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Does this hydraulic part exist? linear retractable hydraulic joint

  1. Apr 6, 2014 #1

    i am looking for linear retractable hydraulic joint,

    basically it is hydraulic cylinder with hole in the rod, it does not perform any work, it does not resist the fluid flow, it just expands and retracts as needed, it acts as a hose but its cylinder based

    is there something like this out there, what the name of such joint, send me link where can i buy it


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  3. Apr 7, 2014 #2


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    What maximum internal pressure will it have ?
    Why not use hydraulic hose with a loop ?
  4. Apr 8, 2014 #3
    Hi it SHOULD hold regular working hydraulic pressures like other cylinders, but the point is just to know if it exists.

    Hose with loop can not be used, because in my application there is no free space for it. Only straight pipe can fit there. Thats the reason for such joint.
  5. Apr 8, 2014 #4


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    The device you are considering would be effectively a hydraulic cylinder and would push the ends apart with hydraulic pressure. O-rings would not work at those pressures. The seals would have to be lip seals as used for a hydraulic piston with rod seals to keep out the dirt.

    You could make one using a hydraulic cylinder with a hollow rod, by changing the connections.
  6. Apr 8, 2014 #5
    Yes so u are not aware of any such device, which can be readily purchased? It does not even have a name?
  7. Apr 8, 2014 #6


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    It is called a hydraulic cylinder with a hollow rod and it pushes things apart.
    There is no simple unit available that has variable length without a pushing force.

    If you really need one you can make one from standard cylinder components.
    By using a second cylinder you can counter the extension force.
  8. Apr 14, 2014 #7


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    You can buy a “double ended hydraulic cylinder” which will be symmetrical with a rod seal at each end. Remove the rod(s) and the piston. Get a hollow hydraulic rod of the same outer diameter as the original. Plug one end of the new hollow rod, then drill a cross hole one cylinder length from the plugged end. Reassemble the original double ended outer cylinder with the new hollow rod.

    One hydraulic connection is the open end of the hollow rod. The other end connection is one of the two original external cylinder ports, plug the one not used. Note that there is no piston in the cylinder. You now have a constant volume adjustable length sliding cylinder with no axial hydraulic force.
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