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How to calculate speed and time in threaded motion

  1. Sep 30, 2005 #1

    if the motion has been through the fastener arrangement or the rotary motion is used to get the linear motion. then how do we have to calculate the velocity and distance nd speeed as well as accelaraion?

    e.g. in a screw and nut arrangement. if i apply the moment of torque/force. the screw is to be traversed from one pich to other then how tho calculate the kinetic energy involved in it. and also the velocity with which it moves
    Last edited: Sep 30, 2005
  2. jcsd
  3. Sep 30, 2005 #2


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    Staff: Mentor

    I'm not exactly sure what you are asking - can you post a diagram?
  4. Sep 30, 2005 #3


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    Science Advisor

    I assume you're talking about something like a lead screw?

    For a single-start screw, the TPI (turns per inch or threads per inch - the same for a single-start) divided by the rotation give linear movements.

    15 TPI spun at 900 RPM would work out to 60 inches/min or 1 inch/sec

    You can find the others from that, but you also should factor in the efficiency of the threads. An ACME-style squared teeth thread, one designed for linear motion, is going to have much greater efficiency at moving a load than a thread design like found on a conventional bolt/nut in a hardware store designed more to 'lock' when under load clamping/fastening. This will influence your power/force figures since the input/output will not be on a linear relationship for conventional threads, and the coefficient of friction will also influence those numbers.
  5. Sep 30, 2005 #4


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    As a note: If you're talking about the velocity/acceleration of the carrier then you really don't need to think about efficiency or friction of the screw. If you are calculating required torque or forces to produce that, then yes, you would need to look at those things.

    Here's a quick and dirty reference from some motion control folks:
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