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pneumatic cartridge design

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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pneumatic cartridge design

Unread postAuthor: sputnick » Mon Dec 29, 2008 2:22 pm

Recently, I have become interested in pre-charged pneumatic cartridges, and having an idea, I went ahead and designed this...

The green is a pipe the same diameter of the barrel, and ideally there would be an O-ring seal on the barrel that would seal against the small green portion.

The cartridge would be fired ideally by a spring powered bolt to slam it against the barrel, using the rear of the green section to punch out the disc that holds the pressure.

This has not been designed with any real size limits, It was designed with a 1" chamber, and a 1/2 inch barrel.

I would greatly appreciate any input, or constructive criticism you have, having never built one, i would not know the typical troubles that arise from pre-charged cartridges
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Unread postAuthor: Mateo » Mon Dec 29, 2008 3:00 pm

ive tried making these and could have been successful but i cant seem to get the pressure in the cartridge right before the blasting point of the disc. i always go a little over and boom! so i just lost intrest after a while. but you should try it. if you get it it could be a cool ad on to the bottom of a paintball/airsoft gun.
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Unread postAuthor: Sticky_Tape » Mon Dec 29, 2008 3:46 pm

I't has been designed before by JSR olny with a 6mm barrel I don't think he got it to work though.
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Unread postAuthor: SEAKING9006 » Mon Dec 29, 2008 3:51 pm

It would be useful for large caliber designs, like a Pak-40 or something.
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 30, 2008 7:08 am

Looks similar to mine ;p

Image
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Unread postAuthor: Ragnarok » Tue Dec 30, 2008 7:35 am

jackssmirkingrevenge wrote:Looks similar to mine ;p

Not quite. I'm not sure exactly what he's going for, but his projectile isn't held within the cartridge. It seems like he'd have to load the projectile, then smoosh (excellent word :D) the cartridge over the end of the breech.

I can't personally see why that's desirable though.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: sputnick » Tue Dec 30, 2008 10:18 am

Ragnarok: The green is not a continuation of the barrel, it is a small piece of pipe the same diameter of the barrel, which is preloaded with the projectile,

And Sorry JSR, I had no idea that you had the exact same design! But with yours, couldnt the projectile roll into the chamber and then not fire?
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Unread postAuthor: psycix » Tue Dec 30, 2008 11:47 am

sputnick wrote:And Sorry JSR, I had no idea that you had the exact same design! But with yours, couldnt the projectile roll into the chamber and then not fire?

A simple thingy like a bolt or rim sticking up can prevent that.

Ragnarok wrote:I can't personally see why that's desirable though.

JSR's cartridge is basically a gun with ahort barrel.
A loaded cartridge can be dangerous to transport.


EDIT
Fixed quote
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Last edited by psycix on Sat Jan 03, 2009 2:53 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 01, 2009 12:51 pm

psycix wrote:JSR's cartridge is basically a gun with a short barrel.
A loaded cartridge can be dangerous to transport.


However, without a loaded cartridge, you can't really have a magazine fed launcher.
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Unread postAuthor: sputnick » Fri Jan 02, 2009 10:25 am

JSR's cartridge is basically a gun with ahort barrel.


Mine is aswell, although the difference is thatmine holds the projectile in the section of pipe that serves as a continuation of the barrel, that way, i could use higher pressures with ammunition like paintballs or othersuch ammo without the fear of them colapsin or distorting under pressure.

Also, Mine is designed usingprimarily off the shelf fittings, JSR's looks like it usesmany custom fabricated parts, which would be labour intensive aswell as impossible for me to make, not having a lathe or any real precision instruments.

Just thought I would clear that up. :D
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Unread postAuthor: sputnick » Fri Jan 02, 2009 10:26 am

JSR's cartridge is basically a gun with ahort barrel.


Mine is aswell, although the difference is that mine holds the projectile in the section of pipe that serves as a continuation of the barrel, that way, I could use higher pressures with ammunition like paintballs or other such ammo without the fear of them colapsing or distorting under pressure.

Also, Mine is designed using primarily off the shelf fittings, JSR's looks like it uses many custom fabricated parts, which would be labour intensive aswell as impossible for me to make, not having a lathe or any real precision instruments.

Just thought I would clear that up. :D
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 02, 2009 11:27 am

As it's not clear from your diagram, what fittings do you intend to use exactly to hold the burst disk in place?
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Unread postAuthor: sputnick » Fri Jan 02, 2009 5:58 pm

Well, since it was designed primarily with 1 inch pvc as the chamber, i was thinking something like a female thread reducer, then maybe take a 3/4 reducer (the CPVC kind, that have 1inch male thread, and go to 3/4 inch pipe), andcut off a section of the threads at the rear, then screw that into the rear, and most likely JB weld it inside, then after inserting the disc, screwing in the rest of the threaded reducer, Again, just snowballing here, it was just a rough idea that will probably need much refinement if it is ever to be made, so I figured the people who have made these with much success would be able to point out the flaws

Maybe tomorow I can make up another diagram for you, however that cannot be untill tomorrow since I am at the cottage, and do not have a decent computer.
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Unread postAuthor: psycix » Sat Jan 03, 2009 2:57 pm

jackssmirkingrevenge wrote:
psycix wrote:JSR's cartridge is basically a gun with a short barrel.
A loaded cartridge can be dangerous to transport.

However, without a loaded cartridge, you can't really have a magazine fed launcher.

You can.
Just use a separate ammo loader, like a blow forward bolt + mag.
But I have to agree that a loaded cartridge is easier, more powerful (no loading system needed) and less complicated.
Basically all bullets of todays firearms are also loaded cartridges.
The propulsion charge and the projectile are loaded together.
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Unread postAuthor: sputnick » Sat Jan 03, 2009 9:33 pm

Here is the revised diagram, labeled and colour coded.
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