More M59 repair fun.

[Hersheyfarm]

As far as beating this machine goes, I don't ram or beat rock with this. I've never ran any attachments front or back. I do try to move the most material and can with the front. Dirt being the heaviest and the m59 struggles with heaping scoops. It's been dry and I was pushing manure and dirt and back dragging dirt where the cows stomp it during winter. That in itself is very hard on front as far as it vibrating and slapping back and forth on the pins. That's when this one broke. The other broke couple months ago. Both snapped right at the grease groove.

 

[mike69440]

Hershey, I've been looking at those pictures and at my own M59 and still don't haven't come up with any explanations that satisfy me.

For those that don't know me, I'm a welder and machinist as well as an mech. eng., and spent a lifetime designing equipment of all types. Still do a bit of it in retirement. And I have the same tractor. Mine is also a 2008 with similar hours. It hasn't been totally problem free but darn near. I also use mine reasonably hard and sure haven't had anything like the problems that Herseyfarm has had.

A couple of things bother me about these pins. Yes, I know from other conversations that Hersey beats his machines hard. We've talked about that before. But even so, there just isn't any easy way to get a shearing stress onto the center of that pin - especially when there's a locking bolt still in place that prevents the pin from sliding laterally.... And what with the decent geometry and bulky end support it is equally hard to see how the pin break could be deflection induced either. And the other bother is that you say this wasn't the first pin you've had break. Hmm....Have you checked all the other pins on the machine? Of course once that pin did break then things could progress just as you said - your sequence sounds reasonable to me - what with the outer half of the pin working it's way out and once that happens the off-center push bending the ear until the hose failed. But trying to see how to initially get enough stress on center of the pin to start the sequence is the problem I'm having.

It's sure sounding like it started as a pin material problem. And that's surprising because Japanese steel is generally right there with the world's best. I assume that the pins are hardened or plated at some point...could that be a clue? Of course there are ways to check where and roughly why a fracture starts. Doing that formally is likely to be more expensive than this relatively inexpensive repair, but any metallurgist and most mechanics who have a 50x microscope and a few chemicals can tell you a lot about a break like this.

For my part, I'm sure going to pull the pins on my M59 and see how they look before the season starts. And I'm going to talk with the guy that owns the local cylinder fab shop to see if I've missed considering something obvious.... then I'm going to sit down and do some more thinking.

I'll not condemn the M59 or it's loader design because of this, but will certainly check mine carefully.
Oh, I forgot to ask; do you use any other buckets or QA bucket attachements on your M59? Is there any missing info there?
Thanks,
rScotty

Rscotty

While some equipment pins are hardened or hardfaced, the Kubota pins are plain carbon steel. Cross holes drilled in pins however especially if the holes are not chamfered nicely are excellent stress risers. I'd chamfer all pin x-holes before reinstall.

 

[SPYDERLK]

Rscotty

While some equipment pins are hardened or hardfaced, the Kubota pins are plain carbon steel. Cross holes drilled in pins however especially if the holes are not chamfered nicely are excellent stress risers. I'd chamfer all pin x-holes before reinstall.

This will not be enuf. Regardless of blending, as you suggest, the weak area will still be at the center and the cross drilled hole will still be there to further accentuate the weakness and will have sharp edges that you cant get to. Cracking will initiate at those edges. Even the orientation of the cross hole relative to loading direction, and depth of the center hole wrt the cross drilling point will affect. ... Theres lots of optimization do do and it would all help. The time to do that is if there were no design choice in the lube matter. Putting a grease zerk on the collar and using solid pins is a straightforward cure.

 

[5030]

Of course you could pay a visit to your local heat treater and have them normailzed. It's not expensive.

 

[Hersheyfarm]

well, all back together and ready for action. I did check my pressure and at idle I'm at 2600psi and 2800psi at 2500rpm's.

 

[rScotty]

This will not be enuf. Regardless of blending, as you suggest, the weak area will still be at the center and the cross drilled hole will still be there to further accentuate the weakness and will have sharp edges that you cant get to. Cracking will initiate at those edges. Even the orientation of the cross hole relative to loading direction, and depth of the center hole wrt the cross drilling point will affect. ... Theres lots of optimization do do and it would all help. The time to do that is if there were no design choice in the lube matter. Putting a grease zerk on the collar and using solid pins is a straightforward cure.

Well, I'll go with your idea about stress risers. It makes a good working hypothesis. Certainly I don't have a better idea and am just now beginning to look at some of the details of the design. I still think that a close look at the broken pins might tell why they failed. What did you see looking at the three pin failures on your 7520?

Frankly I never paid much attention to the pins on the loader and backhoe before. But after taking a closer look at my M59 this afternoon it looks as though all of the pins on the loader and backhoe are made using that same basic design. It'll be interesting to see what I find when I pull a couple of them.
rScotty.

 

[rScotty]

well, all back together and ready for action. I did check my pressure and at idle I'm at 2600psi and 2800psi at 2500rpm's.

Best to check the pins on the other end of each loader arm before calling it done.
good luck,
rScotty

 

[SPYDERLK]

Well, I'll go with your idea about stress risers. It makes a good working hypothesis. Certainly I don't have a better idea and am just now beginning to look at some of the details of the design. I still think that a close look at the broken pins might tell why they failed. What did you see looking at the three pin failures on your 7520?

Frankly I never paid much attention to the pins on the loader and backhoe before. But after taking a closer look at my M59 this afternoon it looks as though all of the pins on the loader and backhoe are made using that same basic design. It'll be interesting to see what I find when I pull a couple of them.
rScotty.

Well, on checking I was wrong on the number. ... I have 4 broken pins at the groove and one still in one piece - altho I replaced 6. :confused2: Something is misplaced?

,,,,,,Anyway the pin that is still whole is cracked nearly all the way around the groove - how deeply i dont know. The crack goes thru the 1/2 cross drilling hole. All the pins at the implement end are now solid. The base ends of the curl and lift cylinders still have grooved pins. Id better check them. The tractor has ~ 1500 hrs; many of them hard loader time.

 

[rScotty]

Well, on checking I was wrong on the number. ... I have 4 broken pins at the groove and one still in one piece - altho I replaced 6. :confused2: Something is misplaced?

,,,,,,Anyway the pin that is still whole is cracked nearly all the way around the groove - how deeply i dont know. The crack goes thru the 1/2 cross drilling hole. All the pins at the implement end are now solid. The base ends of the curl and lift cylinders still have grooved pins. Id better check them. The tractor has ~ 1500 hrs; many of them hard loader time.

When you replaced the pins on the Mahindra what did you use? Did you lathe some up or find a size that worked? Have you compared the pins on the Mahindra with similar pins on your Kubotas?

Apologies in advance for pelting you with questions, but my curiosity is up now, and will probably stay that way until we know a lot more about the design and materials used in these pins. The problem with trying to figure out a fix is that pins could could look very similar and not even be close to being similar in performance and material.
rScotty

 

[Hersheyfarm]

Out of curiosity what would you expect these pins to be made out of? Like a 4140 or 4150, same as gun barrels? And I guess the chrome finish is like an acid treatment or nickel?