[ Back ]

 R/C Servo Information
Additional Servo Information

 Servo Torque
oz. - in
Servos have a certain amount of torque (strength) that is generally proportional to their size.
Servos come in all kinds of sizes, strengths and weight. Torque is the measurement of force given over a distance. For most servos in the USA, torque is measured in oz-in (force in ounces times inches, or ounce-inch). Servo Torque is measured by the amount of weight (in ounces) that a servo can hold at 1-inch out on the servo output arm in the horizontal plane, again at either 4.8 or 6.0 volts to see when the servo stalls as it tries to lift the weight horizontally. The reported result is a measurement something like this: Servo XYZ = 100 oz/in. @ 6.0 V. That means that Servo XYZ is capable of holding 100 ounces using a 1 inch output arm without excessive deflection at 6.0 input volts
To convert oz-in to kilogram-centimeters (kg-cm) just divide by 13.9.

 Servo Speed

Servo Speed is measured by the amount of time (in seconds) it takes a 1 inch servo arm to sweep left or right through a 60 degree arc at either 4.8 or 6.0 volts. A servo rated at 0.22 seconds/60 degrees takes 0.22 seconds to sweep through a 60 degree arc. Some of the fastest servos available move in the 0.06 to 0.09 second range. In some servos, faster speeds may lower torque available.

 How are Servos

The most common details available on a servo are its speed and torque rating.
Nearly all servo packages are listed with brand name, model name / number, speed, and torque output at 4.8 volts and 6.0 volts. Some information about metal, plastic gears or ball bearings may also be listed.

Ball Bearing
- vs -
Plastic Bushing

All servos have an output shaft that passes through the servo case, either through a plastic bushing or a metal ball bearing. Servos operate more accurately and smoothly when equipped with ball bearings on the output shaft. Ball-bearing servos also wear less and remain more accurate than bushing servos as the plastic bushings eventually wear out and cause slop between the output shaft and the case. It's best to purchase ball-bearing servos over bushing servos.

Metal Gear
- vs -
Plastic Gear

Servos have either an all-plastic, all or mostly metal gear trains. The basic difference is metal-gear drive trains are there much stronger and break-resistant than plastic-gear servos. Metal gears can, however, occasionally cause excessive servo gear grind noise and can wear over time. Plastic gear trains tend to strip teeth easily if the servo is moved or forced beyond its limits. There are some special high tech plastic gear available that have the advantage of metal in strength and lower noise then plastic "Karbonite material"

  4.5 to 6.0 Voltage

Servo operate at either 4.5 or 6.0 volts DC. At the higher voltage servos tend to be faster and sometimes stronger, but can heat up faster when stalled or in a hold position with stress forces against the servo output shaft. Some servo controllers require a separate power source from the control source to deliver the higher 6.0 Vdc. Servos operate from 4.8 Vdc to 6.5 Vdc. The current drain (Amps required) depends on the torque being put out by the servo motor, and can be in excess of one amp if the servo is stalled under load.
It is best to calculate 1 Amp per servo when figuring power supply needs for most servos.

of servos are available

Servo Functions

Standard Servo.
Linear Servo.
Low Profile Servo
Slim Wing Servo
Modified Continuous Rotation Servo.
Winch Servo.
Giant Scale Servo
Monster Servos / Heavy Duty.
Modified Gear Head Motor Servo.
High Speed Servo
Retract Servo
Digital Servo

of servos are available

Servo Types

Jumbo - Quarter Scale / Giant Scale
Monster Servo

of servos are Recommended

Servo Chart

Additional Servo Information




Go to Top of Page

[ Top of Page ]

Copyright © 2014 Blue Point Engineering, LLC , All Rights Reserved

Blue Line