Major structural failure on L4610 - ouch !!

[beenthere]

Those are good points you have. Thanks.

 

[rbargeron]

Hello Mark - good to hear your voice. It is true that if a manufacturer wants to back away from a problem there are many factors they might cite. For example if the backhoe was someone else's design, and the subframe was attached inappropriately to the gearcase, then how can they be responsible for that? But this is a Kubota backhoe subframe, intended to reinforce the 3-pt hitch - the part that failed. The winch is Cat 1 - so its operating forces should be covered by generic specs.

But I've already stuck my nose into this a little further than I should - so I'm going to take a seat in the back. Let's see what develops and how the conversation goes.

 

[TresCrows]

There is two ways of looking at this. One, the part was defective or inadequate and broke in normal use. The other is that the part was adequate for intended purpose and broke due to ABNORMAL use and improper use of attached equipment--in which case they don't have to fix it but I agree it would be nice if they did. That looks like cast iron there--is it? Looks to me like he needs a bigger tractor for the work he is doing if he tore the case off. Neither aluminum or cast iron just break or break like that in normal use. Wow, looks like he will need some more hydrualic fluid to /forums/images/graemlins/laugh.gif. J

 

[Bob_Skurka]

_RaT_ I tend to agree with your assessment. IF there was a flaw in the casting then a reputible company will replace it even out of warrenty, however there is a sorts of reason to believe that the machine was used very hard and probably took loads larger than it was designed for and those loads are the likely cause of failure. We really don't have a lot of information to go on, but I suspect the owner is in for a whopper of a repair bill and I suspect that Kubota will find no reason to eat the cost of the repair, and I would consider that fair to both parties involved absent any additional information.

 

[art]

Sure would have been neat to be a chipmuck sitting on a tree stump nearby!

 

[DaGoatMan]

OUCH!!! Looks expensive...I will say this... The inside of the gear housing sure looks good. Those gears look like they are new. I hope this gets resolved without to much pain for the owner.

 

[_RaT_]

I agree Dick, it will be interesting to see how it progresses. When my brother in laws tractor flipped head over heals twice, it bent the ROP's over to about a 40 degree angle. Kubota was very interested in obtaining the ROP's for testing.

 

[Mahlon]

Judging from the photographs, it appears that the winch placed an excessive draft load on the 3ph top link. Draft loads are supposed to be taken by the 3ph drag links; the top link simply locates the load fore/aft.

Notice how thin the casting is in the area of the top/rear rear axle casting, then notice how much thicker it is around the 3ph lift arms & cylinder casting. I'd guess that the failure mode was that after a "tug" the top link cracked and popped out the top/rear rear axle casting, taking the rear of the cylinder casting with it by levering & then cracking it through its weakest portion (through the lift arm shaft bearing area).

I assume that the two drag links and the casting areas supporting them were undamaged?

I wonder what the winch looks like & how low the cable comes off of the winch. I'd want it to be at the same level as the two lower 3ph hitch pins.

In a prior career I've seen large (150 hp) ag tractor transmissions and final drives endurance & load tested to destruction. Have seen entire transmissions and final drives reduced to rubble inside the cases. Have seen 1 1/2" thick castings in pieces. It's not a pretty sight (nor is it cheap), but the designers learn a LOT from these failures.

I wish the owner good luck.

regards,

Mahlon

 

[_RaT_]

Mahlon, I came to somewhat of the same conclusion. The lower links were probably not taking the load. On my Kubota, the lower links are the obvious bulk of all loading. Not only are they much heavier, but if they did fail, would be a very easy fix. I try to be aware of this when using my hydraulic top link as there are times I can get the cutting edge of by box blade into a tree stump, retract the hydraulic top link and have my whole front end up in the air.

 

[slowzuki]

I'd have to dissagree with the assessments of the failure. Without inspecting the tractor carefully we can't tell what what happened.......

Buuuutttt I'd have to say the failure started at the tapped hole, and looking at the direction of the failure, I'm guessing the lift piston was at a high pressure. The pivot pin supports there failed at 90 deg to the direction of the 3 point piston slide direction, which is where the highest stress would be during lifting 3 point loads.

Do kubotas have a relief on the load side of the position control valve?

I suspect this type of failure is what prompted the external cylinders on the L30's.

Ken