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My nearly finished semi auto

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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My nearly finished semi auto

Unread postAuthor: Copperboy » Sat Sep 30, 2006 2:12 am

This is a project ,inspired of Galfisk´s loading mechanism,I´ve been working on for a while, things are progressing slowly but this is how far I´ve come...

It´s a 16mm semi-auto with a "direct piston feeding mechanism"
Main ammo is marbles.

Gun body
http://i103.photobucket.com/albums/m128 ... semi-1.jpg

Right now the whole lot leaks wery much, but I will soon solder it tight.

Here´s an old "drawing" :lol: of it http://i103.photobucket.com/albums/m128 ... itning.jpg , note that the piston now looks more like this: http://i103.photobucket.com/albums/m128 ... G_0535.jpg
(the pilot volume right now is pretty overkill, so that has do be done with sooner or later)

Here´s a video of me testing it
http://s103.photobucket.com/albums/m128 ... t=test.flv
Note that I´m in need of some better sort of pilot/supply valve. There´s a lot of designs out there, how do you think I should solve this problem? The simpler the better...

Internal parts
http://i103.photobucket.com/albums/m128 ... G_0533.jpg

Any thought or suggestions are welcome! And P.S, I know the soldering job look like S**T! :lol:
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Unread postAuthor: CpTn_lAw » Sat Sep 30, 2006 2:42 am

I really like you piston design, and the whole reloading simplicity, though i wouldn't have designed it this way...i prefer "rifle-like" spudguns...
still, this is very nice, and don't forget to give us more pics and vids when it's done!!! have fun with the soldering :lol:
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Unread postAuthor: POS » Sat Sep 30, 2006 11:34 am

You should need some kind of pistol, that depressurises the valve when you pull the trigger, and when you let the trigger go, it should pressurise the gun again. I dont know if it exists, but it is sure I could make it. Got some sort of pic like that posted here somewhere.

Look here :

I wrote:Ok, here is my design. What I miss in the upper design is some kind of valve that stops the airflow to the pilotchamber when the gun is triggered. I found a sollution for that :


The sollution you see as number 1 :
A sort of piston valve, that uses a hollow piston. As you can see, on the left side air at a pressure of 100 psi is feeded to the valve. The piston stands in the forward stand, so the air can flow to the pilot chamber of the main valve of the gun. In the mechanism of "1" you see a spring. This needs to be a very strong spring, to hold the 100 psi. The moving part in the valve has 5 O-rings (the black dots, but you figured that out yourself i guess)

Like this, the gun is in a non firing state. Now when you pull back the moving part, the airflow from the airtank is sealed of, and the airpressure in the pilote valve wil drop, cause the air can flow away trough the right tube at 1. I forgot however to draw the pulling mechanism. It could be just a tiny metal bar soldered or welded to the moving part, wich can be pulled back with a keyring, or you could figure out areal trigger mechanism on that one. Enough room for improvisation.

Anyway, whan you pull it back, the pilote pressure drops, and the gun starts to fire. This is why I use a high pressure tank (300 psi or more) (number 4) and a regulater, or how do you call that thing that reduces pressure (number 3) In that case we have a quite long and continues flow of air and pressure for shooting the gun.

Now when you releas the trigger, the moving part moves up again (in valve number 1), sealing of the exhaust and letting in air in the pilote valve. The main valve closes again, due to the airpressure behind it, and the spring. That's why there need to be a spring. It doesn't need to be a very strong one, but one anyway.

Now what dou you guys thing about that ? Not bad, figuring that out, lying awake in my bed, hay

I think you should be able to trigger the tube thing labeled "1" with a trigger system. That could be a sollution for your problem.
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