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Burst Discs

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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Burst Discs

Unread postAuthor: noname » Sat Apr 14, 2007 11:20 pm

Anyone have any ideas for burst discs other than aluminum foil? I've been testing a new mortar today, and aluminum foil is the only thing I can get to work, except it leaks and takes too long to make discs. I've tried milk jug plastic; that wouldn't fail, even at 120 psi, and when I popped it with a nail, it just let the air out slowly. I've also tried thin cardboard (leaky and wouldn't burst), paper (leaky, but did burst), and some other random crap.
I didn't try soda bottles because they're a bunch stronger than milk jugs, so what's the point?
I guess I could try remote firing it, because PVC will probably hold up better than milk jug plastic. Should I just hide somewhere and keep pumping til it blows?
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Unread postAuthor: frankrede » Sat Apr 14, 2007 11:46 pm

Soak the milk jug plastic in some solvent and let it dry then use it.
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Unread postAuthor: noname » Sat Apr 14, 2007 11:48 pm

Does that make it brittle or something? I'll dump in a couple tonight and try them in the morning.
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Unread postAuthor: frankrede » Sun Apr 15, 2007 12:00 am

I have no idea, but it can't hurt.
They might dissolve overnight, but sure why not.
Maybe you could try and "bake" them in the oven at a low temp.
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Unread postAuthor: noname » Sun Apr 15, 2007 12:40 am

I just soaked them for about 10 minutes in PVC primer and dried them. THey're about 1/2 as thick as before and more flexible. They seem a lot weaker, but 10:30 is a little late to test, seeing as it's so loud it makes my ears ring at 40 psi. I'm embarrassed to say that aluminum burst discs, at 80 psi, outperform my big piston cannonat 120 psi, even though the piston cannon has about 4 more times the chamber space. :oops:
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Unread postAuthor: DR » Sun Apr 15, 2007 8:55 am

Wow!? :roll:

I would venture to guess that the both of you were not members of the former SGTC Forums? - Ha!

Making a burst-disc out of <a href="http://en.wikipedia.org/wiki/Polyethylene_terephthalate">PET (Polyethylene terephthalate)</a> is what I've always used in my hybrids and my burst-disc pneumatics. -The plastic will burst at 800-100psig.

The plastic milk jug plastic is made from HDPD (High Density Polyethylene) and will burst anywhere from 120-150 psig.

Your aluminum foil burst-discs will hold back about 15psig for each layer, but getting a good seal with a thickness past 4 layers is difficult, unless you tighten the living $@#% out of the union.
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Unread postAuthor: noname » Sun Apr 15, 2007 10:20 am

DR's back!
Actually we were both members, I was for about a year, but didn't post much. I didn't really stick my head in much unless I wanted more opinions on designs or my cannons.
I would use PET except I don't have any right now and it's too hard to make enough of them. Yesterday I sat down and made 35 milk jug discs, so now I need a use for them. I would make a hybrid, but my parents won't even let me get into combustions.
As for aluminum burst discs, you are 100% correct, but you also forgot it uses loads of aluminum foil and the discs are annoying got make.
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Unread postAuthor: Kenny_McCormic » Sun Apr 15, 2007 10:22 am

DR wrote:I would venture to guess that the both of you were not members of the former SGTC Forums? - Ha!

noname was but didnt come that often and was mostly there for the bbmgs and ive heard that aluuminum from pop cans works good its what sqort uses in his burst disk cannon
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Unread postAuthor: Fnord » Sun Apr 15, 2007 10:33 am

Inner tube rubber
Playing cards
milk jugs scored with a razor blade
AOL cds
thin plexiglass/sheet pvc
beer cans (Edit: already mentioned)

No idea what will work and what won't, because Ive never done any tests. Im just trying to throw suggestions out.
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Unread postAuthor: noname » Sun Apr 15, 2007 10:36 am

I might be able to try inner tube rubber, and playing cards, I'll also try scored milk jugs. Beer cans, nope. If the regular milk jug didn't fail, why would the thicker metal? Thin sheet PVC, I could probably try that, but I'd be showering the nearby houses (and me!) with tiny shards. Not fun. I'll test in about an hour.
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Unread postAuthor: DR » Sun Apr 15, 2007 11:27 am

noname wrote:
As for aluminum burst discs, ....
the discs are annoying got make.


Geez!- Aluminum foil burst-discs are (by far) the EASIEST to make:

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Unread postAuthor: frankrede » Sun Apr 15, 2007 11:36 am

Soda can aluminum sucks, they burst at less than 50 psi for me.Has any tried sheet aluminum or metal?You can get it in almost any size and is cheap
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Last edited by frankrede on Sun Apr 15, 2007 11:41 am, edited 1 time in total.
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Unread postAuthor: DR » Sun Apr 15, 2007 11:36 am

noname wrote:I might be able to try inner tube rubber, and playing cards, I'll also try scored milk jugs. Beer cans, nope. If the regular milk jug didn't fail, why would the thicker metal? Thin sheet PVC, I could probably try that, but I'd be showering the nearby houses (and me!) with tiny shards. Not fun. I'll test in about an hour.


Inner tube rubber will burst @ ~15psig

Playing Cards are good for a combustion, but will not hold a significant amount of pressure in a pneumatic

Scored milk jugs? - what happened to the "annoying to make" mentality?
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Unread postAuthor: tercero » Sun Apr 15, 2007 11:50 am

Rene Caldera designed and built the original NO2 powered hybrid rockets in the late 90's. I was lucky enough to buy his plans, before he discontinued them. How this ties in, is Rene's design uses PET (soda pop) bottle burst disks to hold back the pressure of whip cream cartridges.
I've never had a failure with them, and they're easy to obtain and make.
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Unread postAuthor: DR » Sun Apr 15, 2007 12:35 pm

tercero wrote:Rene Caldera designed and built the original NO2 powered hybrid rockets in the late 90's. I was lucky enough to buy his plans, before he discontinued them. How this ties in, is Rene's design uses PET (soda pop) bottle burst disks to hold back the pressure of whip cream cartridges.
I've never had a failure with them, and they're easy to obtain and make.


Are you talking about this? :
Image


My curiosity is up, so I think I'll check out the site, for any info. :wink:

<a href="http://qwksite.com/rlmac/rene/microhybrid/tnmh.html">Microhybrid</a>
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