In response to Ed Copeland's question posted in 030904 MMD, the lost
motion compensation (soft pedal) is adjusted by the strength of the
five pneumatics, the respective stop on each one, and by the leaf
spring attached to each lever arm.

The strength of each operating pneumatic is adjusted by varying
the "at rest" opening of each pneumatic.  All the leaf springs should
assist in lifting the lost motion rail.  None should be pushing down.

On the full Ampico B stack, adjusting the hammer rail lost motion is
one of the most frustrating operations.  This is because the "at rest"
position of the entire mechanism is just a bit "springy".

On the bench, it is best to try to do a much preliminary work in
regulation as possible.  With all poppets installed, release all
tension on the five leaf springs.  Then adjust all five compensation
pneumatics to a full open position.  Follow this by setting the travel
limit of each to 3/16 of an inch.  Finally, adjust each leaf spring so
that is just starts to lift its section of the compensation mechanism.

At this point, the individual note pneumatics should be adjusted to
a nearly full open position.  Level the top poppet nuts and install
the stack with an average 1/32-inch clearance from the key bottoms.

Now the final regulations can be made;  individual poppet clearance,
minimum vacuum level, and individual note compensation.  Yes, the
hammer rail lift should bring the hammers within 7/8-inch of the
strings, but that is just a preliminary setting.  The final setting is
done by ear when setting the minimum playing level.  Once this is done,
the leaf springs and travel stops of each compensation pneumatic can
be given final regulation.  None of this can be done quickly.  Slight
adjustments, balanced against minimum vacuum, will find the magic spot
where this fine instrument will just whisper, flawlessly.

Additionally, the loud pedal compensation should be made part of
any fine regulation.  This device, which appeared first in the Ampico
"A" around 1927, has a remarkable affect on the evenness of extremely
soft playing.  Only the earliest "B" models have adjustable loud pedal
compensators.  They are present as screws ("L" and "M")  on the first
intensity regulator.  Later "B" models have non-adjustable bleeds
instead of the screws.  This compensator should drop the stack vacuum
about 1/2 inch as the loud pedal comes on at sub intensity.  Tests will
confirm the exact amount.  If the note compensation test roll is played
with the loud pedal on, the lower vacuum will be present during that
test.  Happy regulating!

Bob Taylor