MX5400 hydraulic arm shaft and control rod damage

SDT

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If that's true, you should be ashamed of yourself! You're being disingenuous and you should know better.
"[D]isingenuous...."

In what way?

You have every right (though questionable reason) to question my expertise, but you have neither reason nor right to question my integrity.

Without knowing me, you have no way to know that I am likely the most honest person that you have ever (or will ever) interface with in your entire lifetime.

SDT
 
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SDT

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I'm not doubting that this happened to the OP's tractor, only the ludicrous explanations. It's the lateral loading, it's the quick hitch etc. Blah, blah, blah.

Explain how the rock shaft sees any lateral loading with a properly set up 3-point.
It you truly doubt "lateral loading" pull the lynch pin securing the link between the upper and lower lift arms on either (or both) or your MX6000. Now set the stop watch on your phone and go out and whatever you might want to do with your tractors. Post back with honest information regarding the time it takes for the link(s) to disconnect.

I'll wait.

Forgive me, but you are beginning to remind me a great deal of Greta Thunberg.

SDT
 

DWilly

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it does not seem to matter whether a cap is bolted on or a snap ring is used on the rock shaft.
Oh, interesting. When you said you've previously seen it happen a few times on left arms, I was working toward the theory that it was due to the different type of retainer on that side. But from this comment, now I'm questioning that.
 

mcmxi

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It you truly doubt "lateral loading" pull the lynch pin securing the link between the upper and lower lift arms on either (or both) or your MX6000. Now set the stop watch on your phone and go out and whatever you might want to do with your tractors. Post back with honest information regarding the time it takes for the link(s) to disconnect.

I'll wait.

Forgive me, but you are beginning to remind me a great deal of Greta Thunberg.

SDT
Wow! And you claim to have been or are an engineer ... of what? Perhaps you engineered paper bags or something. Your lack of understanding of the application of engineering principles is spectacular. Who were these four companies you worked for, and what was your engineering discipline? You are so enamored with erroneous issues that you can't see the woods for the trees.

You were going on about quick hitches a year ago in a thread about rotary cutters and the need for front end weight. You were wrong in that thread, just as you are wrong in this thread.
 

North Idaho Wolfman

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I don't think this has anything to do with lateral loading, quick hitches or anything else. I think it's a case of the rock shaft working loose during use, most likely because the securing nut and plate weren't installed correctly or possibly due to an incorrect heat treat of the rock shaft allowing excessive elastic or plastic deformation. The OP didn't notice the rock shaft moving off the splined shaft, and when spline engagement was insufficient to support the load on the rock shaft, the splines failed and the rock shaft came off.

How any properly adjusted 3-point linkage would allow the rock shaft to come off due to lateral loading is a mystery to me and frankly not possible without significant damage to other components.
If you look at the picture you can see the bolts and the securing plate that is bent from the completely seated position.
So it wasn't a fastening failure.
 

DWilly

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It is not all that uncommon on tractors used to pull a terracer in hard or rocky soil.
That was certainly the case with use of my rear blade in this situation. Rocks and hidden tree stumps. I generally don't go crazy reversing with the blade, but I was using a lot of effort dragging it in forward.
 

mcmxi

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If you look at the picture you can see the bolts and the securing plate that is bent from the completely seated position.
So it wasn't a fastening failure.
I've spent the last 12 years looking at firearms that have been returned by customers with all manner of stories as to how the firearm was destroyed and how it wasn't the customer's error, incompetence or abuse that did it. One of the things you rarely have access to in an analysis is the truth as to how the product was used, but you can show that if the product is used as designed, it's not possible to cause the damage shown. I'm not making any statement as to the validity of the OPs statements re use.

All I can do is point out that the only connection to the rock shaft is a lift arm with a heim joint connection to a pin. I can demonstrate the angle that the lift arm has to make with the rock shaft in order to bind up and be able to transfer any lateral force to the rock shaft. It's up to the members here to decide how the lift arm can approach or exceed that critical angle.
 

mcmxi

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That was certainly the case with use of my rear blade in this situation. Rocks and hidden tree stumps. I generally don't go crazy reversing with the blade, but I was using a lot of effort dragging it in forward.
Again, how does any of that result in a lateral force to the rock shaft if the 3-point linkage is fully present and adjusted correctly. Remove the stabilizers from the 3-point and I can see this being possible. But with them present and adjusted there's no way to laterally load the rock shaft without damage the stabilizers, which you have stated were present, and weren't damaged.
 

DWilly

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I'm a total novice. I admitted that up front. I also admitted to leaving the kickstand down, which I wouldn't have done if I was trying to hide operator mistakes. Sure, I would love to have the warranty cover it, but in the grand scheme of things it's not very important.

