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Need equation for modified sine curve for a cam.

  1. Jan 28, 2009 #1
    I am looking for the equation used to create the cam shape using a "modified sine curve".

    I am pretty sure the information is in the "Cam Design Handbook" by Harold A. Rothbart but I dont want to buy the book for just one equation.

    Any help would be appreciated.
  2. jcsd
  3. Jan 28, 2009 #2


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    It's more than likely just literally a modified sine curve. Nice thing about sine curves is that they are infinitely differentiable, so there are no discontinuities in accelerations/forces, etc.

    Unless someone else has designed cams before.
  4. Jan 28, 2009 #3


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    Yeah, modified sine curve is a good starting point unless you're doing something particular.
  5. Feb 19, 2009 #4
    The modified sine curve divides the complete event length, beta, into three subsections and uses a separate lift expression over each subsection. They are as follows:

    For a total lift of h ...

    for 0<theta<beta/8 ..............y=(h/(4+pi))*(pi*theta/beta-(1/4)sin(4 pi theta/beta))
    for beta/8<theta<7*beta/8 ..y=(h/(4+pi))*(2+pi*theta/beta-(9/4)*sin(4*pi*theta/(3*beta)+pi/3))
    for 7*beta/8<theta<beta .....y=(h/(4+pi))*(4+pi*theta/beta-(1/4)*sin(4*pi*theta/beta))
  6. Feb 20, 2009 #5
    Do a Google search on "modified sine curve" and you will find several entries, one of which is from GoogleBooks. There you can read a portion of Rothbart's book where you can find these equations on p. 75.
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