L48 split for HST repair

[dfkrug]

Looking close there are scuff marks on the head of its screw - and it is loose. The other screw is headless - with the threaded end still in the hole - turns freely (no loctite?).

A question is whether this much thinning is reasonable in only 2000 hours .

It is hard to believe 6y has passed since you started this story, Dick. I have read it all, but now we see the "smoking gun". The "aha" moment is priceless.

With the Kubota method of bearing attachment, I would think they would have used thread-locker, but I do not recall seeing much locker used on other Kub tractors. Their method just does not seem to be a very good choice. I will have to go back and check on what they used in my old B21.

Some makers really LOVE thread-lockers, and some do not. I am working on a Rotax FI engine out of a Can-Am ATV, and it is everywhere.....

As for wear, I had no idea what to expect or what is the wear limit on these bearings. Parts were stupid-expensive and hard to get for the Landini, so I did not replace. Nothing available from those guys at all inside the HST. :-(

 

[rScotty]

Hi Dave - great to hear your voice ! I was hoping you'd see this thread and comment, maybe curate a bit with you knowledge of Kubota HSTs. btw I almost bought a Landini orchard tractor years ago - big power in a small package.

Here are a couple pics of the worn parts. The bearing still in place shows a narrow edge of original thickness and remnants of bronze facing. Looking close there are scuff marks on the head of its screw - and it is loose. The other bearing is trashed, screw head gone - threaded end is in the hole and turns freely.

The HST in the L48 is the same one used in Lxx10 models. The L48 is over twice as heavy as a L3010. Think about the pressure peaks reversing a 4-ton machine vs one only 2 tons. I'd say the cradle bearings have an easier life in the L3010.

Great pictures & story. I don't know anything about HST and swashplate wear, so please bear with my questions.....this is all new to me. Is it common for the wear on the cradle bearings to be so off-center? I'm assuming that the screw is in the center.... but looking at those shell bearings, they look to me to be much more worn on one end than the other. Is that common?
s
That off-center wear makes me thnk that the swash plate had/has a different radius - slightly smaller - than the radius of the shell bearing or cradle, and also that the entire cradle bearing plate was mouned slightly off-center to the swash plate.

If either or both of those were true, then there would be a lot of bearing wear happening until enough bearing surface was in contact with the swash plate to support the load. That could explain the large amount of wear with relatively low hours. In fact, if slightly different radius & off-center then all that wear could happen very quickly.

Why else would it wear more on one end than the other? Or am I missing something here?

As for the loctite, there's no downside to using it here. There are specialized loctite compounds for every type of application imaginable. If I was going to use that screw, I'd use Loctite as well as expose the threads on the opposite end enough to peen or somehow lock the screw mechanicially. But why have the screw in the first place? I'm kind of surprised that the screw is there at all. I'd expect that the bearing shell would be trapped in place when the cradle is bolted up & that would be my design preference.
rScotty

 

[rbargeron]

Interesting saddle bearings, Dick. The way it is secured is a little surprising...Philips head machine screws.

Here a is comparison saddle bearing on a McCormick GX50H (Landini), a similar sized 50hp tractor with servo-controlled swashplate. Most of the exotic material (bronze?) seems to have worn off mine. Pins retained the bearings, and were unlikely to back out. The maker is Bondioli Pavesi, if anyone cares.

Thx for posting. Any pix of the worn out parts?

McCormick (Landini) may be no help but if if you brush up your Italian :thumbsup: and contact Bondioli Pavesi some one may know if there's a wear limit. The center pin looks to have a rounded head, and maybe an oval recess in the face of the swashplate it can ride back and forth in? It sure has more generous bearing and swashplate contact length than Kayaba's.

 

[dfkrug]

McCormick (Landini) may be no help but if if you brush up your Italian :thumbsup: and contact Bondioli Pavesi some one may know if there's a wear limit. The center pin looks to have a rounded head, and maybe an oval recess in the face of the swashplate it can ride back and forth in? It sure has more generous bearing and swashplate contact length than Kayaba's.

IIRC, there WAS a recess in the bearing side of the swashplate so there was extra clearance to the pin. The bearing does look a lot bigger than yours, which is good.

