Hydraulic opinion

J_J · Jan 14, 2011

I have been discussing a hyd situation in the Power-Trac with Bob, who has mounted a hyd winch on the rear of his PT.

I have never seen a situation like this. Bob wants to control the winch from the rear with a single spool valve with PB. He is sending fluid from a front valve via the work ports to the rear valve input ports. . He is attempting to use either valve to control the winch by locking down the other lever.

The big question here is what will happen if the rear valve fluid flows in the reverse direction. Otherwise, in the normal flow of things, with hyd flow into the P port, and exiting the PB port .

If he then reverses the front valve, the fluid will now flow into the PB port and out the IN/P port.

Can you operate a hyd motor with an open center valve using reverse flow?

I think no, or just don't know

Craig Clayton · Jan 14, 2011

Lets try this steo by step.
Pump is supplying hydraulic oil to valve # 1 at inlet
Oil returns to sump from outlet of # 1 valve.
Pressure adjustment is at #1 valve to sump
There is a pair of open center lines to #2 valve inlet and return
Oil returns to # 1 work port through pair of open center lines from # 2 valve
Valve # 2 has a pair of open center work port lines to a hydraulic motor
Hydraulic motor turns input shaft of winch.

So far so good

Aslong as # 1 spool is only moved in the correct direction it should work.
It sounds very similiar as to how I am powering my BH at the moment. I use a soft strap so I only can PULL on the spool valve #1 and I tie the strap arond the ROPS with a slip knot.
Craig Clayton

J_J · Jan 14, 2011

Question is , what will happen if the flow is reversed using the front valve.

Will the winch motor work normally or not at all in reverse flow?

Any fluid used by the hyd motor should exit out the tank gallery on the second valve.

RickB · Jan 14, 2011

J_J said:
Question is , what will happen if the flow is reversed using the front valve.

Will the winch motor work normally or not at all in reverse flow?

Any fluid used by the hyd motor should exit out the tank gallery on the second valve.

I believe it will work as intended. When the second valve is powered through the PB port (reverse flow), the return oil from the winch motor may flow back to valve #1 from the P port of #2 valve and to sump by whatever means that #1 valve returns to tank.

J_J · Jan 14, 2011

I thought the gallery's for the work ports only went to the out or return ports. Is that not correct?

Craig Clayton · Jan 14, 2011

The only problem with applying the first valve in the reverse flow is the gallery will be
have pressure on it when it is not intended to.
The reason I pull my spool by the soft cord is I call my line as a Positive Flow and I know the direction of the oil. This oil goes to the inlet of the BH which is like where it should be.
Craig Clayton

AKKAMAAN · Jan 14, 2011

J_J said:
I thought the gallery's for the work ports only went to the out or return ports. Is that not correct?

agree w RickB...

How would pump connect to cylinder/motor if not through work port??

EDIT:
A load check valve in valve #1, would cause flow pro blems in reverse

RickB · Jan 14, 2011

J_J said:
I thought the gallery's for the work ports only went to the out or return ports. Is that not correct?

That's correct, but with the flow coming IN to valve #2 PB port in that instance, I'm not certain where the flow would go.

The more that I think about this, I'm pretty certain that with valve spool #2 centered in neutral, flow INTO the PB port of valve #2 would exit the P port of that valve.
Also, with the valve spool of valve #2 stroked, the flow entering the PB port of that valve would either go directly to tank via the return port
(edit; that's not going to happen, see my next post),

or be deadheaded by the valve spool. No flow into valve #2 entering via the PB port would pass around the spool and exit the work port of valve #2 to power the winch.

The issue of reverse flow into a PB valve is more of what happens to the pressure flow, not where the return flow ends up. I don't think the intended work will be accomplished, and a simple air test with a rubber-tipped blowgun would answer the riddle without plumbing or mess.

RickB · Jan 14, 2011

J_J said:
I thought the gallery's for the work ports only went to the out or return ports. Is that not correct?

The more I think about this, the more certain I am that flow coming into #2 valve's PB port will be deadheaded when the #2 spool is stroked. Two ways for Bob to accomplish what he wants with components already discussed:
1. Remove the PB sleeve from valve #2 and let return and PB ports be common.
2. Connect the lines from the work ports of valve #1 to P and Return ports of valve #2, plugging the PB port.

