4.3X?? 1

[bklauba]

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

 

[electricpete]

That sounds like a bearing defect.

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

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[bklauba]

The bearings are series 102, specifically, S102HX315.

BK

 

[electricpete]

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

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[bklauba]

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

 

[GregLocock]

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.

 

[electricpete]

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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[bklauba]

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