keep the wheels from falling off (Figure D).
With the chassis still upside down, run the
tracks around the wheel pairs. Push the axle
forward (away from the motors) as you hot-glue it to the bottom of the chassis (Figure E).
Try to get the tracks tight. The chassis will be
tilted forward — that’s fine (Figure F).
Mount the battery holder to the rear end of
the chassis like a rear bumper, using a line of
hot glue (Figure G).
Test the sampler board with AA batteries
to make sure it works (record your voice
and play it back). Cut and strip one end of 2
female jumpers, then unsolder the sampler’s
mini speaker and replace its 2 original wires
with the jumpers (Figure H). Hot-glue the
speaker under the chassis at the axle and
run the jumpers topside (Figure I).
2. Add the head and neck.
Solder 4 insulated wires, each about 4" (10cm)
long, to the back of the SRF05 rangefinder,
to all but the fourth pad along the bottom
(Figure J). These are the board’s 5V, Echo
Output, Trigger Input, and Ground contacts.
Epoxy the SRF05 “head” to a GM10 motor,
perpendicular across the shaft and pointing
away from the small pin sticking up, so the
rangefinder can turn from side to side. During
curing, I held the board and motor in place
with putty and foam tape (Figure K), but you
can improvise another way.
Mount the “neck” motor at the front center
of the chassis so that the head stands vertical
(or leans only slightly forward; not as much
as the chassis) and the rangefinder “eyes”
sit back 5" or so (2mm) from the front edge.
I used a bit of wood just under ½" (10mm)
to prop the front of the motor to let it sit level,
then added liberal amounts of hot glue to
secure it to the chassis (Figure L). Try to give
the mount a small footprint.
Turn the head from side to side. It should
look straight ahead when not touched, and
if it moves much more to one side than the
other, glue fiberglass rods or wooden stops
vertically so that it turns about equally far to
the left and right (Figure M, following page).
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