Page 70 - Build Your Own Combat Robot

Chapter 3:
Robot Locomotion
ward as the other bearing is forced upward. Bending moment forces on a robot’s 51
wheel in combat are sometimes so severe that a gearmotor’s gearcase can be shat-
tered, even if ball bearings are on both sides of the gearcase.
One unique configuration of wheel mounting can possibly save you if your ma-
chine is ever flipped onto its back. Several robots have used identical sets of wheels
on both the top and bottom, with mirror-image sets of top and bottom body
shells; this allows the robot to continue its mobility while “upside-down.” The
other, more popular, method is to add wheels of sufficient diameter to protrude
equally above the top surface, thus allowing continued mobility while “up-
side-down.” This system works well for the low-profile machines; but for larger
machines, it obviously gets a bit more complicated because huge monster
truck-style wheels might obstruct a robot’s mobility. For these types of bots, a
top-flipping actuator can be used to right the robot after a flip.

Selecting Wheels for Your Combat Robot
Wheels are one of the most important considerations in the design of your robot.
They are your robot’s contact with the rest of the real world—namely, the battle
area’s floor. They allow your robot to move, maneuver, and attack its opponent,
as well as retreat from an unfavorable position. Knowing this, your opponent will
do everything he can to remove your robot’s maneuvering ability, something you
should also do to his robot at every opportune moment. So the words “sturdy,”
“tough,”“puncture-proof,” and “reliable” should all come to mind when you select
wheels for your combat robot. And sometimes a wheel just looks too cool not to
be used on the robot—take a look at Figure 3-6.

FIGURE 3-6
A 14-inch diameter,
flat proof, treaded
wheel. (courtesy
of National Power
Chair, Inc.)