Suppose another gear is added to the axis of the planet gear ( A) and moves with the same angular velocity (ωA) forming what is called a compound gear set. Also, suppose this additional gear is in contact with another gear, called a sun gear, mounted on the fixed axis of the rotating arm (B); however, it is free to rotate at its own angular velocity. This new more complex arrangement is shown in Fig. 10.20, where (E) is the additional gear on the axis of the planet gear ( A) forming the compound gear set, and (F) is the sun gear. Point G is the point of contact between gears (E) and (F), and must have a velocity that has the same magnitude and direction whether related to gear (E) or gear (F). This is a similar condition already placed on point C, the axis of the compound gear set on the rotating arm (B).
For this configuration, the angular velocity (ωB) of arm (B) is still the input; however, now the output is the angular velocity (ωF ) of the sun gear (F). Notice that the direction