In MMDigest 980206 John Burton requested information about a two-speed
motor for a Welte-Mignon.  The T-100 (red roll) and T-98 (green roll)
both had provision for motor speed change during the musical perform-
ance.  The T-100 (red) utilized perforations in the music roll to
engage or disengage resistance to increase/decrease the motor voltage.
This allowed the pumps to operate slowly during soft passages, while
increasing speed and output during forte passages.

The T-98 (green) had no provision in the music roll but relied on the
expression pneumatics to close to activate a switch.  The closing of
this switch likewise controlled the motor resistance and hence motor
voltage.

Literature published when these pianos were new stated that motors
would be supplied according to the required voltage and whether DC
(direct current) or AC (alternating current).  Recall that standards
were anything but universal.  A range of motors appear in these pianos
today.  By the 1920's, Mr. Tesla's alternating current was replacing
Mr. Edison's less efficient direct current.  There is a predominance
of AC motors present in pianos sold in the 1920's.

The Welte-Mignon two speed system will only function with a DC motor.
Original installations requiring AC motors did not utilize the
resistance apparatus.  AC motors operate at the high speed constantly.
I have seen original motors replaced with a 1920's period AC motor.
Undoubtedly the service [mains] current changed from DC to AC requiring
the owners to replace the motors.

Technology today allows the use of a DC motor with simple conversion
electronics in an AC environment.  My own 7' Steinway-Welte (T-100,
red) shipped to the first owner in December 1931 had a "squirrel cage"
AC motor which could be wired for either 110 AC or 220 AC operation.
All of the resistance apparatus was preserved under the piano but not
wired into the AC circuit.  I have subsequently found an appropriate DC
motor and re-wired the piano to operate at two speeds.

The motor pictured in the MMD Pictures web page carries a plate stating
"wechselstrom," alternating current in German.  This motor appears to
be from the period but was never used in a two-speed fashion.  If the
owner wishes to operate the piano with motor speed change, then a DC
motor will be required as well as the motor resistor and switches.

Mark Reinhart

 [ Today's brushless direct-current (DC) motors are _very_ efficient.
 [ MMDer Will Dahlgren now drives a Honda electric car up the hills of
 [ San Francisco, and when he goes down the hills the battery is
 [ recharged!  Similar, smaller motors recently propelled an experimental
 [ solar-powered electric airplane to 60,000 feet.   -- Robbie