MX5400 hydraulic arm shaft and control rod damage

[Russell King]

“If there's no ability to resist a force, there's no force vector in that direction.”

Then you have motion in that direction???

When I push a table across the floor there is a friction force restraining the table until the push force overcomes it. There is no horizontal force until I start pushing

 

[TheOldHokie]

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.

Getting the lift arms off the Fords often requires dynamit

“If there's no ability to resist a force, there's no force vector in that direction.”

Then you have motion in that direction???

When I push a table across the floor there is a friction force restraining the table until the push force overcomes it. There is no horizontal force until I start pushing

No. When the table is at rest there is no force present from static friction. That force only comes into existance the moment you apply an external force to the table and grows on magnitude as the external force increases until the table starts to move. At that point the magnitude of the force decreases to the level required to account for sliding friction.

Dan

 

[Russell King]

Getting the lift arms off the Fords often requires dynamit

No. When the table is at rest there is no force present from static friction. That force only comes into existance the moment you apply an external force to the table and grows on magnitude as the external force increases until the table starts to move. At that point the magnitude of the force decreases to the level required to account for sliding friction.

Dan

Sounds exactly like what I said and is exactly what I meant

 

[SDT]

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.

No problem.

Pull the lynch pin, replace it with a bent-over nail.

Post back when the nail shears.

SDT

 

[TheOldHokie]

Sounds exactly like what I said and is exactly what I meant

I am sorry. I did not read closely enough.

Dan

 

[mcmxi]

“If there's no ability to resist a force, there's no force vector in that direction.”

Then you have motion in that direction???

When I push a table across the floor there is a friction force restraining the table until the push force overcomes it. There is no horizontal force until I start pushing

To get the table moving, there's static friction to overcome, and then kinetic friction, the inertia of the table etc. .. sure. But you have to have the ability to resist that force where your body is in contact with a surface. Look at zero force members in trusses. They carry no load, either compression or tension, but they are integral to the structure for other reasons.

 

[mcmxi]

After all this round and around, I hope that the dealership comes up with an explanation of how and why this happened ...and that the OP doesn't have to pay out of pocket.

 

[SDT]

Getting the lift arms off the Fords often requires dynamit

No. When the table is at rest there is no force present from static friction. That force only comes into existance the moment you apply an external force to the table and grows on magnitude as the external force increases until the table starts to move. At that point the magnitude of the force decreases to the level required to account for sliding friction.

Dan

Agreed that removing upper lift arms from vintage Ford rockshafts can be challenging but such lift arms have usually been in place (and often sitting out in the rain) for 6-8 decades, becoming badly corrosion locked over time.

It is interesting to note that the vintage Ford lift mechanism, though similar in design to that used by Kubota on the MX6000 and similar models, uses a MUCH larger rockshaft and considerably heavier upper lift arms.

SDT

 

[SDT]

After all this round and around, I hope that the dealership comes up with an explanation of how and why this happened ...and that the OP doesn't have to pay out of pocket.

I too hope that Kubota decides to cover the repairs to the OP's tractor under warranty, despite my concerns regarding operation. The tractor has very low hours.

That said, any dealership explanation regarding how and why the failure occurred should be taken with a grain of salt.

SDT

 

[SDT]

Agreed that removing upper lift arms from vintage Ford rockshafts can be challenging but such lift arms have usually been in place (and often sitting out in the rain) for 6-8 decades, becoming badly corrosion locked over time.

It is interesting to note that the vintage Ford lift mechanism, though similar in design to that used by Kubota on the MX6000 and similar models, uses a MUCH larger rockshaft and considerably heavier upper lift arms on tractors producing less PTO and drawbar HP.

SDT

 

[GeoHorn]

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.

And yet…there is that original posts’ photograph proving it actually happened. It’s a shame that lift-arm/rockshaft/retainer isn’t as dense as you.… If it were this failure never could have occurred.

 

[GeoHorn]

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!