Much more important to avoid the damage in the future. Given that, it would be stupid of me to hide what I was doing when I'm asking for help. I have plenty of faults, including ignorance in tractor use (which I'm trying to remedy), but not stupidity. If I'm leaving out some context on how I was using it, it's because I don't know about it or don't realize that it's relevant.
 

mcmxi

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I'm a total novice. I admitted that up front. I also admitted to leaving the kickstand down, which I wouldn't have done if I was trying to hide operator mistakes. Sure, I would love to have the warranty cover it, but in the grand scheme of things it's not very important.

Much more important to avoid the damage in the future. Given that, it would be stupid of me to hide what I was doing when I'm asking for help. I have plenty of faults, including ignorance in tractor use (which I'm trying to remedy), but not stupidity. If I'm leaving out some context on how I was using it, it's because I don't know about it or don't realize that it's relevant.
I'm interested in the facts and the truth, nothing else. I want to know how this happened because I'm naturally inquisitive and I'm invested in this because I basically have the same tractor as you. In no way do I think you're being misleading, at least not intentionally, and if a defect caused this it should be repaired under warranty.

No one has explained how it's possible to yank a rock shaft off the splined shaft if the 3-point is set up properly, even if you're pulling a implement and it's catching on rocks, roots etc.
 

DWilly

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The takeaways for me after 90ish comments are:
  1. there are aspects of the 3pt design intended to prevent the lift arms from sliding off the rock shaft, but it can happen, even with the stabilizer bars attached and correctly adjusted,
  2. it's pretty rare, but there are reports of it happening to others in multiple major brands, which the manufacturers are aware of,
  3. it can happen whether the retainer is a snap ring or bolted on plate,
  4. reinforcing the bolted on feedback control rod clip may be a fairly easy way to reduce the risk,
  5. the extent of damage to the splines in this particular case likely can be repaired by cutting/filing, and
  6. operations contributing to the risk probably include one or more of (a) using the back blade in severe offset position and at an angle, particularly in reverse, (b) operating on hard, rough terrain, (c) leaving a kickstand down during operation, and (d) increase in applied leverage by use of a QH (subject to differing opinions as to whether the increase is material).
A lot more information than I would have had without asking. Thanks all!
 
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rbargeron

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I believe I can offer a theory about how the lift arm can get moved sideways.

It's caused by 3pt loads, despite the fact that heim ball joints only transmit force, not twist.

Looking at mcmxi's first picture in post #69, it dawned on me that the lifting rod and lower link pin are in a moving plane that is not perpendicular to the axis of the rockshaft.

Resolving the lifting rod force into components parallel to and perpendicular to the rockshaft axis, there is indeed a horizontal component. Its amount is the lifting rod force times the tangent of the angle by which the rod deviates from vertical (see markup). The stabilizers keep the lower arms from moving, and are not involved. The horizontal reaction is taken at the rockshaft.

Often the horizontal force gets masked by sliding friction within the fits, but lifting and lowering changes the force during operations. Its these moments the arm shifts a little on the shaft in its non-zero clearance, eventually working its way along, a little at a time.

A way to visualize this is with a trolley-type crane. If you push the load along, the trolley follows.

component vectors.jpg
 
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loggin

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I am beginning to wonder if it has something to do with a twisting force being applied to the 3 point. As in when weight is hanging on one arm ( pushing down) and a lifting force is applied to the other arm. In the case of having an offset blade. One arm can not go up and down independent of the other. There is usually some play but there is a limit. The limiting factor to this independence is the rock shaft. The shaft is a solid piece. Then factor in the lift arms are angled out slightly. Add to that lifting up and down a number of times and the constant vibration of engaging the earth and things may start falling apart when too much force is being applied to create this twisting force on the rock shaft. Or perhaps even when traveling and having the offset implement raised and bouncing around as one drives through irregularities.

I certainly do not want to get into heated discussions over this and this is purely speculation on my part.

Just thought I'd share...
 
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rbargeron

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I believe I can offer a theory about how the lift arm can get moved sideways.

It's caused by 3pt loads, despite the fact that heim ball joints only transmit force, not twist.

Looking at mcmxi's first picture in post #69, it dawned on me that the lifting rod and lower link pin are in a moving plane that is not perpendicular to the axis of the rockshaft.

Resolving the lifting rod force into components parallel to and perpendicular to the rockshaft axis, there is indeed a horizontal component. Its amount is the total force times the tangent of the small angle (see markup). The stabilizers keep the lower arms from moving, but an equal force acts on the upper arm, pulling on the rockshaft.

Often the horizontal force is soaked up in sliding friction within the fits, but lifting and lowering changes the force during operations. Its these moments the arm shifts a little on the shaft in its non-zero clearance, eventually working its way along, a little at a time.

