Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 44 users online :: 4 registered, 0 hidden and 40 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Cartridge ejection system?

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.
Sponsored 
  • Author
    Message

Cartridge ejection system?

Unread postAuthor: FighterAce » Sun Feb 14, 2010 8:56 am

Few days ago I made my first working piston valve that has a spring to keep it sealed so it doesnt need to be filled from the pilot valve. Both fill valve and pilot are full metal schrader valves.

Here it is..
Image

Then I started searching for a gun to put it in and then found this bad boy :D
Image

In that sniper rifle, the valve will be positioned somewhere behind the trigger guard in line with the barrel. Its air tank will be above the barrel so its gonna be in reverse then on the pic of the valve. The first thing that struck me when I made the gun 1:1 on paper is that my nail darts fit into that magazine with approx 7mm of clearance on each side. So why not make it magazine fed. I made an animation how the whole thing will work but without the ejection system. Its my first animation so I apologize if I messed something up...

Image

Once fired I will move the barrel forward to unlock the cartridge. By some means, the empty cartridge will fly out, spring pushes a new cartridge into the chamber and the barrel moves back to lock it. The cartridges will be same material as the barrel - green 1/2 PVC. They will have O rings on the ends to make an air tight seal when locked.
The only problem I have is that I dont know how to make the empty cartridge fly out once I move the barrel forward.

Since the air chamber, valve and barrel will be encased in a wooden shell carved into that rifle, the mechanical possibilities are endless, I just need an idea how to do it.
I was thinking about mounting a metal rod to ride a bit behind the barrel with a spring powered plate. When the barrel moves forward so does the rod, once the barrel is in the most forward position, the plate will be aligned with the cartridge and released, pushing the cartridge out. My worry is that the next cartridge will come up before I have the time to move the barrel back and get that plate back into its position so the cartridge has no problems coming up. It could just stop it for a bit and when I move the barrel back, the cartridge comes up or it could jam or even worse empty the whole mag in a split sec.
Any suggestions?
  • 0

User avatar
FighterAce
1st Lieutenant
1st Lieutenant
 
Posts: 286
Joined: Fri Oct 23, 2009 1:28 pm
Location: Croatia/Zagreb
Country: Croatia (hr)
Reputation: 1

Unread postAuthor: Techie » Sun Feb 14, 2010 12:01 pm

the inside barrel could be cut at an angle to slide behind the o-ring and push the cartridge out.

and how did you do the animation? looks very nice :P
  • 0

User avatar
Techie
Specialist
Specialist
 
Posts: 54
Joined: Sun Nov 15, 2009 7:46 am
Reputation: 0

Unread postAuthor: FighterAce » Sun Feb 14, 2010 12:38 pm

If the barrel is cut at an angle then the barrel-cartridge O ring seal will leak.

I made the animation using MS paint and Jasc's animation shop.
  • 0

User avatar
FighterAce
1st Lieutenant
1st Lieutenant
 
Posts: 286
Joined: Fri Oct 23, 2009 1:28 pm
Location: Croatia/Zagreb
Country: Croatia (hr)
Reputation: 1

Unread postAuthor: Techie » Sun Feb 14, 2010 12:52 pm

hmmm...i guess so.
i cant think of anything else, but if the o-rings are sealing to the inner barrel and not the outer barrel you could cut a slit in the outer barrel on either side and push the carts. out
  • 0

User avatar
Techie
Specialist
Specialist
 
Posts: 54
Joined: Sun Nov 15, 2009 7:46 am
Reputation: 0

Unread postAuthor: FighterAce » Sun Feb 14, 2010 1:05 pm

Yes thats what I was explaining in the first post but I would to it mechanically so when I move the barrel forward the cartridge would automatically eject.

I was just thinking about it... if I made the pusher plate big enough it could eject the empty cartridge and then hold the rest until I move the barrel back a bit and retract the pusher plate.
Think that would work?
  • 0

User avatar
FighterAce
1st Lieutenant
1st Lieutenant
 
Posts: 286
Joined: Fri Oct 23, 2009 1:28 pm
Location: Croatia/Zagreb
Country: Croatia (hr)
Reputation: 1

Unread postAuthor: Techie » Sun Feb 14, 2010 1:20 pm

when you say big do you mean thick? otherwise unless you have a really strong spring the carts might get stuck in the spring
  • 0

User avatar
Techie
Specialist
Specialist
 
Posts: 54
Joined: Sun Nov 15, 2009 7:46 am
Reputation: 0

Unread postAuthor: FighterAce » Sun Feb 14, 2010 1:38 pm

They cant get stuck in any spring. The pusher plate is basically a piece of metal mounted on a metal rod(witch is fixed to the barrel) and it can swivel. The spring is behind it pushing it against the empty cartridge. The pusher plate will not go out the ejection port. When viewed from the top it will stretch diagonally across the magazine. Cartridges will be 20mm in diameter so the pusher plate will be lets say 18mm and the spring pushing it will be 10mm max in diameter.
And in the magazine the cart. ride on a plate under witch is a spring that pushes it up.

