On Mon, 31 Mar 2014 08:08:20 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

thunk fired this volley in
:

What happens if you put a bearing within a bearing - the outer race of
the inside one being the inner race of the outside one? Is friction
reduced? Is the maxiumum speed changed? Temp rise?

You increase any inherent 'play' in the system. Also since the 'middle
race' is no longer heat-sunk to a shaft or housing, risk the possibility
of heating it without any way to remove the heat.

And play = vibrations, most usually. Also, how do you securely secure
an outer bearing race into an inner bearing race? You can't squeeze
either. You can't heat it to red hot to interference-fit it. And glue
isn't strong enough.

OTOH, you've distributed the wear over at least twice as many rolling
elements, and if everything were perfect the balls and races would turn
more slowly than a conventional bearing. IF everything were perfect.

I would think the smaller bearing would take most of the revolutions
due to its lower friction surfaces. That might allow a faster spin,
but with the added vibration from play, it might result in a truly
spectacular catastrophic disintegration, too. I wouldn't want my
hands/eyes/body anywhere near it when that happened.

I wouldn't do it.

--
I would be the most content if my children grew up to be the kind of people
who think decorating consists mostly of building enough bookshelves.
-- Anna Quindlen