Build Your Own Combat Robot

FIGURE 3-9
A typical wheel
configuration
arrangement where
an axle is
supported by two
pillow block
bearings. A
sprocket is located
between the pillow
blocks, and the
wheel is located to
one side of the
pillow blocks.
to axles protrude from the “box.” Fortunately for the combat robot designer, the
terrain that the robot is to traverse is usually a flat floor with little deviations from
level. A few bumps may result from joining floor surfaces, and some of the hazards
present an uneven surface area in small spots. However, for the most part, the
floor is flat in virtually all of the popular contests.
Such surfaces may not remain the case for future events, though, so a prospective
designer may want to take into consideration possible variations in floor flatness.
Some present-day contests, such as Robotica, have ramps for the competing robots
to traverse, so builders must plan for a sudden change of the operating plane.
The robot may be high-centered as it starts up a ramp or reaches the top, so flexible
wheel mounting (where wheels can adapt to severely differing floor angles) is a
must in these scenarios. Quite often, placing the driving wheels at the extreme
ends can allow a robot to start up a ramp, but this same arrangement might not
prevent high-centering as the robot reaches the top and teeters in that position. A
series of driven middle wheels would give the robot the final push out of such a situation,
but many of the machines rely on inertia built up from speed to “dive”
over such obstacles.
Mounting Axles Using Various Types of Bearings
Chapter 3: Robot Locomotion 55
Certain styles of bearings seem to be a bit more popular than other types for robot
use, especially in mounting axles for wheels. These are the pillow block and flange
mount bearings. Some catalogs refer to pillow block bearings as those with a base
mount, while other companies call pillow block bearings any configuration that
has holes in a flange or base to bolt onto a surface.