D.L. Bullock writes of a Seeburg motor starting problem.  First let's
talk about how a small single phase piano motor starts.  In addition to
the two pole (3600 rpm),four pole(1750 rpm), six pole (1100 rpm) run-
ning windings in these old piano motors, there is also a special
starting winding and a centrifugal switch that turns this winding on
and off.

The starting winding is slightly out of phase with the running winding
poles.  It is there to give the motor's rotor a nudge from a dead stop
in the proper direction of rotation and to apply extra horsepower
needed at start-up to overcome the heavy load of the vacuum and
pressure pumps, rollframe, etc., until the motor is up to running
speed.  This extra power is needed only for a fraction of a second to
at most a few seconds.  The starting winding is designed only for this
short burst of power and time.  If the starting winding is left
powered-on for too long, it will overheat and burn out in a half minute
or less.

A special centrifugal switch is in series with this starting winding.
It usually has weights or finger elements that fly outward when it
senses the motor is at proper operating rotational speed.  This opens
the circuit and turns off the special starting winding.

There have been many designs of these starting switches over the early
electric motor era.  Century, Westinghouse, Emerson, Holtzer-Cabot each
went through many starting switch designs.  None of these early switch
parts are available today.

                 Starting Switch Repair

The first thing to do is to mark the motor end bell for proper re-
assembly.  Open the rear motor end bell after taping numbers on each
and every wire and marking their proper position on a paper chart.  The
motor starting switch will probably be found to be very dirty after
decades of use.  The motor lubricating oil will have become gummy and
will have collected lots of dust, sawdust, etc.  Clean this switch with
mineral spirits and polish it with very fine steel wool or a Scotch-
brite pad.  Clean and lightly burnish the switch contacts until smooth
and bright.  These contacts are often pitted, but will usually clean
up.  Electrical contact cleaner works well for this.  Make sure you
also clean the switch's moving centrifugal weights, arms, and springs.

At this time check for wear on those items usually made of brass.  Many
times these are very worn or pitted and grooved.  Try to clean these
parts as best possible.  In extreme cases you may have to replicate new
parts yourself to replace badly worn parts.  While you are in there,
check the starting winding with an ohmmeter to see whether it is still
good and intact.

If the old mechanical starting switch is beyond repair, do not panic.
Today there are several modern, solid-state motor switches that will
replace the old mechanical centrifugal switches.  There are several
types on the motor-repair market today.  The MacroStart Solid State
Motor Starter #STM-100-115 is a timed electronic switch about 3/4"
square X 1/4" thick. rated for up to 20 amps at 110-120 volts.  Because
of its very small size, it can easily be hidden inside the motor end
bell.  It has the best On/Off timing I have found for old piano motors.

Another solid state switch is the KB-8 0r KB-10 current-sensing
starting switch, from KB Electronics Inc., Brooklyn, N.Y.  This switch
is much larger and usually must be mounted externally on the motor.
Either of these modern switches can save almost any old piano motor.
They are inexpensive and come with easy-to-follow directions.

While you have your motor apart, clean out all the old bearing oil and
refill with proper motor lubricant.  Many of these old motors used felt
to hold the bearing oil in place.  There was a secret motor bearing
lubricant used in those early days, consisting of #30-#40 motor oil
mixed with fine sawdust to form a paste.  It was sold this way in cans.
The sawdust kept the oil from dripping and flying off the motor shaft
and into the starter switch.  My ninety year old father, a lifelong
electrical engineer, remembers GE marketing this "Special Secret
Electric Motor Lube."  Now that you know the old secret formula, you
can make your own.

If you look inside the motor bearings, you can usually see machined
grooves in the bearings, some of which are figure-eight shaped.  These
are used to distribute the lubricant over the entire bearing and shaft.
Fill these grooves and also the pocket above the bearings with this
secret mixture.  You will not believe how quietly this can make an old
electric motor run.

Brad Hunter
Huntingdon Valley, Pa.