If the carrier is the held component and the sun gear is the input member, the result is reverse overdrive.

If the carrier is the held component and the sun gear is the input member, the result is reverse overdrive.

• A. True
• B. False
• C. True only if ring gear is input
• D. True only if carrier is output

Answer: (B)

In a planetary gear set, when you drive the sun gear and keep the carrier fixed, the planet gears mesh with both the sun and the ring. The carrier’s fixed constraint makes the ring gear rotate in the opposite direction to the sun, but its speed is reduced. The speed relation is typically ω_R = - (N_S / N_R) ω_S, and because the sun gear has fewer teeth than the ring, the magnitude is less than the input speed. So the motion is reverse and underdrive, not reverse overdrive. Therefore the statement is not correct.

In a planetary gear set, when you drive the sun gear and keep the carrier fixed, the planet gears mesh with both the sun and the ring. The carrier’s fixed constraint makes the ring gear rotate in the opposite direction to the sun, but its speed is reduced. The speed relation is typically ω_R = - (N_S / N_R) ω_S, and because the sun gear has fewer teeth than the ring, the magnitude is less than the input speed. So the motion is reverse and underdrive, not reverse overdrive. Therefore the statement is not correct.