Hi all,  I don't think that the Duo-Art tracking device is causing this
problem as described earlier by D.L. Bullock.  The bellows settle in
rewind in the same position they would settle during play with both
ears closed.

If a roll with the paper knocked towards the slotted flange is place
into piano, the system must be adjusted such that both ears are closed
_and_ the roll holes must align with tracker bar holes.  The tracking
device will then run neutral exactly in the same way it will while
rewinding the roll.

If a roll is now played which does not track correctly, the ears will
open and close accordingly and the pneumatic will shift the roll into
the right place.  This will make it roll up straight on the take-up
spool and when the roll is rewound, it will reroll straight with the
pneumatic in its neutral position as above.

Disconnecting the pneumatic from vacuum, will allow it to stay in a
different position that the neutral position while it is under vacuum.
That is not good.

There are several reasons for shredded rolls:

1: The reroll brake is too tight.  In fact, the best one can do is
disconnect it.

2: The paper is brittle.  Some rolls are so brittle that they shred
when the paper just touches the flange.

3: The reroll is too fast for old brittle rolls.  Turning the piano off
and rewinding with the footpedals always helps (if it is a PEDA)

4: The tracking mechanism is not adjusted correctly and it does not run
neutral when a properly wound roll is played.  It will then shred the
roll on rewind because the pneumatic will return to neutral position.
It will only really shred the roll then if the paper is brittle and the
brake is tight.

5: The bushings in the roll mechanism are worm such that the tracker is
not parallel to the roll spool and/or take-up spool.  This will push the
paper to one side on reroll.

To set the system properly, slacken the ears and move them away.  With
tracking in neutral position (while rewinding or under vacuum, adjust
turnbuckle near pneumatic so that the cam on the right of the spoolframe
is about centered on the pin that moves the roll.

Now play some rolls with paper knocked to right side and adjust the
screw under the cam so that the rolls play well and not to any side of
the tracking holes.  Note how all this is done while the tracker
pneumatic still runs at neutral position.

When this all looks good, the tracker ears should be moved close to the
paper so that they remain closed while the paper runs aligned.

Note: the neutral position of the tracker pneumatic is only centered when
both halves are 100% airtight.  If not, it will be off slightly to one
side while under vacuum with tracker ears closed.

If this is set up correctly, then the rolls will always rewind in the
same or better position they played unless there is a defect in the
right roll flange thickness.  I have never seen this though.

All this said, some rolls do shred and there is nothing one can do to
prevent it except from turning the piano off quickly and rewinding by
hand.  I have seen this happen on properly adjusted pianos only when
the roll was so brittle that bits of the paper broke off as it
shredded.

Kind regards,
Bernt Damm