Conveyor Pulley Shafting

Bearing centers, or the distance between two bearings, greatly affect the shafts ability to resist the applied loads. As that distance increases, so does the stress in the shaft. In an application that involves high loads and wide bearing centers, one can choose to use a larger shaft diameter or a higher grade steel to satisfy the strength requirements.

On the other hand, shaft stiffness affects the deflection of the shaft. Deflection relates to how much the shaft sags or deforms under load. Excessive shaft deflection is usually the cause of pulley end disc failure. In addition to the loads placed upon the shaft due to belt tension, bearing centers also greatly affect shaft deflection; the wider the bearing centers, the more the shaft will deflect.

Serious mistakes in shaft selection occur when only shaft strength is considered, and shaft stiffness or deflection is overlooked. Opting for stronger steel properties can solve a shaft strength problem; however a higher grade of steel will not reduce shaft deflection. The diameter of the shaft is the only shaft property that affects deflection. This is a critical point because using higher-grade steel will actually allow a smaller shaft diameter to satisfy the strength requirements.