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burst disk holder's

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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burst disk holder's

Unread postAuthor: SpudFarm » Fri Aug 08, 2008 10:10 am

i just don't want to pay $110 for a forged union from georgia so i try one more time on getting ideas.

come with alternatives on cheap safe and easy holders for 11x mixes at a diameter from 1-1/2" to 2" (yes welding sockets pass but i WANT threads)
then tell me what you think about my little list.

homemade flange (42mm)

malleable union - 2" (better quality than "made in china" ones)

piston valve (not wanted but can be an option)

cam lock (will fail)

burst disks it is going to hold would be aluminium foil or sheet aluminium.


feel free to answer this fast and the best you can so i can get some full power shots off this summer.

(2" threaded BSP forged union wanted)
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Unread postAuthor: starman » Fri Aug 08, 2008 10:41 am

You can probably get metal cam locks to hold together on an a hybrid shot at 11x...you wouldn't want to hold back equivalent pneumatic pressure though. Let me know if you try this.

Ultimately, You may need to machine something from scratch similar to Larda, just not as beefy. Or just suck it up and go for the forged Georgia union.... :wink:
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 10:48 am

hmm, a flange is on the top of the list right now..

a 2" camlock has huge surface area for that kind of pressure.
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Unread postAuthor: starman » Fri Aug 08, 2008 11:01 am

SpudFarm wrote:a 2" camlock has huge surface area for that kind of pressure.


True, but it's all relative. I've found out the hard way how much more difficult it is to hold back against 3" instead of just 2".

For a golf ball you're going to want at least a 1.7" disk anyway for optimum performance.

How big a chamber and barrel length are you planning?
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Unread postAuthor: SpudFarm » Fri Aug 08, 2008 5:00 pm

my barrel is 21foot hydraulic pipe, 42mm ID and 50.01mm OD

chamber is 5" by 55cm.
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Unread postAuthor: Gunner » Sat Aug 09, 2008 3:10 am

I hope that this inspire you but I made homemade "union" just from a few parts for my hybrid cannon and for free.
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Unread postAuthor: SpudFarm » Sat Aug 09, 2008 1:04 pm

look, it clamp's the disk against a steel nipple. i will get one machined out of a 2" steel bar.
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Unread postAuthor: SpudFarm » Sat Aug 09, 2008 2:39 pm

the edit button forked up so i have to doubble post..


i made a diagram over my burst disk holder. hoping for larda to get on with me on this one :D
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Unread postAuthor: Fnord » Sat Aug 09, 2008 5:20 pm

For a golf ball you're going to want at least a 1.7" disk anyway for optimum performance.


Not really. The high temperature gas in a hybrid has much higher particle speed, and thus it doesn't really notice choked flow as much as a pneumatic.

A 1" valve should work fine, but any smaller and you'll probably get less than optimal performance.

I wouldn't recommend a piston valve for high mixes, mainly due to the mechanical stresses. For example, sealing faces tend to get sucked into the barrel even when superglued/epoxied on.
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Unread postAuthor: MaxuS the 2nd » Sat Aug 09, 2008 5:39 pm

I don't think that there will be a need to have an Oring in there, or if you do have an Oring..I don't think that you will need the groove cut in the steel ring because this will probably rip the disc if it were foil and do nothing for it if it was sheet aluminium.
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Unread postAuthor: starman » Sat Aug 09, 2008 11:34 pm

_Fnord wrote:
For a golf ball you're going to want at least a 1.7" disk anyway for optimum performance.


Not really. The high temperature gas in a hybrid has much higher particle speed, and thus it doesn't really notice choked flow as much as a pneumatic.


According to HGDT you'll lose roughly 10% velocity with a 1" disk as opposed to a 1.7"...not a terrible situation but still not optimum.
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Unread postAuthor: SpudFarm » Sun Aug 10, 2008 10:04 am

i am ashemed of myself.. i drew the oring on the wrong side :oops:

_fnord: i wil not ever make any flow restiriction on this gun :P

MAX: if the groove does destroy the disk i will just make a new plate, and when i think of it, the "cam lock" on my barrel sealed perfect so i will have a look at it and make the internals like that.

i would be happy if you guys could talk metric if you can..
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Unread postAuthor: starman » Sun Aug 10, 2008 11:46 am

SpudFarm wrote:i would be happy if you guys could talk metric if you can..


:lol: OK Spudfarm, I'll try real hard....if it will make you happy... :lol:

BTW, the holder design look pretty solid...basically a homemade union.
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Unread postAuthor: SpudFarm » Sun Aug 10, 2008 11:54 am

i am so happy! :lol:

yepp it is like a homemade union, but i am stil looking into more designs that will be easier to make
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Unread postAuthor: Gunner » Sun Aug 10, 2008 12:31 pm

Yeah, metric rules! :D
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