In 1980, when I installed an Ampico A system into my Knabe concert
grand piano, I opted to use an electric motor rather than the original
air motor.

As Spencer Chase suggested in his posting to the 28-4-08 MMD, the
torque demands of a roll drive motor are quite modest.  I used
a surplus DC motor rated at 1/20 HP with separate field and armature
terminals.  Rated speed at 28 volts DC was 3900 rpm, although in my
installation, the voltage range is about 3 to 8 volts at usual tempo
settings.  The torque is quite sufficient with direct shaft drive
(i.e., no gear reduction in the motor).  There is no audible motor
noise, even with the transmission idling in "neutral", so I would
strongly suggest finding a motor with no built-in gear train.

As I recall, I obtained this motor from a surplus dealer, Herbach &
Rademan, in Erie, Pennsylvania.  That was in 1980; the cost then was
likely about $10 or so.

The power supply, rewind switching, and speed control issues are too
detailed to report here, but I'd be glad to share my experiences on
this subject with others who are contemplating such a "re-engineering"
effort.

One caveat here:  Such an installation will have a far more stable
speed regulation throughout the duration of a roll performance than the
original air motor, i.e., with varying drag torque from the paper roll
from beginning to end.  The result is an exaggerated apparent tempo
increase, due to paper build-up on the take-up spool.  This, of course,
is one of the reasons for the larger take-up spool in Ampico's Model B.

This speed increase can be a minor nuisance on larger rolls.  I have
some ideas regarding a simple "fix" for this problem.  I could share
this also with anyone interested in that kind of finesse.  Likewise,
I have photos of my installation, which I could email to those who wish
to inquire.

Best regards to all,
Bill Flynt, Dallas, Texas
tel.: 1-972-644-2493