Backhoe Backhoe Joystick Controls

[flomanno]

I am a new tractor owner and have a L3010HST with a Kubota BL9690 backhoe and FEL The backhoe has four controls for the arm/boom/bucket. Three of the four work fine. The fourth ( the one which operates the left/right swing and the up/down of the boom) moves erratically and is very sensitive to joystick pressure. My dealer says that I need more control on the sticks and nothing can be done to reduce this problem. Is this true? I'd appreciate any comments.

 

[RMulkey]

You should be able to get a flow restrictor for that specific line and slow down the reaction.

Hope this helps.
-Roger

 

[hayden]

Do you mean a BL4690? Not that it really matters, but I've got a 4690 so my comments may be more or less meaningfull if you have the same BH.

Anyway, I also find that the left control (side to side, and boom up/down) are much "faster" than the dipperstick and curl controlled by the right control. I usually operate with the tractor at about 1800 RPM and find the left control sensitive, but controllable if I'm gentle and careful. At teh same time I find myself waiting and waiting for the bucket to curl or the dipper to dig.

You got my curiosity going and I just took a look at the manual and parts drawing for the 4690. There are "restrictor plates" inserted in the hydraulic control lines for the swing, boom, and dipper circuits. On eth boom and dipper, they are only on the rod end of the cyl. For a given oil flow the rod end port will always cause faster movement since the cyl volume is smaller (part is taken up by the rod itself). Presumably this is to slow down the oil so the speed is the same in both directions. The swing cyl has rods on both ends and restrictors on both ends so presumably they are there strictly to slow things down.

It's hard to imagin these have been left out on your tractor so I think yo ujust need togetused to it. Try running the tractor at a slower speed as you get accustom to it.

 

[bcarter]

I find this question very interesting...

I have a Woods 7500 Backhoe on my B2710. Its a close match to the Kubota hoe and I too have seen what I'd call "interesting" behavior with the left hand control. To make matters more confusing, I had the control pattern on my hoe modified to match the SAE standard excavator control pattern (basically, the boom control is moved to the right hand stick, and the dipper control is moved to the left hand stick). The dealer did this prior to delivery by swapping the hoses and relief valves between the appropriate spools.

Not only have I seen that the swing circuit and in my case the boom circuit (left hand controls) run "faster", I've also seen is that the boom circuit will "collapse" when I am lowering a load in the bucket (with the boom control) AND I activate another control. From what I've been able to understand so far, the "speed" issue is related to the flow rate through the valves and if I run the tractor at a lower RPM the control smooths out. However, if I run the tractor at a lower RPM, that's when I see the boom collapsing problem. My guess is that is this caused by starvation of the boom circuit because of the lower flow of fluid...

I believe that the hose from the hydraulic pump is connected to the left had control end of the spool block, but I'm not sure if this would effect/explain the problems that have been described or not.

I'd be curious to see if your dipper control collapses if you run at a lower RPM, and I'd be curious to hear what others have to say about all this...



Bill

 

[Anonymous Poster]

Flomanno,
That's a switch, usually I hear about how slow these backhoes are. If the dealer has actually looked at your problem, maybee it is a case of just getting used to it.

Bill,
The collapsing you are referring to on the boom circuit. Have you noticed that when the boom control is moved full forward there is an extra position (feels like loader float without the detent)? That was designed into the 3ph backhoes in case the center mast (top support) ever disconnects or breaks the backhoe will ride up and try to crush the operator. The theory is if this does happen the worse case scenario is the operator's hand will be on the boom down control and the natural tendency due to the backhoe travelling toward the operator will cause the control to go into this float position and stop the backhoe from continuing it's path. Is it possible that is what you are referring to?

 

[bcarter]

kubmech,

I had considered that... The way my controls are set up now, the valve with the float detent is connected to the dipper control and, it has no effect. (The way the hoses were re-configured, the relief valve for this function is no longer on that spool.)

Its really only an issue when I run the engine at very low RPM. My guess is that the dipper circuit would do the same thing if I had a load raised out on the arm and I activated two functions at the same time - but I've never tried it. Could be a good experiment for this weekend!



Bill