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MMD > Archives > June 2004 > 2004.06.25 > 05Prev  Next

Automatic Shutoff in Late Aeolian Player Pianos
By John A. Tuttle

Hi All,  The auto shutoff assembly pictured in the Archives was made
by Aeolian and is found in the early 'modern' Aeolian players.  It is
triggered by the same hole that is used to trigger auto rewind.  You
might ask, "How can that be?"  Actually, it's really simple.

To prevent the auto shutoff from turning off the electricity to the
vacuum motor when the transmission was shifted into rewind, Aeolian
limited the amount of vacuum that is applied to the shutoff pneumatic.
By restricting the vacuum supply to the pneumatic, the perforation that
triggers rewind is long gone before the shutoff pneumatic has enough
time to collapse and turn off the power switch.  At the end of rewind,
the same hole that triggered rewind stays open and the shutoff
pneumatic slowly (by comparison to the rewind pneumatic) closes and
turns off the electricity.

(By the way, you might also notice that there is a fair amount of
clearance between the wooden piece that activates the cherry switch
and the switch.  _Do not_ reduce that clearance -- it's part of the
'timing scheme'.  Further, I vaguely recollect one assembly in a very
early model that didn't have a restriction.  It's functionality relied
entirely on the distance that the bellows had to travel before reaching
the cherry switch.  Obviously, premature shut off became a noticeable
problem and Aeolian rectified it by installing the restriction.)

I've seen two types of restrictions in the auto shutoff device.  One
is a standard bleed cup that's force fitted into the wood inside of the
pneumatic.  The other is a piece of paper with a pin hole that is glued
to the wood inside of the pneumatic.  The device works exceedingly well
if the rewind valves and pneumatics function correctly.  If they are
leaky or slow to react, sufficient time passes between the time the
first reroll perforation appears and the time the system shifts into
rewind, and the system shuts down prematurely.

In later years, Aeolian modified the design again and put the auto
shutoff valve next to the auto rewind assembly.  Then they ran a vacuum
hose to a smaller pneumatic which is mounted on the left side of the
spoolbox, in the same location as the device in question.  Ultimately,
this smaller bellows became the Achilles' heel of the Aeolian players.
Since the bellows is mounted horizontally, instead of vertically, over
time the moveable board droops down and the flange finger fails to make
contact with the cherry switch.  Also, the quality of the pneumatic
cloth was quite poor and even if the finger can contact the switch, so
much vacuum is lost through the cloth that the pneumatic doesn't have
enough force to turn the switch off.  This is an extremely common
problem in all modern Aeolian players.

Years ago when I first encountered the device, I said to myself, "This
device qualifies for the DIPUTS Award", a Design Idea Predicated Upon
Technical Simplicity.  (DIPUTS is STUPID spelled backwards, and the
word was derived from the acronym "KISS", "Keep It Simple Stupid," in
the early 1970's by Jim Brown and me when we worked in the Calibration
Lab at the Lakehurst Naval Air Station in Lakehurst, NJ.)

John A. Tuttle
Brick, New Jersey, USA

(Message sent Fri 25 Jun 2004, 14:31:24 GMT, from time zone GMT-0400.)

Key Words in Subject:  Aeolian, Automatic, Late, Pianos, Player, Shutoff

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