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MMD > Archives > July 2002 > 2002.07.29 > 08Prev  Next

Adjusting The Pneumatic Finger Tracker System (2)
By Craig Brougher

There is still more to adjusting a double finger pneumatic tracking
system than I was able to tell in the MMD 02.07.27.  So I will continue
on now.

The left finger is the "control finger" of the tracking system because
the left edge of the paper is the control edge of the paper.  When you
see a paper roll that's wider than it is supposed to be, as far as your
player is concerned, that roll must "grow" to the right.  If you start
adjusting your tracker in order to place the center of the trackerbar
over the center holes in the paper, you will have many rolls that will
not track well because all rolls are a bit wider or narrower than
others.  many rolls (good ones) will vary slightly in width from
beginning to end.

This is because the trimmers on either side of the note sheet in the
perforator rely on the pressure of the platen only to hold the paper
down flat and tight, but when a lot of punches are going down through
multiple copies at once (and this is especially true when slick paper
and a dozen copies are perforated at one time) it could be that the
paper ends up a tiny bit narrower in busy portions of the music as a
result of punch displacement, since the paper stretches, "cavitates"
slightly, and springs against each punch, possibly widening the paper
a little, and the trimmers then trim more off.  At least, we know that
it varies slightly and no two perforators are the same.  Also, the
smoothness of paper edges can vary and affect tracking.

So the point about the left tracking finger being the control finger
is what I wanted to stress.  In fact, some players had only one
tracking finger to begin with, and it was always on the left-- but
without an opposing bellows to force the paper to the right.  So when
you try this, you may find that you cannot adjust the tracking fingers
because you do not have a new roll that favors left.  Or, your tracking
finger pads are old and not nearly airtight, so by clamping off the
right finger, the system goes hard over to the right and stays there,
even when the left finger is closed.

Another problem could be that there is no way to swing the right finger
out of the way, as you have in an Aeolian, without opening it's valve,
so there may be no good way to use my first "method." Here's a way to
do it with both fingers intact.  Consider the first way correct for
restored tracking systems that are perfectly airtight.  But use the
first 6 setup steps given and then go to a new roll and the two
tracking fingers method (one way to do it).  New paper rolls from a
good roll company don't need a tracker.  This is why we begin with
paper we can rely on to adjust our tracker to, initially.  Then we
make small adjustments.

7.  Begin with a new perfect roll, preferably with full size holes,
like Keystone or Klavier perforated for Ampicos and Duo-Arts.  It
doesn't matter that your piano is something else.  Many players also
require you to merely bend the tracking finger instead of a screw
adjust.  Let the air motor take the roll through very slowly as you
first watch the tracking bellows to see if it's close enough to center
the roll somewhat.  If both fingers contacts the paper, you will have
to widen the right finger.  Once the paper is traveling only on the
left finger, see where the paper goes.  Watch the bellows also when you
have the paper traveling straight and the note holes on the far left
are exactly aligned with the trackerbar holes.  The bellows, at this
point should be almost equally centered.  Don't make hasty judgments,
especially at the beginning of a roll.  See how it tends to travel and
don't jump to conclusions.

8.  If you don't see the bellows making hardly any corrections as the
paper travels along, possibly you are not close enough with the
tracking finger.  A very tiny adjustment inboard is all that's needed
now, to watch the bellows barely budge back and forth.  If the finger
has to be bent to make the adjustment, as, for instance the upright
Amphion player, take a pliers, snip a piece of 1/8" welding rod and
epoxy it vertically, temporarily to one inside jaw of the pliers.  Then
two more to the other jaw so the single piece fits in-between when the
pliers is closed.  That's one way to make a "bender." Now you can gently
bend things, if you need something like that.

9.  Once a new roll is tracking and barely correcting itself on the
left finger, bend or adjust the right finger back to within 1/64" of
the right edge of the roll.  (This depends on the overall width of
the roll, which varies, as we said.)

10.  If you want the system to track wide rolls (rolls which have
swollen after they were perforated), you will have to give the right
finger more clearance and then allow a little extra tracking error
for normal and narrow rolls.  This can usually be compromised easily
enough, but now is the time to start adjusting the tracking system to
all sorts of old and battered rolls in your collection to see how it
works, and to "tweak" it to a good compromise adjustment.  Do not worry
about the position of the bellows on these rolls, unless they are all
travelling too far in the same direction all the time.  Then your new
control roll was probably tracking off to the opposite side.

11.  If, as you watch rolls being tracked, the bellows either do not
center themselves on reroll or after doing so, you crows the left or
right roll flange, trying to feather or tear the rolls, then your
bellows adjustments are either off (last case), or your tracking system
isn't centering itself as it should (first case).  That has to be
fixed, as it is on reroll that rolls get torn up.

Standard actions have a "centering spring" under their horizontal
bellows that's supposed to counteract the roll chuck spring and roughly
center the system slowly and gently.  If everything else works well,
then the small flat spring under the bellows pair should be adjusted,
or your roll chuck spring needs to be looked at.  It might just be too
strong, as it tends to drive the roll chuck end right, to "screw" on
the cam blade and precess it so that rolls tend to rip on the left roll

One nice little trick you can use to make trackers more "proportional"
is to recover their tracking pads with a soft, long nap leather, like
heavy cabretta.  The long nap "cones" inside the pallet's nipple, and
as it is withdrawn, it gives that side more and more air, instead of
being either just on or off.  What this does for you is to make a
perfect tracking system for narrow and wide paper.  Instead of a
tracking system that just doesn't know what to do on wide rolls and
which lets narrow rolls bump in between two closed tracking fingers,
you will now be able to set your fingers on narrower paper (to a
degree) and still track normal and wide rolls.  This if course depends
on the leverages afforded by the manufacturer, too.  It doesn't work on
some systems as well as others.

Craig Brougher

(Message sent Mon 29 Jul 2002, 15:10:40 GMT, from time zone GMT-0700.)

Key Words in Subject:  2, Adjusting, Finger, Pneumatic, System, Tracker

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