Adding zerk/grease fitting?

[Jason280]

I have an '03 L48 backhoe, with roughly 1100 hours. I've now broken the hinge pin on the FEL 3 or 4 times (I think its called "Pin 7"), the pin that attaches the ram end of the cylinder to the tilt portion of the bucket attachment. This pin has a grease fitting on the end, with a hole drilled through the middle to a center portion groove. The groove has holes, where the grease expands out to lube the pivot. The pin has always broken at this groove. On my much newer 7060, the same pin has no groove, and no grease fitting....instead, the pivot is lubed by an external zerk that is threaded through the end of the cylinder ram (on top). This means the pin is a solid piece, with no extra holes or grooves (to potentiate fractures).

Here's my question. Any reason I can't simply use the newer style pin, and drill/tap the ram end on the L48 cylinder for a zerk fitting? This is how the 7060 is set up, and the pins are the exact same diameter and width. I do understand this leaves the zerk a little more exposed, but I could always tack weld a small collar around it for protection.

 

[Tinhack]

I think I would have done that on the second break.

 

[Jerry/MT]

I have an '03 L48 backhoe, with roughly 1100 hours. I've now broken the hinge pin on the FEL 3 or 4 times (I think its called "Pin 7"), the pin that attaches the ram end of the cylinder to the tilt portion of the bucket attachment. This pin has a grease fitting on the end, with a hole drilled through the middle to a center portion groove. The groove has holes, where the grease expands out to lube the pivot. The pin has always broken at this groove. On my much newer 7060, the same pin has no groove, and no grease fitting....instead, the pivot is lubed by an external zerk that is threaded through the end of the cylinder ram (on top). This means the pin is a solid piece, with no extra holes or grooves (to potentiate fractures).

Here's my question. Any reason I can't simply use the newer style pin, and drill/tap the ram end on the L48 cylinder for a zerk fitting? This is how the 7060 is set up, and the pins are the exact same diameter and width. I do understand this leaves the zerk a little more exposed, but I could always tack weld a small collar around it for protection.

This sounds like a good fix.

 

[sea2summit]

I would imagine this is just fine, if it's the same side that always breaks I'd wonder about the alignment of the FEL/arms/cylinder though.

 

[Smokeydog]

No reason your idea won’t work. Some bushings have grease grooves. My old M5030 had both grease points with protection collars on those very pins.

Broke a lower ssqa pin similar pin on the M59. Previous owner not friends with a grease gun. Replaced the four pins and may at some point replace the bushings. Surprisingly inexpensive. Old pins showed wear on one side probably flexing under load.

Any grease is better than no grease. Moly grease is preferable for these large pin/bushing joints.

 

[Jason280]

I would imagine this is just fine, if it's the same side that always breaks I'd wonder about the alignment of the FEL/arms/cylinder though.

At least once its been on the opposite side, where the rod is for bucket position. The pins are exactly the same, with the exception of the additional "boss" for the bucket rod assbly to attach.

 

[MapleLeafFarmer]

just a little aside.... are you using Kubota OEM pins or aftermarket?

i was told by my local parts supplier that their is so much junk / poor quality stuff flooding the market for some time which probably includes soft / weak pins. He says he regularly de-lists certain suppliers only to find the next in line banging on his door to buy parts flogs him the same inferior stuff. He called it a race to the bottom of quality. Price seems to drive a lot of buyers decisions. He claims it is getting very hard to find high quality / easy to find inexpensive sh@t.

 

[rScotty]

I have an '03 L48 backhoe, with roughly 1100 hours. I've now broken the hinge pin on the FEL 3 or 4 times (I think its called "Pin 7"), the pin that attaches the ram end of the cylinder to the tilt portion of the bucket attachment. This pin has a grease fitting on the end, with a hole drilled through the middle to a center portion groove. The groove has holes, where the grease expands out to lube the pivot. The pin has always broken at this groove. On my much newer 7060, the same pin has no groove, and no grease fitting....instead, the pivot is lubed by an external zerk that is threaded through the end of the cylinder ram (on top). This means the pin is a solid piece, with no extra holes or grooves (to potentiate fractures).

