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4.3X??

4.3X??

(OP)
Recently I viewed a series of acoustic spectra that clearly showed a 4.3 X speed series of peaks, with the speed varied over a 10X range (50 - 500 RPM).  Rotary device was a BLDC motor/flywheel combo, riding on a pair of angular contact bearings, roughly 1.25 inches OD.  

Is this a bearing harmonic (perhaps precessing, sp?)?

BK

RE: 4.3X??

That sounds like a bearing defect.

Do you have bearing part number (to check bearing fault frequencies?)

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RE: 4.3X??

(OP)
The bearings are series 102, specifically, S102HX315.

BK

RE: 4.3X??

I'm not familiar with that part number format. Is it a manufacturer's part number? Which manufacturer?

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RE: 4.3X??

(OP)
It is an R102 series bearing, which has the following dimensional characteristics:

  -  OD       1.2598 inches    (32 mm)
  -  ID       0.5906   "       (15 mm)
  -  W        0.3543   "       ( 9 mm)

There are 11 balls, ref size being 3/16"  (4.75 mm)

After I re-examined the data, the series of peaks appears to be closer to 4.4 X.

BK

RE: 4.3X??

Good oh, so now you can work out the approxiamte bearing frequencies, just like in an epicyclic.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: 4.3X??

Off the top of my head, it looks like outer-race defect frequency would be in the rough neighborhood 4.4x.  It is usually somewhere around 0.4 times number of balls. 0.4*11~4.4

To compute the exact frequency, you also need contact angle.

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RE: 4.3X??

(OP)
Electricpete, thanks, I had worked that out also, but it did not look right to me!  (Sorta like when you kb or write a word down, but the spelling looks wrong).

BK

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