Hi All,  For those who are truly interested in finding out how the
old 1920's-style electric player piano motors really operate, how
they look inside, and how they are serviced, I bring to your attention
the article by Craig Brougher titled, "Servicing the Original Electric
Piano Motor".  The article also covers the operation of the Centrifugal
Start Switch, Construction and Characteristics of a Typical Old Piano
Motor, and Rewinding a Motor.  Complete with pictures and diagrams,
I feel certain you will find this article very informative.  See

  http://www.player-care.com/servicing-the-motor.html 

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA