The SBDP (simple burst disk pneumatic)

[Acdcmonkey1991]

It's been a long time since I've posted a cannon, so I thought it was time to make a simple burst disk pneumatic just to test the efficency of using a burst disk. I am actually pretty surprised, at about 100 psi it went through 2 sheets of drywall, with a clean entry and exit. I might put up damage pics later but for now just pictures. I still have not recieved my 1 1/4 in. to 3.8 in. reducer from mcmaster yet, which I will add when I get it because I think it will give the gun a more overall smooth look.
Specs:
C:B ratio- 1:2 (I think)
Ammo- 3.8 in. steel ball bearings
Burst disk- 7 sheets of wax paper (I ran out of Alum. foil)
Barrel- Aluminum, 3/8 in. 3 feet long
Chamber- all steel, 19 inches with fittings

[jrrdw]

Wax paper, interesting. Never heard of using that before. Good work!

[Acdcmonkey1991]

It works pretty well. I wanted to get a test done tongiht, and I was out of aluminum foil so I just thought , hey, why not?

[bigbob12345]

cool, reminds me of my BDMS
Nice job
Though the chamber is probably a little overkill. You will lose not more than 50fps if you make the chamber half the size.

[JDP12]

yea a bit overkill IMHO... but still nice gun

[Acdcmonkey1991]

Overkill because of the steel parts?
Update: got the reducer

[bigbob12345]

No, overkill becasue of the chamber size relitive to the barrel size.

[Carlman]

hey mate,

does your union seal 100%?

i have made something similar with a galvanized steel union and it still leaks even with bike inner tube for gasket.

thanks man.

[jrrdw]

hey mate,

does your union seal 100%?

i have made something similar with a galvanized steel union and it still leaks even with bike inner tube for gasket.

thanks man.

Try o-rings, sometimes a minor miscut will cause a leak and will be very hard to find exact cause.

[starman]

Are you using a trigger device to initiate the burst or just filling with air until it bursts? From the gun's apparent simplicity, it appears to be the latter.

Drywall is not going to offer very substantial resistance as target material, even 2 or 3 layers. Try some 3/4" plywood and "2 by" material and see what you get.

[Carlman]

its all good now thnx jrrdw

im using packing tape and it seals 100% with no orings or gasket

[Acdcmonkey1991]

What I did to get it to seal is an o-ring I found that fits perfectly, btw starman, it wasnt drywall, it wazs cement board.