According to Eric R Snow :
On 14 Apr 2006 20:04:38 GMT, (DoN. Nichols)
wrote:

[ ... ]

Hmm ... assuming eight balls in the race, that would get you to
33.3 KHz frequency from the balls modulating the airflow.

And the bearing which failed on somebody's finger was 5/8" ID
(15.875mm) -- slightly smaller than the one which you postulated. But
we don't know how many balls it had. No doubt, no fewer than 6, which
would get us to 25 KHz. And we don't know exactly when his hearing
dropped out at that time in his life, nor how much more speed the
bearing got in the time since it passed his hearing range.

[ ... ]

That might hasten the failure of the surface of the balls, but
if they *really* failed, all of that energy stored in the spinning outer
race would be transferred to the finger on which the bearing was
mounted, perhaps twisting it off.

Hmm ... the story did not describe whether the bearing's inner
race remained on his finger -- nor what happened to all of the balls.

[ ... ]

Greetings DoN,

It was me who posted about the exploding bearing. The inner race came
off my finger but it was intact. I'm not sure if it came off because
the bearing came apart or because when the bearing did its thing I
jerked my hand back. The rollers disappeared into the insulation on
the walls. The walls didn't have sheetrock on them where the pieces
struck. I always thought the reason the thing came apart is because
something jammed. A friend's father worked at a lab where things were
spun up in centrifuges until the spinning objects failed. They were
spinning at tremendous speeds. This was when I was about 16 so the 34
year old details are sketchy. But his dad told me how much energy the
small centrifuges used and it required lots of horsepower to spin
small items to the bursting point. Way more than the air coming out of
my nozzle.

Hmm ... you mention the inner race and the rollers -- but not an
outer race. Was this the typical tapered roller bearing, with the cage
traveling with the inner race, and there was no outer race involved? In
that case, yes, you were working with something a lot weaker than the
outer race, so it was more likely to explode at lower speeds.

Anyway -- I'm glad that you were not hurt by this.

Thanks,
DoN.

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