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At left is a conventional Hitec HS-55 micro servo. At the right are two Bob Selman Design magnetic actuators. One controls the rudder while the other controls the elevator. The actuators are small magnets that “float” inside an electrical coil. Proportional control of the flying surfaces are still achieved with these actuators. |
Q-18: I keep reading about "magnetic actuators" to operate control surfaces on a model aircraft and wonder how these devices differ from the common RC servo?
A-18: You will see references to "magnetic actuators" when we talk about micro RC indoor models. These aircraft typically range in weight from 1.5 ounces down to practically nothing (a few grams!).
The tiny actuators are made up of a coil and a magnet. Operating your RC transmitter's control sticks causes the arm on the actuator to displace, or move. Some magnetic actuators are mounted directly on the control surfaces. Recent improvements have produced actuators with regular output arms to which you can attach small control rods.
RC servos motor-driven devices that can be positioned in a precise manner. However, because they require a motor and a feedback potentiometer, the lightest servos weigh roughly 5-6 grams; a magnetic actuator can be as light as 1.5 to 2.0 grams! We are seeing much progress in smaller and lighter-weight RC servos. It wouldn’t surprise me to soon see servos as light as actuators. Of course, the servos have considerably more output torque than the magnetic actuators.