Page 341 - Robot Builder's Bonanza

310 BUILD ROBOTS WITH WHEELS AND TRACKS

• Rubber treads are perhaps the most common, found (for example) on many tank and
earthmover toys. You can rob the toy of its treads and other parts and use them on your
robots.
• Plastic treads are made of rigid segments, linked together using pins or rivets. Several
companies (Lynxmotion, Vex, JohnnyRobot) make plastic tracks for the express use as
robot treads.
• Metal treads are found on high- end die- cast toys, as well as snowmobiles. These are heavy
and expensive and are ideally suited for larger bots.

Regardless of the material, the treads work in the same way: a drive sprocket positively
engages with matching teeth or indentations in the tread. The tread is laid out along more or
less the full length of the robot. Nonpowered idler sprockets or untoothed wheels keep the
tread in place.

G Each kind of track has its own unique method of engaging with its drive sprocket. Whenever
possible, always purchase (or rob from a toy) a track with its corresponding sprockets and
idlers.

BOTS WITH FLEXIBLE RUBBER TREADS

As noted, one of the best sources for inexpensive rubber tracks is toy tanks. These are sold in
different scales, from about 1:64 (miniature) to upward of 1:10 or even 1:6. (The scale is the
ratio of the size of the model to its original. A scale of 1:24, for example, means the model is
1/24 the size of the original. Most toy tanks are in the range of 1:24 to 1:32 scale.)
The robot in Figure 26- 14 was constructed using rubber treads from a 1/10 (approxi-
mately) scale tank toy. The full circumference of the treads is about 26″, large enough to allow
the unusual arrangement you see in the picture. The outside of the treads extends beyond the
body of the robot, allowing it to flip over and still keep going. The robot can start to climb up
a wall, and when it flips over, the motors immediately change direction. The robot doesn’t
have to stop, back up, and steer around the wall.
Look for a toy where the track is not too elastic and where, at a minimum, the drive
sprocket and idler rollers can be removed and placed on your own custom base. Some toy

Figure 26- 14 An invertible tank- type
robot, capable of operating right side up
or upside down. The treads and idler
wheels were pulled from a remote control
tank toy.

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