want to have some variety, but there is no need to stock
every voltage available. I find that I primarily use 5V, 6V,
7.4V, 9V, and 12V. Even as I try to keep my needs under
control, I still have plenty to choose from!
Being able to quickly alter the performance of a motor
by easily changing out the voltage is a handy tool. Having
spare power supplies on hand ensures that a prop will not
be put out of action due to a bad power supply.
If your design requires a motor to operate continuously
or even for extended periods, be sure it is rated for
continuous operation. Many motors have a duty cycle and
are designed to operate up to a specific time before they
must be turned off to rest and recover. Now that I think
about it, this is how I work also!
You want to be sure that the wiring harnesses are built
to withstand the electrical and mechanical stress you will be
subjecting them to. Some of the models available tend to
skimp in this department with extremely thin wire and
flimsy connectors. Buying your motors from reputable and
trusted dealers can minimize this problem.
Check the connectors that come stock on the motor to
ease the task of incorporating your motor into your project.
A little time spent searching for a motor that does not
require modifications to work in your design is time well
Many of the motors you will find listed on the surplus
sites have a high RPM. This does not mean that we cannot
use them, but they will usually require you to gear them
down to get them to perform at a speed that we can
utilize. I have been known to buy several different
models in order to choose the best one to fit my
Verify the electrical requirements of your motor
choice before purchasing it to ensure that it fits
within your build specifications. You need to confirm
that it is not only the correct voltage but that your
choice of power source can supply the necessary
amps to properly operate the motor.
This becomes an even more important
consideration when using batteries to power your
projects. You never want a character to shut down
due to a drained battery, so choose carefully.
Take into consideration the ease of attaching a
linkage to the motor shaft. Many designs have a threaded
hole through the shaft that can provide an easy mounting
option once you determine the size you need. With others,
you may need to spend some extra time figuring out a
We usually work very hard to mount our motors in
precisely the right spot to allow them to be balanced and
operate as efficiently as possible. However, there are times
when it is advantageous to mount your linkage off-center
to provide a more erratic motion. If you go this route, you
want to have an especially solid connection between your
motor and the linkage.
Some good examples of different mechanisms can be
found on the Robives site (see Resources).
Motor Mounting Options
Another important consideration when choosing a
suitable motor is the ease of mounting. Many models
include conveniently placed holes where your motor can be
securely attached. With others, you may need to get
creative as you devise a method to include it.
If your chosen motor does need some additional
fortification, consider the use of metal or plastic plumber’s
tape, hose clamps, or DIY aluminum straps shaped from flat
stock (Figure 1). I tend to avoid more permanent options
such as welding or using ProPoxy to affix my motors in the
event that I ever need to replace a malfunctioning unit.
We are not going to delve into the many controller
options available as that has been covered in another article
in this column (refer to the August 2016 issue of SERVO
Magazine). However, I will mention a couple of inexpensive
and easy to use methods of providing some basic control of
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SERVO 04.2017 15
Figure 1. Strap those motors down!