Here's my question. Any reason I can't simply use the newer style pin, and drill/tap the ram end on the L48 cylinder for a zerk fitting? This is how the 7060 is set up, and the pins are the exact same diameter and width. I do understand this leaves the zerk a little more exposed, but I could always tack weld a small collar around it for protection.

Sure, you can put anything in there that you want. I know that some pins break, and it is just a simple enough of a problem to be interesting to us simple kinds of guys.

What do you think? Have you put any time into seeing why it broke? Photos? A rounded groove is not much of a crack potentiator. As you describe it, it almost sounds like there is more friction on one side of the center groove than the other. That would give it a twisting force to break the pin at the center instead of a shearing force out at the end.

Any chance that the pin is somehow constrained on one side and not the other? That could happen if the the grease goes to one side and not the other? Or maybe different types of grease were used? grease incompatibility is real, and gives you a hardened clay "dam" that blocks grease flow.

I've also saw here on TBN a few years back a complete Kubota technical design foul-up where the pivot pin was fastened against rotation at one end ..... actually bolted to the loader arm.

I ask all these questions because I've found that grease and pivot failures are likely to happen again unless the cause is cured.

I'll see if I can find a diagram. Most pins are free to rotate and are mounted in double shear....which makes it even less likely for it to simply shear and more likely that it is a torsional failure. If that is what is happening, you should probably mount TWO ZERKS at the 1/3 points instead of one at the center. Allow it to rotate - it's hard to beat a free floating pivot pin with a couple of washers and a cotter pin or two keeping it in place. Use a grease with a wide compatibility base chemistry. JD's green modern polyurea type is one of the better ones. There are others. I don't use moly because of the mess. YMMV.

BTW, just to complicate a simple job, ZORO.COM has a great selection of zerks. I went crazy and bought this zerk thread gauge. Do yourself a favor and stick with something simple like NPT....

rScotty

 

[Jason280]

Oddly enough, I have three different Kubotas with FEL's, and it's the only one to ever break a pivot pin. That being said, my old '07 4330 (if I remember correctly, it's been replaced with a MX5400) and newer 7060 both have the external zerk fittings on the pins.

 

[rScotty]

Right. It seems like in every mechanical device there is more than one way to do it. When looking at wear or failure it's interesting to see if there is some simple & better way to make it.

Pivot pins are an example how a little thought can make a big difference. After all, if a designer can't make a pivot pin that lasts, it's probably worth taking a hard look at the rest of the loader.

I will say that the loader on our M59 is well thought out in every detail. I don't know if other Kubota loaders are the same or not.

rScotty

 

[rScotty]

Oddly enough, I have three different Kubotas with FEL's, and it's the only one to ever break a pivot pin. That being said, my old '07 4330 (if I remember correctly, it's been replaced with a MX5400) and newer 7060 both have the external zerk fittings on the pins.

I don't see any reason why an zerk couldn't do its job just as well on the end of the pin as anywhere else. Having a single channel in the pin does put an extra requirement on what grease is used.

 

[jwmorris]

BTW, just to complicate a simple job, ZORO.COM has a great selection of zerks. I went crazy and bought this zerk thread gauge. Do yourself a favor and stick with something simple like NPT....

If it’s in a stressed area, I would probably go as small as I could. Maybe a 1/4-28. lots of fittings out there for that thread And if they do get broken off are generally much easier to remove than tapered pipe fittings.

 

[rScotty]

If it’s in a stressed area, I would probably go as small as I could. Maybe 1/4-28. lots of fittings out there for that thread And if they do get broken off are generally much easier to remove than tapered pipe fittings.

