On Mon, 14 Mar 2016 11:41:28 -0700 (PDT), "
wrote:

On Monday, March 14, 2016 at 12:28:26 PM UTC-4, legg wrote:

Question was re flywheel diameter differences. Motor pulley drives
both. Same belt on two different dia flywheels, yet obtains same
spindle rotation at their separate pinch rollers.

Identical belt speed should drive a smaller dia flywheel faster. Motor
speed does not account for this physical difference, as it is uniform
for both functions.

Supposition is that the difference in flywheel dia is related to belt
thickness, as one flywheel is inside, and other is outside the drive
belt loop.

Um... A flywheel is a momentum device attached to a system to provide smoothing. Many (very much most) DC motors are pulse driven. The flywheel removes these pulses. Tape speed is determined by the capstan motor pulley diameter. FULL STOP.

In these machines a single motor with a pulley on its shaft, drives
the outer rims of the two differently sized flywheels, through a
single belt.

I've measured the spindles at the pinch rollers and they are a
different diameter, as was suggested by DaveC, so belt thickness isn't
responsible for compensation of the flywheel sizes - the spindles are
scaled with the flywheel diameter.

Never occurred to me to wonder about this, before, or to check it out.
Happy just to keep them going.

RL