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Hydraulic Relief 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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Hydraulic Relief Valve

Unread postAuthor: MrCrowley » Sat Apr 03, 2010 8:24 pm

Bought this for $10 the other day, think it would make a really good high pressure valve but was looking for some input of what type of valve to go with. I had a few ideas that were similar to BtB's snap valve.

Schematics

Direct links (for slow internet connection users):
Whole valve
Bottom port
Opposite port/Top port
Valve cartridge
Valve cartridge exploded
Piston/Poppet

Notes:
*Piston has a small hole through the middle of it
*Piston somehow seals with metal on the front. If you put air through the top/opposite port but it is below the force required to open the piston/poppet (because of spring), it will still create a seal and not leak. I'm not quite sure how it does that since there are no o-rings or such that the face of the piston seals against.
*This photo shows which parts of the cartridge are sealed off from what ports when inside the "tee housing" (blue = top/opposite port, red = bottom port)
*Back of cartridge has a 1/4" threaded hole.
*All ports of the tee are 3/8" threaded IIRC.

Might be a bit hard to understand the internals but this thing is definitely capable of being a handy high pressure valve of some sort, most likely some sort of snap/pop-off valve.
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Unread postAuthor: POLAND_SPUD » Sat Apr 03, 2010 8:43 pm

nice find
I am guessing it's one of these http://www.hydraulicspneumatics.com/200 ... 411/Valves

it might be useful as a substitute for high pressure pop-offs (which are hard to get)
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Re: Hydraulic Relief Valve

Unread postAuthor: chinnerz » Sun Apr 04, 2010 2:17 am

MrCrowley wrote:

Direct links (for slow internet connection users):


what a considerate fellow you are :P
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Unread postAuthor: iknowmy3tables » Thu Apr 08, 2010 7:26 pm

ahh, so the piston setup is in a "barrel sealing" configuration. So the the hole in the piston is so the area behind the piston can have equilibrium pressure to the output (since this is a hydraulic valve designed to hold water under pressure), well since your using it for a pneumatic purpose are you going to plug that hole (and possibly provide a vent for the area behind the piston) because it seams detrimental towards the performance in a pneumatic

and if the metal seal doesn't work well enough for air maybe you should put in some oil, combustible oil :twisted:
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Unread postAuthor: MrCrowley » Thu Apr 08, 2010 7:36 pm

Yeah, any plans to turn this in to a pneumatic valve seem to involve plugging up that whole. I'm still struggling to turn this in to anything aside from a pop-off valve though. It is quite tricky because of the low flow and large volume in the cartridge.

I don't really want a full-auto repeater that I can't control because it requires so much gas at high pressures. I was thinking more of a low volume chambered semi-auto controlled by a 3 way. So the chamber would be small, filled with high pressure and the whole chamber would be exhausted once the valve is actuated. The only other option is a semi-auto hammer valve where the chamber is slightly larger but only low amounts of high pressure air are released each time the valve is triggered.

A piston valve is tricky because of the poppet valve, low flow and high volume in the back of the cartridge. I could get rid of the cartridge but the port in the tee the cartridge screws in to isn't a normal thread (like 3/8" for example).

A hammer valve would be better but I would have trouble with the force required to unseat the valve.
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Unread postAuthor: iknowmy3tables » Thu Apr 08, 2010 8:39 pm

your gonna mod this for a piston valve, sweet,

maybe you can use all that space for epoxy to make sure that your pilot attachment thing holds,
however unless you can get a working rubber sealing face, the you'll probably need a significant pressure to get that to initially seal at lower pressures and the only way I'd imagine that happening is with a high breaking pressure check valve, or maybe you could get away with a strong piston reset spring and a check valve

wait I got it, you just want a valve that will operate as a semi auto so why not pneumatically adjust the spring tension see the diagram below, you should be able to make enough change in the spring tension to trigger the valve using a 3-way valve with low pressure air, this way you could also use a cheaper low pressure 3way valve to pilot the whole thing
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 11, 2010 1:32 pm

Looks good, can we expect an HPA auto any time soon?
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Unread postAuthor: MrCrowley » Sun Apr 11, 2010 5:44 pm

Still need to get a high pressure tank and gauge and then my fridgey is complete. Got some hydraulic hoses for $20 the other day.
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