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piston valve - yes I have searched

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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piston valve - yes I have searched

Unread postAuthor: etb » Sat Jul 07, 2007 7:39 pm

OK, am sorry if this is a repeat...

I am planning on building my first pneumatic. I am the type I try and make the best possible first time out. I know i will improve on my own findings but I have to start with something. I live in SoCal so I am no rush because I wont really shoot until I visit my brother in OK.

Sorry, here is my first question. The supah-value, clean and awesome. I understand the exact plans are secret or I can't find. I understand how the piston valve works btw. What I am missing is, when I look at pics of the SV i don't see the valve used to pressurize the chamber. What am i missing. It appears to be a chamber seal valve but that would mean to inlet valve would need to be at the pilot area. What am i missing?

I want to start by making a piston valve with at least a 2" diameter maybe 3". Then I can take to OK and worry about the chamber and barrels.

Thanks...
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Re: piston valve - yes I have searched

Unread postAuthor: Modderxtrordanare » Sat Jul 07, 2007 7:52 pm

etb wrote:What am i missing?


Nothing, you are correct, the Supah valve is indeed a chamber sealer. You fill your cannon through the chamber though. :)
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Unread postAuthor: etb » Sat Jul 07, 2007 7:57 pm

wow i am confused then. How do you apply pressure in the pilot area if filling the chamber on a chamber fill valve??
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Unread postAuthor: MrCrowley » Sat Jul 07, 2007 8:04 pm

Because the piston is o-ring sealed to stop air going into the barrel people make a 'path way' for air to travel through the inside of the piston and into the pilot area/chamber
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Unread postAuthor: etb » Sat Jul 07, 2007 8:10 pm

so the do you use a spring so that the pilot area has a touch more pressure to keep from just pushing the piston into the pilot area and releasing the air while filling?

So for the SV its o-ring? I figured it was just a stopper seal against the chamber side. and o-ring seal on the pilot side. learning, thanks

Plus, where do you get the cap(what do you call it) for the pilot area side?
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Unread postAuthor: origin unknown » Sat Jul 07, 2007 10:30 pm

Just build a barrel sealing piston because it is a lot more simple. Make a valve like the mauler or something. Look at this to help you figure out how these valves work: http://www.spudfiles.com/forums/piston-valves-explained-visually-t8157.html
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Unread postAuthor: etb » Sun Jul 08, 2007 1:31 am

still doesnt answer the one question. how can you have a barrel sealing t-valve with the inlet on the chamber and not the pilot area? What am i missing. Spring?
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Unread postAuthor: Modderxtrordanare » Sun Jul 08, 2007 1:34 am

etb wrote:still doesnt answer the one question. how can you have a barrel sealing t-valve with the inlet on the chamber and not the pilot area? What am i missing. Spring?


Correct. A spring is always used when one decides to fill from the chamber instead of the pilot. Though, it is usually a challenge to get a spring with just the right compressability to seal properly while not hindering preformance.
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Unread postAuthor: etb » Sun Jul 08, 2007 1:41 am

What is the benefit of that? vrs just putting an inlet next to the exhaust?

Plus, I saw someone talk about using an alternate line instead of a equalizing hole in the piston. Good idea?
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Unread postAuthor: Modderxtrordanare » Sun Jul 08, 2007 2:19 am

etb wrote:What is the benefit of that? vrs just putting an inlet next to the exhaust?

Plus, I saw someone talk about using an alternate line instead of a equalizing hole in the piston. Good idea?


There is no real benifit, other than the way the gun is worked. Some people might prefer not to clutter up one plug with a bunch of fittings.

Also, that was probably my post you saw about the alternate line with a check valve. I got that idea from Jackssmirkingrevenge though.


Personally, I just fill from the pilot side of the piston, no hassle of using a spring and it works all the same.
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Unread postAuthor: Gepard » Sun Jul 08, 2007 8:07 am

etb wrote:Plus, I saw someone talk about using an alternate line instead of a equalizing hole in the piston. Good idea?


In theory no, as the chances are than the pipe will increase the pilot volume considerably more than a small equalising hole, and with a larger pilot volume you reduced performance...


BTW, there are pictures of a Supah valve in the Wiki. Apply a bit of thought and you can easily copy it.

Michael
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Unread postAuthor: Modderxtrordanare » Sun Jul 08, 2007 2:44 pm

Gepard wrote:
etb wrote:Plus, I saw someone talk about using an alternate line instead of a equalizing hole in the piston. Good idea?


In theory no, as the chances are than the pipe will increase the pilot volume considerably more than a small equalising hole, and with a larger pilot volume you reduced performance...


BTW, there are pictures of a Supah valve in the Wiki. Apply a bit of thought and you can easily copy it.

Michael


You're forgetting a few things..

If the piston is sealing 100% and you run a seperate line with a check valve around it instead of an equalization hole. The only wasted air you'll be wasting is the air from the pilot area.

Everything else will go to moving the projectile. You won't even be increasing the pilot volume any more than the volume of one side of the check valve, which isn't much. :wink:
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