Boom lift Drive Wheels torque fade

[Ronray]

The hydraulic wheel motors turn the wheels while unloaded, but slows down and stops when load is applied. The service manual says "check planetary wheel drive to be sure engaging disc is not positioned in freewheeling."

So my question is what is the planetary wheel drive, and where is the planetary the planetary wheel drive? is it inside the hydraulic drive motor? Do I have to take the hydraulic motor apart?

 

[Ronray]

And is it possible that this brake cylinder might be engaging when the load is applied?

 

[Ronray]

Well, I just learned that the above picture is not a brake cylinder, it is the two speed position cylinder. So I am wondering if I disconnect it by removing the cotter pin if that will leave the drive motor in low speed which should give the wheels more torque? Just wondering if the Drive motor may have been stuck in high speed, which would have given the wheels less torque?

 

[Ronray]

So I disconnected the two speed shift cylinder, see picture attached, and now the right drive wheel has more torque and turns under load, but the left wheel still does not turn under load. I tried to toggle the shift lever on the hydraulic drive motor with my hand to see if I could get it to change gears manually, but was unable to move it by hand or pushing on it with a pipe. And the two wheel motors shift levers are connected by a long rod. Any thoughts?

 

[Ronray]

An opinion please on the attached screenshot of the drive motor diagram. It looks like there is an internal spring on the main shaft rod that keeps the gears locked into one position unless the lever is moved from 4 degrees to 17 degrees with with a lever that is attached to the two two-speed hydraulic cylinder outside of the motor to compress the spring and engage the alternate drive speed. My question is, what is the default speed of the motor if the 2 speed hydraulic cylinder is disconnected from the spring compression lever, is it the low speed or high speed?

And if it is the low speed, I'm wondering why the left side motor did not engage low speed since the two motors spring compression levers are connected by 1 long rod? Broken internal spring on the left side motor? Or just jammed up somehow?

 

[mikebramel]

You're not shifting gears with that lever but changing the displacement of the motor. More angle (past center)= more displacement = more fluid required per rev = more torque. There is a small drain line on the side of the motor, remove that when the motors are stalled out. Whichever one has more flow under load will be a bigger problem than the other

 

[Ronray]

Thanks Mike. So should I open both of the drain holes on the left and right motor at the same time and compare the flow that way, or just open one at a time?

Not sure what you mean by stalled out. If the drain hole is open, does that mean the wheel will not turn while the drain hole is open?

 

[Ronray]

Mike, actually I could not find any drain plugs on either wheel motor, even though the attached diagram shows a 9/16-18 sae drain port? Unless the drain port is supposed to have a hose attached to it like the smaller hose in the attached picture?

 

[mikebramel]

Yes the drain port runs back to tank

 

[Ronray]

Thanks Mike. So I ran each drain line to separate buckets and engaged the drive wheels for 5 seconds. The right wheel spun without getting traction and the left wheel stopped. The right drain line produced 200cc of fluid and the left one 175cc.

I then completely blocked off the right side motor but the left side motor still stopped after about 2 seconds.

So now I am considering just pulling the left side motor off and disassembling for inspection to see if I can find any broken or worn out parts.

 

[mikebramel]

If the motors are plumbed in parallel the one that breaks loose first will get all the flow.

 

[Ronray]

Not sure what you mean by breaks loose. Does that mean that the wheel that keeps spinning when the other one stops is the wheel that will get more flow?

 

[mikebramel]

They're spinning on muddy ground or you have them in the air?

TBH since the leakage rates are the same I dont think your problem is in the motors

 

[Ronray]

Thanks Mike. When I had both of the wheels jacked up in the air, they would both spin normally. But when I lowered them to the ground, which was soft, they would go forwards or backwards about 6 or 8 in and the left wheel would stop but the right wheel would keep spinning, but not get traction and gradually digging a little deeper into the ground the longer it was engaged.

FYI, I disassembled the left motor to inspect for damage and wear, and found none. So I put it back together and I am going to switch the left and right motors to see if right side behaves the same.

They are behaving kind of like a car with posi traction in the sand or mud where just one wheel spins. I'm wondering which angle 4 degrees or 17 degrees on the swash plates would give the wheels more torque?

I also discovered that there could have been a difference in swashplate angles in both Motors because there was a broken roll pin connecting the two speed shift selector cylinder, which created a lot of free play in the connecting lever. See attached picture.

 

[Ronray]

Okay, so I've been delayed a couple months with this wet weather LOL.

So I found no problems with the motors and I reinstalled them only I switched the left and right motors, and the same Wheels were showing the same traction and torque. So then I capped off the lines to the right side motor to see if that would put more pressure or volume to the left side motor, but there was no change in the left side motor motor performance.

So now I suspect a problem in the valve manifold, like maybe a clogged filter or broken spring or maybe it's just out of adjustment for the left side motor lines?

I'm wondering if these strange looking hex nuts with the Allen screws in the middle pictured are perhaps some kind of volume control adjustment?

 

[TVA]

the tower looking things with adjustments on top looks like counterbalance valves, they are in the same block with parking break releasing shuttle valve and flow divider according to diagram showed in previous Thread

Flow divider is a device which cut the flow to free wheel when you blocked the other. It’s supposed to do that.

I’m not clear what kind of problems you having now?

 

[TVA]

Compare the angles of swash plate lever on both motors at the same position of speed cylinder. Is the connecting rod bent or miss adjusted?

 

[Ronray]

Originally the connecting rod between the swash levers was out of adjustment, but I fixed that and both of the levers are in the fully tilted 17 degree positions, and the rod Is not bent. I just want to see both of the two wheel drive Wheels spinning even if they fail to get traction. Right now just the right wheel will continue to spin.

I'm not sure I understand your comment about the flow divider. If I have the right side motor capped off, will the flow divider give more pressure and fluid volume to the left side motor?

The service manual did not show the individual internal components of the manifold.

 

[TVA]

Like I said in the original thread - that flow divider is mislabeled, it’s a typo. So I can’t tell you how it works.

I don’t think it is gear divider, but gear one will stop everything if it not getting flow because it’s literally two gear pumps on the same shaft.

 

[TVA]

I suggest you take the names and terms I used above, google them, find out how components work and what are the symbols for them. It will help you understand things better and faster!