No announcement yet.

shop made hydraulic cylinder question

  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    The fluid is mostly incompressible but the cylinder and especially the hoses are not. They will expand significantly at full pressure, especially the hose and represent a source of pressure for a few seconds if the leak is very fine, the most dangerous kind at that pressure since it will not be visible. It only takes a moment if you have your hand in the wrong place. I recall in basic training when we received numerous vaccinations using an air injection gun. They warned us not to move when it was administered. One guy flinched badly in anticipation at the moment the gun was triggered. He had a neat series of very freely bleeding slashes in the pattern of the gun head nozzle holes as it raked across his arm while injecting. 10 ksi is a lot more pressure than the vaccination gun uses.
    Free software for calculating bolt circles and similar: Click Here


    • #32
      Although I'm sure dhammer is very aware of the danders involved especially considering the work he does but it doesn't hurt to emphasize the dangers of high pressure hydraulics.

      About two years ago a friend who is a millwright at a sawmill was carrying on a conversation with a co-worker while holding onto a pressurized hydraulic hose. Well I guess his number came up that day because that hose, (which upon later examination looked fine) developed a hairline rupture.
      He lost one and half fingers instantly and they still have not been able to completely remove all of the hydraulic oil from his system. This last point seem to be of great concern to his physicians.

      Oh yeah, system pressure....3500 psi.
      Be safe with pressurized fluids, especially those with a lot of stored energy, like hoses that expand, high volume pumps, jacks under load, etc.
      Home, down in the valley behind the Red Angus
      Bad Decisions Make Good Stories​

      Location: British Columbia


      • #33
        Difficulty in construction high pressure cylinders increases with bore size.Small bore cylinders are cheaper bought than built.

        Cost savings only occur with larger bores(3"+) or special designs.

        Use only hoses intended for 10,000 psi working pressure.Don't skimp,buy Enerpac,OTC or Simplex hoses.

        The hard part will be obtaining seals.Easiest way is to buy a rebuild kit for an OEM cylinder and reverse engineer the cylinder.

        In constructing hydraulic cylinders of any pressure remember to break all sharp corners.On high pressure cylinders don't allow any square shoulders.Radiused corners are the rule since they reduce stress risers.

        Here is one outlet for buying componet materials in small quanities.
        I just need one more tool,just one!


        • #34
          10K PSI is typical for Enerpac type hydraulics, use them all the time from bead breakers to Hollocylinders. At the first sign of hose distress it gets replaced.
          That's the design pressure, not some ticking time bomb.

          I've done the sticking nuts in the rim for spacers too, rusty rims are a b*tch no matter what tools you have.


          • #35
            Originally posted by lazlo
            Does hydraulic tubing come pre-honed?

            Yes. Jorgenson Steel bought out Kilsby Roberts that made rod and tube for the hydraulics and pneumatics industry.


            • #36

              Thanks guys for the warnings about hydraulic hoses. I've been using off the shelf hoses for farm applications and I'd bet they are not rated for the pressures my pump produces. I'll check into it.

              wierd..thanks for the link, looks like they everything I might need. Good idea about reverse engineering an OEM cylinder.

              All the advise, warnings, and links I've received is really helpful. This forum is a great source of information. I'll post a follow up on my progress so others can benefit from whatever I've learned.



              • #37
                Something you can do to help prevent hose problems and to also provide a guard against high pressure leaks is to cover the hose in braided Stainless Steel hose sleeve. You can pick it up at any high performance auto parts shop. Even if the hose is already so constructed a second layer will help provide an extra margin of safety in the type of work you do.
                Free software for calculating bolt circles and similar: Click Here


                • #38
                  I was too bref in my first discription. The only seal required is between the top of the dom and the side wall of the case hardened ground ram two or more O ring would not hurt.The oil just displaces the ram. I have made three jacks this way all work very well.


                  • #39
                    More pics and info

                    Here is some more detail of my 10,000psi/20 ton hydraulics on my shop press which included the psi/"tonnage" data sheet. Note that the pressure guage is "red-lined" above 10,000psi.


                    • #40
                      It can't be cheaper to build your own unless you have access to tools like od and id grinders. With prices like this, even getting a unit professionaly rebuilt, you couldn't buy the materials for this cost.

                      James Kilroy


                      • #41
                        "With prices like this, even getting a unit professionaly rebuilt, you couldn't buy the materials for this cost."

                        You might be surprised. Don't need grinders. TG&P will work, and either hone or buy pre-honed DOM. That one on E-bay is a bit big for the application.