Greetings,  Bruce Grimes asks about what might contribute to
a sluggish sustain pedal on an upright Duo-Art.  I have spent many
hours regulating the dampers and pneumatic mechanism of my upright
Steinway.  I believe that quick and reliable damping can only be
achieved if the dampers are regulated very evenly, so that a slight
movement of the sustain pneumatic will clear the dampers on all strings
at once.  Even with this careful regulation, I believe that the upright
dampers are not quite as effective as the grands and it may not be
possible to achieve the same results.

I did have an odd problem with the sustain pedal valves in my piano
that may be worth mentioning, although it was so unusual that no one
else may ever have the same problem.  I had the damper pedal working
well from the roll but it was not easy to get right.  Occasionally it
would seem that the pedal stayed on longer than it should, but then it
would respond to quick pedal jabs just as it should.

Eventually it became sluggish at certain times in many rolls.  It made
no sense at all: quick pedal codes worked fine until a certain point
in the roll.  Then the pedal would stay on continuously through short
releases and start working correctly again later in the roll.  This
pattern would repeat at exactly the same places in the roll even though
shorter releases would work in some places in the roll than longer ones
that failed elsewhere.

I inspected the bleed and cleaned it out several times, which seemed
to help temporarily, but the problem returned.  I decided to completely
rebuild the valve and pneumatic assembly although it had been rebuilt
only a few years earlier.  What I found was that the hole drilled
between the bleed and the vacuum chest of the unit, whose function was
to provide vacuum to the bleed, was not drilled completely through the
wood.  It was a rather small diameter hole although it could have been
much larger.  In fact, most similar passages are rather large slots and
I was not in the habit of looking for and finding little holes such as
this one.

The original factory drilling only pressed the wood fibers out of the
way on the back side of the wood through which it was drilled.  Only a
small amount of air had to pass through this hole so it worked fine for
many years.  Eventually the partial hole became clogged with dust and
effectively reduced the bleed size, making the pedal stay on.  It is my
guess that the dust was undergoing compression and expansion cycles
that somehow related to the amount of time the pedal was on and
possibly vacuum level.

I removed the wood splinters that were clogging the hole and it has
worked perfectly ever since.

Best regards,
Spencer Chase
Laytonville, Calif.
http://www.spencerserolls.com/