Say you have a hydraulically supported lifting table like pic related.

Say you have a hydraulically supported lifting table like pic related.

Would it be possible to re-engineer it so that you could adjust the pressure keeping the table up? So that it would sink as soon as a certain amount of weight was added, and also raise itself back up as soon as that weight was removed?

For example, if I set the upward pressure to 10 lbs and added 10lbs, the table would not sink or raise. However, if I added 15 lbs, it would slowly sink. If I added 80 lbs it would quickly sink. If I removed all weight it would raise itself back up.

What would be the simplest design?

Would it have to be electrically powered to re-add lost energy, maybe also monitored by an arduino and a pressure sensor?

Or could this be done with springs and hydraulics alone, pure non-electrical mechanics?

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  1. 1 year ago
    Anonymous

    >Say you have a hydraulically supported lifting table like pic related
    you have a hydraulically supported lifting table like pic related

  2. 1 year ago
    Anonymous

    Gas struts

    • 1 year ago
      Anonymous

      Good idea.

      You could probably tap your cylinder pressure circuit and add some sort.of charged accumulator to it and vary the pressure on the accumulator until you get it fine tuned to what you want.

      • 1 year ago
        OP

        As others pointed out, the load on the hydraulic cylinder is probably non-linear, so you'd have at least to measure how a unitary load on the table is transfered to the hydraulic system along the travel of the cylinder. Once you have that plotted out you basically know the pressure needed to keep the table stationary depending on payload and extension. Then a hydraulic system then might be something like
        >low pressure reservoir
        >pump
        >high pressure reservoir
        >regulator
        >relief valve that leads into the low pressure reservoir
        >hydraulic cylinder
        You don't need an active system to accomplish all this, but making a mechanism that accomplishes all this might require more brain energy than you're willing to produce, so a pressure sensor and a couple of solenoids wired with an Arduino will do just fine with very little effort.

        Thank you for the input. I will research these devices.

        What you want is a system that applies a constant force on the platform across its entire range of motion. It's a simple proposition but there are not many simple constructions able to achieve that. The cylinder in that lift is not supporting a constant force across its range of motion. That means that the amount of force it would need to apply to hold up the weight would depend on the height of the table even for the same weight.
        Springs are also not a good way to deal with this because they don't apply a constant force across their range of motion either. If you used a spring you would find that it would sink until it reaches a new equilibrium point depending on what the weight is, and that it would sink to some degree for any weight applied to it. They do not operate in a binary manner that compresses above a certain threshold and is stable below it.

        Instead what you're describing is usually achieved with counterweights. A counterweight system does everything you want it to: it is stable below a threshold, it sinks above the threshold, the speed of the sinking depends on the weight applied to it, and it is self righting. This is because gravity applies a constant force to the counterweight across its entire range of motion. However it would not be as simple as attaching a counterweight to the bottom of the scissor lift for the same reason as the gas cylinder, because the changing geometry of the lift across its range of motion changes the force required to raise or lower it.

        You are mechanically on track to what I'm trying to build!

        Nothing exists like it on the market based on my research.

        Basically, it is a box that you kneel on to act as a counterweight for doing dips (exercise). The box would be placed between any dipping bars (picture). It would apply, ideally, a constant force as smooth as a counterweight, but without actually using counterweights.

        Why no counterweights? Space. I need something for my home gym in my condo, and do not have an expensive (several thousand dollar) dip rack to use like they do at commercial gyms.

        I envision just having a box that I can plug into a wall outlet, that I can set the pressure and perhaps even compact it or use as a shelf when I am not using it.

        • 1 year ago
          Anonymous

          You can make a counterweight system smaller by using pulleys or levers to gain mechanical advantage. With ten times the weight you would only need a tenth of the length of displacement to achieve the same motion.

          • 1 year ago
            OP

            Here is my current home gym. Behind the bench you can see a pulley system I modified my current rack with plumbing pipe. The dip bars are put away above.

            Using the pulley system and a counter weight, I will have a pulling up, or pulling forward force to use.

            I would use the upward force to lift this raising table, however the wire would get in the way of your body as you are trying to dip. I can reposition the wire, but then it would no long pull up, but instead another direction like forwards or down.

            I need to find a way to get that upward force, while still having the wire not be in the way.