I dont think thickness is a major factor but length is. If the plate stretches across half of the magazine then theres a chance of the cartridges coming up at an angle.
  • 0

User avatar
FighterAce
1st Lieutenant
1st Lieutenant
 
Posts: 286
Joined: Fri Oct 23, 2009 1:28 pm
Location: Croatia/Zagreb
Country: Croatia (hr)
Reputation: 1

Sponsored

Sponsor
 


Unread postAuthor: jackssmirkingrevenge » Sun Feb 14, 2010 2:48 pm

Nice work with the valve, why not have the air eject the cartridges for you?

I made the animation using MS paint and Jasc's animation shop.


FTW!!! :D :D :D
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: FighterAce » Sun Feb 14, 2010 3:27 pm

jackssmirkingrevenge wrote:Nice work with the valve, why not have the air eject the cartridges for you?

I made the animation using MS paint and Jasc's animation shop.


FTW!!! :D :D :D


Pretty nice concept but reading the posts I see you had some power issues.
I might use that on my future projects when I'm 100% sure I know how it works and when I'll be able to improve on it. I'm pretty new to piston vales let alone semi auto. Just wanna keep things simple and because it is a sniper I'd like to have that manual action.

When I get some cash I'll make a prototype of that pusher plate to see if it works.
Any other cartridge ejection designs are welcome :D
  • 0

User avatar
FighterAce
1st Lieutenant
1st Lieutenant
 
Posts: 286
Joined: Fri Oct 23, 2009 1:28 pm
Location: Croatia/Zagreb
Country: Croatia (hr)
Reputation: 1

Unread postAuthor: iknowmy3tables » Sun Feb 14, 2010 4:14 pm

there have been several attempts including mine but I know a very down to earth design that can be easily adapted to meet your current design

I recall a cartridge system one of our members (I'd like to credit the person so anyone help me find it if you know it) built where the cartridges were first pushed forward against the barrel and out of the hold of the magazine, a bar attached to the top of the bolt held the cartridge in place in the forward position, but when pulled back the bar stopped blocking the cartridge from exiting so it was pushed out by the fresh cartridge below it. I think the design used a sliding bolt to push the cartridges against the barrel but just as easily it could use a sliding barrel
give me some time to look/draw it up
  • 0


iknowmy3tables
Major General
Major General
 
Posts: 1558
Joined: Fri Dec 15, 2006 3:57 pm
Location: maryland
Country: United States (us)
Reputation: 0

Unread postAuthor: FighterAce » Sun Feb 14, 2010 5:25 pm

Thats pretty interesting.. cant wait to see the details :D

But I see one flaw in that design...

iknowmy3tables wrote:the bar stopped blocking the cartridge from exiting so it was pushed out by the fresh cartridge below it


If the bar is not blocking the cartridge that just replaced the empty one, the 3rd cartridge will eject the 2nd and so on until the magazine is empty.
Its the same problem I explained in the pusher plate design. If it doesnt retract, the cartridges will just go up and out the chamber or jam.

I just realized I too had a fatal flaw... feed lips!
Without them the cartridges will just fly out the magazine but with them they wont go straight up but forward and up at an angle. But thats not all.. for feed lips to work, bullets need to be picked up by the bolt witch moves rear to front. I have a barrel that moves forward to back.
Guess I'll have to redesign the whole thing...
  • 0

User avatar
FighterAce
1st Lieutenant
1st Lieutenant
 
Posts: 286
Joined: Fri Oct 23, 2009 1:28 pm
Location: Croatia/Zagreb
Country: Croatia (hr)
Reputation: 1

Unread postAuthor: iknowmy3tables » Sun Feb 14, 2010 6:58 pm

sorry I don't think I explained it well, the diagram should explain everything,

we really ought to find the creator cause the design is fantastic I recall seeing it after I made my deus ex machina in 2007, and to be honest I felt slightly humbled because the design was just so practical and seemed to be the better design of choice in almost all applications I'm suprised I don't see many adaptations of it

this design has been modified to use a sliding barrel bolt, the original I think used a separate sliding bolt but I might be wrong

one of the issues with the original I recall was that the top retaining piece was really narrow and flimsy looking because the friction of the retaining piece had to be minimized so the cartridges didn't slide back with the bolt, a simple piece of springy metal, a leaf spring if you will, put in as shown and a tapper on that part of the barrel/bolt, as shown, should fix this, it will probably be easier to install on the side but I drew it on the top for viewing purposes
  • 0

Attachments
simplecartridgesystem.PNG

iknowmy3tables
Major General
Major General
 
Posts: 1558
Joined: Fri Dec 15, 2006 3:57 pm
Location: maryland
Country: United States (us)
Reputation: 0

Unread postAuthor: sgtmik » Sun Feb 14, 2010 7:32 pm

That's pretty good. Making the air actuated breech is going to be a little more challenging. It will have to move forward quite a bit so you might get something bulky. Anyway good luck in the project!
  • 0

Check out my YouTube profile!
http://www.youtube.com/user/sgtmik
User avatar
sgtmik
Private
Private
 
Posts: 17
Joined: Thu Jul 31, 2008 10:23 am
Location: St-Hubert, Canada
Reputation: 0

Unread postAuthor: PVC Arsenal 17 » Sun Feb 14, 2010 8:15 pm

Excuse the horrible quality but here is a video of the ejection system on my TFS-Semi Here is a video actually ejecting a spent shell. Notice that I was holding the shell in place because I hadn't built a magazine yet.

