Hello all:  In response to Richard Moody's post about the Gulbransen
with a vacuum motor installed, he is right in saying that just choking
off the vacuum is not the way to go.  The motor is still running at
full speed and by choking it off you have cut off the essential cooling
airflow to the motor.  The motor will surely overheat and present
a possible fire hazard if left on for a long time.

The motor running at full speed is also much noisier than it needs to
be.  By using a speed control, the motor speed can be set to the exact
speed required for a reasonable playing volume.

A light dimmer can be used, but they are designed to work primarily
with the resistive load of an incandescent lamp.  The triac that is
typically designed into the hardware store dimmers is not rated for
the highly inductive load that the vacuum box motors present.  Because
of this, the light dimmer may have a short life or also may overheat.
Use caution when using a light dimmer, and be sure to enclose it in
a fire resistant box in case of a catastrophic failure.

Most of the suction kits on the market today come with a dual-speed
controller that will allow you to set the motor speed separately for both
play and rewind, as typically in the rewind mode much less air is needed.

To read more about the speed controller that we have designed specifically
for player piano electrification, as well as our next generation vacuum
suction box, go to http://www.pianoproservice.com/bergytone.shtml 

Eric Bergstrom - Bergytone Products
PianoProService.com