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Idea for semi-auto layout

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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Unread postAuthor: Technician1002 » Sun Jun 27, 2010 10:38 pm

Why is the air cylinder even needed. With a proper spring and piston mass, the same air that ejects the round can eject the bolt down. With enough mass, the bold would travel slow and would not open to the magazine until the round is spent and the chamber discharged (on my large QDV, about 20 mS). The bolt momentum will carry it past the magazine long enough to spring load the next round before the bolt finishes it's journey and returns chambering the new round.

Just my thought on this. Maybe I'm dreaming, maybe I'm on to something. I have played with an idea like that for a golf ball magazine.

I just don't have the time or resources to try all my ideas. Some work, some don't. The ones that do, work well.
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Unread postAuthor: Lockednloaded » Sun Jun 27, 2010 10:54 pm

Gun Freak wrote:Not understanding that either... If you mean to integrate it into the chamber, it already will be. Got it all planned out, just haven't had the time to sketch the full design

in PVC arsenal's design, the space inside the aircylinder is not only integrated into the chamber, it is the chamber, no other parts
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Unread postAuthor: Gun Freak » Mon Jun 28, 2010 12:27 am

Technician1002 wrote:Why is the air cylinder even needed. With a proper spring and piston mass, the same air that ejects the round can eject the bolt down. With enough mass, the bold would travel slow and would not open to the magazine until the round is spent and the chamber discharged (on my large QDV, about 20 mS). The bolt momentum will carry it past the magazine long enough to spring load the next round before the bolt finishes it's journey and returns chambering the new round.

Just my thought on this. Maybe I'm dreaming, maybe I'm on to something. I have played with an idea like that for a golf ball magazine.

I just don't have the time or resources to try all my ideas. Some work, some don't. The ones that do, work well.


You definitely have a point there, but for me, it would be safer to use a cylinder because it would be tough to find the right spring and piston mass to get that to work perfectly. If I continue with this design, I will MOST definitely give that idea a go, it would be simple enough to make that area serviceable for upgrading and repairing. This will all be taken into consideration in the designing stage. I am still in the musing stage though :wink: Some time this week I will have the design posted for you and others. Thanks as always Tech.

in PVC arsenal's design, the space inside the aircylinder is not only integrated into the chamber, it is the chamber, no other parts

Oh ok cool, thanks for that.
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Unread postAuthor: MRR » Mon Jun 28, 2010 12:36 am

Sorry to say that but nearly all designs have been done before including this one.

POLAND_SPUD started with this design (even he got it from somewhere else) and developed it into his Semiauto MKIII.


Have a look. It's a different configuration but basically the same.
http://www.spudfiles.com/forums/semiauto-mk-iii-vids-t20259.html
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Unread postAuthor: Lockednloaded » Mon Jun 28, 2010 1:09 am

MRR wrote:Sorry to say that but nearly all designs have been done before including this one.

POLAND_SPUD started with this design (even he got it from somewhere else) and developed it into his Semiauto MKIII.


He's not calling it a new design, just a more ergonomic layout, and better magazine positioning.

And Gun Freak, Tech's right, this could be easily achieved with a small detent or long, tight barrel. you'd just be re-desgning the blowback principle.
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Unread postAuthor: POLAND_SPUD » Mon Jun 28, 2010 1:15 am

I had been talking a lot about this design but the first person who built it was either brtrettel or PVC_arsenal.. I built mine 1 or 2 months later

ohh and sorry to tell you that but your design has already been discussed... :wink:
I wanted to use it on MKIII but later I changed my mind
IMO It's worth trying
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Unread postAuthor: ramses » Mon Jun 28, 2010 10:33 am

Gun Freak wrote:
LockednLoaded wrote:the upward force of the ammo being forced into the barrel will damage the barrel or the ammo if the cylinder pushes even a little too far, but this may not be a problem if you custom machine a cylinder.

