The Holtzer-Cabot style QS15 1/8-horsepower motor is perhaps the
most commonly found motor on electric driven pianos from the old days.
I think most Welte Licensee pumps were equipped with these, and
certainly how often they show up on eBay suggests how common they are.
I have just finished restoring one of these QS15 motors. The winding
was carefully removed, cleaned and the windings saturated with motor
winding insulating enamel, the case was bead blasted and repainted,
bearings and oil cups cleaned and fresh wicking and oil installed.
I plugged it in on the workbench with no load and let it run.
Everything seemed fine except that the case gradually warmed up to a
temperature where I could still keep my hand on it, but if it got any
hotter I wouldn't want to do that for more than a few seconds. And
this is with no load on the motor.
I have a second Holtzer-Cabot motor, also frame style QS15, that
I had restored about 10 years previous but never used (it is slated
for a specific piano yet to be restored) and I put it on the bench and
ran it without load. It heated up to the point where it was too hot
to keep my hand on it for more than about five seconds.
My question is, is it normal for this style QS15 Holtzer-Cabot motor
to run this hot? Air flow through the motor is minimal and the
impeller blade on the rear end for cooling is laughable. If this case
temperature is not normal, what might be the cause of the overheating?
I've been discussing this with Robbie and at his recommendation I have
ordered a "Kill A Watt" electricity usage monitor [power meter] so I can
check line voltage and energy consumption of the motor. If there are
shorted winding wires could this also be a cause? If that is the case
I suppose it needs rewinding. Is this (shorted winding wires) a more
common situation with these old motors than previously thought?
For any MMDers having one of these motors in an operating piano, would
you hand check the temperature of the motor after the piano has been
playing for 10 to 15 minutes?