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Attachment problems!

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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Attachment problems!

Unread postAuthor: PaperNinja » Fri Aug 17, 2012 7:14 am

To help describe my problem, lemme give you a picture of my gun.

Image

More:

http://i.imgur.com/YVjck.jpg
http://i.imgur.com/tY1CE.jpg
http://i.imgur.com/XWSGF.jpg
http://i.imgur.com/AgPNi.jpg


My plan was originally to insert my barrel (590 mm MadBull 6.03 tightbore) into the copper tube and use Apoxie Sculpt to seal the gap and keep the barrel in place.

Image

Image

Apoxie Sculpt & other (strong good) glues I have access to.

Image

(Don't worry, I'm getting to my problem ;))

I planned to do something like this:

Image

(with maybe a hopper instead of a stick mag)
As a replacement for blow-forward/back bolts as I was worried of the efficiency of those designs.

I figured the bolt would be moving more slowly than the bb, so by the time the hole has passed over the barrel the bb would have already left it so there would be no wasted power.

My original plan was to install the barrel, then drill holes as needed to install the detent and my mag. Now that my barrel has come, I kinda (REALLY kinda) don't want to drill in it if at all possible. (If there really is no good solution, then I can but...). How can I have the detent and mag fully functional, and have the barrel firmly secured onto the tube, or gun in some way?

Thanks for helping!



NOTE: If there is some SMALL thing I need to make this work, just say "You need JB weld" or "You need this brand detent" or something that :)
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Unread postAuthor: POLAND_SPUD » Fri Aug 17, 2012 8:44 am

uhmm

this is how I did this
http://www.spudfiles.com/forums/semiaut ... 20259.html
works nice but you need some sort of block with drilled ports in it or two Ts
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Unread postAuthor: PaperNinja » Fri Aug 17, 2012 10:09 am

you removed the videos?
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Unread postAuthor: POLAND_SPUD » Fri Aug 17, 2012 6:27 pm

yup - long story short -> the police :D
still have them somewhere though
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Unread postAuthor: PaperNinja » Fri Aug 17, 2012 8:45 pm

Oh ok, I've been looking at your diagram.
Basically to adapt that to my design would be to lead a (thin) air hose from my QEV air chamber to my magazine piston or a blow-forward bolt? clever...

Unfortunately I don't think I'll be able to use your design, I've already bought a lot of valves and such, I don't want all that to go to waste.
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Unread postAuthor: POLAND_SPUD » Fri Aug 17, 2012 8:51 pm

lol no... not at all - you need an air cylinder

1.when the chamber is pressurised and ready to fire the bolt is extended (it has already loaded a new round from the mag as soon as you pressurised the gun or fired it last time)...
2. when you pull the trigger and the gun fires the pressure in the chamber drops to atmosferic and so the air cylinder retracts ()thx to a spring inside the aircylinder....
3. once you release the trigger/pressurise the chamber again the next round is chambered and the whole cycle repeats
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Unread postAuthor: PaperNinja » Fri Aug 17, 2012 9:00 pm

I understand your design :)

My worry is that, while your main air port is UNDER the barrel, mine is behind it as the copper pipe that my barrel is epoxied into is straight, leaving no room for the blow-forward bolt.

One fix I could do would just to have a horizontal mag under the copper pipe, and have my blowforward bolt push UP, and seal against the barrel, Unfortunately that would rule out hopper and I'd be left with a lower capacity stick mag... whatever reloading is cool :D


I think I'll do that, thanks for your ideas!
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Unread postAuthor: POLAND_SPUD » Sat Aug 18, 2012 3:52 am

I don't think I get what you're saying - you don't need a blowforward bolt if you copy my design - an air cylinder does that for you
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Unread postAuthor: PaperNinja » Sat Aug 18, 2012 6:43 am

Well whatever it's called... it's a bolt-shaped thing that blows forward and loads a bb, maybe not technically a blowforward bolt.

I do see the difference though, a blowforward bolt is pushed forward as you fire, your design, imo better, pushes a bolt forward while charged.
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Unread postAuthor: PotatoEnemy17 » Sat Aug 18, 2012 8:24 am

Blow Back! I haven't actually tried this... But I think it would work.
An AK47, for instance, uses this method of reloading. I believe it is called gas blow back. I only drew the blow back part of the gun. Everything behind the bolt is for you to decide.
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Unread postAuthor: Crna Legija » Sat Aug 18, 2012 10:09 am

PotatoEnemy17 wrote: An AK47, for instance, uses this method of reloading. I believe it is called gas blow bac


a AK47 also has 40000 odd psi to push the bolt back, it can work but will take to much fine tuning to run smooth.
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Unread postAuthor: PotatoEnemy17 » Sat Aug 18, 2012 10:16 am

Lucky AK47, I wish I had 40000 PSI to play around with. :D Plus an AK47 has to push the bolt back very far compared to this gun.
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Unread postAuthor: POLAND_SPUD » Sat Aug 18, 2012 10:16 am

Blow Back! I haven't actually tried this... But I think it would work.
An AK47, for instance, uses this method of reloading. I believe it is called gas blow back. I only drew the blow back part of the gun. Everything behind the bolt is for you to decide.

The design I used works well because it's controlled by pressure in the chamber.
Even if you pressurise the gun to mere 50 psi the air cylinder will extend with a considerable amount of force. You just have to make sure that the spring inside the air cylinder is strong enough to retract it rapidly and you've got a perfect system.
Mind you that it isn't really my design - basically the same thing has been used in paintball guns for years


Yours will work but there are many variables that have to be right for it to work:
-pressure
-time the piston is exposed to pressurised gas
-stiction
-friction
-spring force

One of the above isn't right and the design might not operate the way you want it. Most likely it would be a real PITA to tweak all the variables.
Worse yet - even if it works just fine it might not work at all if you use lighter/heavier ammo or if you don't use a regulator to keep chamber pressure constant
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Unread postAuthor: PotatoEnemy17 » Sat Aug 18, 2012 6:32 pm

@POLAND_SPUD Your design is certainly good, but the bolt has the opportunity to be open before the ammunition has exited the barrel, cutting down on the efficiency of the design.
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Unread postAuthor: Crna Legija » Sat Aug 18, 2012 6:52 pm

PotatoEnemy17 wrote:@POLAND_SPUD Your design is certainly good, but the bolt has the opportunity to be open before the ammunition has exited the barrel, cutting down on the efficiency of the design.


you can help it stay closed a bit longer by using a tiny air line from chamber to air cylinder and putting the line near the back of the chamber.
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