According to Joseph Gwinn :
In article ,
Ned Simmons wrote:

In article ,
says...

[ ... ]

I doubt that the airstream from a hand blowoff nozzle is supersonic, so
twice this speed might be hard to attain.

My recollection is that in rocket engines, the flow "chokes" (speed
limited by the speed of sound) in the throat of the engine, and then
goes supersonic only while expanding in the bell.

But -- that limiting speed is the speed of sound in the medium
and at the pressure that occurs in the throat. At the higher pressure,
that may be significantly above the speed of sound at atmospheric
pressure.

Blowoff nozzles have a throat, but no expansion bell.

Well ... modern ones have sort of a bell -- that OSHA mandated
collar with side holes to keep the full pressure from being applied to
someone's skin. :-)


I suspect that lubrication failure leading to galling of the balls and
consequently jamming is the big culprit. Perhaps the race expands enough
from the centrifugal force to rattle around and hasten the failure, but
it seems unlikely to me that it's possible to get the bearing spinning
fast enough for this to be much of a factor. The strain in the
hypothetical 6203 race would be about 0.15% at 100 KRPM - in other words
the bearing might loosen up a thousandth or two at that speed.

This mechanism would have a hard time managing the very precisely
symmetric explosions we have heard reported, so uniform that the finger
isn't torn off.

A recent posting from the individual involved implies that it was
just the inner race and the roller cage, without an outer race involved.

Enjoy,
DoN.

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