Futaba comparison chart
Use these to help you decide on which model fits your
particular needs. My primary servo for light duty is the Hitec
HS-425BB, and it’s the one I use in many of my talking and
moving skull projects. For the price, it’s hard to beat and a
good place to start. If it’s not up to the task, then I’ll start
moving to a model with more torque.
If you’re not familiar with that term, it’s simply the
amount of power a servo will impart with a one inch arm
and is measured in ounce/inches. No need to be overly
concerned with it at this point; just use it in your
comparisons. When you are comparing servos, take note of
the speed which is given in seconds. The lower the number,
the faster the servo operates.
You have a wide range of choices when selecting the
proper motor. AC motors require no special electrical
knowledge to use. Just plug them in. Even though I
occasionally reach for one, I primarily use DC motors; most
often 12V models. There’s a multitude of kinds available
with different speeds and strengths. The many different
motors used in cars can be especially useful. Take, for
example, wiper motors. They can be workhorses for many
of the larger props. They have high torque; a low and high
speed, depending on how you wire them; and most will
allow you to reduce the voltage to get even slower speeds.
When I purchase a wiper motor, I always pick up one
of the wiring harnesses as well. It comes with the
appropriately sized connectors, and makes for a quick and
clean connection to your power source. When shopping for
the power supply, get one with sufficient amps. It’s
suggested that you use one with at least five amps to avoid
underpowering the motor.
I’ve also found many smaller motors from surplus
houses that fit the need when working with smaller
armatures. Please read the spec sheets carefully — especially
when looking for a motor that will operate continuously
and will do so without overheating. Many motors are not
designed for continuous use and require downtime
When it comes to building something that requires lots
of power and/or fast activations, it’s time to reach for the
air. The flexibility of using air will solve many of the
problems that can come up. You can purchase pneumatic
cylinders in a wide range of lengths, as well as bore. If you
need more power, you can increase the size of the bore of
the cylinder or boost the air pressure.
The use of flow controls on your cylinders also allows
some adjustment, and lets your cylinders respond at one
SERVO 07.2015 47
Figure 6. A 110V Christmas reindeer motor which moves an
arm forward and back.
Figure 7. Mechanism that uses a single vent motor to
move a head side to side, as well as up and down.