Page 346 - Robot Builder's Bonanza

BUILDING TANK- STYLE ROBOTS 315

Tread Assembly
Assemble the treads from the Track and Wheel Set using the following lengths for each side:
• 1 each 30- links segment
• 2 each 10- links segments
• 1 each 8- links segment

The segments interlock into one another. Use only your fingers; avoid using mechanical
force or tools to link the segments together, or else the rubber may get torn. It can take a few
tries to get the hang of it. Refer to the instructions that come with the set for details.
To install the tread, loop over the four idler wheels. Wrap the tread around the teeth of the
drive sprocket, and carefully push the sprocket onto the motor shaft. Note: Do not overstretch
the tread or it may become unlinked.
The design of the All- purpose Tracked Robot Base allows for adjusting the tension of the
track— important, because if the treads are too loose, they’ll pop off easily. Remove the
motors, and drill new holes about 3/16″ away from the original set. Remount the motors.

G You can create a slot for adjusting the track tension by drilling several holes close together in
line. Use a thin rat- tail file to remove the material between the holes, thus making a slot.

Replacement FA- 130 Motors
The miniature Mabuchi FA- 130 motor included with the 3- Speed Crank- Axle Gearbox kit is
not very efficient, consuming several amps when the motor is stalled (prevented from turning,
but still powered). If you use electronic control to operate the motors, be sure it is rated for at
least 2 amps, if not more.
Optionally, you can substitute the FA- 130 for a higher- voltage, lower- current version.
Pololu and several other online resources offer 130- size replacements that consume much less
current and can be used with small motor bridge circuits. Consult Appendix B, “Internet Parts
Sources,” for Web links.
Optional: Using Servo Motors
If you prefer, you may use an R/C servo to drive the tracked base. Mount the motor to the
robot base using your favorite technique (see Chapter 24 for some suitable mounts you can
make yourself). Then, interface the sprocket to the motor with these steps:

1. Cut off the molded- in cap on the side of the drive sprocket.
2. Drill out the center using a 1/4″ bit.
3. Drill out two holes in a small round servo disc to match two of the holes in the drive
sprocket. It turns out the holes match exactly when using the small round servo disc
that comes with most Futaba and Futaba- style servos.
4. As shown in Figure 26- 22, attach the servo disc to the sprocket using a pair of 4- 40
3/8″ machine screws and nuts.
5. Use the screw included with the servo to mount the drive sprocket to the motor.

Adding a Second Deck
Need more space? You can add a second deck to the tracked base by removing the nuts on
the top of the corner angle brackets and replacing them with 4- 40 threaded hex standoffs.

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