Stephen wrote:
> I would like to animate a piston type of instrument and am not sure of the
> simplest math to do the translation so I'm asking for help.
> 
> If you think of a circle with a connecting rod attached at a point on the
> circumference e.g. 270 degrees or at "west" on a compass circle, and fixed
> along a vertical slider located below the circle (south of south) such that
> point will move only up and down, then when the circle rotates clockwise for
> the first 90 degrees (from 270 to 360) the connecting rod will move up at
> the lower end and move up and clockwise at the upper end.
> 
> How can the angular movement of the connecting rod be modeled simply?
> 
> One answer is to define the end points and calculate for each degree of the
> circle rotation the new points along the circle and the vertical slider path
> and redraw the connecting rod at the new points.
> 
> Can this be accomplished through rotation/translation of an existing
> connecting rod?

To find the upper fastening point of the rod when the
lower fastening point is fixed, you can draw a circle
around the lower fastening point. The radius of this
circle should be the equal to the length of the rod.

Now the upper fastening point is where the two circles
intersect. You'll find 0, 1 or 2 intersecting points,
so you might have to choose (the right) one.

-- 
Tor Olav
http://subcube.net
http://subcube.com

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