I have recently overhauled a 1920s Steinway Grand Duo-Art, and removed
the rotary pump and electric motor for inspection and reconditioning.
The rotary pump was in excellent condition internally and I had merely
to tighten up the screws that held the fixed pneumatic boards to the
sides of the case in order to prevent slight vibration and associated
noises.

The electric motor was a very sturdy and heavy US built model, rated
at 220 VAC.  It had worked okay up to then, but I advised that it
should be inspected by a competent firm specialising in motor rewinds.
The firm recommended that it could and should be reconditioned.  This
was carried out.  I then fitted everything back and ran a three hour
test during which time I performed further regulation of the Duo-Art
in accordance with the service manual.

At the end of this time I was somewhat alarmed to find the case of the
motor was very warm -- hot, even.  Clearly a lot of this heat was going
to go up on to the soundboard.

Although the motor is having to propel a rotary pump of some significant
size and power, would it be expected to run hot after three hours of
continuous use?  The wiring was cool to the touch and the whole connection
protected by a 3-ampere fuse.

 [ I asked Roger exactly what work was performed to rebuild the motor.
 [ -- Robbie

I believe that the windings were replaced and that it was properly
tested.  The firm that I used are specialists in rewinds so I expect
them to have done a proper and safe job, which cost £140 -- about
250 USD.  Where I live in Birmingham it's a very competitive engineering
marketplace; there are lots of auto shops and small repair firms.

Having said all that, I now feel obliged to go back to them and check
on what they did.  When I felt the case of the motor I got no shock --
just a _very_ warm hand.

Roger Waring - The Pianola Workshop
Solihull, West Midlands, UK
www.pianola.co.uk