Dain-Owens wrote: I don't know what a Reeves drive is (clip)I hadn't heard
the term "treadmill" used for an external lathe motor.
^^^^^^^^^^^^
A Reeves drive is a belt drive with a means of changing the pulley
diameters, thus providing a continuously variable ratio.

Treadmill, in this context, does not have a special meaning. The reference
is to borrowing the variable speed drive from an exercise machine.