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MMD > Archives > June 2003 > 2003.06.13 > 09Prev  Next

Fix the Tracking System to Avoid Roll Tearing
By Pete Knobloch

Ed wrote:

> The tracking system is an important feature, however, I have seen
> quite a few pianos where the tracker is useless on rewind as the
> trackers source of suction is shut off when the piano is put into
> reroll.

Here is another 2 cents of wisdom.  The tracker system is definitely
and important part of the player.  I want to say that the tracker
should be disabled during rewind, just like it is designed.  When the
roll is rewinding at a fast speed, the tracker system can not keep up
with the rapid horizontal changes as they are feed from the bottom

The other problem is that the fingers are sensing the wrong thing.
Let's say that during play, the tracker senses that the paper is
wandering too far left.  To compensate, the top roll is pushed to the
right.   For the system to work during re-roll, just the opposite is
needed to work.  Since the problem is having the paper rub against the
outside flanges, we want the top roll to move with the paper movement.
If the paper wanders to the right during re-roll, we want the flange
to also move to the right, not to the left as it is currently doing
with the tracker.

If the tracker is enabled during re-roll (which is bad), then there
will be a time during re-roll that the paper is too far to one side
while the tracker system is also pushing the paper against the wrong
side.  This will force the paper into the flange with twice the amount
of force than if the tracker system was disabled.

The Pianola, Duo-Art, Themodist style players do have vacuum applied to
the tracker pneumatic during re-roll but it is disabled during re-roll
due to the vacuum removed from the cut-off pouch block.  With both
tracker bar hoses closed, the tracker pneumatic goes to the center of
its travel and doesn't move.

Most tracker systems either center the roll or position it closely to
where it was left when the lever was thrown into re-roll.  Some do it
with springs, some with cut-off valves, some with breaks or gears being
disabled during re-roll.  I don't know of a better way of doing it.

Pete Knobloch (Tempe Arizona, USA)

(Message sent Fri 13 Jun 2003, 17:20:54 GMT, from time zone GMT-0700.)

Key Words in Subject:  Avoid, Fix, Roll, System, Tearing, Tracking

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