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Trigger mech for a hammer valve?

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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Trigger mech for a hammer valve?

Unread postAuthor: Alex345 » Wed Sep 13, 2017 10:37 am

So I got this cannon lying around here basically 80% done and it can also fire with the necessary preparations, but it's still far away from something you can pick up, pull the trigger and shoot.

It uses a large piston valve with the hammer valve of an old fire extinguisher to vent the pilot. I can shoot it by hitting that valve with a large hammer. But i'm completely lost on an actual trigger mechanism as that would require a very tough spring.

Some ideas?
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Re: Trigger mech for a hammer valve?

Unread postAuthor: jackssmirkingrevenge » Wed Sep 13, 2017 10:46 am

Some ideas?


If you don't want to make something from scratch, there are plenty of products that can be adapted for the job:

chop up one of these

chop up one of these

chop up one of these

chop up one of these
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Re: Trigger mech for a hammer valve?

Unread postAuthor: Alex345 » Thu Sep 14, 2017 11:23 am

Don't think a toy gun's hammer would do much tho, i even doubt if the hammer mech from an actual gun would do anything as the principle of that is basically the large heavy hammer transferring all it's energy to the firing pin's tiny surface, and the return spring of a firing pin is also pretty weak. I can barely push the valve down with my thumb even without any pressure on the pilot.

I think you'd need to cut a sten gun's barrel off and mount it so that the bolt of the gun would hit the valve when you pull the trigger :mrgreen:

The staple guns seem plausible, but i think i would need a very decent one to even attempt opening the valve. Were talking a push button type valve from a CO2 extinguisher that normally uses a hinged lever to open it, and the pilot pressure is roughly around 500/650 psi. Last time it shot a ball of kitchen paper through one side of an old fake leather shoe at point blank range.

I remember reading something on this forum about some kind of free floating valve? I probably said it totally wrong but i think they use them on PCP rifles, had something to do with the valve's stem ending in a separate chamber that was equally pressurized as the main chamber so you only needed a weak spring to keep it in place and a lot less force to open it? Hope that made some sense :p
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Re: Trigger mech for a hammer valve?

Unread postAuthor: jackssmirkingrevenge » Thu Sep 14, 2017 11:40 am

I think you mean a "balanced spool valve".

I had made one for my Apache Fireball refurbishment.

See also Brian's original thread.
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Re: Trigger mech for a hammer valve?

Unread postAuthor: Alex345 » Sun Sep 17, 2017 4:38 am

Yes that's the one i think! Bought some wire rod, washers and O-rings yesterday, gonna try and cobble something together today. If it's really that easy to push open i could probably use some kind of fast acting servo to open it, or maybe even a very small pneumatic piston leaching air from a mini air chamber operated by a blowgun...

Thanks! Is that the same type of valve the marshmallow cannon uses? :p
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Re: Trigger mech for a hammer valve?

Unread postAuthor: jackssmirkingrevenge » Mon Sep 18, 2017 5:09 am

Alex345 wrote:Thanks! Is that the same type of valve the marshmallow cannon uses?


yes
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