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Force calclulations on a drum

  1. Sep 21, 2012 #1

    wzrdstrm

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    I'm doing some work were its necessary to calculate the force acting on a drum via a wire rope. If I have a known weight acting on the rope already and I want to back calculate the minimum torque necessay for a motor connected to that drum to hold that load, do I add the diameter of the rope to the radius of the drum to do so?
     
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  3. Sep 21, 2012 #2

    Mech_Engineer

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    It depends on how many wraps of cable you have on the drum. In general you will need to take into account the diameter of the wire for a couple of wraps on the drum.

    Here's an example in off-road vehicle winching:

    http://www.pangaea-expeditions.com/resources/winchworksheet/index.html
     
  4. Sep 21, 2012 #3
    What sort of hoist system is this? If a crane or elevator, then all sorts of standards and requirements apply.
     
  5. Sep 21, 2012 #4

    wzrdstrm

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    Simple design only, not for commerical review/standards. We have a motor connected to a gear box (1:1) ratio, connected to a drum that has wire rope wrapped half way across the drum on the root layer (1st layer). What I am expecting is that that if the drum had a root diameter of 100 inches (including lebus grooving) and a roper diameter of 2 inches, for calculation purposes we would have an effective drum radius of 52 inches for the first layer. Is correct?
     
  6. Sep 21, 2012 #5
    Center of drum to center of rope. 51 inches. But if you measure carefully, the Lebus shell will probably make that number a little different. Just measure total diameter including the rope layer and divide by 2. Then subtract one inch.
     
    Last edited: Sep 21, 2012
  7. Sep 21, 2012 #6

    wzrdstrm

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    Confused, why subract one inch? the total diameter would be

    2 X Rope diameter + Root Drum Diameter
     
    Last edited: Sep 21, 2012
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