You forgot:

7. mcmxi is a self-impressed interloper rude and disrespectful to whom he doesn’t agree or cannot fathom their opinion.

Please keep us posted about Kubotas’ response.

 

[mcmxi]

And yet…there is that original posts’ photograph proving it actually happened. It’s a shame that lift-arm/rockshaft/retainer isn’t as dense as you.… If it were this failure never could have occurred.

Oh, so the lift arm wasn't connected when this happened? Yep, I can be dense at times, but not this time.

 

[mcmxi]

You forgot:

7. mcmxi is a self-impressed interloper rude and disrespectful to whom he doesn’t agree or cannot fathom their opinion.

Please keep us posted about Kubotas’ response.

I would expect nothing more of you and can honestly say that you add nothing of any significance in any post other than to confirm that the only thing bigger in Texas is the size of the egos and the size of the hole between the ears. Please stay in Texas.

 

[mcmxi]

Let's not forget SDT's first post in this thread, and the first response. Followed by "I don't know how this could have happened" to "the quick hitch" was responsible. Perhaps it's hard for some to remember what they said a couple of days ago. But this guy was a design engineer at four companies and is one the self-appointed tractor experts on this forum. You'll need front weights to run that rotary cutter, you're quick hitch will mess up that rotary cutter .... wrong and wrong. Absolutely 'ucking useless.

I despise self-appointed, delusional, know-it-all, anonymous types that frequent gun forums, tractor forums and the like. And the 'ucking sheep that are so clueless that they can't tell the difference.

I cannot see how that could have happened without serious abuse.

Then ...

Retainer bolts appear to be properly tightened yet something forced the upper lift arm off of the rock shaft.

Left side rock shaft bushing has moved left of design position. Bushing could have forced arm past retainer but don't know of anything internally that could cause that to happen. Who knows?

Were sway bars properly installed and adjusted?

Then on hearing of the use of a quick hitch ...

Quick hitch?

That's new information.

The quick hitch moves attached implements rearward a bit extending the lever arms attached to the tractor hitch, multiplying forces proportionally.

Yet another reason why I do not use quick hitches.

 

[DWilly]

Great news today. Kubota approved the warranty claim and parts are on order. ETA on the parts is later this week (too late for the Biggest Snowfall of the Year), so I should have it back first of next week. Joy is restored in Mudville.

 

[SDT]

Let's not forget SDT's first post in this thread, and the first response. Followed by "I don't know how this could have happened" to "the quick hitch" was responsible. Perhaps it's hard for some to remember what they said a couple of days ago. But this guy was a design engineer at four companies and is one the self-appointed tractor experts on this forum. You'll need front weights to run that rotary cutter, you're quick hitch will mess up that rotary cutter .... wrong and wrong. Absolutely 'ucking useless.

I despise self-appointed, delusional, know-it-all, anonymous types that frequent gun forums, tractor forums and the like. And the 'ucking sheep that are so clueless that they can't tell the difference.



Then ...



Then on hearing of the use of a quick hitch ...

Bingo.

Quotes are exactly what I said and exactly what I meant.

Don't remember telling you that a quick hitch will "mess up" your mower.

I'll wait for a link.

SDT

 

[SDT]

Great news today. Kubota approved the warranty claim and parts are on order. ETA on the parts is later this week (too late for the Biggest Snowfall of the Year), so I should have it back first of next week. Joy is restored in Mudville.

That is good news.

SDT

 

[S-G-R]

Great news today. Kubota approved the warranty claim and parts are on order. ETA on the parts is later this week (too late for the Biggest Snowfall of the Year), so I should have it back first of next week. Joy is restored in Mudville.

Good to hear!

 

[GeoHorn]

Great news today. Kubota approved the warranty claim and parts are on order. ETA on the parts is later this week (too late for the Biggest Snowfall of the Year), so I should have it back first of next week. Joy is restored in Mudville.

Aren’t we all ecstatic that mcmxi doesn’t run the warranty dept at Kubota?