Input: green crank.
Violet pin traces a Cassini oval.
Its equation:
(y^2+x^2)^2-2c^2(y^2-x^2) = d^4-c^4
d^4 = 4(a^2-b^2)c^2
a: length of yellow bars
b: length of blue bars
c: distance from rotary axis of pink rocker to center line of grey runway.