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Tractor hydraulics accessory circuit

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  • Tractor hydraulics accessory circuit

    Hydraulics question for you hydraulics experts. I have a Kubota L48 TLB with backhoe and front loader. While the backhoe is mounted I want to power a hydraulic motor off the accessory circuit (hydraulic pump #3) which powers the backhoe swing while retaining use of the swing function. The spec for this circuit is 12.66 gallons/min at 2800 psi with the tractor running at 2600rpm. The accessory motor i want to spin consumes 28in3/rev thus my calc says at 2800 tractor rpm this accessory motor turns 104 rpm as long as I am not actively using the swing function. I will be running the tractor mostly at 1400rpm so I'm "assuming" the hydraulic motor will spin at 52 rpm. I want it to go half that fast. My thoughts are I can plumb the line for this circuit in parallel to the swing circuit with either a off/on valve. It would be nice if the valve had some type of adjustable throttling to control the motor speed. Questions: 1. Does this seem like the right approach? 2. What is the correct term for a hydraulics off/on valve with throttling function when I order one? I prefer a valve that I can flip off or on that will stay in that position but maybe kick off in case the motor jams. Thanks for your collective insight.

  • #2

    This is a 16 GPM Pressure Compensated Adjustable Flow Control with Relief. It might be what you need.

    A very good site to ask about tractor related stuff is
    Location: Saskatoon, Saskatchewan, Canada


    • #3
      For what its worth Kabuto uses an open center hydraulic system, so how are you going to power the motor and still use the swing.


      • #4
        Originally posted by duckman View Post
        For what its worth Kabuto uses an open center hydraulic system, so how are you going to power the motor and still use the swing.
        Drat! I knew there was something I was overlooking. This will take more pondering. I'm trying to build a motor powered implement that will replace the bucket but still allow me to swing it around and position it. There must be a way as they make hydraulic add on thumbs for these units.

        Delayed thoughts: maybe I can use an open center valve, single throw. The valve intake and center is plumbed in series with the swing circuit. When in the off position fluid simply flows into the valve and out the center to the swing. When then valve is engaged, the fluid is diverted to the motor and returns from the motor to a tee that is tied to the open center exit of the valve which then flows to the swing. See any significant problems with this?
        Last edited by 914Wilhelm; 12-09-2012, 01:26 AM. Reason: More thoughts puny as they are.


        • #5
          Check with your 'hoe supplier and your loader supplier. Ask for a "power beyond" capability. What that will do is allow you to daisy chain another standard control valve in the circuit to control the motor.

          The power beyond adaptor typically isolates the pressure relief dump from the return on the existing valve and directs the flow from the relief valve to the tank return and the original return path through the new downstream valve. The plumbing will likely have to include a separate line for the relief valve tank return.

          It is likely that the loader circuit is still live at the same time the 'hoe circuit is. If so, another option is to use the valve and plumbing for a grapple if it is available.
          Design to 0.0001", measure to 1/32", cut with an axe, grind to fit


          • #6
            Are you building a brushcutter to mount to your hoe? Sorry, just being nosy. Another option might be to use a PTO powered hydraulic pump (assuming that you TLB has a PTO).

            +1 on Lots of good information on that forum along with a nice bunch of guys. They have forum dedicated to tractor hydraulics.



            • #7
              It could be done using a priority flow divider. It's basically a valve that splits one supply into two, which gives one of the splits priority in getting pressure/flow.
              If you get the right valve, you'll be able to use it to set the hydraulic motor speed, and give it priority over the swing. You could prioritise the swing, however you'd then need an additional flow control valve for the motor.