A Simple Hydraulic Steering Question

[Henro]

Another thread on a different forum put a big question mark my mind...

I have hydraulic steering on my BX and I think on my B2910 as well.

In that thread I mentioned the person questioned if his steering wheel should continue to turn when the front wheels stop turning, due to load in his loader, or for whatever reason really.

I guess I could try turning my wheels fully on one of my tractors, and see what happens. Somehow I think the steering wheel will not keep turning if I hit the travel limit, but it is raining...and...that's my excuse for not going out and seeing what happens!

So the assumption is if the wheels do not turn (for whatever reason), the hydraulic pressure relief valve will trip open. If this happens, would the result be a steering wheel that still continues to be able to be turned without much resistance (while the wheels remain stationary) ?

If so, why would that happen? If I could imagine an answer I would not ask...This could actually be the way things work. I never have experienced such an issue in normal operation, and I do not try to turn beyond the physical limits so this possible situation is all new to me.

 

[NCL4701]

I would say yes, the wheel will continue to spin on at least some models. It is my understanding (and I am open to further education) that my L4701 has hydrostatic steering. If I’m in close quarters, low speed, and I need to move the wheels a long way as quickly as possible sometimes I don’t spin the wheel as much as throw it. Never had the steering wheel stop or found a true stop on the steering wheel motion. Never heard any relief valve type sounds or any other extra sounds when the front wheels reach their limit of travel. I don’t keep turning it knowing the front wheels are as far as they go, but it’s hard to believe it doesn’t spin some after the front wheels reach their limit when I throw it.

 

[boz1989]

There is hydrostatic, and hydraulic assist. Your 2910 is hydraulic assist, there is a linkage running from the column to the front. Hydrostatic is just hoses, and can slip. The assist is set and will not slip.

 

[Dave_eng]

Allow me to remind you of the important feature with both power steering systems. If Engine stops while the tractor still moving you still can control the front wheel steering direction.

In the integral box style, there is a slender torsion element which twists when the steering wheel is turned to activate the hydraulic flow to provide the assist. This torsion element has mechanical stops which limit how far it can be twisted. These mechanical stops allow you to steer with no engine power.

The hydrostatic system provides steering control when engine is stopped by turning its control valve into a hydraulic pump powered by the rotation of the steering wheel. It is called a GEROTOR which stands for "generated rotor." This manual pump is providing hydraulic oil under pressure to the hydraulic cylinder steering the front wheels.

Which ever one you have try a simple experiment and turn off the engine while still moving to see how much control you have. The effort will be greater but you will have control!

Dave

 

[Henro]

Allow me to remind you of the important feature with both power steering systems. If Engine stops while the tractor still moving you still can control the front wheel steering direction.

In the integral box style, there is a slender torsion element which twists when the steering wheel is turned to activate the hydraulic flow to provide the assist. This torsion element has mechanical stops which limit how far it can be twisted. These mechanical stops allow you to steer with no engine power.

The hydrostatic system provides steering control when engine is stopped by turning its control valve into a hydraulic pump powered by the rotation of the steering wheel. It is called a GEROTOR which stands for "generated rotor." This manual pump is providing hydraulic oil under pressure to the hydraulic cylinder steering the front wheels.

Which ever one you have try a simple experiment and turn off the engine while still moving to see how much control you have. The effort will be greater but you will have control!

Dave

I am still a bit confused.

I think I will first try to turn the wheels on both tractors to the limit with the engines running and the tractors not moving, and see what the steering wheel does.

I do not think there is a mechanical connection on the BX between the steering wheel assembly and the cylinder that controls the wheel position. Sounds like on the B2910 there is...

Will report back afterwards.

 

[Dave_eng]

I am still a bit confused.

I think I will first try to turn the wheels on both tractors to the limit with the engines running and the tractors not moving, and see what the steering wheel does.

I do not think there is a mechanical connection on the BX between the steering wheel assembly and the cylinder that controls the wheel position. Sounds like on the B2910 there is...

Will report back afterwards.

Looking forward to your report on the field test.

Dave

 

[NCL4701]

Which ever one you have try a simple experiment and turn off the engine while still moving to see how much control you have. The effort will be greater but you will have control!

Dave

The GEROTOR sounds pretty impressive and I do believe you…

But I’m not doing that intentionally. I’ve never been much good at trust falls.

Edit: Come to think of it, I have turned the wheels with the engine off while servicing the tractor. It was pretty obvious there was no direct mechanical connection from the way the steering wheel moved and felt compared to the movement of the front wheels. Never really thought about how it worked. Kind of chalked it up to some magic beyond my comprehension.

Thanks for the explanation.

 

[Henro]

Looking forward to your report on the field test.

Dave

Got to the tractors today.

B2910 steering locked solid when the travel limits were reached. Not surprising after reading Dave's explanation.

BX2200 acted differently, and is something I never would have noticed, as I do not have a loader and therefore little reason for the steering to be stressed unless the limits are reached, and I would have no reason to keep trying to turn the wheel at that point.

So with the BX steering at either limit, when I keep trying to turn the wheel, it actually does turn after the wheels cannot turn anymore. It was a bit jerky and slow in movement, and took some (not a lot) effort to turn, but it would turn probably as long as I wanted to play the game.

I soon stopped as doing this falls into the abuse category in my mind. The action was like one would expect if a hydraulic pressure relief valve were opening and bleeding off some fluid, which the steering unit could then replace with a slight turning of the steering wheel.

Now I have to dig out the WSM and look at the hydraulic diagram and see if a PRV is shown that is connected in some way to the steering cylinder circuit. I suppose there could also be a PRV internal to the GEROTOR unit, and if so the effect would be the same.

Edit: A quick look at the BX2200 WSM shows a PRV built into the steering controller, AKA the GEROTOR per Dave's description.

 

[chim]

So far I've had 3 different Kubotas. The B7500 and L3200 both had hydraulic assist, operating much the same as power steering in a car. As stated, they had a mechanical connection between the steering wheel and the front wheels. That keeps the steering wheel indexed to the front wheels. The suicide knob always returned to the same clock position when the tractors were going straight ahead.

The L4240 has hydrostatic steering. There's a hydraulic connection that interrupts the series of mechanical connections between the steering wheel and the front wheels. The suicide knob on tis tractor ends up at random places all the time. When I first got the L4240, I noticed it. It was something that I quickly forgot and it no longer bugs me.

 

[Toyboy]

There is a strong possibility that the O ring on steering cyl piston on the BX is leaking and allowing the bypass of oil. If, when you using the BX you have to keep correcting the line of travel then it's pretty conclusive. This seems to be a common problem with them.

 

[whitetiger]

There is a strong possibility that the O ring on steering cyl piston on the BX is leaking and allowing the bypass of oil. If, when you using the BX you have to keep correcting the line of travel then it's pretty conclusive. This seems to be a common problem with them.

There is a strong possibility that you need to reread post #1.