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  1. #1
    Member
    Join Date
    Jul 2008
    Posts
    45
    Location
    Western Oregon
    Tractor
    Ford/NH Model 1920, Allis Chalmers Model G

    Default Backhoe question

    Hi, I have a Woods Groundbreaker 8' backhoe on my Ford Model 1920. It is getting its hydraulic feed from a rear remote port on the tractor; when I'm using the backhoe I have to lock the rear remote control in the open position to operate the backhoe controls. This was the recommended setup according to the salesman...

    Here's the odd thing I notice, especially now that I'm getting to be a bit more proficient with the backhoe: of the two joysticks that control the backhoe main operation, only one can be non-centered and respond at a time. That is, if you try and extend the first link (left control) while extending the second link (right control) only one action occurs (extending the second link). The net result is that I can't seem to get smooth motion of the whole assembly - everything has to be done in discrete steps that are dictated by moving the controls separately. This is not what I see the operators on Real Equipment doing!

    Within a single control I can do multiple actions - it will curl the bucket while pulling in the second link, since both of those use the right hand joystick.

    So my question is, is this likely the intrinsic nature of the Woods backhoe? Meaning that the two controls are in series? Or do you think it is just due to the way that this particular unit is plumbed to the rear remote? Not enough flow? Thanks in advance for your thoughts,

    Kurt

  2. #2
    Platinum Member
    Join Date
    Oct 2006
    Posts
    734
    Location
    Thumb, Mich

    Default Re: Backhoe question

    I believe that you are a little light on pump capacity to be able to operate more than one function at a time. I have a Woods 750 Backhoe on a NH1920 but the hoe has its own pump (PTO powered). With the engine rpm at PTO speed multiple elements can be operated simultaneously. You might try increasing your engine rpm to obtain more flow. If you are already at PTO speed or higher rpms you are already at maximum flow.
    The Opti-Mist

  3. #3
    Veteran Member
    Join Date
    Apr 2009
    Posts
    1,023
    Location
    Port Angeles WA

    Default Re: Backhoe question

    Quote Originally Posted by rootytoot View Post
    Hi, I have a Woods Groundbreaker 8' backhoe on my Ford Model 1920. It is getting its hydraulic feed from a rear remote port on the tractor; when I'm using the backhoe I have to lock the rear remote control in the open position to operate the backhoe controls. This was the recommended setup according to the salesman...

    Here's the odd thing I notice, especially now that I'm getting to be a bit more proficient with the backhoe: of the two joysticks that control the backhoe main operation, only one can be non-centered and respond at a time. That is, if you try and extend the first link (left control) while extending the second link (right control) only one action occurs (extending the second link). The net result is that I can't seem to get smooth motion of the whole assembly - everything has to be done in discrete steps that are dictated by moving the controls separately. This is not what I see the operators on Real Equipment doing!

    Within a single control I can do multiple actions - it will curl the bucket while pulling in the second link, since both of those use the right hand joystick.

    So my question is, is this likely the intrinsic nature of the Woods backhoe? Meaning that the two controls are in series? Or do you think it is just due to the way that this particular unit is plumbed to the rear remote? Not enough flow? Thanks in advance for your thoughts,

    Kurt
    This is the prize one pay when one don't pay the prize!
    Open Center system, Constant Flow.....versus.... Closed Center system, Constant Pressure.

    You have an OPEN CENTER system, OC, wich means with all control valves, CV, in neytral, the whole pump flow circulates through the CV's back to tank, at a low pressure. You have 4 CV's and they are supposed to be hooked up power beyond (parallell).
    When operating a system like this, pressure need to be built up to overcome load in the actuators. Pressure is getting built up by restricting the OC in one or several CV's. This is a process that happens in the beginning of pulling/psuhing the CV lever(the spool in the valve). If flow is low, spool need to be moved further to build pressure. At a certain point the spool also start directing part of the flow to the work port. At the end of the spool movement, the OC is fully closed and all flow goes thru work port. From neutral the spool can move about 1/2 inch to end. At the end of joystick this is about 4-5" due to leverage.

    If 2 or more CV's are operated at the same time, flow will go to the actuator that has the LEAST resistance first. Usually when this actuator reaches the end of stroke the next actuator start moving. THIS IS A PROBLEM!!!

    To solve this problem we need to make sure enough pressure is built up in the beginning of the CV spool stroke, close to neutral. This wont happen unless there is a HIGHER FLOW, raise RPM!!! Use throttle pedal for this!!! DO NOT SET A FIXED RPM!! That will make system over heat after a while. Learn to use the throttle pedal when you need more flow to move faster.
    Move the CV lever, for the heaviest work load , the most, and the CV levers for light work loads less. This is a hands on LEARNING EXPERIENCE.

    Note 1:
    Maximum pressure (when relief valve bypass flow) can only be reached if CV OC is totally closed. A closed center (it is enough if one valve of four close the center) also makes the operation most efficient on energy (as long as relief don't open for by-pass) because no flow will be linked to tank trough the OC. If 50% of flow goes back to tank through the OC, then 50% of used energy will be wasted as heat.

    Note 2:
    It takes students about 40 hrs of practice to learn decent crane/excavator operation on an OC system. Less than half time with a Closed center-Constant Pressure, CP, system.

  4. #4
    Member
    Join Date
    Jul 2008
    Posts
    45
    Location
    Western Oregon
    Tractor
    Ford/NH Model 1920, Allis Chalmers Model G

    Default Re: Backhoe question

    Thanks for the advice... you're right, I haven't been running the RPM's very high. I'll give that a shot next time!

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