As a preface I would like to say that I don't believe in irreversable
modifications to any worthy instrument.

John Tuttle says he had never met a plactic that he liked.  I have met
several. Teflon, nylon, ABS, celluloid, bakelite and several other
plastics have excellent properties and have stood the test of time.
Even urethane poly vinyl chloride and poly ethylene have their uses.
The problems arise when the plastic is misapplied or inadequately
tested.  I use teflon on Duo-Art spill valve arms and find that it
works better than buckskin and lasts forever. If I had a worn shaft
bearing I would consider a teflon bushing as oppesed to the original
brass.

John McClelland asks about cheap electric drives.  I have a cheap
solution, but I would not use it on any machine with restorable
original parts.  I made mine for a vorsetser I was building.  There are
very high quality DC motors available surplus that were used as reel
and capstan motors on high speed tape transport decks.  They were
originally run at fairly high speed, but with reduced voltage will run
very quietly with sufficient torque for a spool motor. I used a square
cross section rubber belt to provide greater speed reduction than can
be had with ladder chains.  This retains more of the motor torque since
the torque declines with applied voltage. A 3 amp variable voltage
regulator with a suitable adjustment potentiometer controls the speed
accurately enough since the motor is so oversized compared to the
load.  I can simulate extreme load variations and the speed barely
changes.  Some of these motors have a built in tachometer which can be
hooked up to a meter or digital panel meter to provide a tempo
indication. I used a DPM with an adjustable voltage divider to get a
direct indication of tempo.  It agrees with my tachometer completely.
The whole mess cost about $40.00 including the tempo indicator.  If you
are not a resourcefull scrounger, the parts might cost as much as $100,
but certainly no more.