Page 95 - Build Your Own Combat Robot

Build Your Own Combat Robot
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I nternal Combustion Engines
Not all robots use electric motors to drive and power the weapons. Some robots
use internal combustion engines to perform this important task. These engines are
much smaller than those found in automobiles and are usually obtained from gas-
oline-powered lawnmowers, rototillers, or even weed whackers. The energy density
of gasoline is about 100 times greater than that of batteries, and this makes gasoline
an attractive source for powering large combat robots. Conversely, gasoline is also
the main factor in not selecting this method of power—it is flammable and dan-
gerous. Figure 4-9 shows a 119 cc air-cooled, two-cycle, gasoline-powered cut-off
saw by Partner Industrial Products. This saw, equipped with a 14-inch diameter saw
blade, was used as the primary weapon in Coolrobots super heavyweight cham-
pion Minion.
Because most combat robots use electric motors, this book will not go into de-
tails of how to use internal combustion engines in combat robots. By reading the
rules and regulations of the BattleBots competition, you will get a good under-
standing of what is allowed and not allowed with gasoline engines. The key ele-
ments for a gasoline-powered robot is to be able to control the engine if it is upside
down, making sure that the fuel does not leak and that fuel flow remains constant
in the rough jarring environment, and that you can throttle the speed up and down
as you need to. A lot of the gasoline safety and performance schematics will be
similar to those of high-powered gasoline-powered model aircraft. Good candi-
date gasoline engines for combat robots are chainsaw engines, because they have a
carburetor that can operate in all positions.
Since internal combustion engines operate in one direction only, a transmission
that has a reverse gear must be used if the gas-powered engines are used to drive

FIGURE 4-9
K1250 14-inch,
119 cc gasoline-
powered engine
prior to being used
as a weapon
system in Minion.
(courtesy of
Christian
Carlberg)