BH77 Stabilizer arm broken and cylinder rod snapped

[KyleH]

Was digging a stump out today and the stabilizer arm broke and the cylinder rod snapped.

Sort of expected this to happen at some point as they seem undersized for the amount of stress the BH77 can put on them. The tractor gets pushed and pulled around by the backhoe too easily, which puts a lot of force on those arms which can lead to them breaking off apparently.

Obviously was not being gentle with the backhoe but somewhat expect that it should stand up to the stress of being pushed or pulled on provided it's not been tampered with by increasing pressures or modified it to get more leverage, etc.

Gave the dealership a call, they were busy but took the time to call me back after closing to see what was wrong, that was nice of them for sure. He asked me to email some pictures and he will have a look tomorrow to see what he can do. He said he's never heard of one of these breaking, I expressed concerns about how thin the material is, about 1/8" steel, as I was thinking it should be 1/4" thick. He suggested it could just be a bad weld, and should not have broken no matter how hard I worked the machine. Hopefully Kubota feels the same, if not I will be making some that are much stronger than the ones that come on them, perhaps add a brace to the existing arms from the backhoe frame.

As much as I like the size of the B2650 and the BH77, I may need to upgrade to something that's built heavier for what I expect it to do.

 

[100 td]

Interesting to say the least! Did you have the front of the machine raised with the bucket dug into the ground? If not, then the push pull of the hoe could do this easily I expect. Once cleaned up it will be interesting to see if some of the damage has been done previously, meaning cracked before, you should be able to see old cracks oxidised and the new tears clean. I would also pull the other side and sand/shot/bead blast then dycheck/crack test it as well. If it's a newish machine, hopefully they will come good for a repair. A recent dipper tear on the orange forum is also interesting, I wonder if they have downsized some materials in the last couple of years?

 

[Tomtint]

Looks like there is some rust on the welded area, may have been broken a while and finally snapped. .02

 

[Tompet]

Looks like there is some rust on the welded area, may have been broken a while and finally snapped. .02

First time hearing of this part failure. Something to check, thanks for posting. You mentioned something heavier built, same thought I have once in awhile....maybe a B26....

Make sure you post resolution of story!

 

[KyleH]

I try to dig in with the loader bucket a bit, but it doesn't seem to help much, the BH77 has enough power to pull the B2650 around with ease. I think reinforcing the arms with a brace will be the way to go for me, I'd prefer they were overbuilt from the factory though.

Have to wait and see what they say, worst case I'm out an arm and a rod I guess.

 

[kcott1973]

I have some experience with weld destructive testing and it appears that the weld failed due to lack of weld penetration into the sleeve. I hope Kubota will take care of this for you. I work at a major industrial equipment manufacturer and they frequently take failed parts from the field and test and inspect them in the lab.

 

[CreekyB]

hard to tell 100% from the pics but I agree, looks like bad welds from the pics.

Hopefully not just an underbuilt weak point. The BH77 is what is on my L2501 as well.

 

[KyleH]

I would prefer to see 1/4" steel tube used, as well a brace or wider piece of tube to resist bending as easy. May be something I can fab up to ensure it doesn't happen again. Going to need to invest in a bigger welder I think.

 

[My Hoe]

I would prefer to see 1/4" steel tube used, as well a brace or wider piece of tube to resist bending as easy. May be something I can fab up to ensure it doesn't happen again. Going to need to invest in a bigger welder I think.

I'm sorry that happened, but thankful no one was hurt, and that you shared it with the group.

I'm also sorry for the long-ish post, but I believe many will be rather interested at the theory I float at the end (which I hope I'm wrong about...).

I'm no metallurgist, but I too (as have others) thought I saw rust in the weld--though it may just be dirt/mud. If rust, I agree, could have been a poor weld, partially cracked already.

And not to be the "Safety/Legal Police", nor to belabor the obvious, but if you weld anything on the (new) pieces that (I EXPECT) Kubota is going to install on your machine, of course, any future failures (to that part, and/or any damages/bodily injury that can be possibly be found to be "proximately caused" by the failure of a part you modified) WILL be blamed on your (uncertified?) welding/modifications. It's not (necessarily) fair, I know, but that's how corporate lawyers make their bread.

So, especially since this is the first we've seen of this type of failure, I would suspect bad metallurgy/welding, and I would NOT plan on modifying things myself, were I you, both to avoid being blamed for any future failures and because, again, since this is not a known failure, I respectfully submit that the stabilizers may be just fine, as is, IF properly welded, and, of course, with sound base metal. Just my .02.

Your dealer sounds very responsive, which is great! If things turn sour (which I doubt they will), however, I assume there are "Zone Reps," as there are in the auto-biz, which you can also ask to speak with. And Kubota Corporate, themselves, whose representatives I have found willing to pick up the phone and answer far less serious questions than yours.

Just curious--year tractor went into service? Hours on the tractor/hoe?

Oh--and did you have the rear tires off the ground (as we see commercial operators doing, commonly)? Or were they lightly on the ground which, IIRC, my BH77 Operator's Manual recommends, which kind of surprised me, given how the "Big Boys" operate their (commercial) machines.


Whoops--one more question: are your rear tires filled, or not? The reason I ask is, as I'm sure you know (and again, IIRC), Kubota recommends NOT running filled tires while operating the BH. (As if we've all got a second set of rear wheels lying around, and the time/equipment/strength to change them back-and-forth.)

I ask because I HOPE you haven't accidentally discovered the answer to the long-debated question of WHY Kubota doesn't want the hoe operated with filled tires. Again, with the assumption that the (HEAVIER, FILLED tires) would be lifted off the ground, by the stabilizers--which again, IIRC, the BH77 Manual says NOT to do. (And IF this is the reason, then you would be absolutely correct, as you stated, about your theory that square-tube stock of the stabilizers should be thicker than it apparently is....)

Good luck, and let us know.

My Hoe

 

[LD1]

I too am wondering how old.....and how many hours are on the machine?

It looks too new for that to have happened. A backhoe should not be able to tear itself apart no matter how hard you work it. Digging stumps is not abuse. Its just digging. The only thing I consider "abuse" when operating a backhoe or trackhoe is hammering/slamming the bucket into things.