Which bearing type is typically used in the bottom position of a vertical shaft motor?

• A. Sleeve bearing
• B. Ball bearing
• C. Thrust bearing
• D. Bronze bearing

Answer: (C)

In a vertical shaft motor, gravity and operation create forces along the axis of the shaft that push or pull the rotor endwise. A thrust bearing is designed specifically to resist these axial (along the shaft) forces, keeping the shaft from moving up or down and maintaining proper alignment. That makes it the natural choice for the bottom position, where the rotor’s weight and any thrust during starting or loading are most directly carried.

Ball or sleeve bearings mainly handle radial loads—forces perpendicular to the shaft—and aren’t optimized for endwise thrust, which can lead to wear or misalignment if used alone. Bronze bearing refers to the material used in some sleeve bearings and isn’t a dedicated axial-thrust solution. So the bottom position uses a thrust bearing to reliably support axial load and maintain shaft position.