Many, if not most Duo-Art mechanisms I have come in contact with
rewind the roll at far too great a speed, and when combined with a
rewind brake that is too tight, the results are predictable and not
pretty, at least with vintage rolls.  Recut rolls may fare better,
but even they are not immune to damage.

Step #1 is to adjust the rewind brake to be extremely light or
disconnected altogether.  Step #2 is to reduce the amount of vacuum
channeled to the air motor during rewind.  With the Ampico "A", this
is an extremely easy task; all you have to do is close off the tube
that pilots the rewind valve inside the motor governor, at which point
the rewind speed is under direct control of the Tempo slider.  With
the Duo-Art, it's a little trickier because the rewind speed slider
is a mechanical linkage and modifying its geometry is less intuitive.

The attached photos show the underside of a Weber upright that is
about to leave my shop.  Grands can be similarly modified.  Photo #1
shows the unmodified linkage.  Photo #2 shows the linkage in the "Play"
position where the outer leather nut and felt washer are in their
original positions, but the inner nut and washer have been moved "down"
the shank about 1-1/2".

Since this is beyond the threaded portion of the shank, there is
nothing to keep the nut in this position, especially if it loosens up
with age, so I added a set screw collar at the appropriate position on
the shank.  Now when the rewind position is selected (photo #3), the
linkage "slides" along the shank for that 1-1/2" rather than moving it
and at the end of the stroke moves the rewind speed slider only about
1/4" rather than opening it fully.

This is enough to have a very controlled rewind speed, which can
still be increased via the Tempo control if needed or dared.  It also
guarantees the pump is "unloaded" to some degree, because you _don't
ever_ want to completely block a steamboat pump (which is what is in
this particular piano).  Also, _don't_ ask me why I know this fact!

John Grant

 [ Unmodified linkage
 [ http://www.mmdigest.com/Attachments/16/10/17/161017_123311_Duo-Art%20Linkage%20-%20Unmodified.jpg 
 [ Linkage in Play position
 [ http://www.mmdigest.com/Attachments/16/10/17/161017_123311_Duo-Art%20Linkage%20-%20Play.jpg 
 [ Linkage in Rewind position
 [ http://www.mmdigest.com/Attachments/16/10/17/161017_123311_Duo-Art%20Linkage%20-%20Rewind.jpg