Major structural failure on L4610 - ouch !!

[_RaT_]

So Ken, your thought is that the ram actually broke it off? I don't know that that is possible with the way the relief system works. At any rate, I asked my dealer if he has ever seen such a situation as that and of the many thousands he has sold, not one has had a failure pictured here. The cylinders on the outside had as much to do with increasing lift capacity and ease of acessability as it did with anything. I must also say Kubota has increased the strength of the lower links as well on the L30 series. All steel and thick steel at that.

 

[tosh]

WOW, how big and what kind of logs were you handling? Were you lifting the butt of the ground to drag it? Good luck on the repairs.

 

[bgott]

When my NH was in the shop last year they had an M series (4800 or 4900, I forget which) setting next to it with the same damage. The tech told me the operator had hit something with a box blade while backing up full speed.

 

[L3710GV]

My guess is he had front of tractor chained off to a tree or something solid, and was useing to big of a winch, and was pulling on something below the winch spool.

The three point arms are held up by that shaft, and pulling below the winch would put alot of downforce on the three point arms, combined with the force being put on upper three point mount trying to hold winch from rotateing, and the force being put to the casting by the hydraulic piston (3")-- its easy to see how it broke.

Kubota is aware of some weakness in the upper three point attachment- when put to extreme loads- they make a reinforcement for it, which extends some of the load up and over the shaft. The xtra suport was mandatory with use of a three point backhoe.

I put these reinforcements on my L3710 (same case as L4610) after reading about it right here on my favorite web site /forums/images/graemlins/smile.gif I also posted about welding the original angle mount brackets to the new reinforcement bracket, so it will remove some of the load off of the original atachment bolts. Also have an xtra bracket if anybody needs one, and all the part #s for this upgrade.

 

[grandad]

As you probably know, I have the same tractor and BH as shown... so this touches very close to home for me. Again, we are mostly left to guess, but I'm thinking your way that this was more likely to be from some kind of extreme load or shock to the top link.

There is indeed a relief valve (it's adjustable... wonder if it was it out of adjustment) that should prevent a cylinder driven overage, unless maybe it inconveniently failed just when the operator went to pick up a giant redwood trunk with the winch.

I don't know that the BH subframe really changes the 3pt setup very much regarding capacity or strength. Whatever broke this one would have done it with or without the BH.

But "ouch" is right! Sorry to see this happen.

 

[Mahlon]

Just found out what one of these log skidder winches looks like. Confirms my suspicions. The 3ph drag links are actually in compression when using one of these, and the draft load on the top link is probably double whatever the winch is pulling. Ordinarily that shouldn't be a problem, but what happens when you get snagged?

regards,

Mahlon

skidder winch pic

 

[AndyR]

The skidder loads can vary depending on whose skidder you use. I have a Norse that has 2 positions for the sheaves (pulleys) and almost always use the lower one.

I think it would be usefull to look at the winch this fellow was using to see what shape it is in. This kind of breakage looks to me like what you can get if you are trying to pull a log over some stumps while driving forward vs. using a snatch block to route the cable to the side.

 

[art]

Most skidding winches work off a bottom rack for log hook-up when transporting. I'd say he was hooked off the top by the winch cable not off the bottom. There might have been a buching plate and he hit a hard obstacle while backing in to bunch the logs. Will the manufacturer pay for a mistake? No not normally, why should they unless it's there mistake.

 

[slowzuki]

My concern is that lots of people use 3-point winches on compact tractors. I have never seen a failure due to one. The kubota dealer here will slap one on for you when you buy your tractor. Many dealers have packages with a fops, front skidder type blade and 3pt winch.

Some of the winches have a clutch too for when dragging from the top point. Others have a pawl that engages for transport.

 

[rbargeron]

A few more details - the owner told me he was moving forward, skidding some logs and the winch was "up". He came up over a small rise and heard it break, and heard the oil pouring out. It didn't completely rip away from the tractor - the pictures show it after some unbolting of the bent subframe.

This description of things leads me to think the skidding load finished it off but something else had happened earlier ? The backhoe subframe weld is cracked and bent near the left side connection (top picture).