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Hydraulic Disassembly Bench (Thesis Project)

  1. Aug 14, 2009 #1


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    Hi Guys and Girls,

    I am a final year mech engineering student doing my thesis.

    My project is to design a bench and apparatus to "strip" cylinders. This requires the end caps to be removed (or clamps in some cases). The rod to be extracted, sometimes requiring large force, and the piston retaining nut to be removed.

    Now I am in the research stage and as a basic idea I have though about using hydraulic cylinders to extract the rod from the barrel. As for the retaining nut I had the idea in my head of coupling a reasonably large hydraulic motor to a planetary reduction.

    I am probing for ideas, suggestions or any sort of information if you guys may be of some help. I am new here so apologies if I am expecting too much.

    PS> the cylinder I am basing the design around is a 10.5" bore, 1145mm stroke, approx 780kg. The retaining nut is torqued to 8000Nm (plus or minus 800). I want to design for approx 15 000Nm if possible to account for cross threading or overloading (that is ensure bench and motor etc. are capable)

    THanks. Sorry about the novel... ha ha.
  2. jcsd
  3. Aug 14, 2009 #2


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    Welcome to PF, Gix.
    I've never disassembled an hydraulic cylinder, so I'm not quite sure what procedures are necessary without seeing some sort of diagram.
    Might I assume that this rig does not also have to reassemble the cylinder?
  4. Aug 14, 2009 #3


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    Hi mate thanks for the welcome.

    Ideally it will have the capability to re-insert the rod into the barrel.

    I can do up a sketch sometime today (keeping in mind im from aus so time differences ha ha).

    I am just chasing some information on the best methods to use hydraulics (motors couple to gearbox, high power cylinders etc.) I need pretty big torque to remove the retaining nut and high power from cylinders to extract the rod.

    I will get a sketch done up soon.

    Thanks for the help.

    Are there any gurus with hydraulics on here (unfortunately our university doesnt teach hydraulics and/or welding :( )
  5. Aug 14, 2009 #4


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    We have a couple. The first that come to mind are Brewnog and Fred Garvin, but there are others as well. Unfortunately, I'm not one of them.
  6. Aug 15, 2009 #5


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    Interestingly enough, I recently have contemplated building something similar to what the OP is describing. However, I can't say I've ever needed anything very complicated to reinstall the piston/ram assembly back into the cylinder bore. Mainly I would want something that catches the remaining oil and drains it out the bottom of a trough and something that is able to pull the piston/ram assembly out of the cylinder bore. A suitable vise can be attached to this rig to hold the ram from turning while a large air impact wrench is used to loosen the nut that holds the piston on the ram. Currently I use a hoist with a hydraulic jack on it to remove the piston/ram from the cylinder bore. I just hook each end with a chain and start pulling. It's a bit messy when it comes apart, hence the reason for wanting a bench/trough to do it.
  7. Aug 15, 2009 #6


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    Yeah mate the trough is in the concept design.

    I am mostly concerned with a strong method of extracting the rod from the barrel and the cracking of the retaining nut. I dont think an impact wrench will provide enough torque for this (8000Nm).
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