Page 340 - Robot Builder's Bonanza

BUILDING TANK- STYLE ROBOTS 309

Figure 26- 13 Tank- style robots use rubber,
Figure 26- 12 Gears used to transfer power from a plastic, or metal treads, along with a drive motor
central motor to a pair of wheels. The gears must be and a series of unpowered idler wheels that keep
carefully positioned or else the teeth may not mesh the treads in place. Low- cost toys are a common
properly. source of useful rubber treads.

G You must be very careful to align the gears with the proper spacing, or else they won’t mesh
properly. The mechanism will bind if the gears are too close together, or slip and chatter if
they’re too far apart.

For small robots (let’s say, under about 8″ to 10″), Tamiya makes several products that can
be used to create belt- or chain- drive 4WD bases. First is the Tamiya Ladder- Chain Sprocket
set (#70142), which consists of plastic molded sprockets and individual links of chain that you
connect together. Add or remove links to make the chain the exact length you wish. Because
of the parts assortment you get, you will need two complete sets for one robot base.
Another method is the Tamiya Track and Wheel Set (#70100), which comes with molded
plastic sprockets and rubber 1″-wide tracks. This set is normally used to make a tracked
vehicle (see later in this chapter), but it also works well as a belt- drive system for a 4WD
vehicle.

Building Tank- Style Robots

Another popular form of the rolling robot is the tank tread design, so called because it uses
treads (or tracks) similar to those on military tanks. Like 4WD robots, tank tread bots don’t
need a balancing caster or skid. They use differential steering like 2WD and 4WD bases and
are expressly designed for use over uneven terrain. Figure 26- 13 shows a representative
homebrew tracked- drive robot, made with a rubber tread stolen from a 1/8- scale tank toy and
refitted over a plastic base.

FINDING THE RIGHT TANK TREADS

The first order of business is to locate a suitable tread or track for the tank- style robot. Com-
mon tread materials are rubber, plastic, and metal.

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