            So here is the question. Suppose I made it so that the wire pulled forward - Okay. Now looking at my first picture, would it be possible to then translate that into an upward force? Like it could just pull on the gas strut itself (although it would have to be reversed with another pulley) and lift the table just from that.

            Also this might mean I would have to use a ton of weight just to get a little upward pull, which would be beyond the capacity of what's available, or what my rack can handle. Ideally, I would want a 1:1 to a 1:2 ratio at the worse.

            • 1 year ago
              OP

              Actually, I could apply the same principles as this here:

        • 1 year ago
          Anonymous

          This is the most autistic shit ever, just get a dip station that folds under your bed. If you are too much of a dyel use stretchint bands to hold your knees or get a shorter dip station so you can do half dips where your legs are resting on the floor. The fricking greeks didnt need any of this shit.

          Or better yet, go to a strongman gym and tell them you arena weak limpwrist autist and want to stop being one.

          • 1 year ago
            Anonymous

            Here OP, Is this shit too difficult to do?

            • 1 year ago
              Anonymous

              Or this, which is even easier. Better yet, why don't you just do regular dips like a man should?

            • 1 year ago
              Anonymous

              Yes it is, I would rather build a scissor lift with a hydraulic actuator controlled by an arduino

              • 1 year ago
                Anonymous

                You fricking autistic c**t, go lift heavy stones instead of wasting your time here.

                Take your scissor lift and start benchpressing it instead you c**t.

        • 1 year ago
          Anonymous

          Oh you want a gym machine. Well, look into the one used in the ISS, can't remember the name of the machine right now. The principle is very easy: a cylinder under vacuum and some smartly devised leverages allow constant force to be applied as if you were lifting weights on Earth. That said, the scissor mechanism is an unnecessary complication: I'd either start from scratch or find another starting point.

  3. 1 year ago
    Anonymous

    What you want is a system that applies a constant force on the platform across its entire range of motion. It's a simple proposition but there are not many simple constructions able to achieve that. The cylinder in that lift is not supporting a constant force across its range of motion. That means that the amount of force it would need to apply to hold up the weight would depend on the height of the table even for the same weight.
    Springs are also not a good way to deal with this because they don't apply a constant force across their range of motion either. If you used a spring you would find that it would sink until it reaches a new equilibrium point depending on what the weight is, and that it would sink to some degree for any weight applied to it. They do not operate in a binary manner that compresses above a certain threshold and is stable below it.

    Instead what you're describing is usually achieved with counterweights. A counterweight system does everything you want it to: it is stable below a threshold, it sinks above the threshold, the speed of the sinking depends on the weight applied to it, and it is self righting. This is because gravity applies a constant force to the counterweight across its entire range of motion. However it would not be as simple as attaching a counterweight to the bottom of the scissor lift for the same reason as the gas cylinder, because the changing geometry of the lift across its range of motion changes the force required to raise or lower it.

    • 1 year ago
      Anonymous

      >This is because gravity applies a constant force to the counterweight across its entire range of motion. However it would not be as simple as attaching a counterweight to the bottom of the scissor lift for the same reason as the gas cylinder, because the changing geometry of the lift across its range of motion changes the force required to raise or lower it.
      Eccentric design of the pulleys for the counterweights could do it.

    • 1 year ago
      Anonymous

      no, he wants a tuned system with a threshold, he wants selectable balance scale

      try fricking reading sometime

      • 1 year ago
        Anonymous

        Balance scales use counterweights, frickass.

  4. 1 year ago
    Anonymous

    As others pointed out, the load on the hydraulic cylinder is probably non-linear, so you'd have at least to measure how a unitary load on the table is transfered to the hydraulic system along the travel of the cylinder. Once you have that plotted out you basically know the pressure needed to keep the table stationary depending on payload and extension. Then a hydraulic system then might be something like
    >low pressure reservoir
    >pump
    >high pressure reservoir
    >regulator
    >relief valve that leads into the low pressure reservoir
    >hydraulic cylinder
    You don't need an active system to accomplish all this, but making a mechanism that accomplishes all this might require more brain energy than you're willing to produce, so a pressure sensor and a couple of solenoids wired with an Arduino will do just fine with very little effort.

  5. 1 year ago
    OP

    bumping for input

    • 1 year ago
      Anonymous

      I'll input this dick in your ass for bumping this moronic thread.

      • 1 year ago
        Anonymous

        I'll input your bumping for ass your thread this dick in moronic

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