Angle of the pink twin equal crank is A = 90 deg.. The crank length is a. Angle between sliding directions of the runways is B = 90 deg.. Transmission ratio of linear displacement between the blue slider and the yellow one is 1. When the blue slider moves regularly, so does the yellow.
Position of the crank bearing can be arbitrary.
Transmission ratio of 1 can not be kept if A differs from B
Advantage over rack-pinion drive: high precision of transmission at low manufacture cost.