Damon Atchison wrote asking about a tubing connection diagram for the
Themodist piano he is working on.  He said:

> There are three nipples on the pump: one of 1-1/2-inch diameter
> and two of 1-inch diameter.  Where do they go?"

There are so many variations over the years that I can not speak with
any authority.  The player system in my 1912-era Aeolian Pianola
Themodist (called Solodant by other companies) has two big hoses from
the pump reservoir: one huge hose to the Themodist expression unit, and
a smaller hose to the airmotor governor.  Another medium size hose goes
from the expression unit to the pedal apparatus.

> Are there two tubes that supply suction to the stack?

Yes.  The action stack of the Themodist player is divided into bass
and treble halves; each half has its own large (1-inch) supply hose at
the end of the stack, and each large hose connects to its own port on
the expression unit.  Two different suctions are available inside the
expression unit, called theme and accompaniment.  The louder theme
suction is the same as in the main reservoir behind the foot pedals.
The harder you pump the pedals, the louder becomes the theme level,
as on a regular player piano.

The softer accompaniment suction comes from the knife valve regulator
on the bottom of the expression unit; the suction level is controlled
by the force of the long adjustable spring.  The spring can be adjusted
as you prefer for 6 to 10 inches accompaniment suction.  The main
suction supply for the expression unit is via the large 2-inch hose
connected to the reservoir.  (This hose is 1-1/2 inch diameter in later
production.)

Accompaniment (regulated) suction is normally applied to both halves of
the action stack via one-way check valves.  Louder theme level suction,
controlled by the Pianolist's pumping, is applied via pouch valves;
these are sucked open whenever the pair of theme accent holes ("snake
bites") pass over the tracker bar.  The operator (the "Pianolist") can
also control the application of theme level by moving the hand lever
which moves a slide valve to apply theme suction to the stack.  A third
slide valve inside the expression unit shuts off all suction to the
stack (and the pedal system) when the music roll is rewinding.

Return springs are often installed to return the bass and treble slide
valves to a normal position.  Some owners prefer that the springs
normally hold the levers in the soft (accompaniment) position.  Other
owners (like me) spring the levers to be normally in the loud (theme)
position so that standard 88-note rolls can be pumped without holding
the levers.

The air motor governor (tempo regulator) connects to the main reserve
with a 1-inch hose, and another 1-inch hose goes from the governor up
to the air motor.  The governor unit has two slide valves: one is oper-
ated by the Play-Rewind hand lever (along with the cutout valve in the
expression unit).  The other slide valve slowly uncovers a tapered slot
which throttles the flow to the airmotor; this is connected to the
Tempo lever.

The knife valve regulator on the bottom of the governor unit provides
a constant suction to the throttle valve.  It's about 3 inches water
gage suction, which is less than the suction for the softest playing.
When the piano is switched to Rewind the slide valve in the governor
connects the full pedal reservoir suction directly to the airmotor.

Some Themodist actions have two roll tracking fingers (or "ears"),
other actions have one finger.  In the double-finger system the flapper
valves on each side of the music roll are connected to two cutout
pouches in the primary box (not shown) which control a pair of linked
opposed pneumatics that adjust the spool position.  In the single-
finger system, one flapper valve on the left edge of the roll connects
directly to a single spool-positioning pneumatic, with no cutout.

Both methods work well during playing, as long as the leather facing on
the edge-sensing finger seals the tube completely.  But the later 2-ear
design has one advantage: during reroll the primary box is not under
vacuum, so the cutout pouches close, isolating the flapper-nozzle
lines.  Now the double adjusting pneumatic has full vacuum on both
sides, and its movable board automatically centers itself, thereby
centering the spool for a neater, tear-free rewind.

All this is hard to make clear in words, so I have made a couple
of rough schematic diagrams.  All the required hose paths are shown
functionally, but the actual physical arrangement may be different.

Best regards,
Richard Vance

 [ See Richard's drawings at the MMD Tech site:
 [   http://mmd.foxtail.com/Tech/    -- Robbie