The roll frame I was asking about [140419 MMDigest] has no clutches.
The play motor armature disengages from the gear box by a spring and
the loss of magnetic field.  The speed control is a rheostat and diode
circuit that slows the 120 volt play motor by DC braking action.  The
rewind motor is also directly connected and free wheels during play.
Side plates are unfinished aluminum with steel spacer rods.

The "finger" falls into a slot in the take-up spool and activates
a pallet valve that trips a lock and cancel valve unit.  Player Piano
Company used to sell these by special order back in the 80's and 90's,
but I never did learn who the manufacturer was while I was working
there.

Gordon Ramsey - Ramsey Music Service
Wichita, Kansas
ramseymusic@toast.net.geentroep [delete ".geentroep" to reply]

 [ Photo of mystery roll frame
 [ http://www.mmdigest.com/Attachments/14/04/21/140421_211843_Unkroll%20frame.jpg