Both alternatives are flawed in that when the winch creates a high load and flow into the PB/return side of valve #2 approaches RVF pressure, the spool seals of valve #2 will become compromised, sonoer or later.

Best solution with common hydraulic components is to mount the two valves in parallel and feed either one or the other via a selector valve, either manual or electric.

J_J · Jan 14, 2011

AKKAMAAN said:
agree w RickB...

How would pump connect to cylinder/motor if not through work port??

EDIT:
A load check valve in valve #1, would cause flow pro blems in reverse

What I meant to say was that the work ports used fluid from a cyl or motor dumps into the OUT/TANK port. So if you pressurize the out port as in a reverse condition, you stand a good chance of damage to the valve since the psi on the out port is about 500 psi. If the winch motor loads up, you will far exceed that pressure.

J_J · Jan 14, 2011

AKKAMAAN,

Do you have software to set up something like this as a simulation.

AKKAMAAN · Jan 14, 2011

J_J said:
What I meant to say was that the work ports used fluid from a cyl or motor dumps into the OUT/TANK port. So if you pressurize the out port as in a reverse condition, you stand a good chance of damage to the valve since the psi on the out port is about 500 psi. If the winch motor loads up, you will far exceed that pressure.

Is this how it was supposed to work??

And when valve#1 is shifted in "reverse", this happens...Load check in valve #2 blocks flow, and PRV in valve #1 opens

J_J · Jan 15, 2011

I really don't know how the fluid flows in a reverse situation. There have been several instances on here where someone connected the valve backward and the valve cracked. With the second valve in neutral, and PB installed, the fluid would just flow through the valve back to the first valve. If the first valve is shifted to reverse flow to allow winch operation, the fluid now enters the PB port of the second valve. From there, just guessing. But if the fluid makes it to the motor, the expended fluid will exit the OUT port, and no fluid will flow back to the first valve. If the OUT/tank port is plugged, I see a deadhead situation.

Is there a check valve in those spools? I know there are load checks in most valves, but are only functional when shifting the spool.

DonnieP · Jan 15, 2011

I had a valve hooked up for a short time with supply in PB port. If you moved the valve half stroke, you would get some fluid out work ports, but not full flow. If you stroked the valve full stroke, there was no flow and the safety would lift.

Donnie

glastron23 · Jan 15, 2011

JJ.. this can not be done with this configuration, he if wants to control the winch from the front or rear he will need to install a selector valve then have 2 control valves. do not use motor spools and T the hydraulic lines in at the motor. If he is using this on a winch, the motor can not be driven be the load on the winch cable as the winch worm and bull gears can not be reverse driven...

J_J · Jan 15, 2011

I believe all hydraulic winches can be reverse driven, unless there is a reverse gear setup. There is no free wheel on this winch, so in order to pull out the cable, the winch has to be reverse driven.

Look at post #96. that is the winch and valve.

http://www.tractorbynet.com/forums/power-trac/170326-winch-modifications-10.html

http://www.surpluscenter.com/item.asp?item=9-7861&catname=hydraulic

http://www.surpluscenter.com/Instruct/I9-7861.pdf

glastron23 · Jan 15, 2011

Sorry about that JJ, what i meant by reverse driven is that a load on the cable can not turn the worm gear to drive the motor. The motor can be turned either CW or CCW. The winch he has is a planetary drive system, there should be some kind of internal braking system, it looks like he has a Warn winch?? What model is this?? Some of these models can and some not be driven both ways. There is a T handle on the winch with a yellow tag, this should be the release for the drum to free spool??? Jim

2458n · Jan 15, 2011

I have just purchased a hydraulic winch off of a rollback truck. The motor is on the winch; the valve went with the truck bed. What type of valve do I need to run this off of an open centered tractor system? I currently have a valve off of a log splitter. Thanks for any help.

DonnieP · Jan 15, 2011

What about putting a tee each port of the motor and hooking the work ports of the two valves in parrallel. Port 'A' of valve 1 and port 'A' of valve 2 to one of the ports on the motor and port 'B' of valve 1 and port 'B' of valve 2 to the other port on the motor. I know when you activate one of the valves, you'll be back feeding to the corresponding port of the other valve, but I believe it should handle that, shouldn't it? It would be no different than driving around with a load in your FEL.

Donnie