The large wheel(A) was
called a friction disc. Its rotational speed was controlled by
the power source. The smaller wheel(B) at the end of the rod was
called a friction pulley.
It rubbed on the friction disc and could be moved from or toward
the center of the disc. As it was
moved outward its speed would increase or if moved inward the
speed would decrease. The ideal setting was about 230 rpm.