According to Ned Simmons :
In article , says...

[ ... ]

It could simply be giving a little kick to each ball as it
rotates past -- picking a different part of the sloping trailing edge of
the balls depending on speed, so the actual speed of the bearings could
exceed the airflow velocity.

I think it much more likely that air bouncing back off the balls and
retainer interferes with the airstream from the nozzle. I'd be surprised
if the balls reached anywhere near the velocity of the air, and I doubt
the airsteam approaches the speed of sound.

Possible -- I have no way to prove any of this -- nor any desire
to explode bearings in the test process. :-)

[ ... ]

Huh, look what a google on - supersonic air flow blowgun - turned up...
http://yarchive.net/metal/ball_bearing_spinup.html

Interesting, I get a:

================================================== ====================
Not Found

The requested URL /metal/ball_bearing_spinup.htm was not
found on this server.
================================================== ====================

when I try that URL. What is it -- this discussion?


In a strange sense, yes. But 13 years ago on this very group. This is
the thread on google...
http://tinyurl.com/loxlq

O.K. That one worked.

It seems that nothing was settled that time, either. :-)

Thanks,
DoN.
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