PARTS IS PARTS:
Susie’s Saga Continues –
The Beginner’s Guide
to Mot rs
● by Morgan Berry
In the last issue of SERVO, we introduced you to Susie — a young
girl trying to begin a career in
combat robotics. We’ve had quite a
few inquiries into the fate of this
young robotics heroine, and we are
happy to report that the information
Susie learned about gears was the
first stepping stone on her path to
combat robotic greatness. In other
words, Susie has been kicking some
serious robot butt since she
completed her first robot: The
Destroyer! But now, after a year of
victory upon victory in the local
competitions, Susie has her eyes set
on a big, national level youth
robotics contest two weeks away,
and she realized her little Destroyer
isn’t going to cut it for the fierce
competition she will face.
She decides to rebuild Destroyer,
but due to time constraints she can’t
possibly change everything she
would like. What should Susie focus
on to give her bot the extra edge
against all those other robotics
prodigies? After examining her bot
closely, her answer is obvious.
The motor she bought from her
local hobby shop bargain bin is just
downright puny. She’s geared the
motor to increase her torque as
much as she can, but it’s not
enough. All the best driving skills in
the world can’t make up for a weak
motor. Susie immediately sits down
at the computer and begins
researching motors.
One of the older competitors in
Susie’s league, Bobby, learns of his
friend’s plan to upgrade her motor
and tells her about a great tool that
helped him out the last time he
bought a motor. The Robot
Marketplace — one of the many
online stores for robot lovers — has a
search engine to help determine
what kind of motor a bot needs.
This seems like an obvious place for
Susie to start, so she logs on and
scrolls through the questions: “Does
your motor need to be brushed or
brushless?” “What nominal motor
voltage do you require?” “What is
the maximum current the motor
should draw?” Susie’s eyes widen;
she doesn’t even begin to know
how to answer the questions. So —
like any good scientist — Susie starts
at the beginning.
The first question on the list is
brushed or brushless. Susie does
some research and learns that DC
motors typically have an electrical
switch called a commutator which
changes the direction of the current
in the motor in order to create the
rotating force, or torque. In a
brushed motor, a metal brush is
used to contact the surface of the
commutator and create a current. A
brushless motor replaces this metal
brush with an electrical system,
making it more efficient and less
susceptible to wear than a brushed
motor.
38 SERVO 10.2011
