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Soda Bottle Cap Burst Pressure

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Soda Bottle Cap Burst Pressure

Unread postAuthor: PVC Arsenal 17 » Sat Dec 18, 2010 5:39 pm

Does any know or currently have the means to test the pressure at which common soda bottle caps burst?

I recently got 30 or so soda bottle preforms and I want to see if I can make "flash bang" noisemakers with them. The preforms are obviously extremely thick since they haven't been inflated yet, but they still have threads for caps to go on.

If the caps burst at typical 1X combustion pressures, I will displace the air inside the preforms with a fuel/air mixture and cap them. The caps will be drilled so a thin pyrotechnic fuse can go through them. The noisemakers could then be stored indefinitely and set off simply by lighting the fuse and throwing. The caps would be easily replacable of course, and since the preforms themselves are so durable, they could be used many times.

Thanks
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Unread postAuthor: jimmy101 » Sat Dec 18, 2010 5:49 pm

A typical soda bottle (or cap) shouldn't have any problem holding a 1X combustion mix pressure. Indeed, they are used in water rockets and regularly pressurized to 120 PSIG which is almost the maximum theoretical pressure in a 1X.

You'll need >1X to consistently rupture a typical soda bottle.
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Unread postAuthor: saefroch » Sat Dec 18, 2010 9:51 pm

PVC Arsenal 17 wrote:The noisemakers could then be stored indefinitely and set off simply by lighting the fuse and throwing.
Probably won't work for very long, since it's unlikely you'll be able to make everything seal perfectly, unless you have some special way in mind to seal around and through a fuse.

Just also another note: They probably wouldn't just be noisemakers, but also like rockets. As soon as the fuse burns down and ignites the fuel/air mixture, it will be exhausted out the hole that used to be occupied by a fuse. The only viable option I see to make a combustion noisemaker is to use electronic ignition, which would be very expensive for such a device.
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Unread postAuthor: inonickname » Sun Dec 19, 2010 1:43 am

Some epoxy should seal it well enough (or even blutac?) to hold an atmospheric mix. A 1x mix won't do, an oxy-fuel mix probably could though.
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Unread postAuthor: Killjoy » Sun Dec 19, 2010 3:05 am

You could glue the fuse in, and then dip the end with the fuse in wax. You should have a good seal then and no issues lighting the fuse. But I agree with above, the gasses from combustion will probably escape out the fuse hole unless you can generate a very rapid pressure increase.

Drawing on my experience with water rockets from the past six years, the cap should hold past the pressure a 1x mix with propane or mapp generates with air.

Based upon leakage from the fuse hole and and the pressures needed to cause the cap to fail, a higher fuel air mix or some sort of fuel and with a better oxidizer (ie. oxygen) will be needed to cause such an expansion of a gasses that the pressure loss from the fuse hole becomes irrelevant and the cap will fail. For fueling to a higher mixes, plug type schrader valves (the ones with the rubber bulbs on the end) could be fitted in the cap for introducing the oxidizer/adding air and recovered after firing.

My two cents.
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Unread postAuthor: PVC Arsenal 17 » Sun Dec 19, 2010 2:44 pm

Well it seems the idea won't work. Thanks for all the replies. I'm still going to give it a try when I have some free time. If it shoots like a rocket, that's cool too. I'll also try scoring the cap to weaken it.

I intended to hot glue the area around the fuse and dip the fuse in wax so they can be stored.

1/2" PVC just barely fits inside the preforms. I can take advantage of that and make a simple attachment which would allow me to a use a more conventional hybrid chamber (pipe fittings) with soda caps as burst discs. I'm not sure how well epoxy or other adhesives will stick to PET. I'll have to look into that.

If you guys have some money to spend, buy a few of these. They're quite useful. Watertight, obviously, and damn near unbreakable.
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