LA344 / BX2680 Bucket Dump/Roll Issues

[TomSweazy]

BX2680, LA344 w/SSQT. I have two issues related to hydraulic control for the roll/dump motion of the bucket.

1. When dumping the bucket (a.k.a. roll forward), the bucket dump action will suddenly free fall the last several degrees of rotation as if it's been fully released from any hydraulic control. The free fall ends with quite a "clunk" as the bucket reaches a mechanical end of travel, which I hope is not the bucket cylinder reaching an abrupt internal hard stop. Besides this being an annoying characteristic, I'm concerned that this will cause premature wear & tear on front loader mechanical components including the bucket cylinder. If I "dump" the bucket extremely slowly, it will reach the end of hydraulic travel without the free fall, but this technique would be exceptionally inefficient from a productivity viewpoint.

2. When the front edge of a slightly-rolled-forward bucket is lowered to the ground in order to scrape soil or mulch from a smooth surface, the bucket will roll back freely ~20 degrees before "hitting a hydraulic stop" in the bucket cylinder. It's as if there's no hydraulic pressure being applied initially to the bucket cylinder to stop bucket roll back. To counter this, I have to lower the bucket close to the ground and (hydraulically) dump the bucket to force the front edge to the ground and then lift slightly to avoid taking weight off the front wheels.

The dealership stated this was normal operation when asked when the tractor and loader were new less than one year ago. I'm curious if other BX80-series owners with the LA344 have experienced either of these two issues, and if so, was there a solution.

I've uploaded two brief videos to a professional photo & video management website if you have interest: https://www.smugmug.com/gallery/n-hLrJ9X


Best Regards
TomSweazy

 

[RCW]

Tom - as far as the roll function, completely normal in my opinion.

Think about the geometry of the hydraulic cylinder compared to the cylinder's mounting point on the bucket. It gets to a point where the bucket mount is nearly vertical, and as such progresses the roll function quicker at the bucket's cutting edge, which is a longer radius from the cylinder/mount center point.

Probably a poor way to 'splain it, but I think you're fine. It's just geometry.

As far as #2; I'm having trouble comprehending. That said, there are some incompatible functions on many Kubota loaders. What I mean is that unlike some tractors, many of Kubota's loaders can deal with two motions at once.

However, there are a couple motions that are incompatible, probably for safety reasons. All the way from BX's to the big ones.

Not sure your issue is related. Take a look at this graphic on your loader and see if it could be the culprit.

Notice the blacked out segment at 7 o' clock?

I don’t know what you’re doing with the loader control when you took your video, but wonder if the multi-function limitation may be a cause.

If operating the loader in the area of the black-out multi-function, just a little wiggle on the joystick can cause some unexpected movement, or pause in operation.

I notice it most as a pause in lifting while curling with a heavy load. You may be noticing a curl that is unexpected. Again, it takes just a little movement with the joystick....

For what it’s worth, I believe Kubota accommodates multi-function in their sub-compact tractors better than most other manufacturers. Some are strictly one movement at a time, if I remember correctly.

Not sure it's your issue, but it came up within last year or so.

 

[Roadworthy]

Have somebody operate the bucket in the manner you described while you stand to the side and watch to see exactly what's going on.

 

[TomSweazy]

RCW, thanks for the considerable thought and feedback about my post, and thanks Roadworthy for your good question. I unfortunately didn't have an assistant (or longer arms!) to take a side view, but I realize that a side view would have helped to show what I was doing with the controls. I read my post again this morning and see I could've done better explaining the test conditions and observations.
- I use the terms roll-back and dump for bucket motions; lift & lower for the loader arms.
- For each of the issues & corresponding videos, I was commanding only one motion: either pure dump or pure lower. (Thanks RCW for the roadmap!!.... it never caught my eye about the 7pm position which is shown in my LA344 manual. It explains a subtle characteristic I've experienced).
- Similar to RCW's thoughts on geometry, I originally had the same thought. Geometry was suspect because the effective lever arm for the roll-back/dump function becomes quite short as the bucket rotates forward. (I haven't evaluated the opposing bucket + changing effective lever arm).

As a result of this "shortened lever arm", much more retraction force is required by the bucket cylinder to provide a consistent roll-back torque to counter the opposing torque as driven by bucket weight. I think this can worsen the symptoms, but I'm not certain it's the root cause for the following reasons:
1. When I slowly command a pure dump, the bucket is under hydraulic control for the entire dump range all the way to the hard stops without any free fall.
2. The center cylinder effortlessly rolls the bucket back from the dump hard stops indicating the hydraulic force is sufficient to overcome the short lever arm. The difference of course is that when rolling back, the fluid is applied to the bucket end of the cylinder working against only the bucket weight/torque. However, for dumping, the tractor-end of the cylinder is pressurized to PUSH/extend the cylinder but at the same time the bucket weight is also trying to PULL the cylinder out. This may be a clue into how the hydraulics are functionally configured.

It appears as if the dump motion becomes free floating towards end of dump travel. It's like the hydraulic fluid is not proportionally shared between the two ends of the cylinder: e.g. the fluid on the bucket end of the cylinder runs lower faster than the fluid that is supplied to tractor side of the cylinder. I'm not claiming that's what's happening, but only presented as an "as if".

Perhaps related to the above is the other issue, specifically the bucket seeing to roll-back freely for a short range without commanding it to do so as the front edge touches the ground during a pure lowering command. Could this be an intentional automatic narrow-range float mode for roll-back/dump function? Another way to describe this symptom is that if the bucket is hydraulically lifted off the ground and then partially dumped (extending the bucket cylinder), I can physically grab the front edge of the bucket and rotate it backwards (human force roll-back). The amount I can roll the bucket back is most for the fully dumped position and less so as the bucket starts in a further rolled-back position, but I think this a geometry thing and a better method would be to measure the free float linear motion of the cylinder piston.
But if while doing this someone hydraulically commands the bucket to dump, it will stop my ability to roll the bucket back. While not necessarily a valid theory, a observer might say that the hydraulic fluid is low and hence creates conditions where an empty volume in the lines needs to be pumped up to overcome any free floating conditions e.g. like air in your car's brake lines.

Whoa, probably way too may words and a test for your patience. These issues aren's show stoppers and I'm enjoying and benefiting from every minute I'm using my BX!! It's just that I would feel much more comfortable to know every BX80-series owner has the same symptoms and I'm not dealing with something that will eventually require an expensive resolution after the warranty period.

Best Regards
TomSweazy

 

[PoTreeBoy]

I'll just add that if you look at larger loaders, you'll see an additional lever and link between the cylinder and bucket. This changes the geometry and lessens the effects you've noticed. It also adds weight and complexity. In your case I'd just say slow it down manually (and maybe throttle down a bit). And keep it well greased - wear will make it more noticeable.

 

[TomSweazy]

Thanks all for taking the time to consider and respond to my questions.
Best Regards