If memory serves, the Ampico-B take-up spool OD and flanges are
substantially larger than on most other player pianos.  This was done
to permit playing those long (15 minute) rolls.

The large OD has another desirable benefit:  It serves to reduce the
*change* in torque required from the spool motor from beginning to
end of the long rolls.  Since that torque must be transmitted
through the turns of paper already on the take-up spool, the large OD
reduces the likelyhood of paper slip.

With proper adjustment of the feed-spool brake (*reducing* hold-back
torque as the roll is fed to maintain a constant web tension -- as
succinctly described by John Grant), the Ampico-B should be capable
of nearly flawless feeding of even large rolls.

-- John Rhodes

John D. Rhodes - AA7HL  Vancouver, WA  [jrhodes@teleport.com]¶
"The theory comes easier if you know the right answer."