Steering Valve help

[amitysanimal]

I bought a steering valve off a New Idea Uni combine to use to convert my 1977 Kubota B7100 to power steering. I can't find any info about the valve, it had a decal on the bottom but it was painted over and trying to remove the paint removed all info. The problem I have is that when I hook up the pressure and return lines, I get zero oil out of the 2 ports that go to the steering cylinder (when I turn the steering wheel). There is oil flowing through the valve, at least coming out of the return line. I took a similar sized steering valve off one of my Dads payloaders, hooked it up the same way and it worked fine.

Any idea as to why this valve won't work? Could it be a simple fix? Something I'm overlooking?

I can probably take it back but its an hour or so drive one way and not positive if they will give me any trouble swapping it for another.

Any help will be greatly appreciated,

amitysanimal

 

[Farmerford]

The valve is not necessarily defective. The steering wheel is connected to the spool valve inside the orbital valve body (the names for these parts are not uniform) through a centering spring. The valve admits hydraulic fluid to the work ports (going to the cylinder) only when the spool valve resists the turning force of the steering wheel sufficiently to overcome the centering spring tension.

Resistance by the spool valve comes from both the viscous drag of the oil in the valve and resistance to the gerotor turning by the steering cylinder. With no steering cylinder connected, the only resistance to the spool valve turning is the viscous drag of the oil in the valve. If the centering spring is relatively strong (as it might be on a combine to keep the steering from being too sensitive), the viscous drag of the oil alone may not be sufficient to overcome the spring tension. Since there is no oil in the gerotor (because the work ports are open), the steering wheel is probably turning the gerotor as well through the torsion spring, but there is no "manual" pumping of oil by the gerotor (as when the engine is off) because the spool valve has not shifted against the torsion spring as it must to admit oil to the gerotor.

If you connect the orbital valve to the steering cylinder, and then move the cylinder manually to purge air from the hydraulic lines so that the gerotor (work ports) part valve will be filled with oil, you may well find that the valve functions properly.

 

[amitysanimal]

That is interesting.

Before I made the brackets for this to fit my tractor, I hooked the valve up to the steering cylinder. It started to work, the cylinder was very jumpy, mostly because it was full of air, but it did attempt to move at least. When I took it apart to make all the brackets, no oil came out of the cylinder. I didn't run it long enough to remove all the air, just wanted to see if it was going to work.

I assumed it was going to work, made the bracket for the steering valve and for the steering cylinder, hooked it all back up and got nothing at all. Tried bleeding air out of the lines while turning the wheel, nothing.

Any chance this valve needs more pressure than the valve I got to work of my Dads? The valve of my Dads has a bigger ?rotor? or ?vane? than the one that won't work. So that would mean the valve with the smaller ?vane? would require more pressure right?

Thank You Farmerford, your help is greatly appreciated,

Cleve

 

[Farmerford]

Cleve:

The valve probably worked a bit the first time because there was residual oil in the gerotor. Once you turned the wheel without admitting fresh oil (because the spool valve did not shift) you manually pumped that residual oil into the lines, which caused the cylinder to shift a bit.

If air is the problem, turning the steering wheel is not likely to remove it because the viscous drag alone in the orbital valve is not enough to overcome the torsion spring. Instead, you should manually fill the steering cylinder and lines with oil, and then have someone try to turn the front wheels to one side while moving the steering wheel in the opposite direction (with the motor running). This might cause the oil in the lines to exert enough resistance against the gerotor to get the spool valve moving. Once the lines and cylinder are filled with oil, any effort to turn the wheel will meet the resistance of the oil in the gerotor (which the turning wheel is trying to force back into the cylinder) and shift the spool valve.

I note you are in Maine. Try this (if) since it is cold outside. Leave the valve on the tractor and let it sit out overnight. That will thicken the oil in the valve. When you first start the tractor in the morning, before the oil has a chance to warm up, turn the steering wheel rapidly on way and then the other. The increased drag from the cold oil may be enough to get the valve working, and keep it working enough to purge the air from the system.

I don't think system pressure (at least within a broad range) affects the operation of the oribital valve.

 

[amitysanimal]

Thank You so much, all of what you said makes perfect sense. I will try all of these things when I go back up to work on it next Wednesday. I'll reply here after I get back.

Thanks again,

Cleve