In response to Doug Wiggins question [191112 MMDigest], the stopwork
is there to keep the spring in its optimum torque range.  Disc boxes
do stall on chords when they loose power.  The torque curve of
a clockwork motor suddenly its free fall at the end of the optimum
range -- nothing gradual about it with a hearty spring.

However, if we still get the problem with a few winds on the coils,
then we need to consider the springs lubricant.  From new, a spring
will soon settle into it's own comfort zone; in areas of the windings
that the have the most internal movement they will, over time, force
themselves dry of lubricant and increase frictional resistance, thus
making it difficult to push the disc through the chord.

There are one or two ways of overcoming this.  The spring can be
removed, examined and the windings carefully cleaned of what's left
of the original grease, polished, lubricated and reassembled -- time
consuming, at best.

The easy way: 20+ years ago I had this problem with a large Polyphon.
As a motorcyclist I was aware of an aerosol chain lube on the market.
It had great reviews as the compound is delivered in a very thin
penetrating fluid designed to get into the rollers and links.
Subsequent rapid evaporation leaves an effective, anti-fling deposit
of light grease, exactly as it states on the can.  The Polyphon motor
was slowly wound and, as each winding loosened slightly, a little
application was delivered.  After five minutes work, job done and the
machine is still performing as smooth as you would like.  Happy days!

I've heard it said that air supply is a precious commodity in pneumatic
instruments.  A certain compliance and lack of frictional resistance is
equally precious in a clockwork motor to ensure trouble-free running.
To state the obvious, this resistance needs checking through the entire
drive train.  A 'dry' gantry or one slightly distorted star wheel can
cause the same issues.

Mark Singleton
Lancashire, UK