Does continuous-rotation bearing life apply unchanged to a yawing bearing?

The short answer

No. A yaw bearing can experience limited-angle oscillation, dwell and changing loaded zones rather than steady full revolutions. A continuous-rotation fatigue calculation may therefore omit important application conditions. The bearing maker must assess the actual oscillatory duty and the other relevant contact or lubrication mechanisms.

Describe the motion in physical terms

Give the angular amplitude, cycle frequency, dwell periods and load direction during motion and rest. A total number of angular degrees accumulated does not necessarily reproduce the contact history of the same number of continuous turns. The same small raceway region can remain repeatedly loaded. This is a mechanical duty description, separate from the yaw controller’s directional deadband or filtering strategy.

Separate several possible assessment limits

The bearing may need checks for contact loading, repeated oscillation, lubrication replenishment and stationary load exposure under its specific design. A large dynamic rating cannot by itself prove that every short oscillation is satisfactory. Conversely, the presence of oscillation does not establish that a bearing is unsuitable. The necessary conclusion depends on the selected bearing and documented application evidence, not a blanket rule against small-angle movement.

Request an oscillation-specific selection statement

Ask the supplier to assess the measured or design yaw-motion spectrum alongside simultaneous forces and tilting moments. Clarify how its calculation and maintenance instructions address limited motion and dwell. Rothe Erde technical guidance concerns actual slewing-bearing installation and use; it is not a MARSTON yaw-bearing specification. Do not convert the example duty into equivalent continuous hours or invent a grease interval. Accept the selection only when the maker’s stated assessment covers the intended movement pattern. Include whether oscillation revisits the same loaded region or moves around the raceway over time. That contact-history description is more informative to the bearing supplier than one averaged rpm assigned to intermittent yaw movement.