Page 198 - Robot Builder's Bonanza

MAKING ROBOTS FROM CONVERTED TOY VEHICLES 167

but since you have two vehicles (see Figure 16-5), you still gain independent control of both
wheel sides.
The drives in the picture were taken from a pair of Tamiya Monster Beetle Jr. toys (catalog
# 17001); the same 4WD drive is used in a number of Tamiya toy products that differ only in
the car body used on top— examples include the Juggernaut Jr. (catalog # 17014), and the
Toyota Hi- Lux Monster Racer (catalog # 17009). The removed wheels are replaced with 1/8″
Dura collars; this prevents the axles from coming loose in the chassis. The collars are locked
in place with a miniature set screw. The set screw comes with the collars.
Whatever vehicles you use, be sure they are the same exact type. Variations in design
(motor, wheel, and so on) will cause your robot to “crab” to one side as it attempts to travel a
straight line. The reason: The motor in one vehicle will undoubtedly run a little slower or faster
than the other, and the difference in speed will cause your robot to veer off course.

USING PARTS FROM VEHICLES

It’s called repurposing. Toys can be a terrific source of parts that would otherwise cost a lot
more if purchased as honest- to- goodness “robot accessories.” This is especially true of wheels
and tank treads.
Because of the economies of volume production, a $10 toy may contain four wheels that
would otherwise sell for $5 each— a savings of 50 percent. The same is true of rubber, plastic,
and even metal tank treads, which are hard to find in any case. A pair of rugged rubber treads
specifically for robotics could retail for between $30 and $50, yet a toy tank with the same
treads might sell for $19.95.
Figure 16-6 shows a motorized remote control tank outfitted with rubber treads, drive sprocket,
and “idler wheels” that keep the tread in place. It’s operated by two motors, one for each
tread— there’s even a third motor on this toy, used to swivel the cannon turret back and forth.
The majority of these toys are imported from China, where stock comes and goes, so you
never know what will be available, or for how long. That can be frustrating, but if you’re on
your toes, you can snatch a bargain when you least expect it.
I bought four of these tanks for experimenting, and within six months the source for them
was dry, the item replaced with some other toy vehicle (that unfortunately wasn’t as good— that’s

Figure 16-5 This 4WD robot base was
constructed from two motorized toy models.
The models used a single motor to power four
wheels. For each motor the wheels on opposite
sides were removed; a metal collar (fastened in
place with a set screw) prevents the axle from
coming out.

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