Why are bottle jacks so hard to lower?
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    Default Why are bottle jacks so hard to lower?

    As the title says, why are bottle jacks so hard to lower? I bought a brand new OTC 20 ton bottle jack. I can back the valve screw clear out and I still have to stand on it to get it to go down.

    Is there a way to improve this? My Enerpac pancake cylinders have an internal spring and they always retract. All of my other OTC gear is top notch.

    Maybe this is a dumb question.

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    Quote Originally Posted by ewlsey View Post
    As the title says, why are bottle jacks so hard to lower? I bought a brand new OTC 20 ton bottle jack. I can back the valve screw clear out and I still have to stand on it to get it to go down.

    Is there a way to improve this? My Enerpac pancake cylinders have an internal spring and they always retract. All of my other OTC gear is top notch.

    Maybe this is a dumb question.
    You hit it on the head, there's no return spring. There's not much one can do but over time seals may relax a bit and let it drop easier.

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    Quote Originally Posted by ewlsey View Post
    As the title says, why are bottle jacks so hard to lower? I bought a brand new OTC 20 ton bottle jack. I can back the valve screw clear out and I still have to stand on it to get it to go down.

    Is there a way to improve this? My Enerpac pancake cylinders have an internal spring and they always retract. All of my other OTC gear is top notch.

    Maybe this is a dumb question.
    Simply brand-new-seals, I'd guess.

    All of mine will "creep" down, but I have to push "a little" if I want them down right away to go onto another lifting point. None are"magical". Cheap to medium. One is even HF, as is one of the low-profile trolley jacks.

    Oldest is...1966 vintage, Taiwanese. Newest three are 2 each 5T "toe" jacks, not HF, but Chinese anyway, and a HF 20-tonner a year or more still in the carton. The Toe jacks have EXTERNAL springs, otherwise, "gravity" + a nudge. But not MUCH of a nudge.

    What brand & model yah got?

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    Quote Originally Posted by thermite View Post

    What brand & model yah got?
    First post says it is an OTC 20 ton.

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    Quote Originally Posted by moonlight machine View Post
    First post says it is an OTC 20 ton.
    Stone me, but an OTC dealer lists a 20-tonner with NO return spring, and another OTC 20-tonner for more MONEY ~ $843, specifically, that DOES brag it has a return spring.

    My guess is Wes is $$$ better-off, even if he DOES have to push a ram now and then!


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    When a jack lowers, the fluid returns to the res thru an orifice. It's small. Lowers fast when there's a load on it, but not so fast when there's no load. It's all about the orifice. They're all the same. I own a bunch of these that I use on farm equipment, and Class 8 trucks. Have to stand on the 20 tonners.

    This might splain it.

    Hydraulic Jacks Home Page Information Archive/Inside A Bottle Jack Animation Page

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    Look at it another way. You REALLY want a small orifice on the bleed side, otherwise you couldn't control the speed when lowering a load.

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    you expect hydraulic seals to hold back 10,000 psi (yep, that's about how much there is on a HF 20 ton jack) yet retract under its own weight?


    might need a hydraulic equivalent of maxwell's demon to keep the oil on one side and the air on the other for such a 20,000:1 friction ratio.

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    You also have a bit of resistance from seals, actually quite a bit of resistance.

    But mostly, it's a flow thing.

    I recently built a grapple. The jaw was running way too fast. Had to slow it down.

    Flow is speed, so the goal is to reduce flow. I bought some blank flow reducer fittings. They're simply a fitting that has no hole in it. You drill the hole to suit your needs.

    To come up with a satisfactory speed, I wound up with a 1/16 hole/orifice.

    This will reduce flow, but not pressure. Same power, just slower speed. One drawback is that it generates a lot of heat. An orifice is best used on an intermittent circuit (hydraulic cylinder, not a hydraulic motor).

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    I ramble

    For y'all that are needing to control flow in a hydraulic system, and don't want to spend a ton of coin...…….this is a simple flow reducer fitting. You can pick them up for about 5-6 bucks a pop.

    heavy-duty-hinges89.jpg It's simply a swivel fitting that you can put anywhere in the line. I like to put them at the cylinder.

    Drill it to size.

    heavy-duty-hinges90.jpg

    You can buy them pre-drilled to standard sizes if you don't want to mess with it.