On my B21, the swashplate pivot used full-round plain or needle bearings installed in both sides of the housing. Removal required removing external side caps, which I did not do. There was no discernable wobble.

As for the maker (BP), even if I could contact them, they prob would not sell me the bearings, tho they MAY have told me the service limit. Like many tractor makers, Landini sells only the whole HST. Kudos to Kubota and Deere.

If I had this L48 project and could not buy replacement bearings, I would substitute something of the same or similar radius, then machine the hole and width/length. Prob an engine crank or rod bearing, sold by size.

And use Locktite. And staking the bolt in back is a good idea, too (RSCOTTY).

 

[rbargeron]

Great pictures & story. I don't know anything about HST and swashplate wear, so please bear with my questions.....this is all new to me. Is it common for the wear on the cradle bearings to be so off-center? I'm assuming that the screw is in the center.... but looking at those shell bearings, they look to me to be much more worn on one end than the other. Is that common?
s
That off-center wear makes me thnk that the swash plate had/has a different radius - slightly smaller - than the radius of the shell bearing or cradle, and also that the entire cradle bearing plate was mouned slightly off-center to the swash plate.

If either or both of those were true, then there would be a lot of bearing wear happening until enough bearing surface was in contact with the swash plate to support the load. That could explain the large amount of wear with relatively low hours. In fact, if slightly different radius & off-center then all that wear could happen very quickly.

Why else would it wear more on one end than the other? Or am I missing something here?

As for the loctite, there's no downside to using it here. There are specialized loctite compounds for every type of application imaginable. If I was going to use that screw, I'd use Loctite as well as expose the threads on the opposite end enough to peen or somehow lock the screw mechanicially. But why have the screw in the first place? I'm kind of surprised that the screw is there at all. I'd expect that the bearing shell would be trapped in place when the cradle is bolted up & that would be my design preference.
rScotty

I don't really know anything about HST either so please bear with me too.

Regarding possible radius difference I don't believe there is much of one, if any. I tried feeler gauges at the ends of the new bearings and didn't find gaps with the swash plate. With a film of oil it moves in the new cradle smoothly with no detectable radial or side clearance.

The swash plate doesn't have fixed axes - it floats however the cradle dictates and is only restrained by the bearings. The other side has a near-mirror finish for the pump slippers.

I believe uneven wear can result from how a machine is operated.

For loader work, its common to either fill or empty the bucket while moving forward slowly or even stopped. Then it is shifted into reverse to move away. However shifts from reverse to forward often take place while the machine is still rolling backward. I think too much of that can eventually produce uneven cradle bearing wear.

Moving the HST pedal to a desired position establishes a regulator set point that puts hydraulic pressure on the servo piston, moving the swash plate accordingly. Once the set point is reached the swash plate stays still until the pedal is moved somewhere else.

In Kubota HSTs with side-by-side pump and motor, the top of the swash plate leans away from the engine in reverse, and leans toward the engine in forward. It's vertical in neutral.

Shifting to forward causes the servo piston to move the swash plate down, rubbing against the lower area of the cradle, and tilting the top of the swash plate toward the engine. The piston load persists until the machine is moving forward at the desired speed. If an operator doing loader work tends to move the machine quickly and/or shift to forward while moving backward, the lower part of the swash plate and cradle is loaded more of the time than the upper part. Its the lower part of our cradle that's worn more.

Another detail that affects swash plate loading is the external damper on the pedal linkage. It's there to prevent spiking hydraulic pressure due to abrupt shifting (stomping the pedal). Its a 2-way gas shock - they wear out - and if not functioning the system is more exposed to high momentary loads - and cradle wear.

Regarding retaining the bearings, without the screw nothing prevents them sliding out of position. Dave's bearings in his Bondioli Pavesi cover more of the circle and have a pin too. I like your idea of a containing pocket - there's plenty of room in there to improve it but modifying an existing one is not practical. The basic problem is the present bearing material isn't tough enough for the application. Dick B.

 

[MHarryE]

Interesting saddle bearings, Dick. The way it is secured is a little surprising...Philips head machine screws.

Here a is comparison saddle bearing on a McCormick GX50H (Landini), a similar sized 50hp tractor with servo-controlled swashplate. Most of the exotic material (bronze?) seems to have worn off mine. Pins retained the bearings, and were unlikely to back out. The maker is Bondioli Pavesi, if anyone cares.

