Constant pumped flow hydraulic output on Kubota L4630

[swa]

Just bought a 1989 McConnell Swingtrim hedgecutter. Needs some work but is basically operational.

It requires a constant flow of 12 L/min (Litres per minute) that goes into a hydraulic control box before returning to the tractor. The hydraulic control box has three ram functions to position the cutter bar, and a motor on/off that opens the flow to drive it. The motor also has a low pressure release pipe that goes back to the hydraulic tank.

My issue is with the hydraulics and how I should set them so that I have a constant pumped flow going through to drive the functions as directed by the control block.

On the Kubota L4630 I have three external ports using two spools at the back (see picture). #1 is a single port and number 2 is a double port. Another picture shows the control levers in the tractor.

Question; which ports to use to get a constant pumped flowpath and what (if any) controls to use on the tractor?

Question; anyone know the best rev setting on the tractor to get a pump flow of 12 L/min

 

[RandyT]

Assuming 3 hoses. The 2 that go to the control box would be connected to port 2 in detent. The motor drainback hose or case drain I think could be connected to port 1 with it in detent for non-pressure float.

 

[hayden]

You could use the 2 port control (control #2) to supply pressure and return to the attachment. But you will have to hold the control level on all the time while using it. In my experience these Kubotas do not have a detent for constant-on like is needed to operate a motor. So you will need to cobble together some way of locking the control on in the correct direction.

As for the case drain, it really needs to go directly to the hydraulic reservoir and not be shared with the hydraulic return line. Return lines typically have too much back-pressure, which is why case drains are separate lines in the first place. If you try to use the return line you are likely to blow out the seal on the trimmer motor.

As for flow, the specs say 37 lpm which would be at max engine rpm. So 12 lpm would be at about 1/3 of rated engine rpm. But I would also expect those specs, and the ability to get that flow out through one of the remotes is optimistic, at best. You might also want to keep an eye on hydraulic oil temp while running the machine. I think the hydraulics are typically used for very intermittent operations, so continuous use will heat things up a lot more, and a lot faster.

 

[Harry in Ky]

As usual, a number of options offered, but who knows which actually apply to your specific tractor configuration? First thing I would ask is how often (and how much) is this attachment likely to be used? What does the "control box" consist of? Is there any sort of speed control in/on the box? If not, I would be seriously considering adding one. That would allow you to control the flow to the motor and operate at a practical speed no matter what engine RPM you choose.

If I were doing this I would be looking at using a non detented remote valve manually tied open when in use to supply the unit. Detented valves have a pressure release mechanism. If the system pressure exceeds that setting the valve cancels and returns to neutral. That can be annoying. If you tie it open and the pressure exceeds the setting it can create heat. The return side would go directly to tractor sump. That would eliminate any restriction on the case drain (and insure you can't accidently power it up backwards).

 

[swa]

As usual, a number of options offered, but who knows which actually apply to your specific tractor configuration? First thing I would ask is how often (and how much) is this attachment likely to be used? What does the "control box" consist of? Is there any sort of speed control in/on the box? If not, I would be seriously considering adding one. That would allow you to control the flow to the motor and operate at a practical speed no matter what engine RPM you choose.

If I were doing this I would be looking at using a non detented remote valve manually tied open when in use to supply the unit. Detented valves have a pressure release mechanism. If the system pressure exceeds that setting the valve cancels and returns to neutral. That can be annoying. If you tie it open and the pressure exceeds the setting it can create heat. The return side would go directly to tractor sump. That would eliminate any restriction on the case drain (and insure you can't accidently power it up backwards).

To answer your questions/comments Harry:
- Little use but for a few hours at a time
- control box has a lever to open flow to the cutter motor plus three levers to allow bi-directional use of rams to lift and strech the arms and angle the cutter blade
- no speed control on the box, it would require a 'free flow external kit'
- I hear you on the detent tripping back and the heat issue
- not sure about the return side, Kubota dealer happy to use the same spool and agreed with the idea of holding the lever open
- no issue with the direction

I appreciate the input, thanks

 

[swa]

Assuming 3 hoses. The 2 that go to the control box would be connected to port 2 in detent. The motor drainback hose or case drain I think could be connected to port 1 with it in detent for non-pressure float.

