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Burst Discs are out of style

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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Unread postAuthor: DYI » Thu Aug 07, 2008 7:47 pm

put it this way, a 64 layered aluminium foil disk over a 2" area has a burst pressure of around 1000psi.


Just to make sure no one is confused, a 1.5" union has an opening almost 2" across. I measured a 32 layer disk in a 1.5" union to burst at a differential pressure of about 400 psi, sometimes a bit more, so Spudfarm is probably very close to the mark in this case.

I'd be wary about this temperature sensing valve of yours. Unless it's insanely fast and accurate multi-thousand dollar equipment, most of the power will have been wasted to heat loss before it opens.
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Unread postAuthor: Gippeto » Thu Aug 07, 2008 9:31 pm

If it's like most "industrial" instrumentation, the cost is going to be prohibitive.

No mention of the orifice size either.

Might want to check that. Of the valves I have worked on, none have had the orifice as large as the mounting threads.

This means, you will have a heavy poorly performing canon and an empty bank account to show for it. :(
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Unread postAuthor: starman » Thu Aug 07, 2008 9:49 pm

Now explain again why you don't want to trust a burst disk? Burst disks are fairly plain and straightforward technology and proven to be highly effective.

What is there about them not to be "trusted"?
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 9:19 am

starman: i have had multiple golfballs fired at 30psi (3x preignition) pressure while sitting behind the gun and almost been hit by the ricochet.

hope this becomes a small problem when i get my new union/money or a piston valve.
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Unread postAuthor: starman » Fri Aug 08, 2008 10:27 am

SpudFarm wrote:starman: i have had multiple golfballs fired at 30psi (3x preignition) pressure while sitting behind the gun and almost been hit by the ricochet.

hope this becomes a small problem when i get my new union/money or a piston valve.


Yep ricochet golf balls are a real threat, especially ones fired from a burst disk gun of any sort...could not only hurt you, but could be deadly. Make sure whatever you're shooting will be fully penetrated and back stopped and you are behind protection of some sort. A helmet wouldn't be a bad idea actually.
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Last edited by starman on Fri Aug 08, 2008 10:29 am, edited 1 time in total.
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 10:28 am

starman: when i get it working on 11x they will NOT come back since they pulverize on 150psi :D
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Unread postAuthor: starman » Fri Aug 08, 2008 10:33 am

SpudFarm wrote:starman: when i get it working on 11x they will NOT come back since they pulverize on 150psi :D


That's cool Spufarm...looking forward to some pulverized golf ball pics when you get it working... :wink:
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 10:42 am

haha, i can't find then since they fly to the sides. (then i know where they go)
i might find some that hit the ground under the target if the muzzle blast don't blow them away :D

and i don't think i will fire much GB's when i can fire steel and lead :D
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Unread postAuthor: jimmy101 » Fri Aug 08, 2008 1:02 pm

If you want to get rid of the burst disk in a hybrid you might consider using an electrically piloted valve. (Or an electrically piloted pilot valve.)

Create a circuit that automatically opens the valve a set time after the ignition is triggered. I would suspect that that would be a delay of a few tens of milliseconds. It would take some testing to figure out exactly how much the delay should be for optimal performance.
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Unread postAuthor: Davidvaini » Fri Aug 08, 2008 1:05 pm

I personally don't think burst disks are out of style.

For example my Burst Disk Cartridge design works perfect for airsoft and smaller applications.
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Unread postAuthor: Gunner » Fri Aug 08, 2008 3:25 pm

Even though burst discs have little longer reload time but they do always work :wink:
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Unread postAuthor: psycix » Fri Aug 08, 2008 5:43 pm

Gunner wrote:Even though burst discs have little longer reload time but they do always work :wink:

Nope. Not always.
Some disks may leak or blow before ignition.
Sometimes, when using disks with a burst pressure thats near the peak pressure of your gun, they simply dont blow.


I think that a heat-actuated valve is way too slow.
By the time the gas heated up the sensor, and the valve opens, the pressure probably already dropped.
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