3 way pilot valve idea

Check out my YouTube SpudGun Channel! · Sat Aug 29, 2009 1:03 am

Thought of this when I was bored in physics, probably has been thought of before and a similar design probably exists somewhere on the forum but i'm just thinking out loud here.

The point of this valve is to be able to pilot a piston valve without turning off the air source. So it basically works by pushing the secondary piston (one in the picture) forward, filling the chamber and sealing the main piston valve (not shown in the picture), air will seap around the back of the secondary piston making it close up against the chamber side as there is slightly more area. Once you pilot this area, the piston is forced back and exhausts the air from the main piston valve out in to the atmosphere triggering the main piston valve.

Well that's the idea anyway, anyone see any issues with the design? I'm sure there's some I've overlooked.

edit: Just to make it clear, this is a pilot valve. Like a blowgun. The only difference is that this valve allows you to pilot while inlet air is still flowing (hopefully!).

MRR · Sat Aug 29, 2009 3:10 am

Where are you going to mount the barrel?

I think the main problem with this design is that you have a massive loss of pressure through the pilot valve unless it closes itself right after venting.

Edit:
Also the incoming air from the inlet works like a bumper and decreases opening time.

Check out my YouTube SpudGun Channel! · Sat Aug 29, 2009 6:15 am

The side labled chamber is where it would be mounted to the back of a co-axial or barrel sealing piston valve, this 3-way valve acts as a pilot valve for that.

I think the main problem with this design is that you have a massive loss of pressure through the pilot valve unless it closes itself right after venting.

Which is a good thing if this is mounted as a pilot valve to a barrel sealing or co-axial piston.

Also the incoming air from the inlet works like a bumper and decreases opening time.

Yeah that's true but I was hoping that if the pilot volume of the piston that this valve is attached to is small enough, all the air might be able to be vented before it is closed prematurely. It wont be as fast opening as if there were no inlet air, but it might just open fast enough and dump the air fast enough to work.

Technician1002 · Sat Aug 29, 2009 12:31 pm

I'm failing to see this valve in the overall launcher picture. Would it be possible to incorporate an overall picture with this valve in a typical application?

As I see the valve now, I see the chamber and pilot ports loosely coupled so as in filling the chamber, the diameter differential between the pilot and chamber will cause the valve to open a small amount and bring the pilot up to a fraction of the pressure in the chamber. (assuming the valve seats leak free)

As drawn, the valve would eq the pressure between the in and chamber to the supply pressure with the pilot regulated to a percentage of about 90% of the supply pressure. So assuming the supply is 100 PSI, the chamber will reach 100 PSI, the pilot 90 PSI. If the pilot is vented, the chamber will dump into the pilot. So what's the point?

The rest of the launcher and how this would interact would be most helpful.

POLAND_SPUD · Sat Aug 29, 2009 1:03 pm

I know what you were aiming at and I am sorry to tell you that but I doubt it will work and I can't see any reason for it to be built...

for me it seems overly complicated yet it still wastes more air than a normal 3 way valve... spool valves don't really cost that much...

jeepkahn · Sat Aug 29, 2009 1:08 pm

You basically drew a shuttle/piston style qev, all of my qev piloted cannons can fired while the air supply is hooked up and flowing, performance suffers slightly due to the air pressure behind the piston/shuttle, but it does work for quickly firing shots without having to fiddle with valves turning them on and off...

PVC Arsenal 17 · Sat Aug 29, 2009 1:45 pm

POLAND_SPUD wrote:for me it seems overly complicated yet it still wastes more air than a normal 3 way valve... spool valves don't really cost that much...

This.

A commercially made normally open 3-way valve or something along the lines of that would perform the same task more efficiently and wouldn't set you back that much in cost. If you're worried that a small 3-way valve wouldn't have the flow necessary to pilot a larger sized piston, just use a cascading setup. Piston --> QEV --> 3-way --> constant air source.

Another alternative to this is the sleeve valve (slide check). They're available in several sizes, have excellent flow rates, and they're by far the cheapest option.

Willdebeers · Sat Aug 29, 2009 2:41 pm

Technician1002 wrote:I'm failing to see this valve in the overall launcher picture. Would it be possible to incorporate an overall picture with this valve in a typical application?

