Help finding special pilot valve

Eddbot · Sat Apr 25, 2009 5:37 pm

Hey everyone, I'm having trouble finding a pilot valve that fits my needs on my own, so i was hoping to enlist the help of all those with more expertise than myself. Anyway, I need a pilot valve that can control two lines. When at rest, one line needs to remain closed and the other open, when it's activated, the open one needs to close and the closed one needs to open.

I hope that makes sense...if not I'll sketch something up in mspaint later.

My main problem is that i don't know what that would be called or if it is even commercially available.

So, any help would be appreciated.

Hotwired · Sat Apr 25, 2009 5:55 pm

Sounds like a 3 port spool valve IMO.

You can get the general idea of how it works from this old concept sketch:

The middle port has a plug in it for a particular reason but you should be able to see what it would do if it wasn't plugged.

The picture is not exactly how they work but operationally it's the same, at rest one port is connected to the middle, push spool in and first port is closed off, second port is now connected to middle port.

Not generally cheap, cost about £25-30 for a 1/8" BSP button actuated one where I am.

I'm having this funny sense of having seen someone build this design recently.

Nah, Poland used a 5 port spool valve and a continuous flow design rather than working off a precharged tank.

Eddbot · Sat Apr 25, 2009 6:16 pm

I forgot to mention that they both go to the pilot on a QEV where one side fills and the other side pilots...

Thanks, I've found a couple of candidates on ebay for about 10 bucks, i don't know how many squiggly L's equal a dollar...

Anyway, on one of Humphrey's product pages they list a bunch of the ones I've found on ebay.
If you wouldn't mind taking a look, the most promising one that i've found is the 31P model, there are some others listed on ebay too, but i don't know which one fits my needs best.

Hotwired · Sat Apr 25, 2009 6:28 pm

Yeah 31P looks workable.

Also, yup perfectly workable for a pilot:

I have a library of my old concept sketches

That was one for a compact silenced-ish pistol type design.

The fill port will need a check valve of course.

Eddbot · Sat Apr 25, 2009 6:33 pm

Thanks, this was kind of the main part of my new gun and i never got around to figuring it out. So now i can get to work on it, well...after it gets here.

My library of concept sketches is all in my head, and it's pretty unorganized in there...

Hotwired · Sat Apr 25, 2009 6:48 pm

Hmm, those Humphrey TAC valves are smashingly small.

Of course they have terrible flow because they've been miniaturised so much but that won't be a problem if they're piloting an appropriate valve.

An avalanche system for example could use one of those to pilot a small QEV which pilots a larger valve or even a larger QEV to pilot an even larger valve. The limits of madness are unimaginable.

The really important thing is I now know they exist. The ones I previously knew of couldn't be grasped and operated by one hand.

I'm now tracking down a UK supplier to find out how much it'll cost me to get my mitts on one.

Eddbot · Sat Apr 25, 2009 7:00 pm

Well, thanks for the help, I hope you can find a supplier.

POLAND_SPUD · Sat Apr 25, 2009 9:17 pm

yep spool valves are the best option

I agree that buying a 1/4" one is a better idea because they have much higher flow

buying it on ebay might take sometime - I've noticed that some of the people haven no idea what they are selling, which is a good thing because they sell them real cheap... you just need to find such offer and you are set

a 5 way valve would work as good as a 3 way valve... but you need only a 3 way one