SpudFiles

Cannon name: P.B.D.C. (Pnuematic Burst Disc Cannon)
Barrel: 2 feet of 3/4" sch40
Chamber: 1 foot of 2" sch40
Union: 3/4" sch80 rated for 130 psi
Fill valve: Metal Schrader valve
Gas source: Compressor, Bike Pump, CO2 tire inflator
Primary Burst Discs: Punched out vinyl shower curtain liners
Primary ammo: Empty 12 gram cartridges.


Other parts include:

2"-3/4" bushing
2~2" couplings
2" plug

Last night at Lowes I saw that they had PVC unions so one in 3/4" and decided to build the simple burst disc. I will fire it tomorrow when the glue is all dried.

This gun is the definition of simple and cheap. For a beginner this is as simple to construct and fire as a basic combustion. Great gun to start out with.

Yay Nice. I bet that cost you less than $10

Yeah, the union was the most expensive thing which cost me a whopping FOUR DOLLARS!!!

Cheap is the way to go.

I was going to send it to my cousins but they just got arrested for trying to set off a dry ice bomb in a construction site.

lol dumbasses the trick is not to get cought

Even worse than that was they waived they right to remain silent and confessed to the cops everything. They could have got a lawyer and made up some bullshit story of why they had dry ice and soda bottles on the construction site.

Lol even more of a dumbass. They should have said that used it to keep thier sodas cold.

Yes i know that would freeze them

That is a very simple cannon. I am unfamiliar with burst disk cannons. So when the chamber reaches a certain psi it breaks the shower curtain and works in place of a valve?Nice cannon btw.

Burst disks cannons are suprisingly rare... and I am suprised.

They yield the best performance, and their only sacrifice is that they can sometimes fire randomly.

They yield the best performance

I don't completely agree with that statement, in burst disc cannons the "valve" (burst disc) opens almost instantaneously but it doesn't always open completely, a lot of times the disc only bursts open very slightly only letting the air escape though a small rip or hole.

I think it is posible to get rid of the random fires by placing a ball valve prior to burt disk section so that when you open it the hpa will begin flowing into the bust disk section and pop it. You would have to fill the chamber to a pressure that you know the disk will never withstand and then some because of all the dead space, and i dont think you will sacrifice much flow either, and if the ballvalve is one of the big pvc ones then i think that you would have quite a nice gun. And it might even be an economic gun if you shop smart.

Correct me if I am wrong, but wouldn't adding a ball valve defeat the purpose of having a burst disk?

I would say so; the ball valve will only be slightly open by the time the burstdisk fails.

Acctualy, I know how to model this using the GGDT!
(skitters off)

The burstdisk will be exposed to full pressure within a few milliseconds of the balvalve starting to open;
Assuming the ballvalve takes .1 seconds to open fully, and the space between the 'disk and the valve (distance) it takes (time) for the disk to be subjected to nearly full pressure:
1" : 15 ms
5" : 20 ms
10" : 25ms
20" : 30ms

As you can see, even the largest "dead space" only allows one to open the valve 1/3rd of the way before the disk ruptures.

Well I fired this gun for the first time this morning and I have to say I was really impressed! It lobs a 12 gram pretty far. I only used thin plastic for the first few tests but I'll move on to some thicker stuff later.

I am actually pretty happy I invested $10 into making this cannon. It's a fun little toy to mess with. Not as powerful as some of my others but it has potential with stronger burst discs.


Oh yeah... can I apply this in that contest??

id say so. nice gun btw
i think ill build one

Read <a href="http://www.spudfiles.com/forums/viewtop ... &">THIS</a>.

Spudgun Build-Off! wrote:Threw all the moaning and growning, its here! This topic will be stickied and locked. If you would like to seek a answer or submit a cannon PM me by clicking the "PM" button at the bottom of this post. In your subject put "Spudgun Build-Off!". For a cannon being submitted to the contest use the same Subject title, and in the body of the document provide a link to the cannon and the name of the cannon. Before a cannon will be accepted this form below MUST be filled out:

Read people, read!