Guest lecture · Part 2 · §2.2

Bearing Kinematics — where the fault frequencies come from

Balls roll, they do not slide. That one constraint fixes the cage speed as a fraction of shaft speed — and everything else follows by counting how often a ball passes a defect.

The bearing

FIXED TO HOUSING SHAFT OUTER RACE fixed INNER RACE rotates with shaft n = 9 BALLS held by the cage CAGE rotates at FTF OUTER SPALL fixed at 12 o'clock INNER SPALL orbits with shaft
Shaft f_r
29.95 Hz
Cage FTF
11.93 Hz
Outer BPFO
107.4 Hz
Inner BPFI
162.2 Hz