I want a system to move something in the opposite direction to the driven thing, but twice the distance. I'm thinking the below system of pulleys. I just wonder if it will actually work or will it just stick and not want to move? And then how to avoid that happening? enter image description here

  • $\begingroup$ So, the outer pulleys are fixed in space, the inner pulleys move in a fixed relationship with the motor and LOAD is to move twice the distance that the motor does? $\endgroup$
    – Transistor
    Nov 15, 2023 at 20:40
  • $\begingroup$ @Transistor yes $\endgroup$ Nov 15, 2023 at 21:38

1 Answer 1


enter image description here


  • If the motor moves to the right by distance $x$ then the inner left pulley most move the same distance.
  • This will increase the length of the fixed end by $x$ and the length of the top left string by $x$ and will require $2x$ of string to be drawn from the bottom.
  • The load will move by $2x$.
  • $\begingroup$ I think this will have problems actually - since both ends are fixed, all the pulleys need to be exactly the same diameter and in line in both planes for the total path length to remain the same, otherwise there will be tensioning issues. And if they're the same and in the same planes, then the line is conflicted at the bottom running along itself, which will cause tensioning issues again. $\endgroup$ Nov 16, 2023 at 10:49

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