A sheave should be placed __________.

• A. As far from the bearing as possible
• B. As close to the bearing as possible
• C. At the mid-point between bearings
• D. Anywhere as long as aligned

Answer: (B)

When a pulley is mounted on a shaft, the belt tension pushes on it and creates a bending load on the shaft. The bending moment on the shaft depends on how far the pulley is from the bearing—a longer lever arm means a larger moment, more shaft deflection, and higher stress on the bearings. Placing the sheave as close to a bearing as possible minimizes that lever arm, reducing the bending moment, keeping the shaft stiffer under load, and lowering the tendency for misalignment and excessive bearing wear. This improves overall alignment, vibration performance, and bearing life. Placing the pulley farther away or in the middle without considering bearing proximity would increase bending effects and potential misalignment, making operation less reliable.