On Tue, 20 Jan 2009 15:24:09 -0500, Andrew Erickson
wrote:

They do indeed reverse 120 times per second (60 full cycles per second),
but so does the field coil, so the relative magnetic polarity of the one
with respect to the other stays the same. ...

That's the way I understand it and I won't quibble on whether it's 60
or 120 time/sec. Kinda depends on the definition of "reversing". So
"reversing polarity" of the brushes - which I interpret to mean
switching leads - won't have any effect on rotation direction of a
universal or any other type of AC motor. That would be no different
than reversing the plug in the wall socket.

On the other hand, breaking the motor open, and doing some internal
rewiring might accomplish the mission.

Tom Veatch
Wichita, KS
USA