Dear all,  Jim Ridgewell has encountered a few more anomalies on his
British-built Weber Duo-Art upright.  I hope to be able to point him
in the right direction.

Firstly, the two vacuum tappings on the motor switch valve-box.
On pre-1924 Webers from the Hayes factory, the motor switch valve-box
was controlled by a primary valve-box.  This was either integral to
the tracking/theme primary valve-box on the bass end of the stack, or
it was a separate unit fixed on top of that tracking/theme valve-box.

This primary valve-box contained two mushroom valves -- one being
operated by the "motor port" on the right-hand side of the tracker-bar,
the other being controlled by the take-up spool port when the Repeat
switch is in the "Off" position.

Either of these ports being open will operate its respective valve,
producing an atmosphere signal which in itself is not sufficient to
overcome the bleed in the motor switch valve-box and thus turn the
motor off.  But with both ports open, and both valves producing an
atmosphere signal, the signal is sufficient to overcome the bleed, and
the switch is thus turned off.  The supply to this primary valve-box
is taken from one of the tappings on the switch valve-box.

The other tapping was sometimes used to power the tracking bellows
valve-box, and sometimes as the vacuum supply to the Duo-Art function
switch in the spool-box.  In the earlier Duo-Arts, the tracking
mechanism moved the roll itself and not the tracker-bar as in later
(post-1924) versions.  To avoid the roll being tracked on rewind,
the tracking bellows both had vacuum applied during rewind, as the
valve-box was supplied from either the motor switch valve-box or a
similar "constantly live" source.  The tracking ears were prevented
from operating their valves on rewind by means of cut-out pouches in
the bottom of the valve-box, these only being activated by a vacuum
tapping from the expression box during play.

The pallet valve on the switch valve-box was an idea that wasn't used
for very long at all, as it was superceded by a simpler (and probably
cheaper and more reliable) method.  Aeolian wanted to prevent the
'roller-blind' effect, occurring when the roll tab came off the take-up
spool at the end of the rewind process and clattered away noisily until
the vacuum in the system was exhausted.  One way was to introduce a
"Dump valve" which was triggered by the motor switch operating, as in
Jim's instrument, but I've only ever encountered a couple of these.
The usual method was to have a spill valve on the moving board of the
motor switch pneumatic, which uncovered a hole in the board by means of
a screw inside pushing it open when the pneumatic closes, thus
exhausting the system quickly.

The five-point connector block beneath the air-motor allows for the
extra tube from the switch valve-box to the left of the stack, as
mentioned above.

I hope that this helps.

Kind regards,
Mike Boyd
Rye, UK