MJC wrote:


And I have long thought that with the small diameter of the capstan it
must be the availability of excellent, and cheap, bearings for the shaft
that made it possible to keep the wow and flutter down to acceptable
levels...


** The vast majority use plain bearings and rely on a flywheel to
do the rest.




Sure, but my point was that any chatter in the bearings is just as bad
as rotational variation and is not damped by the flywheel. So the plain
bearings have to be accurate and long-lasting.


** You have completely forgotten the damping effect of side-ways pressure from the pinch roller.



..... Phil