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full auto pneumatic

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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full auto pneumatic

Unread postAuthor: CYANIDEGENOCIDE » Wed Nov 12, 2008 3:41 pm

Image

I saw this image and thought it could work with minor redesign.
Instead of the spring in the back use air pressure to move the bolt. Put the spring in the front to recoil the bolt. The bolt itself will need to be a hollow (like a thick walled pipe) so it can slide over the protruding breech. The breech will need holes drilled in the sides to let in the propelling gases. The rear of the bolt will have a plate that covers the hole so air would not escape.
When the bolt slams foward the plate stops on the back of the barrel, air passes the plate goes through the bolt, entering the peripheral holes and out the barrel. The spring recoils the bolt which picks up the plate off the barrel and seals it again.
A simple magazine feed with a housing, follower, and spring and viola.
Of course a massive chamber at maximum pressure would be required. Using a progressive rate spring I think it could work for burst fire until the spring and the air pressure find their equilibrium. Does this seem feasible? Have I missed something major?
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 12, 2008 4:01 pm

it's hard to follow what you're suggesting without a diagram but are you suggesting a variation of the blow-forward breech?

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Unread postAuthor: CYANIDEGENOCIDE » Wed Nov 12, 2008 4:07 pm

Thanks JSR, I knew you'd be along to simplify what I was suggesting. Generally yes thats it, looks like its not a new idea.
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 12, 2008 5:58 pm

I think it could work for burst fire until the spring and the air pressure find their equilibrium.


This is largely why this sort of breech has failed as full auto under constant flow. What you need is a mechanism that shuts off the air flow once the bolt has move forward, allowing it to return unopposed before firing again.
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Unread postAuthor: Pilgrimman » Wed Nov 12, 2008 6:11 pm

It would be labor-intensive, but you could grind the stops out on a PVC ball valve, and attatch a motor to it for on-off airflow.
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 12, 2008 6:36 pm

.. while you're at it, drill another hole through which you can load ammunition ;)

The idea's been proposed before, what puts me off is that you're adding an external source of power, not to mention a considerable one giving the amount of friction ball valves normally offer.
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Unread postAuthor: jitup » Wed Nov 12, 2008 6:52 pm

The ball valve would work if you are using 1 inch or smaller pipe, or you found a way to lubricate it. Also I think you can some how leach a little exaust gas off from the rear of the barrel to operate the valve. I would suggest using some sort of a "slip valve" for lack of a better term. It should be spring loaded and you will probably have to make it your self.
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Unread postAuthor: SEAKING9006 » Sun Nov 16, 2008 9:27 pm

It seems everyone has forgotten about my autocannon design. :?
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Unread postAuthor: THUNDERLORD » Sun Nov 16, 2008 11:23 pm

jackssmirkingrevenge wrote:
I think it could work for burst fire until the spring and the air pressure find their equilibrium.


This is largely why this sort of breech has failed as full auto under constant flow. What you need is a mechanism that shuts off the air flow once the bolt has move forward, allowing it to return unopposed before firing again.


My latest idea on that involved a spring plunger (Similar to a tire gauge),
The plunger tube would be inside the chamber and the solid rod (like a tire gauge stick) on the outside of the air chamber.
The rod would press a valve that pilots (trigger) the piston (once the correct chamber pressure was reached).
And the "fired" air would then enter the blow forward bolt chamber.
Seems like the pressure on the plunger could be high enough to open the pilot valve due to the diameter difference(?).

...Or possibly a gas vent near the end of the barrel , Just like a gas assisted rifle bolt, except to depress the piston pilot, firing into the blow forward bolt as well(?)

In a few of the old posts involving ball valve repeating ideas that I recall, valve opening speed, ROF/ feeding issues, Besides friction, wear For example if the ball valve took care of loading it would need a separate valve behind it or the opening speed is that of the BV. Course then there's no need for a blow forward bolt, a different design (and performance) completely.

Anyway cool topic. This one's mostly why I got into SF's: http://www.spudfiles.com/forums/6mm-semi-added-trigger-and-mag-t10075.html 8)
Also, I like the image of the SMG although it would look better IMO if it showed shell extraction and ejection.
:P 8)
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Unread postAuthor: nibbler125 » Sun Nov 16, 2008 11:43 pm

here is a vid of a completed one


http://www.youtube.com/watch?v=LfHw-DCoCDs
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 17, 2008 6:41 am

SEAKING9006 wrote:It seems everyone has forgotten about my autocannon design. :?


Relatively complex electronics are something that I would personally want to avoid.

THUNDERLORD wrote:Besides friction, wear For example if the ball valve took care of loading it would need a separate valve behind it or the opening speed is that of the BV.


Not really, if the ball valve is doing loading an firing, then the projectile would only start travelling down the barrel once the ball valve was fully opened, unlike a "normal" ball valve cannon where the projectile would start moving the instant the valve is cracked open.

