SpudFiles

Perhaps a spring mechanism to pop the shell out would make it easier to accomplish. Maybe even settling for semi-auto with a hammer being pulled back to initiate the spring loading while at the same time looking like it is the source of ignition.

A bolt-action rifle would fit the bill.

Well it seems like it would work...

However I'm actually working on a pneumatic cartridge design right now along with a hybrid... For the hybrid I was just going to use burst discs and air/MAPP. in 3/4" caliber as a side note... may neck it down

I feel it'll be difficult to fuel, but we'll see what happens I guess.

Good luck with yours

SEAKING9006 wrote:A bolt-action rifle would fit the bill.

Not in my case, I want to see this sort of action:

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hahah.

well good luck JSR..

why don't you want to just use an air/propane mix?

Because of the pressurizing?

ilovetoblowthingsup wrote:why don't you want to just use an air/propane mix?

Because of the pressurizing?

Pretty much, pressurisation means complicating the cartridge body to accomodate a burst disk, which is fine for a one-off launcher but with cartridges, you're going to be making lots of them so you want them to be as simple as possible.

The numbers _Fnord throws out, 360 fps sound reasonable for the setup. However, this is easily accomplished with even basic pneumy setups.

Wouldn't you like something with a little more whistle...like in the 700-1000 fps range? for all the trouble you would put into a system like this?

hmm

for mine i'm going to use a burst disk holder of a 1/4" coupler and a 1/4" pipe nipple... fits almost perfectly in copper pipe. Also commercially available!

However, I'm going to test my pneumatic cartridge first.

It's copper pipe with a toolies style valve in it...

I'll start a thread about it when I get home.

starman wrote:The numbers _Fnord throws out, 360 fps sound reasonable for the setup. However, this is easily accomplished with even basic pneumy setups.

Wouldn't you like something with a little more whistle...like in the 700-1000 fps range? for all the trouble you would put into a system like this?

No doubt about it, I can easily double that velocity for a 1 gram projectile with my 6mm burst disk, but this would not be about maximum performance. It's more of a mechanical interest project, seeing that spent brass fly

Good luck JSR can't wait to see the results

ilovetoblowthingsup wrote:Good luck JSR can't wait to see the results

I'll start off with some chrony tests for a sealed barrel, obviously some performance will be lost with an ejecting cartridge but I'll have an idea of what it will be like - have to get my hands on some oxygen first though, I'll see if i can get myself a small cylinder on Monday.

The spark gap in your diagram is not how it should be. You need to get the electrode closer to the chamber wall in order to ensure that it sparks there and not outside of the chamber. But you were probably already aware of that.
How will you make sure that there is no air in the chamber, simply purging it with O2?

You will need to use airtight projectiles in order to prevent leakage.

I think you should definitely start off with bolt action (or pump action).
Stop continuing the blowback failage.

psycix wrote:The spark gap in your diagram is not how it should be. You need to get the electrode closer to the chamber wall in order to ensure that it sparks there and not outside of the chamber. But you were probably already aware of that.

Naturally.

How will you make sure that there is no air in the chamber, simply purging it with O2?

Pretty much.

You will need to use airtight projectiles in order to prevent leakage.

It would take weeks for the composition to change, it just needs to be a tight fit.

I think you should definitely start off with bolt action (or pump action).
Stop continuing the blowback failage.

Blowback is in fact the easiest to make. Both bolt and pump action require a rim or groove on the cartridge and claw on the bolt face to grip it.

Bit of an update on this, I made a crude electrolysis setup in a bid to give an oxygen/butane atmospheric pressure "hybrid" a go, tried it out yesterday with sodium chloride but naturally I got a nice smell of chlorine gas from the positive terminal. I'm going to give it another go later with sodium hydroxide, yay for working in a lab

I got a nice smell of chlorine gas from the positive terminal.

:angel10: :angel10: :angel10: :angel10: :angel10: :angel10: :angel10: :angel7: :angel7: :angel7: :angel7: :angel7: :angel7:

I get the feeling that when you finally land on a cartridge you're happy with, it's going to be adopted by NATO or something.