Gordon Stelter asks whether anyone can suggest a suitable replacement
for the old electric motors found in our pianos, and then suggest that
the old motors should be displayed in a glass case.  My own experience
leads me to support Doug Bullock in his suggestion that these motors
should be restored, and that once restored they will operate safely.
All efforts should be made to reuse the original motor, not just for
sentimental reasons, but for good technical reasons.

The biggest problem is that of shaft length.  It is possible to find
modern motors of the same voltage and pole numbers, i.e., it can have
the same power rating and speed, but I have never found one that is
as short in overall shaft length as the original.  Some installations
preclude the use of a longer motor than what was originally fitted.
I have found this particularly problematic on early German pianos where
the motor is fitted behind the soundboard, within the depth of the
wooden frame.

The next problem is that of mechanical noise.  All original motors have
plain bearings.  All modern motors have rolling bearings.  The latter
may be more efficient and require little or no maintenance, but they
are noticeably noisier than plain bearings.  Of course, this is one
reason why an original motor may become hot with continuous use, e.g.,
lack of regular lubrication or lack of attention to the wick
lubricators.

Old motors are heavily made out of cast iron.  Modern motors are mostly
made from aluminium (some readers may spell this aluminum) with iron
being used only for the winding cores.  With aluminium, any internally
generated vibration will quickly be dissipated as noise, whereas old
cast iron motors run really quietly.

Modern motors are generally fully sealed, supposedly for safety.  This
necessitates the addition of an external fan on the back end, to assist
ventilation and the hotter running of the motor.  For these reasons you
will find that modern motors are much smaller than their predecessors,
per unit power.  The fan is another source of noise.

If you are worried about the motor getting warm, then consider this.
Power for power, a modern motor will always run much hotter than an old
motor.  Modern economics dictate that all designs are optimised for
cheapness, so modern motors will be designed to be smaller and to run
at higher temperatures, but the insulation will also be designed to run
at that higher temperature so both are safe if not overloaded.

So there is only one solution -- rebuild the original motor.

Best wishes for Christmas and the New Year,

Nicholas Simons, GB