4 bar mechanism, Perpendicular Bisector, 3 points to make a circle

Years ago I wrote up how to make 3 points into a circle, probably for a CAD program or similar.

Then I was working on a 4 bar mechanism, and I wanted a refresher on the kinematics on it.

In the end you are just drawing 3 equal lines in 3 different positions.

Then you connect the first point of each position and make a circle! Repeat for the second point of each position.

You can solve for the circle centers by hand with a protractor and a compass and a ruler. Once you know the circle centers you are 90% done.

Some linkage lengths result in impossible swings of the linkage. (e.g. violates the rule of triangles about side lengths)

Emulating it in blender isn't too bad.

And now you can try out 4 bar linkages relatively fast and see when the linkages break.

peteristhegreat/4-bar-mechanism.md