I have timewave data which looks like perfect BPIR of a bearing as it goes in and out of the loadzone. However the timewave groups of impacts is cage apart not rotational speed. The difference in the peakes in the bunch are BPOR. Is it coinsidental there spaced 4.2 hz apart or is cage truely modulating BPOR. Were changing the bearing next week reguardless. I atached the wavefore if anyone has another thought.

Mike

Mike,

For a fixed outer race its defect frequency is calculated as the frequency that N number of roller elements pass or roll over a defect, while they all "orbit" at cage frequency (fundamental train frequency, FTF). Put in another way, each rolling element passes over a defect every 1/FTF seg. That's why BPFO=N*FTF

One way to interpret your time waveform is that only 4 out of the 17 rolling elements in your bearing are hitting a bearing defect on the outer race. This could mean that the cage is distorted, damaged or broken. Maybe there is no outer race defect at all and just a broken cage. IMO changing the bearing was a good call.

Were changing the roll next week but may be several weeks before we tear into it. I will post back what we find..

Mike