Another variation would be to have the mechanically rotated ball valve provide the pulsed air (not necessarily electrically powered, one could use an air motor, but this would greatly increase your air consumption) and use a blow-forward valve for reloading.

THUNDERLORD wrote:My latest idea on that involved a spring plunger (Similar to a tire gauge),
The plunger tube would be inside the chamber and the solid rod (like a tire gauge stick) on the outside of the air chamber.
The rod would press a valve that pilots (trigger) the piston (once the correct chamber pressure was reached).
And the "fired" air would then enter the blow forward bolt chamber.


Interesting thought, though if I've understood it correctly, isn't this a more complicated variation of having a piston valve or QEV piloted by a pop-off valve?

THUNDERLORD wrote:Also, I like the image of the SMG although it would look better IMO if it showed shell extraction and ejection.
:P 8)


Take a look here ;)
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Unread postAuthor: THUNDERLORD » Mon Nov 24, 2008 2:25 am

jackssmirkingrevenge wrote:...
Relatively complex electronics are something that I would personally want to avoid.

That's one reason I was excited about the plunger pressing a pilot valve idea.
But Now that I understand the pop-off piloting, I feel like I've reinvented the wheel, with different components. :wink:

As for the gas assist I think the ROF would need to be slowed somehow to allow the chamber to refill quick enough. (Since it will probably launch faster than fill)(?)

THUNDERLORD wrote:... or the opening speed is that of the BV.

:oops: I should've put a (?) after that and I did think about it later.
Closing time may waste air in this case (?)

jackssmirkingrevenge wrote:...Not really, if the ball valve is doing loading an firing, then the projectile would only start travelling down the barrel once the ball valve was fully opened, unlike a "normal" ball valve cannon where the projectile would start moving the instant the valve is cracked open.


Looks like I have a use for the BV's I have just sitting around.
Also after "firing" the ball part of the valve will release air into the magazine possibly becoming as pressurized as the reservoir. So I believe the mag. should have a vent hole(s) (?)...
Besides that the ballistics of round shot are slightly lacking.

THUNDERLORD wrote:Also, I like the image of the SMG although it would look better IMO if it showed shell extraction and ejection.
:P 8)


jackssmirkingrevenge wrote: Take a look here ;)

:shock: YIKES! I've seen that before surfing the web. I don't really want it on my harddrive(child'splay to me). But I had to look because it's got Caselman plans for sale!!! 8)
That guy seems like he wants to do what us wasps in america did.
Didn't get us that far IMO, but there are plenty of guns around now. Wonder if they'd let me join the BNP(?) :P :wink: 8)
BTWThis one's cool too.
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Unread postAuthor: Ragnarok » Mon Nov 24, 2008 2:47 am

THUNDERLORD wrote:But I had to look because it's got Caselman plans for sale!!!

I believe JSR (or someone at least) found a set of plans for the precise price of nada. :P

Link's somewhere on the forum, but I haven't the time to dig it up for you, sorry.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: THUNDERLORD » Mon Nov 24, 2008 3:23 am

Ragnarok wrote:
THUNDERLORD wrote:But I had to look because it's got Caselman plans for sale!!!

I believe JSR (or someone at least) found a set of plans for the precise price of nada. :P

Link's somewhere on the forum, but I haven't the time to dig it up for you, sorry.


I might send that guy 12 pounds just for the heck of it though! :P
Yeah I got to work early tommorrow myself. I'll search later.
Thanks Ragnarok. And JSR and all.

LOL from that link:
Only through mass non-compliance with all gun and knife
laws will we ever overthrow Britains anti-gun fascist gun laws.
"Vengeance will be mine, one bullet at a time"

I've wondered if that could be possible except without the vengeance part
Course IDK guns are mostly for shooting in rural areas so there aren't as many people. And they're more spread out and they could easily bust them all and make money and crappy jobs building/ working jails.
And that many on the city streets is just not good IMO.[/rant]

EDIT: I don't think it would work. For example, Just look at the current drug culture situation. It's quite obvious that america has/ is on the "Goooood drugs" not that weak stuff either. The cities have whole streets covered and littered with paraphenelia and drugs on every street. (zombie whackos too) Yet people get sentenced to years for simple possesion and most families have a member affected by the laws or prison. And they keep building more jails too. Poor trashy places build jails to get federal tax money from it since they're too stupid to do anything else. Or they just draw out longer alternative punishments (for years). So IMO it won't work. But it's harder to arrest people who are armed but not that many would be hard enough to battle...anyway.[/rant]
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Last edited by THUNDERLORD on Mon Nov 24, 2008 3:53 am, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 24, 2008 3:30 am

Have a look here for all your Caselman needs ;)
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