Page 136 - Robot Builder's Bonanza

ALTERING THE PLASTOBOT DESIGN 105

(on/off and direction) or use electronic control. These topics are covered in Chapter 22,
“Using DC Motors.”
These motors draw low current for the torque (turning power) they provide, allowing you
to use most any kind of electronic control. When free- running (no load), the motors consume
only 40 milliamps; at stall (the motors are physically prevented from turning), current rises to
a still- respectable 360 milliamps. The low current demand of the motors lets you pick from a
wide variety of motor drive circuits.

See Chapter 21, “Choosing the Right Motor,” for more on motor torque, milliamps, current
FYI measurements, voltage, and other motorific specifications.

If you’ve built the centerline wheels version of the PlastoBot, be mindful of maintaining a
weight balance that slightly favors the end with the ball caster. This prevents the robot from
tipping over on the end without the caster.

Altering the PlastoBot Design

Feel free to experiment with the design of the PlastoBot base. For example, by increasing the
chamfer, you can make an octagonal base. Just cut off more of each corner.
You can also fashion your own motor mounts using standard fasteners and strips of flexible
plastic. Figure 10-9 shows an octagonal PlastoBot base with holes for mounting motors up to
about 1″ wide. The idea for the mounts is shown in Figure 10-10: drill two holes just wider
than the width of the motor. Using machine screws and nuts, attach a strip of flexible plastic
to the top. Tighten the screw against the bottom nut to hold the motor in place.
Candidate plastic includes pieces stolen from construction toys, clamps for cable and wire
management, and household odds and ends. The basic requirement (besides being the right

All holes 1/8"
unless otherwise
specified

1"
1" (approx.)

1" (approx.) 1" (approx.)
1/4"
(in center)

Figure 10-9 One of many
alternative base designs for a robot
1"
made of plastic. A hexagonal base
2" may be constructed by cutting off the
6 four corners of a square.

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