SpudFiles

Well i went and bought the pan liner or pvc sheet whatever you prefer to call it. It works very well at a single layer i used it at 5x 2 times and 1 7x before it got to cold for the propane to get enough pressure in it. The only problem i had was that its " burst " properties were not so good. It simply had a small rip in it. >>>

OK that's interesting. My initial thoughts are that it doesn't blow out nearly enough to get the flow you will want. While that crack will let out the pressure, it will also act like a flow restricter.

Ideally, you want the disk to completely disintegrate. If you have seen aluminum foil or masking tape burst disk shots, you'll see that the whole 2" opening has been mostly blown clear...like this...



This was blown out by compressed air. My combustion ignitions blows the opening out utterly and entirely.

you may want to score lines into it, across the diameter of it, to make it split open. Given stress concentration points, a crack or tare will propagate much more easily.

the other possiblity is that you score a circle slightly smaller than the I.D. of the union, and see if that will rip out entirely.

I will probally just stay with my aluminum can burst disks they blow out completely.

I got the same effect when I tried using rubber sheet for burst disks, wasn't impressed. And it failed at a pathetic pressure, something like 20psi.

It is amazing how difficult it is to find decent burst disk material. Many people have gone down this road and always seem to drift back toward aluminum. The masking tape is workable up to about 7-8 layers, but only practical on a camlock setup. Aluminum still seems to be the winner for union holders.

Too true starman. I'm going to be testing things like anti-stick baking paper, different tapes, glad wrap, cellophane and rose petals for ultra minis (I know these will work, you can use them like a burst disk just with your hands and the sound is impressive)

starman wrote:Aluminum still seems to be the winner for union holders.

I have realized that as well; you have any tips for using aluminum burst disks? I made a few a while back that were either 6 layer or 8 layer to use in my hybrid at 6x-8x (3/4" union). The problem was none of them sealed at all.

In order for the union to seal i recomend adding a o-ring to the union. A 1.5" union can use a 2" PVC union O-ring just a fun fact. I think next thing on my list to try is ..... well back to aluminum

FishBoy wrote:

starman wrote:Aluminum still seems to be the winner for union holders.

I have realized that as well; you have any tips for using aluminum burst disks? I made a few a while back that were either 6 layer or 8 layer to use in my hybrid at 6x-8x (3/4" union). The problem was none of them sealed at all.

Maybe try some vaseline gunked in between the first layer and the union seal. Trigun's O-ring is probably the ultimate answer.

I've been meaning to try those cardboard beer coasters from restaurants...it's hard to find them though, except the ones you get there. I drove all over town one day looking for them, came up dry. Undoubtedly, a restuarant supply company would have access to them, just no consumer level places I could find.

I got the same effect when I tried using rubber sheet for burst disks

It seems like that burst disk material has to be brittle.
Soft materials just make a small tear and bend open a little. Brittle and hard stuff cracks to pieces and is completely destroyed.

When I use milk bottle plastic, I open the union and there is always a perfectly circular hole, fully open . I like trigun's idea of soda can metal but what pressure does it burst at?

No material bursts at a set pressure.
You need to specify the diameter too.

Well I believe coke cans are made fairly consistently; lets say we cut a burst disk out of the side of one and put it in a 3/4" union. What would be a reasonable estimate of burst pressure?

starman wrote:It is amazing how difficult it is to find decent burst disk material. Many people have gone down this road and always seem to drift back toward aluminum. The masking tape is workable up to about 7-8 layers, but only practical on a camlock setup. Aluminum still seems to be the winner for union holders.

Just as a side note, I've been using starmans tape setup for golf balls. It works great and I don't use it on a camlock, but apply it directly to my coaxial breach face. I use three layers of tape for my 1x combustion and the results are impressive.