The commonly used slewing bearing is a four-point contact ball structure. Since it is composed of two inner and outer rings with a steel ball in the middle, if it is installed horizontally, there will be forces in two directions.

The first is the vertical pressure. Due to the relative movement of the inner and outer rings, there are three points that receive the greatest force.

The second is the tilting force between the inner and outer rings, just like breaking bread. The breaking force is termed the overturning force. Due to the relative motion of the inner and outer rings, the overturning force will cause uneven stress on the four points. Therefore, this overturning force is most likely to cause damage to the track.