On Friday, March 11, 2016 at 1:22:14 PM UTC-8, DaveC wrote:
Oh, smarter-than-I people,

http://imgur.com/WPEoOu1

The 2 belt-drive capstan flywheels in an auto-reverse cassette mechanism are
different sizes. (Motor drive pulley will be in the small loop end of the
belt in illustration above.)

How does that result in the same tape speed in both directions?

Confused...

Looks like my Nakamichi cassette deck. They used 2 different sdiameter
capstans / flywheels running at different RPMs BUT the same tape speed
closed loop drive (both pinch rollers always engaged). They said they did
that so that the capstans won't slowly go in and out of phase which causes
wow and flutter to go up and down. By running different RPMs they go in and
out of sync so quickly we don't notice it. As the belt stretches and
contracts around the flywheels, the lead capstan will alway run slightly
faster (tape speed wise) than the trailing capstan which keeps the tape
tension correct on an auto reverse machine regardless of the direction. My
deck is only single direction and the wow/flutter is nearly imperceptible.

Then I went digital so who cares about cassettes?

G²