I am looking for a way to convert rotary motion to linear, but it should take less energy to get back to initial position than when going from initial position to the end position.

Specifically, a screw mechanism pushes a spring with multiple of full motor rotations. Then it stays in this ending position for a while as screw prevents the spring from pushing the mechanism back. Now, I'm looking for a mechanism that will retract back to the initial position with less work than before, f.i. with a single motor turn in the same or opposite direction.

For example, a lipstick mechanism works with a cam and a pin. Imagine that this mechanism pushes a spring and you can draw the pin out of the cam so the spring will push back. The problem is how to do that with a single rotational motor.

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    $\begingroup$ Have a look at how clicky pen mechanisms work - can you apply this theory? It takes a long stroke/force of your finger to push the pen into it's locked position (tip exposed), but only a small stroke followed by letting go to release it back to the start... $\endgroup$ Sep 24, 2018 at 11:32
  • $\begingroup$ you could split your forces by direction with two ratchets. at that point they can be geared however you wish. your biggest issue is likely that you are probably using a screw because you need a significant force, and that comes at a cost of friction on the screw. is the motor truly powerful enough to supply all the needs of that friction in one stroke? if not, you may need to design the ratcheting into your nut to release it. $\endgroup$
    – Abel
    May 5, 2022 at 13:02

1 Answer 1


If you dont need the spring to stay at the ending position for a while with the help of the screw, you can design the screw such that it facilitates back driving (i.e. once the applied torque by the motor is removed, the spring force will be able to drive the screw back to its original position.)


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