    Funny thing was, it took me about 2 days to find these in Tulsa. Every supplier I talked to didn't have a clue as to what they were. I thought that was strange

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    Quick note on using port restrictions for flow control on cylinders-

    If you restrict flow on the rod side of the cylinder only (say to limit extension speed) it is possible to over pressure the rod side components from the intensification effect of the cylinder bore/rod area ratios. This problem becomes more apparent as the bore/rod ratio approaches 1:1.

    Fr'instance- a cylinder with an 8" bore and 6" rod produces about a 2.3:1 intensification.

    It's why the make those handy valves that restrict in one direction but give full flow in the other, among other devices...

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    For spring selection, the venerable HF 20-ton air-powered jack uses two springs, about 1" diameter. In a week I could measure their force if anyone's interested.

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    Honestly since owning a decent 10 ton cylinder enerpac knock off i hate messing with bottle jacks, so much more comfortable being able to raise - lower a nice 6+ feet away from the load not laying under the damn thing. I even use it for Tyre changing. Really should make it a bigger base though for some stability.

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    Quote Originally Posted by adama View Post
    Honestly since owning a decent 10 ton cylinder enerpac knock off i hate messing with bottle jacks, so much more comfortable being able to raise - lower a nice 6+ feet away from the load not laying under the damn thing. I even use it for Tyre changing. Really should make it a bigger base though for some stability.
    Step on up to the air powered "shoebox" pump with the footpedal style valve,
    you'll be in heaven....
    Air Hydraulic Pump - 1, PSI

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    ^ Nah there as noisy as fuck and i then have to drag a air line. Its next to zero effort lifting even 1 ton of load with a 10 ton cylinder. Don't generally use air tools on most of what i do either, again noise and dragging the air line just sucks, normally its 18V lithium makita stuff tool wise so not even any cables, just makes things happen so much faster not messing with airlines and cables.

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    Quote Originally Posted by adama View Post
    normally its 18V lithium makita stuff tool wise so not even any cables, just makes things happen so much faster not messing with airlines and cables.
    Wow, you have Makita powered jacks? When's that going to be released to the rest of the world?

    Me personally, I keep & run a ISO VG 10 thin oil in every Jack, Pump or Enerpac I own. No down sides to it. It still doesn't rust. Last I checked, it was still non-compressible. And the Farmers son in me, prevents me from paying what Enerpac want's for their VG 32 with special blue dye oil.

    Thinner oil makes it all that better to feather off a jack, or at the end of a job when you just have to stand on the bastards to get them down.

    Regards Phil.

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    Quote Originally Posted by machtool View Post
    Wow, you have Makita powered jacks? When's that going to be released to the rest of the world?

    Me personally, I keep & run a ISO VG 10 thin oil in every Jack, Pump or Enerpac I own. No down sides to it. It still doesn't rust. Last I checked, it was still non-compressible. And the Farmers son in me, prevents me from paying what Enerpac want's for their VG 32 with special blue dye oil.

    Thinner oil makes it all that better to feather off a jack, or at the end of a job when you just have to stand on the bastards to get them down.

    Regards Phil.
    .
    agreed. often somebody put too thick a oil in the jack thats why its hard to move.
    .
    only reason for thick oil is if it leaks or goes down by itself fast. often thick oil is put in to compensate for leaking internal parts.

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    I'll trade you all of my old bottle jacks that won't pump up for all of yours that don't want to come down

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    Cool

    Quote Originally Posted by DMF_TomB View Post
    agreed. often somebody put too thick a oil in the jack thats why its hard to move.
    Can you please stop agreeing with me, Totally fucks up my LinkedIn account when you chip in. I can only cover a certain percent of moron.

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    [QUOTE=machtool;3291443
    Me personally, I keep & run a ISO VG 10 thin oil in every Jack, Pump or Enerpac I own. No down sides to it. It still doesn't rust. Last I checked, it was still non-compressible. And the Farmers son in me, prevents me from paying what Enerpac want's for their VG 32 with special blue dye oil.[/QUOTE]

    Yeah, enerpacs pretty dang proud of that oil, that said i just use Q8 oils std iso VG10 hydraulic oil in mine, same as i feed the jones and shipman hydrulics. As to jacks, i have been known to use ATF in them before too, that also works pretty dang good at least above freezeing.

    Also helps with the Enerpac stuff to ditch the quick release fittings and attach cylinder to pump directly and a bit more permanently, really speeds things up not having to get the oil through those fittings!


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