Thx for posting. Any pix of the worn out parts?

I toured Bondioli & Pavesi’s hydro assembly area in 2007 because we were contemplating switching our low end product to them. Our team gave them a unanimous thumbs down for assembling hydro transmissions in an unacceptable environment. They make good product but assembling hydros in the same area they were building parts for planetary drives was unacceptable, especially compared to other manufacturers with clean rooms.

 

[dfkrug]

I toured Bondioli & Pavesi’s hydro assembly area in 2007 because we were contemplating switching our low end product to them. Our team gave them a unanimous thumbs down for assembling hydro transmissions in an unacceptable environment. They make good product but assembling hydros in the same area they were building parts for planetary drives was unacceptable, especially compared to other manufacturers with clean rooms.

Was the plant in Italy?

I agree that HST innards have to be kept very clean. Inside the B&P HST I mentioned were 2 high-pressure hoses that had rubber over steel braid construction, like most hyd hoses. The hot oil environment inside the HST caused the rubber to deteriorate and crumble when you touched it. What were they thinking?

Despite the problems, lack of parts support, and lousy service manual, the tractor had a smooth 4-cyl 2.2 liter Yanmar engine, and the HST was a delight to operate after it was fixed.

 

[MHarryE]

Was the plant in Italy?

I agree that HST innards have to be kept very clean. Inside the B&P HST I mentioned were 2 high-pressure hoses that had rubber over steel braid construction, like most hyd hoses. The hot oil environment inside the HST caused the rubber to deteriorate and crumble when you touched it. What were they thinking?

Despite the problems, lack of parts support, and lousy service manual, the tractor had a smooth 4-cyl 2.2 liter Yanmar engine, and the HST was a delight to operate after it was fixed.

Yes, the plant I visited was near a Bologna. Checking their website, they now have a facility dedicated to hydrostatics. Went through a similar growing experience with Comer Industries, also of Italy. That region of Italy is filled with power train manufacturers - and Ferrari. They are precision gear manufacturers and are near low cost casting suppliers and were decimating the US suppliers with lower cost higher quality planetary drives. Most of those drives used on skid steers and the like are driven by hydrostatic motors and at the time they were starting to build their own hydros to supply a complete package.

 

[dfkrug]

Went through a similar growing experience with Comer Industries, also of Italy.

Comer makes many of the gearboxes on our tractors' 3-point mowers, posthole diggers, etc., tho the factories are often in China these days.

Not many HSTs made in China yet, but quality is getting better and better. When buying Chinese machinery, the vendors will brag about having American/Japanese/Euro hydraulics, if they do.

 

[rbargeron]

Back on reassembling the L48, an aspect I wanted to cover was replacing the seals on the front propeller shaft. When Kubota relocated it inside instead of running underneath, a transmission oil seal was added at the clutch housing. These seals have been prone to leaking and have been redesigned. Whenever a machine is apart the seals should be replaced with the new version.

A split job benefits from rolling supports and enough room front and back for the needed moves. This shaft is a case in point.

On the L48, Lxx10, and maybe others, the shaft itself is one piece, a little over 3' long, running from the back of the engine into the differential housing. If the machine is split at the engine, the shaft will be sticking out the front about 8" - see separation drawing attached.

If you're splitting it further back, the shaft will tend to remain in place, sticking out to the rear instead. On the L48 our first split was behind the HST - the attached pic is when it was going back together, the shaft is sticking back a lot.

The front driveshaft seal parts to be replaced are 2 seals and the 2 sleeves, parts 09, 12, 13 on attached. The sleeves are smooth outside with rubber lining to hug seal the shaft. The new sleeves are now 0.010" tighter fit on the shaft and require about 75 lbs to slide along - I made a helper tool.

When the machine goes back together, the rear end of the shaft has to fit into its splined coupling (see pic). There's a curved rib in the casting web (zoom up the pic) that helps guide the shaft end into place I had already bolted the clutch housing and HST back in place and I used the red hooked wire in the other pic to lift the shaft slightly as the back of the tractor was rolled forward. Went into the coupling nicely. Hope this is useful. Dick B