Did I bust something on the loader hydraulics?

[Tx Jim]

Yepper I like my morning coffee only I'm not the one beating the AIR in hyd system dead horse!

 

[Smokeydog]

One thing I’ve noticed on the M59 is when lowering the loader there is a notable load on the engine. This is confirmed by an slight increase in loader lift pressure by gauge.
Given the loader capacity I thought this maybe a hydraulic feature to better control heavy loads by controlling the opening of opposing cylinder valves? This prevents low pressure or vacuum on the lifting side of cylinder.

Don’t know if this is a design feature, adjustable valve function or fluke? Haven’t noticed this on other Kubota tractors to this level.

Seals on hydraulic cylinders and pumps do well of preventing oil loss or leaks under pressure. Do little to prevent air leakage into system if there is internal vacuum.

 

[npalen]

I would suspect that the better tractor hydraulic systems sync the load checks with the pump output (slight increase in pressure as you mention) to prevent the overrunning and subsequent cavitation.

Large industrial hydraulic presses with heavy rams use what is called a counterbalance valve to achieve a similar result. They "power down".

Edit: "Load checks", for anyone unfamiliar, are check valves in the loader's control valve that prevent the load from immediately free falling when the valve is shifted to the "down" position.

 

[fishdrivel]

I was carrying a 16' log in my grapple and I clipped a standing tree on the left side. It wasn't crazy hard, i.e. the tires didn't come off the ground, but the left side of the tractor dove a bit. After it was over the loader was no longer level side to side, the left side was down about an inch and a half to two inches. I guess I was hopeful it'd be a bent SSQA torque tube which seems fairly straight forward to correct, but the SSQA faces are square. I can see nothing bent visibly.
Looking at the loader arms, one is definitely higher than the other. In use, It seems I can lift to max height evenly (as best I can tell) and I can press down so the implement sits flat on the ground, but I can also dig in more on the left side since it is uneven. I really don't know what's wrong. After I shutdown, I always relieve the hydraulic pressure by lowering the 3pt hitch, and the loader arms, I also toggle the loader joystick to release any remaining pressure once completely shut down. We often use the bucket top as a seat, and it's always been solid. This morning I noticed this (shutdown overnight and not started this morning), there is no pressure in the hydraulic system, all 4 rams move when I step on the bucket. Any ideas, and it is related to my uneven issue?

Video of what I am seeing New video by JCoastie

If you bent something, understand that the design engineers design all the components for an equal stress.
It is possible that a sum of tolerances has accumulated.
This meaning there is now, "a little bit off here and a little bit off there" There a lot of other good ideas posted but if you cannot find anything wrong, it is possible you have just tweaked the whole assembly.

 

[rScotty]

If you bent something, understand that the design engineers design all the components for an equal stress.
It is possible that a sum of tolerances has accumulated.
This meaning there is now, "a little bit off here and a little bit off there" There a lot of other good ideas posted but if you cannot find anything wrong, it is possible you have just tweaked the whole assembly.

Is that type of design common now? With computers I guess it might be. A simple steel loader frame would be the kind of place it would happen first.
But just because a new technology can be used doesn't mean it is.

You know, analyzing stresses on any component used to be the most expensive part of a design. A designer would pick two or three places he felt were critical and ballpark the rest. Quality & reliability meant accepting that something was overbuilt in many areas. But with 3D computer drafting programs all of a sudden defining stress anywhere in an assembly suddenly becomes trivial. It's as simple as pick a load, choose whether to optimize for profit or reliability, & push a button.

Much as I hate it, you do have a point. I wonder how that will affect repair?
One thing is for sure, that type of design could sure change how lightweight tractors are built.
rScotty

 

[fishdrivel]

Is that type of design common now? With computers I guess it might be. A simple steel loader frame would be the kind of place it would happen first.
But just because a new technology can be used doesn't mean it is.

You know, analyzing stresses on any component used to be the most expensive part of a design. A designer would pick two or three places he felt were critical and ballpark the rest. Quality & reliability meant accepting that something was overbuilt in many areas. But with 3D computer drafting programs all of a sudden defining stress anywhere in an assembly suddenly becomes trivial. It's as simple as pick a load, choose whether to optimize for profit or reliability, & push a button.

Much as I hate it, you do have a point. I wonder how that will affect repair?
One thing is for sure, that type of design could sure change how lightweight tractors are built.
rScotty

What I am very reluctant to post, When you have a "tweak" you can often push a counter load on the structure.
That might mean putting the loader under an immovable object and restressing it the other direction.
That should be done carefully and slowly and patiently.
I would do it but I would not recommend it!

 

[npalen]

What I am very reluctant to post, When you have a "tweak" you can often push a counter load on the structure.
That might mean putting the loader under an immovable object and restressing it the other direction.
That should be done carefully and slowly and patiently.
I would do it but I would not recommend it!

One member suggested, several posts back, to chain a very long pole across the top of the bucket then, with the bucket clearing the ground, apply down force manually at the far end of the pole. This would seem to be a reasonably safe method as opposed to using tractor hydraulic power but even with this method care must be taken to prevent an accident.

 

[airbiscuit]

So I did the bucket movement test. I curled the bucket back and lowered it to the ground. Jumped on the bucket edge, and very little movement. Both the curl and lift cylinders were locked. Pushed the loader valve forward to float. Jumped on the bucket edge and there was a fair amount of movement. The curl cylinders were locked, but the lift cylinders went up and down, which makes sense because they were in float.

 

[JWR]

If you bent something, understand that the design engineers design all the components for an equal stress.
It is possible that a sum of tolerances has accumulated.
This meaning there is now, "a little bit off here and a little bit off there" There a lot of other good ideas posted but if you cannot find anything wrong, it is possible you have just tweaked the whole assembly.

Exactly what I tried to say in post #66. Almost certain to be the whole issue. Nothing to do with 'air' or other things.

Keep in mind that the OP said it works just fine. He has no operational issue at all, just the 'out of level.'

 

[npalen]

How could air in the hydraulic system possibly cause the loader to be twisted?