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MMD > Archives > December 1997 > 1997.12.02 > 15Prev  Next

Duo-Art at Lowest Intensity
By Craig Brougher

Chris Morgan's problem of a Duo-Art playing too loud sounds a little
different to me than what others describe -- or, at least, he described
it in such a way that I got the picture better.

As we've already noticed by the archives, there are lots of reasons
why a Duo-Art might "play too loud," but Chris defined it as stack
evenness.  So he is speaking of the latitude required by the setting
of the zero intensity.  In other words, his problem of "playing too
loud" is necessitated by the unevenness of the piano notes or player
stack (or a combination of the two) when adjusting the expressions.
So I will assume for the moment that the expression works fine, and the
problem is "fine tuning."

It is still hard to tell to what degree this problem exists, so I will
ask him to tell us, by using an _accurate_ vacuum gauge, what the
minimum zero intensity has to be, in order to play all the notes.  Some
of us live with 8" of vacuum, and for others, 4.5" is barely tolerable.

In the meantime, I will say that -- although a Duo-Art will play at
4.5" -- it will not do so cheerfully.  It was designed for a zero
intensity of 5."  And while I have rebuilt some Duo-Arts with
valve/pouch combinations which made them a bit more sensitive (as the
system evolved over the years), the best way of doing it consistently
on all players of all Aeolian designs was to

  1) make sure that the trackerbar tubing was clear all the way
through to the stack by cutting new gaskets and giving each tube a
clean gasket nipple,

  2) Rigorously bench-test each valve before the pneumatics are put
on, so you can get into any that aren't quite snappy enough to fix

  3) Test each shelf of the stack after the pneumatics are put on, to
test the valve gaps and any sluggishness due to pneumatic problems in
combination, and

  4) Rigorous final assembly test of the completed stack for leaks,
binding up, and other problems with the strikers.

When the stack is replaced into the piano, you must take all lost
motion out of the player between the strikers and the keys.  No player
plays as well when a gap is left between its strikers and the key tails
(grand), or whippens (upright).

From here, the problems will be with the piano action, and specifically
the dampers.  On all grands, the damper lever rails lift out.  On many
of these player grands, the levers are fitted with an additional spring
(beside the lead weight).  On a Steinway grand, for example, you will
find that these springs have slipped up, since they were just "stabbed"
down into the wood, anyway.  You will also find that sometimes, many of
the lever flanges have broken off the flange rail, anyway, giving the
lever lost motion in back when it should be merely hinged.

After all the physical problems with the levers are fixed, you need to
even up the spring tension.  This is done by holding the rail upside
down somewhat, so the levers can "fall" by gravity against their
springs, and noticing, by "swinging" the rail, which springs are weak.
When you have bent the weak ones so they can all "swing" together, it
is ready to replace.

Now what you have is a damper lever rail whose springs are adjusted
approximately even.  You can also do it with a spring gauge like the
kind I built myself decades ago, but that's another topic.  This way
works just fine, and will give you an even damper system, spring-wise.

When everything is back in place and the piano action itself has been
correctly adjusted too, you will notice that you are able to lower the
zero intensity considerably more than before.  If you can comfortably
get each note to play at 5" of vacuum in Accompaniment and 5-1/4" Theme
(use something other than a worthless Marshalltown Gauge) then you are
easily within factory specs.

There is just no way a Duo-Art is ever going to achieve the super soft
playing characteristics of an Ampico, because the Ampico design is
continually feeding back valve travel losses and leakage to its
expression system, which automatically compensates for it instantly.
The Duo-Art is designed to be entirely roll-operated, and so cannot
compensate for anything, automatically.  That forces you to even out
the player and piano perfectly if you want to fine-tune your Duo-Art to
accomplish all it was capable of doing on each roll.

Craig Brougher

(Message sent Tue 2 Dec 1997, 14:38:41 GMT, from time zone GMT.)

Key Words in Subject:  Duo-Art, Intensity, Lowest

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