In planetary gear trains, which option can be used to hold stationary members and is sometimes described as capable of external hold?

In planetary gear trains, which option can be used to hold stationary members and is sometimes described as capable of external hold?

• A. Sprag-type one-way clutch
• B. Servo and band mechanism
• C. Hydraulic clutch
• D. All of the choices can be used as holding devices

Answer: (D)

Holding a member stationary in a planetary gear train is about providing a reliable way to prevent rotation when needed, so torque can be redirected or the system locked in a chosen state. A sprag-type one-way clutch accomplishes this by locking against motion in the undesired direction, effectively preventing backdrive and keeping the held member from turning. A servo and band mechanism uses a friction band around a drum connected to the member; when tightened, it clamps the drum and stops rotation, acting as a brake to hold the part in place. A hydraulic clutch achieves the same result by using hydraulic pressure to engage a friction element, creating resistance that prevents rotation. Because each of these approaches can be used to fix a planetary gear member in place under the right control conditions, all of them can function as holding devices.

Holding a member stationary in a planetary gear train is about providing a reliable way to prevent rotation when needed, so torque can be redirected or the system locked in a chosen state. A sprag-type one-way clutch accomplishes this by locking against motion in the undesired direction, effectively preventing backdrive and keeping the held member from turning. A servo and band mechanism uses a friction band around a drum connected to the member; when tightened, it clamps the drum and stops rotation, acting as a brake to hold the part in place. A hydraulic clutch achieves the same result by using hydraulic pressure to engage a friction element, creating resistance that prevents rotation. Because each of these approaches can be used to fix a planetary gear member in place under the right control conditions, all of them can function as holding devices.