Lengths of the crank and the connection rod are equal.
The crank, the connection rod and two short links creates a rhombus.
Equation of traced ellipse: (x.x)/(a.a) + (y.y)/((a – 2b). (a – 2b)) = 1
the coordinate origin O is the fixed revolution joint center of the bue crank.
Axis Oy is vertical.
Axis Ox is horizontal.
a is length of the crank.
b is length of the short link.