I sort of lean toward a 1/4" BSPT mysef - having always had a bias in favor of the British Standard threadforms for liquid sealing. That BSPT thread is so marvelously complex... and specifications call for it to be finished with a rounded top to the thread - a task guaranteed to win you friends at the machine shop.

I believe the swing arms on Royal Enfield Interceptors and Vincents both used that thread - as well as some older MGs, so they should be easy enough to find at any of those dealers.

Note that BSPT and BSPP (tapered and parallel) can be interchanged in some sexes but not others. *
Those tricky Brits were so way ahead of their time !!
rScotty

* Oh - just for simplicity, the rule is straightforward: a tapered male can fit a tapered or parallel female. That is, a BSPT (tapered) male thread can fit both a BSPT (tapered) and a BSPP (parallel) female since the taper of the male will fit equally into a cylindrical thread. Got that?

 

[mikester]

just a little aside.... are you using Kubota OEM pins or aftermarket?

i was told by my local parts supplier that their is so much junk / poor quality stuff flooding the market for some time which probably includes soft / weak pins. He says he regularly de-lists certain suppliers only to find the next in line banging on his door to buy parts flogs him the same inferior stuff. He called it a race to the bottom of quality. Price seems to drive a lot of buyers decisions. He claims it is getting very hard to find high quality / easy to find inexpensive sh@t.

Thats where Amazon and Flea-bay come to save the day

 

[Smokeydog]

The L48 was the first series of TLBs. Built tougher and higher capacities than its agricultural cousins. The B20 sold me on how useful a tank tough and versatile a dedicated tractor loader could be.

The SSQA lower pin broke on the M59 at the center grease groove of the pin. Those pins probably see more force, range of motion and dirtier environment of all the other loader pins. Grapples, my favorite attachment, probably increases the stress component. Pin wear causes flexing and eventually breakage. I could see and measure pin wear. Rather small diameter especially at the grease groove for a high capacity loader. Wether design flaw or design weak link feature to protect other more expensive components is debatable. Might step up the lube frequency and quality of the grease on just those pins if the problem persists.

One of the reason I installed a Kubota Soft Ride (KSR) system on the FEL. Reducing shock loading of components under load. Hope it gives the components as much comfort as the operator.

 

[rScotty]

If it breaks at the center groove, it almost has to be torsional rather than shearing stress.
For it to be flexural stress doing the breaking, it would have to have a LOT of slop.
Someday I'll get my KSR system set up, but I don't think that will have
an effect on the pins breaking.
Are the problem pins shown in any of those pictures?

 

[Smokeydog]

Part 190.

New
Companion
Broke

1080hrs questionable maintenance.
400hrs of heavy lifting since without problems.

 

[rScotty]

Part 190.

View attachment 787956
New
Companion
Broke

1080hrs questionable maintenance.
400hrs of heavy lifting since without problems.

Thanks for the photos. I think that puts it to rest. It looks like either design or maintenance rather than due to poor material.

Frankly, I don't like a pin design that constrains one side of a pin like that. It can lead to lube starvation and a torsional failure - as I believe it has here. Would regular maintenance have changed things? Reduced the wear? .... I just don't know. Regular maintenance with the wrong grease can cause similar problems too.

Bottom line is that particular pin design is a question mark in my mind. It's obvious what the designer was trying to do, and not all bad - but I'm just not completely comfortable with it.

I don't see it as a pending disaster - just a weakness - so I'm not inclined to drop everything & run out and make up different pins and lube channels. But now with 1100 hrs, what I am going to do is pull the pins on our M59 and inspect them.

I'll post to this thread when I do so. I always did want to grow up to be a tribology detective..

rScotty

 

[jwmorris]

Part 190.

View attachment 787956

That’s the “notch effect”. The radius is intended to reduce breaks but they still have created the weak spot.

 

[rScotty]

Part 190.

It looks like the associated bushing is part 020. Impossible to tell the length from the picture and the shop manual is no help. How did it look?