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Force exerted by hand on a lever

  1. Jun 23, 2017 #1
    Is there a generally accepted ball-park figure for the force a human can apply to a lever? Obviously, I am not thinking of an Olympic weight-lifter or of my three-year-old granddaughter - just the turning moment generated by the 'average' person standing up and pulling/pushing on an horizontal lever.
     
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  3. Jun 23, 2017 #2

    scottdave

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    I'd say a reasonable amount is 60 pounds force or so for 1 hand. Maybe 100 if you use both hands, for a short period of time. You could jerk it and momentarily get a lot more (think of trying to loosen a bolt, or pulling a nail out of a board.
     
  4. Jun 23, 2017 #3

    CWatters

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    Google found..

    https://www.ccohs.ca/oshanswers/ergonomics/push1.html

    Table 1 suggests someone pushing or pulling something like a truck or cart shouldn't exceed 225 N (50 lbf)
     
  5. Jun 23, 2017 #4

    berkeman

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    To back up the estimates by @scottdave I looked at typical car wheel lugnut torques, since we all need to be able to change our car tires by hand (or have a AAA card...).

    http://www.hispecwheel.com/files/LugNutTorque.pdf

    Depending on the size of the lugnut, they list 90-160 foot pounds, which for an 18" breaker bar is 60-107 pounds of force. :smile:
     
    Last edited: Jun 23, 2017
  6. Jun 23, 2017 #5
    Thanks, folks. berkeman hit the nail on the head. Using a torque wrench is almost exactly the situation I have in mind for this problem.

    Thanks again to all for your prompt response.
     
  7. Jun 23, 2017 #6

    berkeman

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    Glad that all the responses helped.

    Keep in mind that in Engineering, we look at the whole problem to figure out the best solution. You did not post your application (and if it is proprietary we will not pry), but the best overall solution often involves other considerations.

    For example, you can get a higher force if you can use your body weight safely (no back stress issues). You can get a higher force if you can push-pull with your two arms. You can get a higher peak force as @scottdave said if you can apply an impulse to get things started, etc.
     
  8. Jun 23, 2017 #7
    Certainly, Engineering is holistic.

    In this case, the application is almost exactly what the first post said - an average bloke pulling on a lever :smile:

    I wholeheartedly agree. Safety is priority. :bow:

    It is a delight to me that people in this forum take the holistic view rather than only the "pure mathematics" aspect. It's a special delight because I am working in engineering but suffering from very limited mathematical ability (teflon brain o0)). I look forward to future discussions.
     
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