M925A2 Hydraulic System Mods

[Jbulach]

Sorry, got mixed up with another thread that showed (I think) a valve like you want in series, like I describe. I thought it was page 1 in this thread, but am mistaken.

Read the "power beyond" that rhurey posted. I'm not sure about the sleeve they speak about but it surely can be done. Flow and pressure can be controlled at each spool...probably blocked ports when in neutral.

If I could find an open center valve with blocked work ports in neutral that was a direct replacement for the trucks factory installed winch control valve, it would make all my modifications much easier.
I'm search for one now!

 

[tobyS]

The pressure gauge at the input to the crane's stack is 500 PSI. The crane's valves are all OC and that's just the pressure with no work being done. (or my gauge is crap, but...) 500 is what I assumed the restriction from the system of having a 1" pump pushing through a 3/4" selector and down ~15' of 1/2" hose to a 3/8" valve stack and back to the tank was.

The pressure at the crane's valve input rises to 2K when the crane is in use. The relief at the selector dumps at that point. The crane's valve's internal relief opens at about 1200 PSI. (You can hear the flow change, and see the input keep rising till the selector's relief cuts in).

It sounds like your gauge is correct, doing what I would expect. You're right about the restriction causing the back-pressure. Look at the laminar flow charts for pressure and speed in certain size pipe/orfices.

Why don't you set the relief on the crane up a bit if you want more power?

 

[tobyS]

If I could find an open center valve with blocked work ports in neutral that was a direct replacement for the trucks factory installed winch control valve, it would make all my modifications much easier.
I'm search for one now!

Am I correct, you have the winch, a dump bed and the plow with lift and turning? That's four sections and all of them need blocked ports in the middle. Don't confuse blocked ports with open center. Also, you will need needle valves for speed control on all but the winch. Some valves may have that built in.

If you only want to add the plow and not replace the winch valve, there are remote cable operated valves where a joystick could have both up and down and left and right (2 axis). That would be sweet. Here is an example.

http://www.ebay.com/itm/remote-cabl...ar-/232086826107?_trksid=p2141725.m3641.l6368

 

[Jbulach]

What I'm finding on line, looks like the M925 should have a Vickers CM11 series valve, rated at 30GPM and 3000 PSI. I look tomorrow to see if I can find any numbers on mine to confirm.

 

[Jbulach]

Am I correct, you have the winch, a dump bed and the plow with lift and turning? That's four sections and all of them need blocked ports in the middle. Don't confuse blocked ports with open center. Also, you will need needle valves for speed control on all but the winch. Some valves may have that built in....

Yes, thats correct, ideally a four section valve maybe five to allow for the next project.
The winch does not have blocked ports, my understanding is, this is so that the motor can coast to a stop, however I think for my limited use it would be fine with blocked ports also.

But I guess ideally would be...

Front winch: double acting, float ports
Dump bed: double acting, blocked ports
Snow plow angle: double acting, blocked ports
Snow plow raise: single acting, blocked port
Possible future rear winch: double acting, float ports

 

[Jbulach]

Also, the only thing I might need more speed control for than the trucks throttle, would maybe be the snow plow up, but I'm betting it would be fine with the way I plow.

 

[rhurey]

It sounds like your gauge is correct, doing what I would expect. You're right about the restriction causing the back-pressure. Look at the laminar flow charts for pressure and speed in certain size pipe/orfices.

Why don't you set the relief on the crane up a bit if you want more power?

One valve on the crane's monoblock is for the winch on the crane. Which has a 1,000 PSI rating. So I need to add another relief valve (or 2?) to protect it if I'm going to raise the available crane pressure more. Or move it to a different valve using the power beyond option. Hasn't been a problem yet, so haven't had to tackle it.