Build Your Own Combat Robot

FIGURE 6-4
Clamping method
to produce a secure
motor mount.
Thermal Considerations for the Motor
Chapter 6: Power Transmission: Getting Power to Your Wheels 113
One of the drawbacks of using a higher-than-recommended voltage on a DC motor
is the possibility of overheating. Even though combat matches generally last only a
few minutes, intense heat built up in a motor can destroy it. This is not a power
transmission issue, but it certainly is a mounting consideration. Some motors use a
fan at one end to draw in air for cooling, but the intermittent action of the motor
may mean that the motor is cooking in its built-up heat while it is off. You must
also remember that the windings that heat up are in the armature, which is the rotating
component that is isolated from the case, so heat sinks are not as effective as
one might think. If the armature heats up too much, it can begin to disintegrate,
slinging wire pieces all over the inside of the motor. If that happens, you’re in for a
bad day.
How can you keep these motors cool? If you’ve run the motor on your bench
while under load and you’ve noticed that the case gets extremely hot, you may
want to mount it in a machined aluminum block to absorb and conduct the excess
heat away from the motor. Some competitors have also used a small blower to
force air through the motor to augment the fan. Have the fan run even when the
motor is off to continue the cooling process as much as possible.