Thanks Randy, tried that and it will flick back to neutral a bit. might need some 'persuasion' to stay open!

 

[swa]

You could use the 2 port control (control #2) to supply pressure and return to the attachment. But you will have to hold the control level on all the time while using it. In my experience these Kubotas do not have a detent for constant-on like is needed to operate a motor. So you will need to cobble together some way of locking the control on in the correct direction.

As for the case drain, it really needs to go directly to the hydraulic reservoir and not be shared with the hydraulic return line. Return lines typically have too much back-pressure, which is why case drains are separate lines in the first place. If you try to use the return line you are likely to blow out the seal on the trimmer motor.

As for flow, the specs say 37 lpm which would be at max engine rpm. So 12 lpm would be at about 1/3 of rated engine rpm. But I would also expect those specs, and the ability to get that flow out through one of the remotes is optimistic, at best. You might also want to keep an eye on hydraulic oil temp while running the machine. I think the hydraulics are typically used for very intermittent operations, so continuous use will heat things up a lot more, and a lot faster.

The Operator manual suggests a return with a secondary low-pressure return to the hydraulic resevoir.

 

[Harry in Ky]

To answer your questions/comments Harry:
- Little use but for a few hours at a time
- control box has a lever to open flow to the cutter motor plus three levers to allow bi-directional use of rams to lift and strech the arms and angle the cutter blade
- no speed control on the box, it would require a 'free flow external kit'
- I hear you on the detent tripping back and the heat issue
- not sure about the return side, Kubota dealer happy to use the same spool and agreed with the idea of holding the lever open
- no issue with the direction

I appreciate the input, thanks

Then you have no "speed control" for the cutter other than engine RPM. Marginally effective yes, but certainly limited. I still maintain a brand valve to control motor speed is a "better" way to go, as well as one common return to sump for the entire system.

I'm thinking something like this. They're easy to find and simple enough to install. It can be made to control total flow through "the box" or only the motor. That would depend on just what "the box" consists of and how it's put together.

Your machine, your project, your choice.

ebay.com/itm/127129521627?_skw=hydraulic+flow+control+valve&itmmeta=01KAH6MM39T883QC0V2QBR1SPN&hash=item1d99828ddb:g:xvcAAeSwyTNoejfE&itmprp=enc%3AAQAKAAABAFkggFvd1GGDu0w3yXCmi1dFiOCUMeKe0Oxw%2BfOjyhTqqsdWgtAS9G3O0FRfWg2AU0GLCN3TMliMDtHuexSxV3

 

[shirleyujest]

To answer your questions/comments Harry:
- Little use but for a few hours at a time
- control box has a lever to open flow to the cutter motor plus three levers to allow bi-directional use of rams to lift and strech the arms and angle the cutter blade
- no speed control on the box, it would require a 'free flow external kit'
- I hear you on the detent tripping back and the heat issue
- not sure about the return side, Kubota dealer happy to use the same spool and agreed with the idea of holding the lever open
- no issue with the direction

I appreciate the input, thanks

The "Little use but for a few hours at a time" causes me to be concerned. Many hydraulic systems on farm tractors are not designed to run motors for more than a short period of time. I would consider a pto powered hydraulic pump. The early White Farm Equipment air planters were powered this way.

 

[swa]

The "Little use but for a few hours at a time" causes me to be concerned. Many hydraulic systems on farm tractors are not designed to run motors for more than a short period of time. I would consider a pto powered hydraulic pump. The early White Farm Equipment air planters were powered this way.

Thanks. My flail hedgecutter is a PTO driven separate unit with its own resevoir tank. Same manufacturer albeit 30+ years apart, and this one is designed to be run from the tractor external flow port system.