Balanced Valve Design for HPA?

[rsterne]

I need some help in designing a valve for HPA that won't be hard to turn and hence will be easy to use to fill a gun from an unregulated tank.... The simple valve that Ninja use to push open the pin valve on their regulator tends to bind as soon as it's pressurized.... I realize that is parly because of the diameter of the shuttle (ie sealing O-ring), and partly because they use relatively coarse threads.... but I want to remove those forces (or most of them) so that it operates as smoothly as the valve on a SCUBA tank where you can crack the valve a tiny amount and control the flow very precisely.... I've searched balanced valves and 99% of what comes up is the valve for a shower to keep you from getting scalded when the water pressure changes (totally useless)....

Can anyone give me a hint on how to build such a valve in the simplest possible manner?.... I want to incorporate two into an aluminum block, along with a gauge showing output pressure (ie to the gun) and bleed valve, to use two 90CI/4500 psi tanks in a Cascade setup for filling my airguns.... Each tank will just bolt to the block using a hollow stud and each will have it's own small pressure gauge (reading tank pressure) and fill fitting.... The requirements for the valve are that it be easy to turn when under pressure (or not) and capable of being opened a very small amount to precisely control the flow rate during filling the gun....

Bob

[Big Bore Bart]

Use the Ninja pin valve, but open it with a 90* cam.   O-ring seal on each end of the cam, two E-clips, and you are in business. Possibly the easiest way I can think of.

[rsterne]

I wasn't planning on using the Ninja pin valves at all, just mounting the tanks directly to a piece of bar stock with integral valves, fillers and gauge mounts.... as I don't need the regulators.... but thanks for the suggestion....

Bob

[Rescue912]

Hi Bob. Have you looked at something like the spool in a hydraulic valve that moves across the pressure instead of into/out of it? I switch 5K+ PSI hydraulics with 24V solenoids because the shift is not in the direction of the pressure. The bleeder on my 4500PSI tank works the same way and with 3300PSI in the line I can easily push it with my finger to bleed the line.

Not sure if that makes sense at all but being able to throttle it would take a little tweak to the spool but should be manageable.

[MultimediaMan]

How much flow (maximum) would you need (from each tank, valve and from the "aggregator" valve)? Most of the requirements are out there, but how much flow needed is not. The Pin Valves Paint Ball tanks use are somewhat impractical, even dangerous, at HPA pressures (not from a mechanical strength perspective, just because of the relative force needed to unseat a pressurized fitting of that size is so high).

I say this because the Shoebox has a dandy little bleed valve mechanism built into it... IIRC, it is rated for nearly 10K psi; at 4.5K, it turns with gentle thumb pressure. Perhaps this/these could be adapted for the purpose?

[rsterne]

If I can fill a 500cc tank to 4500 psi in a minute that would be tons of flow.... The typical use will be to top off a 13CI (213 cc) tank from 1500 psi to 3000 at about 100 psi per second maximum.... The plan is to fill from tank #1 to 3000 psi (or less) and then close that valve and top off from tank #2 in a classic cascade system.... When the first tank drops below 1500-2000 psi, it will be refilled from my Shoebox.... The other tank will be used as tank #1, and the newly refilled tank will become tank #2.... Each tank will have a male Foster fill fitting and a small pressure gauge (as used on a regulator) just for checking tank pressure, upstream of the control valves.... The outlet of the system will have a good quality 5000 psi liquid filled gauge with 100 psi increments (1.5 - 2.5"), about a 12" hose with female Foster to connect to the gun, and a bleed valve....

Bob

[MultimediaMan]

I thought that's what you were describing... just needed to make sure. 

So this is just for cascading, not regulation. A switching manifold of sorts. I'm not sure a single piece of barstock would be the easiest way to do this. Mind you it could be done, but I'm talking about setups and the like.

As you know, I'm am admirer of the Hayabusa Project. The tank adapter you made for the project was a really neat piece of engineering, but I'm not certain it was the easiest way to do this... I've been plotting something similar for a while (Time being in endlessly short supply).

I would make the tank Unions as a type of Banjo bolt:



The manifold itself would simply be a cross-drilled bar with threaded holes for the plugs, gauges and foster fittings and reamed holes for the Banjo bolts. The Banjo bolts would be retained by a flange at one end of the bolt, and the Tank itself would be the retainer for the other side.

On the flanged side of the banjo bolt is where I would put the transfer valves: simple pin and ball valves as part of the banjo bolt. The pressure bearing part of the valve would be assembled from the threaded side, so the the actuator pin would be captive even if the valve screw were to be removed completely. The pin would be small diameter ~1/8" with an o-ring to seal it, and hole for the pin would be stepped at the flanged side to capture the pin. A larger diameter, fine pitch ram screw, with reduced diameter at the tip would be threaded into the flanged side of the banjo bolt, to push against the actuator pin and open the ball seat.

The idea would be to make about 95% of the banjo bolt on the Lathe (the only thing you might have to do outside the lathe is cross drill the banjo bolt for the manifold airways), and make the manifold block on the milling machine, with simpler operations.

 

[rsterne]

Sounds like a good design.... I'll have to ponder the details....

Bob