This shows both motor mount locations.
The lower motor is attached to the
swinging inner frame. In fact, the base of the swinging unit is built
just to have a place to attach the motor.
The arrow is pointing to another swing point. The 1/2"
PVC which has the skull attached at the top is placed thru a 3/4" 4 way
tee. It remains loose allowing the motor to turn the 1/2" PVC for the
left/right head movement.
The 4 way Tee has 3/4" to 1/2" bushings on the two
sides to hold it tightly in the structure which the 1/2" PVC slips in
from top to bottom.
There is an identical 4 way tee at the top, just below
the skull.