Lester Wolf inquires about paper slipping on new jumbo rolls on his
Ampico B mechanism (MMD 16.03.16).  He correctly deduces that the
problem results from the newer paper not having as much "grab" as the
older papers.  He's also on the right track in trying to tighten the
music roll 'play' brake band.  This adjustment should be so there is
as little "lost motion" as possible, i.e., the braking action should
begin as soon as the braking pneumatic starts to collapse.

Less obvious in the analysis is the condition of the cloth on the
pneumatic.  This _must_ be _absolutely_ air-tight as possible, with
no corner leakage, etc., so make sure it is recovered with the best
available cloth of the proper weight.  Any leakage in this cloth
reduces the braking force that it can develop and exacerbates paper
slipping.

I erred in the referenced message (15.05.02.06) when I said, in the
third paragraph, that there was only one reference to the "adjustable
friction clutch" on the music roll drive [supply] spindle" in the 1929
Service Manual.  There is a second reference on page 52, paragraph #7,
but note that there is still no adjustment procedure given for this
clutch.

I should also note, in regard to leakage through the cloth covering the
play brake pneumatic, that if that leakage exceeds the amount of vacuum
that is passed through the #55 constriction in its supply tube (call-out
#9 on the Control Valve Block, Fig. 27, p.[50], then the braking power
of the pneumatic will be nil, even when the Music Roll Brake Control
'needle valve' is completely closed at the beginning of play.

Failure to "restart" after one of the periodic "snubbing" brake events
during rewind is a different problem.  For this you need to tighten the
axial clutch that is on the supply spool shaft, outboard of the music
roll play brake drum.  This is the component curiously omitted from the
1929 Service Manual.  See the drawing at the link below.

John Grant

 [ Ampico B Fig. 25 Redrawn - Torque Adjustment
 [ http://www.mmdigest.com/Attachments/16/03/20/160320_001035_AmpicoB_Fig25_Redrawn.jpg