In this example, I used a reverse acting air cylinder alongside the barrel to eject spent shells after each shot. The cylinder rod has a simple ramp at the end which pushes down on a spring plunger. For ejecting, the system worked very well, however you'll notice that this gun lacked the "barrel-locking" feature you have in your design. That is something I've been working to incorporate into one of my projects for months now and it's a very important feature.

Just a suggestion:
Having the shells eject from the same position they go to when they enter the breech presents a problem in that the top shell is exposed to the magazine stack and the ejection port at the same time. Because of this, the magazine stack may push up on the top cartridge and cause it to simply roll out of the ejection port or at least become crooked, causing it to lock in improperly. With this setup, a detent to address that problem can also be a pain in the ass to incorporate. However, with a setup that pushes the shells backwards and away from the place they enter, in other words staggering the magazine port and the ejection port, prevents the magazine stack from influencing the top shell. Doing so also gives you the freedom to work with better detent systems (a detent is still necessary) and gives you more room to attach a magazine well.

If you're using steel cartridges, a magnetic detent system could work very well.
  • 0

Attachments
se2flaw.PNG
The blue circle shows the open space that makes the top shell likely to fall out without a detent.
se2flaw.PNG (19.23 KiB) Viewed 2234 times
RSP-1.PNG
In this design, the shell enters the gun and is pushed backwards to a new location. This prevents the unwanted space that can cause the shell to fall out as it isolates the magazine port and the ejection port. In this case, the two ports are completely separate but they may also staggered to cut down on length. The amount of stagger should probably be at least half the length of the cartridge.
RSP-1.PNG (11.59 KiB) Viewed 2234 times

PVC Arsenal 17
Major General
Major General
 
Posts: 1762
Joined: Mon Mar 27, 2006 4:18 pm
Location: United States
Reputation: 1

Unread postAuthor: iknowmy3tables » Sun Feb 14, 2010 9:58 pm

the breech is not air actuated, it's moved and locked by a bolt, a sliding barrel design will requires that the barrel is locked when fireing, I set the design up to be a manually bolt action sliding barrel design like Fighter Ace said,
Once fired I will move the barrel forward to unlock the cartridge. By some means, the empty cartridge will fly out


@fighter ace: about your pusher plate idea on your above diagram, others have thought of it before, but it's never been sucessfully used as far a I can tell, I even tried implementing it into the deus ex machina when I couldn't get it to work and I realize some fundamental difficulties in the physical setup, be patient with me because it's a little complicated; so in the stack of cartridges where your top cartridge is exposed to the ejection port however you don't want the cartridge to fall out accidentally, so the design will use some sort of canyon or groove that the cartridge will be pushed into when a new cartridge is loaded, no mater what some kind of force has to push it away form the ejection port when the locked barrel isn't holding it or else the cartridge will simply fall out or not be aligned when the barrel does lock due to the most mild forces, so for example the top cartridge is pushed by the magazine spring in to a curved surface on top of the reviver cradling the cartridge so the surface of the receiver creates a force to hold cartridge in place, so to eject the cartridge reliably the spring on the pusher must generate a force that greatly exceeds the force holding the cartridge in place, so the spring can't be nearly a light as you probably think. but to make matters worse the pusher must retract AND the new cartridge must pop up into position before the bolt/barrel comes in contact with the cartridge. so a set length of the stroke bolt stroke for reloading the force, or work in this case, is dedicated to pushing the pusher back down and at least 3/8 inches of the stroke should be left to delay the bolt so the cartridge has time to pop up and in my and additional stroke length of any more than 2inches is excessive so you have less than (2-3/8=13/8=1 5/8 ) 1 5/8 inches of stroke length to reset the pusher but even worse, your have to translate the force 90 degrees through sliding the bolt against some sort of plane which with have large amounts of friction, and the the plane will have to be tailored so at no instant instant the force required to continue moving the bolt will become excessive

that above probably wont fully make sense to you. the point is the forces your dealing with in a pusher system tends to be much more than most people expect

edit: holy crap I wrote that
@pvc arsenal, I see you covered a little bit on separating the ejection port from the magazine, however I highly disagree with separating them completley you can overlap the ejection port and magazine to reduce length and bulkiness so and a 50% overlap provideds almost just as much saftey, also if you want to be able to load from the ejection port you need overlap
  • 0


iknowmy3tables
Major General
Major General
 
Posts: 1558
Joined: Fri Dec 15, 2006 3:57 pm
Location: maryland
Country: United States (us)
Reputation: 0

Next

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'