Page 71 - Build Your Own Combat Robot

Build Your Own Combat Robot
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You must also remember that the floor in a combat robot arena is not exactly
like Grandma’s living room floor. It includes some of the most destructive and de-
vious hazards the contest producers can conjure up in their sadistic minds.
Metal-cutting saw blades, spikes, hammers and even water can all come together
to ruin your robot’s day. You shouldn’t waste time worrying that another ma-
chine or the hazards operator will attack your pride and joy in a contest. It will
happen. Prepare for the worst. Have a wheel configuration and tire construction
that will survive far more abuse than you can deliver in your garage tests, as you
will be shocked at what a full-blown match can do to your machine.
You might be looking at a set of 20-inch bicycle tires for possible use in your ro-
bot, thinking, “If a 150-pound bike rider can jump over curbs and logs for days on
end, tires like these should survive a 3-minute robot battle.” If you watch a few ro-
bot combats, though, you’ll see that wheel failure is not caused by downward
force or even force from the front of the machine. What kills wheels is force from
the side, hitting one side of the wheel, and bending or breaking the shaft or hub. A
killer robot will “taco” a bike tire in seconds, or shred its spokes. Leave bike tires
for benign robot designs.
Another favorite wheel of the beginning robot builder is the kind found on
lawnmowers and other garden tools. Their ability to bounce over rough ground
may seem to make them good potential robot wheels, but the same applies here as
in bike tires. They cannot take side-bending forces. Most of the newer types use
cheap plastic rims instead of metal. You find wheels and tires from so many
sources—such as toys, disability equipment, hand-held golf carts, and barbe-
cues—that we will not further elaborate. Consider the original intended use of the
equipment and the expected loads the design team might have considered. Many
companies have cut quality in areas to compete in the market pricewise. Look at
all parts of the wheels you intend to use. Be cautious and use good sense here.
One of the best sources of tires and wheels for combat robots is from industrial
applications. The hard rubber tires used in industrial parts carts made to handle
thousands of pounds are among the best. Aerospace surplus yards generally have
several varieties of these wheels, both mounted and unmounted. These wheels
have stout rims and extremely tough tires. Some are non-rotating types and others
are mounted in swivel assemblies as large casters. Most of these industrial wheels
do not have any sort of tread, as they are used in passive applications that do not
require traction.
Figure 3-7 shows a heavy-duty drive wheel.
One of the most popular wheel types used in combat robots are go-kart
wheels, which come in a wide variety of rim and wheel types and shapes. They
are readily available and easy to mount to a robot. Many top competitive ro-
bots use go-kart wheels.