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Comment by bluGill

7 hours ago

That is common and you can't run two different cylinders at the same time. Depends on how the pump and valves are plumbed of course. Sometimes you can run more than one but you split power.

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bluGill

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HPsquared  7 hours ago

That sounds like it could be solved with more valves.

  • bluGill  3 hours ago

    it's not that easy.

    You can run your cylinders in parallel, however that means whichever cylinder has its easiest time moving is going to capture a proportion more share of the power. If things are not perfectly balanced, which in reality they're never going to be, that means the cylinder that needs to work the hardest is going to work the least. And so it's going to take a huge amount of effort to control.

    Alternatively, you can run your cylinders in series, however that means that if you're trying to feather one to move slow, all the others are going to have to move slower too.

    You end up needing multiple pumps in order to make this work well, but pumps are rather expensive and so that's going to bring your costs up. Plus, multiple pumps mean that you're going to potentially want more power than your motor can deliver.

    All the above can be solved with careful engineering. However, engineering is expensive too in order to get this right and it's going to take a lot of work.

    • HPsquared  3 hours ago

      I was thinking in terms of pressure regulating valves on each output. That would solve the problem of different actuators needing different pressures, at the cost of efficiency as the pressure drop across each valve is converted to heat. Or flow control rather than pressure control maybe?

      I presume aircraft hydraulics must do something like that, as they have multiple moving parts under servo control (which must involve some clever valves).