SpudFiles

I was wondering how effective this would be.

The gun would have two burst disks (one in each union in the diagram).
The two burst disks would have between them a volume to act as the pilot, and on one end of this pilot would be a pressure chamber, and on the other side would be the barrel.

The chamber and the pilot would each be filled to just under the burst disk's breaking point (e.g. if the breaking point is 60PSI, raise them both to ~50PSI)

Then fill the chamber so that the difference between the pressure in the chamber and the pressure in the pilot is just under the disk's breaking point (in this example, the chamber would be raised to ~100PSI.

To fire the gun, simply vent air out of the pilot until the difference in pressure between the chamber and pilot bursts the disk between them, and then the pressure from the chamber dumps into the pilot, bursting the other disk, and launching the projectile.

you would have to have a way to shut of the pilot valve as soon as its piloted so you dont loose pressure

This has been done before, it's a form of triggered burst disk. You don't really need to shut off the pilot, just make sure your pilot valve has very little flow, to reduce loss. Also try and keep the pilot volume low... you want it to vent quickly enough that there's no appreciable delay when firing, and if your pilot valve has low flow then you're going to need a low pilot volume to achieve that.

The pilot does for a double disk piloted burst disk does not have to be fast. A small bleed screw works fine to cause one disk to fail, thus causing a failure of the second disk. Little is lost out the pilot.

It's in the

I know it's not what you're asking... but have you considered building a detent gun ?

You'd probably need a lightweight sabot if you want to launch just anything that fits the barrel

jackssmirkingrevenge wrote:It's in the

Ah. I didn't really think such a simple design had not been thought up before.

I guess that answers my question if it's in the wiki, it's probably because it works .

I was thinking about potentially using it for a huge cannon at some point down the road, but mostly I just wanted to know if the idea actually worked.

POLAND_SPUD wrote:I know it's not what you're asking... but have you considered building a detent gun?

For larger calibres I think it's better to go for a burst disk, with a single disk and reasonably high flow valve you'll get almost instantaneous firing.

Somethingalong these lines.

yeah maybe... though I still don't understand what the point is in using two burst disks (I know how it is supposed to work but I don't think it is any better than a burst disk + blowgun (or any other valve) combo)

Poland probably to improve response time.

Gun Freak wrote:Poland probably to improve response time.

Indeed. I thought it up when me and my friend were contemplating making a huge gun (We figured that if we had to buy PVC in 10' lengths at Home Depot, why not make a 10' gun?). This way we wouldn't have to wait while the compressor took it up those last few PSI to burst the disk, we could just vent a little bit of air.

mlz3000 wrote:(We figured that if we had to buy PVC in 10' lengths at Home Depot, why not make a 10' gun?)

I like the way you think
Pretty good idea of yours though, I mean its smart, you just got beat to it Same thing happened to another guy here. He was a french dude who came here to share his gun with a QDV on it thinking it was original only to find out that Technician1002 had already made one

Gun Freak wrote:Same thing happened to another guy here. He was a french dude who came here to share his gun with a QDV on it thinking it was original only to find out that Technician1002 had already made one

This was even worse

Gun Freak wrote:Poland probably to improve response time.

Thing is, with huge cannons, you're not exactly holding them to your shoulder and tracking a moving target, if you're lobbing objects far away at a 45 degree angle, or blasting domestic appliances at short range, a 1-2 second delay between opening the valve and the cannon firing shouldn't really make a difference.

This way we wouldn't have to wait while the compressor took it up those last few PSI to burst the disk, we could just vent a little bit of air.

who said you can't fill the gun to 90psi (assuming that the disk burst at 120psi) and then fill it to 120psi when you want to fire it?

POLAND_SPUD wrote:

This way we wouldn't have to wait while the compressor took it up those last few PSI to burst the disk, we could just vent a little bit of air.

who said you can't fill the gun to 90psi (assuming that the disk burst at 120psi) and then fill it to 120psi when you want to fire it?

That's what this design intended to avoid. With a huge chamber and a small compressor, that would take longer to fire than this design.

But I agree, If I even end up making a burst disk pneumatic, it will probably be just a single disk, and to fire you just fill the chamber until the disk bursts.