That's what I thought he meant.... Yeah it would be easy to just grind down the cylinder until it no longer pushes the ammo too hard.



One could also buy a cylinder with the desired stroke and a threaded shaft. With a coupling, threaded rod, and loctite, you could adjust the length of the shaft until it is where you want it, then loctite it in place.
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Re: Idea for semi-auto layout

Unread postAuthor: MRR » Mon Jun 28, 2010 11:04 am

@Lockednloaded
So he didn't call it a new design? :wink:

Gun Freak wrote:I've been musing about semi autos and got an idea for a new design that I had never seen done before. Instead of making all the dead space between the QEV and the projectile, why not put the air cylinder and mag under the barrel with the cylinder facing up and the mag parallel to the barrel? the projectile could then be closer to the valve... here is a quick sketch...
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Unread postAuthor: btrettel » Mon Jun 28, 2010 2:17 pm

POLAND_SPUD wrote:I had been talking a lot about this design but the first person who built it was either brtrettel or PVC_arsenal.. I built mine 1 or 2 months later


I've seen some discussion of who did this first and I thought I'd offer my take...

The idea to use an air cylinder in semi-auto seems to originate with Ragnarok, though I have no idea if he made a prototype. CaptainSlug independently developed a similar idea with his ABP5K. A few months ago I recall finding a large bore spud gun from the mid-2000s that used an air cylinder as well, but I can't find it at the moment.

The idea to use an air cylinder isn't new, but the air cylinder+QEV+3way valve idea is fairly new and novel.

I independently developed my system without knowledge of the functionality of any earlier guns aside from CaptainSlug's ABP5K. My designs in June and early July 2008 used a QEV and two valves, but I then realized I could replace the functionality of the two valves with one DCV in mid-July judging by my McMaster-Carr orders. I vaguely remember sitting in my parents' basement when I realized I could replace two valves with one 3 way valve... it was a serious revelation to me. I am not aware of anyone who used 3 way valves aside from slide valves with QEVs prior to myself.

In late July I asked CaptainSlug about air cylinders. I posted FANG 1 in a partially completed state in late August. By late November I had the gun in its final state.

PVC Arsenal 17 seems to have started thinking about this in October 2008. So it seems I beat him in conception but not fully in execution.

Who made it first doesn't really matter, but this is what I know.
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Unread postAuthor: POLAND_SPUD » Mon Jun 28, 2010 2:41 pm

http://www.spudfiles.com/forums/the-sem ... 12225.html

heh... beaten

I completed the first version of the semiauto in December so that was almost exactly 1 month later than you
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Unread postAuthor: btrettel » Mon Jun 28, 2010 3:25 pm

That's 2007, not 2008, so it's a while before me. I wasn't aware of that. Nice.

It's real odd this idea wasn't more well known in the past as it's really simple and works well.
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Unread postAuthor: Gun Freak » Tue Jun 29, 2010 12:24 pm

Ok Poland, I've seen your semi many times, not saying this is a new concept. Just a new layout! I was only wondering why nobody used this layout over the other way (cylinder behind the qev with big dead space) because it seems way better and more compact.
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Unread postAuthor: Lockednloaded » Tue Jun 29, 2010 6:10 pm

the cylinder isn't necessary if you get a tight bore barrel, just have a "blowdown bolt" kind of like blow back, but suited to your configuration. here's my design, just reconfigure it a little
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Unread postAuthor: clemsonguy1125 » Tue Jun 29, 2010 6:52 pm

Or something like this
(JSRs Animation)
EDIT-Sorry about the quality
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Unread postAuthor: Gun Freak » Tue Jun 29, 2010 9:02 pm

Lockednloaded wrote:the cylinder isn't necessary if you get a tight bore barrel, just have a "blowdown bolt" kind of like blow back, but suited to your configuration. here's my design, just reconfigure it a little

I know, I understand the blowback configuration, I already said I'd look into it, thanks.

@clemsonguy that concept is completly different and not applicable here.
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