Input: pink crank rotating regularly. Output: orange crank rotating regularly. The cranks rotate in the same direction with the same velocity Lengths of cranks : a Lengths of blue bars : 2.5a Lengths of green bars: 2.5a 2.5a Distances between stationary bearings: b b b can not be larger than 4a. Green curve: locus of center of joint between two green bars. Because here b = 2a, part of the locus is nearly straight.