Backhoe problem

[piper184]

On my backhoe the swing was wild and chaotic to the point of being nearly uncontrollable. The problem was because of the geometry of the machine the full flow through the valve couldn't be easily feathered by the less than high quality control valve. The solution was to install restrictions in the lines to the cylinders. In my case this was done at the adapter that connects the hose to the valve body. It is internal and no way to see if it is installed unless you take it apart. In my case moving the hoses to another valve without the restriction would cause more issues than it fixes.

The OP's problem certainly sounds like a restriction that is intermittent. If there is a similar restriction device on his BH there may be debris in it that is floating around as the fluid moves back and forth and maybe doesn't completely block the hole in the same manor each time. Otherwise as others have said I would suspect an internal hose failure

It most certainly sounds like a hydraulic problem but as others have said, what if it is a mechanical problem with some of the pivot points. Putting the bucket out as far as it can go and swinging requires the most force from the cylinders and visually exaggerates the image of the problem.

Does the problem occur at the same point in the arc if the bucket is curled all the way back so the hoe is all folded up next to the tractor? An interesting experiment might be to disconnect the cylinders at the pins and get them out of the way. Then with the engine off, try to move the bucket by hand through the entire arc of movement both in the fully retracted and fully extended position. This would separate the mechanical from the hydraulic troubleshooting paths.

 

[2515R Dude]

How hard would it be to swap the hoses with the outrigger valves for a test? If the swing and boom work on those valves you can tell your dealer the problem is definitely in the first two valves in the series.

Great idea, I'll try this.

A pressure tester can be as simple as being just a "tee" fitting with the same threads as the hoses. A suitable gauge is a glycerin-damped 5000 psi stainless type.

It is what he is going to do.

If you have the time, do a search here on TBN on the Kubota M59 backhoe swing problem. You will find threads all the way back to about 2008. From day one that model has had occasional problems with the swing. Most commonly problem is that one day it will suddenly swing one way but not the other. In every case it ultimately resolved without anyone ever figuring out why....

If there no solution it is not going to help

How does the Branson BH design their swing geometry? Got a diagram? Some BH use one swing cylinder and some two. Geometries vary. Your dealer sounds great; the tech team sounds a bit lame. That is partly a generational decline in mechanical abilities everywhere ..... but luckily here on TBN we have an advantage over traditional shop mechanics.

rScotty

I posted the diagram a couple of days ago and will attach it again. Is it what you are looking for?
Yes, it uses two rams. And my dealer is a great guy, however, he is not super knowledgeable in mechanics, it is why he parrots what BS he was feed by Branson geniuses.

The OP's problem certainly sounds like a restriction that is intermittent.

Yes, it is my feeling too, but how to find it

It most certainly sounds like a hydraulic problem but as others have said, what if it is a mechanical problem with some of the pivot points. Putting the bucket out as far as it can go and swinging requires the most force from the cylinders and visually exaggerates the image of the problem.

Does the problem occur at the same point in the arc if the bucket is curled all the way back so the hoe is all folded up next to the tractor?

Yes, at same point, but when the dipper stick and the boom are curled the problem is not so apparent because less force is needed to swing it.

An interesting experiment might be to disconnect the cylinders at the pins and get them out of the way. Then with the engine off, try to move the bucket by hand through the entire arc of movement both in the fully retracted and fully extended position. This would separate the mechanical from the hydraulic troubleshooting paths.

I'll try it for sure, but i suspect it is going to be free because when i manually try to swing the boom, it moves freely as long as the play in joins allows.

 

[piper184]

Interesting that the "hiccup" always occurs at the same point in the arc. That would seem to indicate a mechanical binding not hydraulic.

Here is an idea: Remove both swing hoses from the valve body and put the open ends in a bucket. Then manually move the boom through the entire swing arc. The first couple of times will be purging the oil out of the cylinders and hoses. If there is a restriction you may or may not be able to feel it. I am betting not.

However, once the oil is out if there is any mechanical problem you should be able to feel that. I would curl the bucket up as close to the tractor as possible so that it lowers the mechanical advantage you have. If it moves freely that should eliminate any questions about the hinge pins and possible internal flaw of the cylinders.

