descibing a circle diameter help needed

Discussion in 'SolidWorks' started by mikemcdermid, Sep 14, 2004.

  1. mikemcdermid

    mikemcdermid Guest

    Hi all

    I need some help if i might ask

    I need to Model a chainwheel and drive its diameter by the pitch of
    each tooth.

    the pitch is 12.5 mm or 0.492" for our american buddies

    what i need to do is describe diameter as a result of the tooth pitch
    x the number of teeth

    im puzzled this is probably really easy to some of you guys i can only
    describe the diameter of the circle using dimensions and not the
    circumference

    any help
     
    mikemcdermid, Sep 14, 2004
    #1
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  2. diameter = (number of teeth) x pitch / pi
     
    Bill Chernoff, Sep 14, 2004
    #2
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  3. mikemcdermid

    Arlin Guest

    That equation can come close, especially for large sprockets with a lot
    of teeth, here is a more accurate forumala:
    diameter=2*pitch*SIN((90-180/#_of_teeth)*ATN(1)/45)/SIN(360/
    #_of_teeth*ATN(1)/45)

    This equation includes the conversion to radians as solidworks requires
    (all SWX trig functions input/output radians)
     
    Arlin, Sep 14, 2004
    #3
  4. mikemcdermid

    TheTick Guest

    I just answered a similar post on eng-tips.com. Is this the same
    poster???

    Anyhoo, for a chain, look at the problem as a circle circumscribed
    about a polygon with "n" equal sides and length equal to pitch "p".
    Draw a line from the endpoints of one segment to the center, and
    calculate the radius by bisecting the resulting isoceles triangle.

    The result:
    diameter = pitch / sin(180°/n)
     
    TheTick, Sep 15, 2004
    #4
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