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cup shaped bursk disk

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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cup shaped bursk disk

Unread postAuthor: jean » Sat Jan 19, 2013 10:26 am

ok im thinking
of a cup shaped burst disk machined out of delrin or something
or made by deep drawing with vacuum out of some sort thermoplastic

-allows a quick change
-act as a check valve
-act as sabot


what do you think about this?

jean
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Last edited by jean on Sat Jan 19, 2013 5:39 pm, edited 1 time in total.

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Unread postAuthor: MRR » Sat Jan 19, 2013 4:17 pm

The cup piston has to be much wider than the barrel or it doesn't work. In this configuration it has to travel back the entire length of the cup to reveal the barrel.

I actually don't know what you try to achieve with a cup shaped burst disk.
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Unread postAuthor: jean » Sat Jan 19, 2013 5:09 pm

hi MRR

it is a little difficult to describe for me...

both pic are burst disks!!

the idea is a burst disk that is

-easy to change
-can act as a ceck valve
-no oring
-no glue
-no leaks
-up to high pressure
-can act as a sabot

think about a cartrige like this
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Unread postAuthor: MRR » Sat Jan 19, 2013 5:32 pm

ok im thinking
of a cup shaped piston/burst disk machined out of delrin or something
or made by deep drawing with vacuum out of some sort thermoplastic


Ok, I get it now, the OP was a little misleading though (I had a piston hybrid in mind).

...

Wouldn't machined burst disks be too expensive if you used them regularly? Vacuum shaped burst disk on the other hand should work nicely.

I think I know what you are trying to achieve with this design (read BTBs pump post) and I think it is not worth the effort.
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Unread postAuthor: jean » Sat Jan 19, 2013 5:35 pm

thanks for you reply (edit ist now)
and here the idea
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 19, 2013 10:28 pm

It would be a little annoying to machine in quantity, and since you're still having to use a threaded fitting to replace it you might as well be using a normal burst disk...
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Unread postAuthor: jean » Sun Jan 20, 2013 2:05 am

machine this would be annoying but with vacuum forming .. may for a low quantity of shotgun style cartridges (sabot)

how do you fill the cartridge with a normal bursk disk and wouldnt it leak at real high pressure?
o-ringed plug and bolts instead of threaded plug...


jean

and here the first try with vacuum forming
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Unread postAuthor: Labtecpower » Mon Mar 04, 2013 5:47 am

and here the first try with vacuum forming


That looks pretty good!
What kind of plastic did you use on this one?

It may be easy to seal this kind of burst disks with an O-ring put in a slot in the barrel..
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Unread postAuthor: jackssmirkingrevenge » Mon Mar 04, 2013 8:17 am

Not at all bad... the problem of still needing a threaded connection to be able to fit it still negates the advantage though in my book.
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Unread postAuthor: mobile chernobyl » Mon Mar 04, 2013 11:23 am

sacrificial obturating ring FTW :D

Calculate shear forces and utilize a material with well known material properties.

That's my goal when I start on the semi-auto hybrid at least!

(Graduating in 3 months!)
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Unread postAuthor: jackssmirkingrevenge » Mon Mar 04, 2013 12:21 pm

mobile chernobyl wrote:That's my goal when I start on the semi-auto hybrid at least!


Image

Cartridges?
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Unread postAuthor: jean » Mon Mar 04, 2013 12:57 pm

hi

why not a closed foam rubber..no need for an o ring...

@jack the idea to drop an cartridge in a pump to fill it isnt bad. with this sort of burst disk a filling valve isnt needed.

i only need an locking mech for the idea i mentioned further and the ignition seems an problem... i use a spark gap instead of the nichrome-wire but it wont ignite.

anyway im a bit busi today...
jean
edit the plastic i use was from a salad..
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Unread postAuthor: mobile chernobyl » Mon Mar 04, 2013 7:13 pm

jackssmirkingrevenge wrote:
Cartridges?


Silly cartridges... they certainly don't utilize the biggest advantage of a combustion gas gun - gaseous propellant! :D
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