ceramic bearings and ball VS roller

[wobblywalrus]

A thing to think about when converting from ball to roller bearings.

In many applications the ball bearing inner race(s) and some spacers are on a shaft.  There is a nut on the shaft end and it is tightened down.  The shaft including a portion of the threaded part are in CONSTANT tension.

In the typical roller conversion we use little to no preload.  The shaft and a portion of the threads are in a variable, and sometimes, cyclic state of RELAXATION and TENSION.  Now fatigue life is a concern, and it is especially critical if the rotating component exerts a cyclic load on the shaft.  ie, out of balance wheel, etc.

Usually the parts we work with are over engineered to the degree that this is not a problem, but it should be considered when modifications are made.

On another note, internal friction manifests itself as heat.  Sometimes simple operating temperature comparisons will tell us a lot about bearing type, lube and its application, and preload.  "Cool running = fast running."

This is backwoods engineering, not very sophisticated, just some ideas.