As I see the valve now, I see the chamber and pilot ports loosely coupled so as in filling the chamber, the diameter differential between the pilot and chamber will cause the valve to open a small amount and bring the pilot up to a fraction of the pressure in the chamber. (assuming the valve seats leak free)

As drawn, the valve would eq the pressure between the in and chamber to the supply pressure with the pilot regulated to a percentage of about 90% of the supply pressure. So assuming the supply is 100 PSI, the chamber will reach 100 PSI, the pilot 90 PSI. If the pilot is vented, the chamber will dump into the pilot. So what's the point?

The rest of the launcher and how this would interact would be most helpful.

It is a pilot valve for a piston valve / diaphram valve. It's supposed to dump the air.

ramses · Sat Aug 29, 2009 3:51 pm

I think that where it says "chamber" in the picture, He means that that port would go to the pilot area of the "main" valve. I think it would be much easier to use a QEV and pilot it with a small 3 way valve, even a pushbutton.

Check out my YouTube SpudGun Channel! · Sat Aug 29, 2009 3:53 pm

As requested Technician, a drawing with the full launcher in mind. Of course it's out of scale, I just did a quick edit.

What you see now is a normal, out of scale, coaxial piston valved launcher with it's piston (orange). This is attached to the pilot 3-way valve which is the original drawing and is the red piston.

edit: yeah I could just buy a 3 way valve but I can't find any NZ suppliers, can't buy from McMaster and can't be bothered paying for shipping to NZ from another website. Though i'll be in NY at the end of the year so I can buy some stuff then I guess. In the mean time, if I have enough time, i'll whip this up on my school's lathe.

POLAND_SPUD · Sat Aug 29, 2009 4:26 pm

done...

http://www.macvalves.co.nz/distributors.html
http://www.macvalves.co.nz/mv.html#7

or

http://newzealand.rs-online.com/mobile/ ... &R=3146367

I hope that prices are in AUD dollars

EDIT

I know that at least some of you consider poland to be a 3rd world country but even here there are dozens on-line shops selling pneumatic stuff... and there are hundreds of normal shops too

so if you say that you can't find QEVs or something in your country this doesn't mean that there are no suppliers at all... but that you couldn't find them...

Check out my YouTube SpudGun Channel! · Sat Aug 29, 2009 4:52 pm

Even if they were that's ridiculous. I know of those sites and I don't count them as a pneumatic supplier because of their ridiculous costs.

QEV's are about $80NZD for a 1/2" one on there as well, such a shame because its the only NZ website I can find with QEVs.

I had a feeling this had been done before, just wasn't sure and gave up searching for a 3-way valve schematic after a quick 5 minutes but I assumed they'd operate pretty similar.

So it will work? Not sure if i'd ever get round to making one, but I might do for shits and giggles one day.

POLAND_SPUD · Sat Aug 29, 2009 5:33 pm

ohhh yeah sorry I've just checked AUD to PLN exchange ratio... I can get this:
http://newzealand.rs-online.com/mobile/ ... &R=1892866
for almost the same price..
but in PLN not $
http://www.elektro-automatic.com.pl/cat ... _53_74_291

I guess that there have to be cheaper suppliers... it's only a matter of finding them... but hey industrial valves will always be expensive... that's why I buy most stuff on ebay or similar sites

these companies might be worth checking... most of them don't sell online so you'll have to email them

http://www.bayteck.co.nz/products_pneumatics.htm

http://www.airequipment.co.nz/#

http://www.c2c.co.nz/products.asp (apparently you can get clippard products from them)

https://enep.festo.com/irj/servlet/prt/ ... ustomer_nz

and last but not least... this is a PDF document with some cool info -> http://www.c2c.co.nz/pdf/Clippard%20Sch ... ymbols.pdf

Check out my YouTube SpudGun Channel! · Sat Aug 29, 2009 5:48 pm

Wow you really do know how to find good suppliers

I guess the advantage of making one like the design I posted is that you can make them in much larger sizes. But then again, if you're making large 3-way valves, chances are your main chamber will take time to fill anyway. So turning a ball valve to stop your inlet gas while firing, and then turning it again to fill up the chamber after firing is hardly an inconvenience.

POLAND_SPUD · Sat Aug 29, 2009 6:03 pm

if you are really looking for a ghetto method for venting without wasting too much air you can always put a small needle valve or restrict the flow in some other way on your air source...

I suppose that with some tweaking filling could take several times longer than normally (while still being fast) but at the same time you would waste several times less air...

well... at least for me this seems as a more straightforward way than yours... maybe it's just my laziness

but usually the simplest and the easiest solutions work the best for me