A way to visualize this is with a trolley-type crane. If you push the load along, the trolley follows.
Further to my theory of the case:

The MX5400 range of the stabilizers seems to allow several inches of off-center implement adjustment. When at the max, the more canted lift rod's angle can apparently apply too much side force for the strength of the arm's retainer bracket. I hope your dealer discusses this with Kubota.
 
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SDT

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Wow! And you claim to have been or are an engineer ... of what? Perhaps you engineered paper bags or something. Your lack of understanding of the application of engineering principles is spectacular. Who were these four companies you worked for, and what was your engineering discipline? You are so enamored with erroneous issues that you can't see the woods for the trees.

You were going on about quick hitches a year ago in a thread about rotary cutters and the need for front end weight. You were wrong in that thread, just as you are wrong in this thread.
Post back after you've pulled the lynch pin and headed out to work.

Again, I'll wait.

What I will not do is attack the integrity of someone that I do not know. Doing so would reflect badly upon my integrity as does your attack upon my integrity reflect upon your integrity. For similar reasons, I will not engage in ad hominem attacks despite your wont to do so.

Regarding, engineering experience: It ain't bragging if you've done it.

SDT
 
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whitetiger

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I am beginning to wonder if it has something to do with a twisting force being applied to the 3 point. As in when weight is hanging on one arm ( pushing down) and a lifting force is applied to the other arm. In the case of having an offset blade. One arm can not go up and down independent of the other. There is usually some play but there is a limit. The limiting factor to this independence is the rock shaft. The shaft is a solid piece. Then factor in the lift arms are angled out slightly. Add to that lifting up and down a number of times and the constant vibration of engaging the earth and things may start falling apart when too much force is being applied to create this twisting force on the rock shaft. Or perhaps even when traveling and having the offset implement raised and bouncing around as one drives through irregularities.

I certainly do not want to get into heated discussions over this and this is purely speculation on my part.

Just thought I'd share...
You and rbargeron are seeing what happens correctly. A heavy side draft and or angled force can place a side load on the arm which tries to push it off the rock shaft.
 

PoTreeBoy

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Further to my theory of the case:

The MX5400 range of the stabilizers seems to allow several inches of off-center implement adjustment. When at the max, the more canted lift rod's angle can apparently apply too much side force for the strength of the arm's retainer bracket. I hope your dealer discusses this with Kubota.
I think you and loggin have it. As long as the lift rods are hanging perfectly vertical they don't exert a side load on the arms. But if they are spread apart at the bottom, weight on the implement causes a horizontal component of force pulling the arms apart. The more angle of spread, the larger the side force, but I wouldn't expect a large load.
Our blade I think is a class 2 adapted to class 1 for the Ford, so it's pretty wide and spreads the lift rods a fair bit. But we've never had a problem with it. The Kubota retainer must be pretty weak, or OP is really overloading it.
Edit to add: at first I was thinking that uneven load side to side, or lifting one side with weight on the other, causing a twist would be necessary (and might magnify the effect), but now I think even an even load would cause the effect.
 
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mcmxi

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Post back after you've pulled the lynch pin and headed out to work.

Again, I'll wait.
I'm not going to entertain your ridiculously foolish idea of an experiment. If you think about vibration and the constant loading and unloading of the rock shafts during use, a two year old would soon figure out that the lift arms would/could vibrate off the pins. The fact that the hardware on these tractors relating to lateral loading of the 3-point linkages is so minimal should be evidence enough that lateral loading is not a thing.
 

mcmxi

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I believe I can offer a theory about how the lift arm can get moved sideways.

It's caused by 3pt loads, despite the fact that heim ball joints only transmit force, not twist.

Looking at mcmxi's first picture in post #69, it dawned on me that the lifting rod and lower link pin are in a moving plane that is not perpendicular to the axis of the rockshaft.

Resolving the lifting rod force into components parallel to and perpendicular to the rockshaft axis, there is indeed a horizontal component. Its amount is the total force times the tangent of the small angle (see markup). The stabilizers keep the lower arms from moving, but an equal force acts on the upper arm.

Often the horizontal force is soaked up in sliding friction within the fits, but lifting and lowering changes the force during operations. Its these moments the arm shifts a little on the shaft in its non-zero clearance, eventually working its way along, a little at a time.

A way to visualize this is with a trolley-type crane. If you push the load along, the trolley follows.

Just as in truss analysis, you have to consider the reactive forces at the joint, i.e. both ends of the lift arm. Go look at "method of joints" analysis for a truss. There is little to no ability of the heim joint and sleeve to resist a force axially in reference to the pin on which it resides. If there's no ability to resist a force, there's no force vector in that direction.

There is a moment generated by loads on the rock shafts about the splined shaft, but the lever arm is short, and the loads are typically balanced. In addition, the loads cause the rock shafts to rotate towards the center of the tractor.
 
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