1) Set a point B on b, draw circle with center at B, radius = d.

2) Let C be one intersection-point of that circle with c, so that BC = d.

3) Set a point A on BC.

4) We want the path of A, as B moves on circle b.

Choose the geometric-locus (CTRL + 3) and click at B and A.

This creates the geometric-locus of A (red curve).

Choose the pick-move tool (CTRL + 2), catch and move A along BC, to see how the

locus (red) varies, depending on the location of A.

- For A near B it is almost identical with circle b,

- For A near C it is almsot identical with a circle arc of c.

BC is the middle link of a 3-link gear system.

There are critical sizes of d, which make the system collapse.

When d is too small or too big.

The system has a normal behaviour only for values

X <= d <= Y . For certain constants: X, Y, depending on the two circles and their position.

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