FIGURE 3. A puppet’s
eyes are easily motorized
for computer control.
FIGURE 2. The interior of the head is
cramped. The miniature servos shown
move the eyes and eyebrows. Notice
the magnets on each side.
much at once. Figure 1 shows the
altered head before painting.
The back of the head was cut
away to allow easy access to the
inside. Magnets were epoxied in
appropriate positions (on both pieces)
to hold the cut piece in place and still
allow easy removal for repairs.
Figure 2 shows the interior of the
head, which contains three miniature
servos: one for the mouth, one for the
eyes, and one for the eyebrows. The
details of how you mount your servos
depends on the features you want and
the space available in your puppet’s
head. It is also important to realize
that you can purchase servos in various
sizes with a wide variety of torque,
speed, and noise levels, so consider
your needs carefully.
external mockup to provide additional
detail. Eyes are easily made from wooden
balls that rotate on a bolt or rod. Stiff
wires protrude from the rear of each
eye and up through a plastic wafer
that ensures the eyes move together
based on the servo’s motion. It is
important to use a slot as shown instead
of a hole because the opposing rotational
motions can cause binding. The use of
the bell crank in Figure 2 allows the
motor to be mounted away from the
eyes. This can be very advantageous
when working in a confined space.
The puppet’s body is shown in
Figure 4 and is constructed primarily
from wood. Padding may be needed
to make the body look more natural
under the clothes. His full height is
28 inches. The legs are made from
PVC pipe. One leg of the pants is
pulled up to show the pipe.
Most of the bell
cranks, disconnects, and
other apparatus I use are
mechanisms designed for
model airplane construction and can be found in
many hobby stores. Your
local hardware store can
also be a great source for
small pulleys, lazy-susan
bearings, and such.
FIGURE 5. The
head is hinged to
tilt forward and
mounted on a lazy-suzan bearing to
handle rotation.
It is difficult to see
how the eye assembly is
constructed in Figure 2,
so Figure 3 shows an
Figure 5 shows how the head is
mounted on a hinge to allow a
forward tilt under control of the
neck-mounted servo. The lazy-susan
bearing gives the head the ability to
rotate. The neck is connected to a
servo mounted in the body using a
short piece of rubber hose. The
flexibility of the hose connection
prevents binding by allowing for
twisting and bending (much like
FIGURE 4. The
puppet’s body
is hinged to
allow side-to-side tilt. The
legs are made
from PVC
pipe.
SERVO 11.2008 37
