Sorry if this is out of robotics, but this seemed the closest. A motor has to be used to rotate three cranks. They are in the same plane, but each should not run at the same time.
Only one that occupies a central position, corresponding to the motor, should rotate. The discs are mounted in rectangular frame that can be slid to bring the required disc to the central position.
Can anyone suggest a method to achieve this? (Basically coupling and uncoupling the motor shaft from whatever disc is in the centre.)