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Shoulder mounted actuators ?

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Gadget999, Feb 1, 2017.

  1. Gadget999

    Gadget999 Well-Known Member

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    I have seen plenty of sims that have 2 actuators mounted at the rear at shoulder level

    what is the benefit of shoulder mounting ?

    why not fit attach them lower down ?
  2. crammy

    crammy Active Member Gold Contributor

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    the lower you mount them the more load would be needed to move the seat
  3. Gadget999

    Gadget999 Well-Known Member

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    that must depend on where the center of gravity is - which I imagine would be much lower than shoulder height
  4. crammy

    crammy Active Member Gold Contributor

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    it has more to do with leverage. Think as an example a spanner. the longer the spanner, the easier to move
    • Agree Agree x 1
  5. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    The load remains the same but as the design leverage length is significantly smaller in a compact design you need more torque to move the same load.
  6. abs

    abs Active Member Gold Contributor

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    also the lower the actuator, the higher the risk of torque stress on the actuator rods . but it is a good question . at first glance there should be no difference . maybe some tried . but then again why put the actuaors below shoulder level?
  7. BlazinH

    BlazinH Well-Known Member

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    It’s easy to understand this if you apply a little common sense. It has to do with where the pivot point is located. When a seat moves on a pivot point that’s at the bottom of the seat, its common sense that the topmost part of the seat will move further and faster the bottommost part of the seat. Therefore, generally speaking, mounting on the top vs. the bottom requires more movement of a motor/actuator than it does at the bottom to obtain the same amount of movement of the seat and that’s what creates more leverage.

    However, you can more or less achieve the same amount of leverage mounting at the bottom as you can at the top if the distance from the pivot to the mounting point is the same at the bottom as it would be when mounting at the top. For example, the top of my seat is about a meter from the pivot point so it would need to be about a meter from the pivot point when mounting at the bottom also to achieve an equal (of close to equal) amount of leverage. But in most cases that's less practical than mounting at the top.
    • Agree Agree x 2
    • Informative Informative x 1
    Last edited: Feb 10, 2017
  8. Gadget999

    Gadget999 Well-Known Member

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    i have thought about this and can see the advantage of a longer lever angle, but the reason for the shoulder rod mounts is to do with rigidity - the closer the push point is to the main fulcrum (ie cv joint) the more wobbly the whole thing becomes - i will try it both ways and report my results
  9. PiaMan

    PiaMan Active Member

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    I think of it like a large boulder balanced on a smaller rock. If I wanted to move the boulder I wouldn't get below it and try to lift. I'd place my hands at the top of the bould and "tip" the boulder. Less effort required. Same concept as a sim seat.