Transmission Between Skew Shafts by Hobsons Joints

Input: pink crank.
Output: blue crank.
The input and output cranks are skew at 90 deg. angle.
Angular green bars have cylindrical joints with pink, blue and yellow cranks.
Violet conrod is translated along an ellipse.
The mechanism has unstable positions when the planes created by axes of two joints of each crank are vertical.