probably with a union modified in the way you describe.

If you don't want to use Aluminum foil, you can also use coke cans cut into disks. You'll have to verify this but I think one layer bursts at around 80-100 PSIG. They're a little trickier to seal, but it's another option.
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Unread postAuthor: SpudFarm » Sat May 17, 2008 10:43 am

or i can make a holder myself to hold sheet metal..

i will use foil up to 5x wich will be the most used mix since it will be heared long away.

i used 16 layers for 4x in my 1" union and that tells me i need about 64 layers at 4x in a two inch union.
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Unread postAuthor: Maniac » Sat May 17, 2008 11:02 am

I wonder if you can use some Kevlar that stuff is pretty strong.
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Unread postAuthor: SpudFarm » Sat May 17, 2008 11:04 am

kevlar will ruine me..

i may use some steel net in neoprene
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Unread postAuthor: frankrede » Sat May 17, 2008 12:01 pm

One sheet of sheet metal+a custom neoprene gasket will do wonders
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Unread postAuthor: SpudFarm » Sat May 17, 2008 12:13 pm

i have it on my thought that sheeet metal just slip out of a union.

this is a hard task :P
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Unread postAuthor: D_Hall » Sat May 17, 2008 1:06 pm

Question: At such pressures why do folks use unions rather than flanges?
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Unread postAuthor: psycix » Sat May 17, 2008 3:26 pm

I think that sheet metal along with a gasket material might be your best bet.
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Unread postAuthor: MrCrowley » Sat May 17, 2008 4:15 pm

D_Hall wrote:Question: At such pressures why do folks use unions rather than flanges?

Reloading times?

Though I 'spose once you get to a certain scale and pressure, loading times go out the window anyway.
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Unread postAuthor: D_Hall » Sat May 17, 2008 4:22 pm

Yeah, that's my thought. After a certain point any convenience of the union goes away.... And the flanges have huge benefits in the "how to keep the disc in place" arena.
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Unread postAuthor: SpudFarm » Sat May 17, 2008 4:23 pm

MrCrowley wrote:
D_Hall wrote:Question: At such pressures why do folks use unions rather than flanges?

Reloading times?

Though I 'spose once you get to a certain scale and pressure, loading times go out the window anyway.


yeah.. take of the 20 foot barrel cut a disk that is about one roll of aluminium foil then screw it all together to discover the disk burst when you fuel. damn that is the worst thing that can happend.

i may try to come up with something to cut down on the reloading time.

anyone has an fast reloading system that can hold sheet metal?
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