Tamiya kit includes a crank arm fitting (Figure 3) to which
we fixed the two strings which led to the hand on the fret
board and the hand that would appear to strum the guitar.
Even though the 3.5V cell phone charger provides just a
little more voltage than what the motor is rated at, we
didn’t have any trouble with heat or excessive wear in our
limited use. However, if you plan to run this little motor
system for an extended period of time, you might want to
play it safe and stick to the recommended 3V specified by
the manufacturer.
For the two dancing skeletons, we used a pair of
200 RPM 12V gearhead motors I purchased from Parallax
(Figure 4). These motors were used to drive the wheels in
the now retired Parallax Stingray robot (see the June 2014
SERVO Magazine for a review of the Manta Ray — the
Stingray robot’s replacement). These high quality motors
are actually a little high RPM for this application.
In order to slow them down a bit, we drove them with
a pair of repurposed wall wart style 7.5V power supplies
(see sidebar on power supplies). As these motors are
discontinued now and they were a little fast for this
application to begin with, I would suggest you look at
some lower RPM motor offerings by some surplus
electronics vendors (I’ve provided a listing of some
suitable candidates in the Resources section).
Unlike the Tamiya gear motor kit which came with a
pair of crank arms, the Parallax drive motors had a quarter
inch flatted shaft and were simply used to directly drive
September 2014 57
FIGURE12B. The
PVC pipe can also
be used to route
the wires to the
motor.
FIGURE 12A.
Hose clamp
around motor
body and PVC
pipe.
FIGURE13. The completed
TriodelosMuertos. FIGURE11. Patiodoor
wheel with
holes drilled
for string
anchoring.