If you can feel the hiccup after the oil is out, then you can disconnect one cylinder at the pin and retest. Then the other one and retest.

I don't think you have a mechanical binding problem and if you do it has to be significant to make the hydraulics slow down so you should be able to feel it when swinging through the entire arc by hand.

Other than that all I can think of is back to the hydraulics. As a process of elimination the next idea is a bit of screwing around but with some extra hoses you might be able to plumb the swing cylinders to the FEL valve, say the output lines to the bucket tilt cylinders. That would take the BH valve out of the equation and may give you some clues or confirmations. Flow and pressure tests are probably easier to set up if you have the parts needed.

 

[ning]

Going out on a limb here but
could it be a mechanical binding problem inside a cylinder?

 

[piper184]

Going out on a limb here but
could it be a mechanical binding problem inside a cylinder?

I think a slightly bent rod would cause a cylinder to bind in a certain part of the stroke. Bend it far enough and it just jams and won't go any farther. Other internal damage might be able to cause the same effect.

 

[2515R Dude]

ok, tried some things today:
1. Disconnected the rams from the boom. The BH swings freely by hand. So, no problem here.
2. Ran the rams without connecting them to the boom. Interesting note. The rams are connected between them hydraulically (llok the the diagram on the "Swing Cylinder" part) The oil coming out of one cylinder under the pressure goes to another cylinder to help in the movement, but the movement is not correlated between them as i would expect. They act like there is air inside. When one rod extends, it takes a while for another to start retracting,. I would expect it would to it immediately since all oil coming out of one cylinder immediately goes to another. But they behave with delay like there is a cushion or an absorber.
3. Swapped the hoses with the outrigger valves. no change.

4. I recorded the video, It came out terrible but you can get the idea

 

[oldnslo]

2515
Since the swing cylinders were not mechanically tied together when you did your test the cylinder with least resistance will move first and then 2nd cylinder. One cylinder would have pressure to blind end the other to rod end so blind end would have greater working area and probably extend before other cylinder with pressure in rod end.

Be nice if TYM - Branson had a detailed schematic for the valve stack vs all of us trying to guess what is going on

 

[rScotty]

ok, tried some things today:
1. Disconnected the rams from the boom. The BH swings freely by hand. So, no problem here.
2. Ran the rams without connecting them to the boom. Interesting note. The rams are connected between them hydraulically (llok the the diagram on the "Swing Cylinder" part) The oil coming out of one cylinder under the pressure goes to another cylinder to help in the movement, but the movement is not correlated between them as i would expect. They act like there is air inside. When one rod extends, it takes a while for another to start retracting,. I would expect it would to it immediately since all oil coming out of one cylinder immediately goes to another. But they behave with delay like there is a cushion or an absorber.
3. Swapped the hoses with the outrigger valves. no change.

4. I recorded the video, but YouTube is "checking" it. Dont know how long it will take.

Yes, I did see the original diagram. It's interesting. I've not seen a hydraulic diagram quite like that before. It looks to be set up for ordering parts rather than hydraulic info. What we could use for troubleshooting is a little more detail on how the various valves regulate the flows.

BTW, I believe that the diagram you posted disagrees with the description of how you describe the flow in #2 above. It is hard to be 100% sure without a flow or schematic diagram - and without more details about the T part BY400-8800111.....but if it is a simple T....then the way I see it, that diagram doesn't show that the oil coming out of one cyinder goes to the other cylinder to help in the movement. That's good. It would be odd if it did.

My guess is that in each extension direction the combined expelled flow from the cylinders is returned back through the valve to the sump without any regeneration. Take another look and see what you think.

rScotty

 

[K5lwq]

The fact that it showed no change in behavior when you used the outrigger valve normally would suggest the problem is not the valve but a hose or cylinder. But we have multiple functions involved so that baffles me. I guess it would be possible that the entire valve stack is affected but is only visible on the swing and boom because of its mass?

I really hope the dealer comes up with a solution and we find out what the issue was because this one has me stumped.

 

[2515R Dude]

I really hope the dealer comes up with a solution and we find out what the issue was because this one has me stumped.

The dealer just relays what branson told him, "it is supposed to be like this".

Can you guy look at the video and compare it to your tractor. IS IT SUPOSED TO move like THIS?