Need equation for modified sine curve for a cam.

[sgt_rock]

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 don't want to buy the book for just one equation.

Any help would be appreciated.

 

[minger]

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.

 

[brewnog]

Yeah, modified sine curve is a good starting point unless you're doing something particular.

 

[Dr.D]

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))

 

[Dr.D]

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.