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Design and Theory

In RoundRail linear bearings, the load capacity changes when the bearing is rotated around the shaft relative to the load.  The published Dynamic load capacity of a Thomson Ball Bushing Bearing is only valid when used in the optimal orientation.  Loading at an orientation other than the optimal orientation will require de-rating the load capacity.

If we graph the load capacity of the Ball Bushing® bearing vs the orientation to the ball tracks, we end up with a graph like below. 

Load capacity of the Ball Bushing® bearing vs the ball tracks

The image on the left shows the load pressing between the two bearing plates. In this case, the load will be shared by two bearing plates. This orientation is the optimal orientation and where the bearing can carry its maximum load.  

The image on the right, the bearing has been rotated and the load is applied directly over one of bearing plates. In this situation, the load is riding mostly on the one bearing plate. This orientation is where the bearing is at its lowest capacity.

To calculate the load capacity for a particular orientation, read the correction factor off the graph then multiply by the published rated load capacity.  Note: the load correction factor graph varies based on the product design and number of ball tracks.  See the product specifications to see the load correction factor graph for a specific product.

How the Orientation of a Thomson Linear Ball Bushing Bearing Affects its Load Capacity

This video provides more detail on how the orientation of the linear bearing affects the load capacity. 

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