Most servos will also specify
output torque, usually at either 4. 8
volts (standard for model airplanes),
or both 4. 8 and 6 volts. The higher
the torque, the more powerful the
motor. Some manufacturers specify
torque in ounce-inches (oz-in) while
others use the metric measurement;
typically gram force centimeter or
Newton centimeter. You can use one
of the many free online conversion
calculators (do a search on Google to
find them; one is convert-me.com)
so you can compare apples to apples
— or in this case, ounces to ounces.
For whatever reasons, few
manufacturers specify current
consumption of their wares. If you’re
interested in these specifications,
you’re best off making them yourself.
The servo will have a different current
consumption depending on whether
it’s idling (holding still without a load),
under load, or in transit. All servos will
consume the most current when their
output shaft is held stationary, and
the motor is commanded to move to
the opposite extreme.
Pololu’s servo inventory includes a variety of GWS brand servos.
Wing servos, including the powerful
(but slow) BP148T, rated at 100 oz-in.
Modified servos include the S35,
which comes from the factory ready
for continuous rotation.
Sources
Servo Manufacturers
Budget Robotics
www.budgetrobotics.com
Small selection of GWS brand
servos, both standard and modified.
Central Hobbies
www.centralhobbies.com
Carries JR, Hitec, and Futaba
Check here for datasheets and
specifications of popular servo brands.
For the most part, these companies
do not sell directly to the public.
The Jameco Robot Store offers a selection of standard and specialty servos.
Airtronics
www.airtronics.net
Futaba
www.futaba-rc.com
GWS
www.gws.com.tw
Hitec USA
www.hitecrcd.com
Online Servo Retailers
These listings include online sources
for servos. Many also sell mounts,
wheels, and other servo accessories
useful in assembling complete robots.
Balsa Products
www.balsapr.com
Reseller of the low-cost Grand
SERVO 06.2008 65
