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Boom Lift salvage yard

Discussion in 'Other Construction/Demolition Equipment' started by Ronray, Sep 6, 2019.

  1. Ronray

    Ronray Well-Known Member

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    Any way to get a manufacturers diagram and or part list on this block that is better then what I already posted from the marklift service manual?

    20190403_192905.jpg
     
  2. TVA

    TVA Senior Member

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    Yes! Sorry! Fat fingers and was in a hurry!
    If the problem is missing ball: you can find one in places that sell fasteners, that’s if you have both seats for it!
    If not - if it’s possible drill and tap for plug , to block the passage between two inlet port, but in line shuttle valve and plumb it outside the block with tee fittings.
     
  3. TVA

    TVA Senior Member

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    I’ve looked, not very hard though, didn’t find anything.
     
  4. TVA

    TVA Senior Member

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    Could it be that ball inside the fitting, probably the one with needle valve? Anyway if it’s inside the fitting it’s got to be one with seals and it being cross point.
     
  5. Ronray

    Ronray Well-Known Member

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    Not sure what you mean by Cross Point? And by needle valve do you mean that parking brake T fitting that screws into the top of the valve block pictured? And if so, I don't see how that could cause leakage, unless there was a leak inside the parking brake or brakes? But then again, I did have those lines to the parking brakes capped off when I took the pressure readings on the four block exit ports.

    20190808_232725.jpg
     
  6. Ronray

    Ronray Well-Known Member

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    I understand what you're saying about drilling and plugging the passage between the two Inlet ports inside the block, but wondering if you could diagram the tees and where those lines would go?
     
  7. Ronray

    Ronray Well-Known Member

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    20191003_204753.jpg 20191003_204610.jpg 20191007_170858.jpg
    Well, I discovered that there was an allen screw retainer in that shuttle valve, but instead of there being a ball on the other side, there was what looked like a bushing and tiny washer, see picture below. So when I plugged that channel, it stopped the leakage between the two Inlet ports and then I started getting the full 2500 lb of pressure in the outlet ports of the valve block. It seems like that little bushing with the hole in the middle defeats the purpose of the shuttle valve. So I'm wondering if someone substituted that bushing with the hole for a steel ball?

    But now that I have the full 2500 lb going to each wheel motor, a different problem arises, there is no backflow of hydraulic fluid from the wheel motor. The attached picture shows big big beefy backflow hose disconnected over an oil pan.
     
  8. TVA

    TVA Senior Member

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    Plugging the shuttle valve will make you loosing the release of breaks. No return flow means your counterbalance valve is not working. As counterbalance controls the outlet of the motor.

    It so happens they I’m currently working on the same thing but on a lot larger machine - 100 ton travel lift. Because of the water in the hydraulic fluid the tiny drain holes were plugged up which in turn led to hydro locking of counterbalance valve poppets resulting in bending and scoring of the plunger that push on the poppet by cross release piston.
     
  9. Ronray

    Ronray Well-Known Member

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    Thanks TVA. Actually I completely bypassed the counterbalance valves and the drive brake manifold, and you can see this in the picture if you zoom up and follow the forward drive hose connections. But I did not plumb the parking brake needle valve into that direct line, because I just wanted to see if fluid was passing through the hydraulic motor through the return line.

    So would it be necessary for the wheel to be spinning in order for fluid to be passing through the drive motor return line?
     
  10. TVA

    TVA Senior Member

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    It’s actually good news, because you have no cross port leakage! If nothing comes out of case drain it is another very good news!
    Now all you need is cage (release) the breaks!

    Just take the seat out, the one you unscrewed with Allen wrench, select ball bearing that matches the seat in diameter, drop the ball inside, don’t forget to use thread lock on that seat, and you should be OK!
     
  11. Ronray

    Ronray Well-Known Member

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    Okay, so the ball bearing cannot be larger than 1/4 inch in order for it to drop down the cavity, but it must be larger than 5/32 so it does not come back through that retainer bushing that I photographed last night and posted. So I would say 3/16 or 7/32 inch ball bearing? Which would you suggest?
     
  12. TVA

    TVA Senior Member

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    0D06B89A-C8F4-47D5-93C5-FB3EA59A635D.jpeg
    It kinda looks like that bushing is one of two seats for the ball, it looks like ( if I’m not mistaken) first you need to drop the ball, than install the bushing, than tighten that bushing against the shoulder machined in the blocks body. Am I wrong?

    If I’m right, then you need to select ball that will seal against the chamfer marked by red circles on the picture
     
  13. Ronray

    Ronray Well-Known Member

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    Yes TVA, that is right, and that would be a 3/16 inch ball. But I'm curious, what would prevent that ball from blocking the other common outlet for that shuttle valve?
     
  14. TVA

    TVA Senior Member

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    Pressure differential! The side that has more pressure pushes the ball against the seat of the side that don’t have pressure, effectively sealing it from leakage to return circuit.
     
  15. Ronray

    Ronray Well-Known Member

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    Thank you, that makes perfect sense!
     
  16. Ronray

    Ronray Well-Known Member

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    So would blue Loctite 242 be a good choice for that Allen screw seat? And I'm wondering would it be resistant to Dexron II transmission fluid, which is what this machine has for hydraulic oil?
     
  17. TVA

    TVA Senior Member

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    I use blue lock title in this application of any brand I can get my hands on! It’s important to use some kind of thread lock so the seat will not back out! As of compatibility of thread lock with fluid - you got to read up on it or contact manufacturer or the distributor. I mostly deal with hydraulic oil.