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Thread: Relief Valve For Thumb

  1. #1
    Senior Member Danny Steel's Avatar
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    Relief Valve For Thumb

    I would like to fab a thumb for my 3 ton X

    My problem Is understanding where to put the relief valve
    And also what kind of relief valve to use.

    Thanks
    Danny

  2. #2
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    Quote Originally Posted by Danny Steel View Post
    I would like to fab a thumb for my 3 ton X

    My problem Is understanding where to put the relief valve
    And also what kind of relief valve to use.

    Thanks
    Danny
    I normally fit a 5 port crossline relief valve, teed into the A & B lines, anywhere between the valve and the cylinder. It relieves from port A to B and from B to A. The 5th port goes back to tank, this stops pressure intensification when the cylinder is forced in, and acts as a make-up to stop cavitation when the cylinder is forced out.

  3. #3
    Senior Member Danny Steel's Avatar
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    Quote Originally Posted by Harry Dart View Post
    I normally fit a 5 port crossline relief valve, teed into the A & B lines, anywhere between the valve and the cylinder. It relieves from port A to B and from B to A. The 5th port goes back to tank, this stops pressure intensification when the cylinder is forced in, and acts as a make-up to stop cavitation when the cylinder is forced out.
    Sounds like It should be plunbed In near the pump then

    I thought that there could be a valve that got plumbed right at the thumb cyd. ports

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    My machine already had a aux circuit with the relief valve built in. Perhaps yours is the same.
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    Super Moderator willie59's Avatar
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    When you say you would like to fab a thumb, I assume your machine already has an auxilliary circuit on the boom? Or are you going to have to add that as well?
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    Senior Member Danny Steel's Avatar
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    Quote Originally Posted by watglen View Post
    My machine already had a aux circuit with the relief valve built in. Perhaps yours is the same.
    They tell me up here, That any Kubota mini x That came from the US
    Needs a reliel valve in stalled, The Kubotas bought here In CA, have them built In

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    Senior Member Danny Steel's Avatar
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    Quote Originally Posted by ATCOEQUIP View Post
    When you say you would like to fab a thumb, I assume your machine already has an auxilliary circuit on the boom? Or are you going to have to add that as well?
    Correct....It has the 2 pipes with 1/2" plugs In them, on the stick

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    Senior Member Danny Steel's Avatar
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    Super Moderator willie59's Avatar
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    On most machines like that, there are ports on the auxilliary control valve to install relief valves, they may just have port plugs installed in the ports which blocks the internal port to tank. If so, simply remove the port plugs and install proper relief valves, that's the easiest fix for your problem.
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  10. #10
    Senior Member Hendrik's Avatar
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    Quote Originally Posted by Danny Steel View Post
    They tell me up here, That any Kubota mini x That came from the US
    Needs a reliel valve in stalled, The Kubotas bought here In CA, have them built In
    The auxillary circuit has a relief valve to prevent damage, however it may not be set to the correct pressure for thumb application, which from memory should be 75% of the pressure in the bucket ram.
    BTW that trench is a little crooked

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    Our local and jap imported KX 41/61/72's have all had port reliefs fitted in the auxiliaries, 2500psi down from 3500 main. Put a gauge in one of the pipes and see what you've got.

    2500psi for a thumb sounds about right, as long as the bucket will just push it back.

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    I just put a thumb on my Kubota 2010 model which was plumbed for auxiliary but it did not come with the relief valve fitted, strange IMO...

  13. #13
    Senior Member Danny Steel's Avatar
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    Quote Originally Posted by Hendrik View Post
    The auxillary circuit has a relief valve to prevent damage, however it may not be set to the correct pressure for thumb application, which from memory should be 75% of the pressure in the bucket ram.
    BTW that trench is a little crooked
    The wind was blowen hard that day...LOL

    Guys, where Is tis relief valve located?


    One other thing, Not sure If It aplies here but,......... On the Digital panel
    I hear that you can adjust the auxiliary pressure. If that's the case, Why do we need a relief valve?

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    Quote Originally Posted by Danny Steel View Post
    The wind was blowen hard that day...LOL

    Guys, where Is tis relief valve located?


    One other thing, Not sure If It aplies here but,......... On the Digital panel
    I hear that you can adjust the auxiliary pressure. If that's the case, Why do we need a relief valve?
    Factory reliefs will be one on either side of the auxiliary spool in the main valve. Follow the hoses back from the boom piping.
    Panel adjustment would probably be for flow, not pressure, but I'm not sure on your model.

    What model is yours?, I'll see if I can find a pic
    Last edited by Harry Dart; 10-15-2010 at 09:57 PM. Reason: additon

  15. #15
    Senior Member Danny Steel's Avatar
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    Quote Originally Posted by harry dart View Post
    factory reliefs will be one on either side of the auxiliary spool in the main valve. Follow the hoses back from the boom piping.
    Panel adjustment would probably be for flow, not pressure, but i'm not sure on your model.

    what model is yours?, i'll see if i can find a pic
    kx71-3

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