Fig. A: Diagram of Beetlebot running free, not bumped
into anything; both motors draw current from the right
battery only. Fig. B: Heat-shrink tubing acts as tires,
giving traction to the motor shafts.
Fig. C: Switches and motor plate glued to the back
of the battery holder. Fig. D: Bent paper clip threaded
through a bead and glued to the rear end of the
battery holder to make a rolling caster.
1.5V motors ( 2) You can often scavenge these
from toys, dollar store fans, etc.
SPDT (single pole double throw) momentary
switches with metal tabs ( 2) You can scrounge
these from an old VCR or mouse, or buy new
ones for $1–$4 apiece.
Electrical wire around 22 gauge
AA batteries ( 2) You can also use AAAs.
AA battery holder
Spherical bead plastic or wood
Heat-shrink tubing to shrink to the widths of the
motor shafts and the antennae connectors
Black electrical tape
Terminal connectors, spade type, small ( 2)
1"× 3" piece of scrap metal plate I used aluminum.
Paper clips ( 4)
Cyanoacrylate (Super/Krazy) glue or epoxy
Soldering iron and solder
Toggle switch (optional) for on/off switch
FOR THE SHELL (OPTIONAL)
Round plastic lid I used a lid from a container of
hair gel, but you can also use a peanut butter
jar lid or anything similar.
Auto body filler putty or epoxy glue
Black and red enamel paint and primer
Small, thin magnets ( 2) to attach shell to body
5. Use cyanoacrylate glue or epoxy to glue the motor
plate down onto the back of the battery holder, just
behind the switches (Figure C). Orient the motors
so that the left motor spins counterclockwise as you
view it from below, and the right one spins clockwise.
For aesthetics, I then covered the plate with black
6. Unbend a paper clip, slip it through the bead,
and bend it symmetrically on either side to make
a caster (Figure D). Attach each end of the clip to
the corners of the battery holder at the back. I used
hot glue — not very professional. You could also try
bending the clip ends under and soldering them to
the battery connection tabs, but if you apply too
much heat to the tabs, you might melt the plastic
and ruin your battery holder. Beware!
Next we’ll wire up the circuit, but first, an explanation: the key is that the 2 batteries work separately.
Battery holders usually connect cells in series and
combine their voltages, but with the Beetlebot, a
wire soldered between the 2 puts them into separate
subcircuits. The motors draw from only 1 battery
at a time. Each switch’s common connection (C)
runs to a motor. The switches’ normally open (NO)
terminals connect together and run to the battery