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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: Mr.Tallahassee » Sun Sep 25, 2011 6:26 pm

It's been a little while since I've been on. I came up with an idea I want to try out. It's a simple idea but it requires more precision than I can give with simple power tools. Basically it's two halves that are bolted together with high tensile strength bolts. The piston will most likely be steel and the body will be aluminum. Both plugs will be steel. The pilot side o-ring has slots bored into the piston for a floating o-ring and the tolerances are fairly tight. The piston could possibly be used for a loading mechanism on the barrel because of the two o-rings in the middle of the piston. The point of this design is to try to be compact and powerful while also being a generic shape that could be incorporated into many different body styles.
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Unread postAuthor: Gun Freak » Sun Sep 25, 2011 6:50 pm

:lol:

Without area for pressure to act on it won't open :wink:

Unless I'm missing something...
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Unread postAuthor: POLAND_SPUD » Sun Sep 25, 2011 6:52 pm

uhmm it won't work
there is no air to act on the barrel side of the piston so there is nothing to open the valve when you pilot the pilot side
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Unread postAuthor: Demon » Sun Sep 25, 2011 8:03 pm

Well, there actually is if the barrel seat is smaller then the piston's OD.
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Unread postAuthor: POLAND_SPUD » Sun Sep 25, 2011 8:07 pm

well it is but there is no way for air to get there.. sure it could be modified
but it's not that there would be a lot of force acting on it anyway
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Unread postAuthor: Gun Freak » Sun Sep 25, 2011 8:12 pm

Something like this'd be better.
Still think this isn't really such a great idea though. :roll:
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Unread postAuthor: Mr.Tallahassee » Sun Sep 25, 2011 11:18 pm

Well, there would be area acting to pull the piston back. The slots I mentioned would have sufficient area to pull back the piston. They would more likely be holes rather than slots but I'm sure that won't matter. I have a different mod below. This was intended for small caliber such as bbs and high pressures from a HPA tank and to be completely self contained while maintaining semiauto function.
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 25, 2011 11:50 pm

Ignore the naysayers, it will work as originally drawn. Air can get into the tiniest of spaces and they should know better.

Am I right in seeing that there's a notch near the rear o-ring groove to allow the air to flow from the pilot to the chamber but not vice versa?
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Unread postAuthor: POLAND_SPUD » Mon Sep 26, 2011 7:10 am

The point of this design is to try to be compact and powerful while also being a generic shape that could be incorporated into many different body styles


Pretty much what I wanted to achieve with this -> http://www.spudfiles.com/forums/main-va ... 20300.html

though it could load ammo too...
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Unread postAuthor: Technician1002 » Mon Sep 26, 2011 8:29 am

In general the valve will be relatively slow. The reason is the overall length in relation to the diameter is huge. If made from metal, the weight will be high, resulting in relatively slow accelleration. Much faster speed can be achieved with a traditional barrel sealing piston valve where the piston length is no longer than the piston diameter. Additional speed can be reached with lightweight piston materials.

The porting on a coaxial piston valve with chamber open all the way around is considered fully open in a shorter piston movement than a single side port valve. A lighter piston moving less distance to fully open will result in a substantially faster valve.
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Unread postAuthor: Mr.Tallahassee » Mon Sep 26, 2011 3:20 pm

You are correct JSR. That is in place for the limitations of the mighty MS Paint. :lol: My intention is to drill carefully placed holes to act in the same manner as grooves cut into a washer piston. It'll be tricky but it should work. Another incorporation into the gun I will build around this is an o-ring detent to utilize the most power from the slow piston. This could be made into a washer piston (yes it's going to be small) but may bend unless I also use a durable bumper.
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