Canandaigua C.H.I.E.F.S. News

Smoke Signals From The Bench

Some reading I've been doing lately about the increased interest in 1/2A and smaller models using the rapidly improving electric flight applications kinda got me to think about a control method that was popular a long time ago. This control method was nicknamed "CAR" for a mechanically coupled control of aileron and rudder together using a single servo.

As we know most 4 channel systems now are streered primarily by use of the ailerons. The rudder for most of us is used to counter the engine thrust for control on takeoff, and to a lesser degree for control on final just before touch down. Well with the desire to reduce weight for electric flight and with mini and even micro servos having greater torque, "CAR" could be an excellent method to eliminate one servo.

Well you might think that may not be a good idea for some maneuvers such as the wingover into a spin. You would be right except if this is done correctly, where the plane must first be made to stall as this really is a stalled turn. In a stall remember the ailerons are ineffective so use of "CAR" should not be a problem. Keep in mind that due to the additional stress this application will put on a single servo it should be used for models that use no larger than a .19 gas engine or a 400 electric motor.

Now lets look at just how to setup a "CAR". There are a variety of methods which one to use really depends primarily on where the wing is mounted, high wing, shoulder wing, mid wing, or low wing, and whether you want to go to the extra effort to configure your servo so that it has a double ended output shaft.

With the one servo mounted in the fusealage just behind the wing in a shoulder wing plane. One end of the shaft goes to a torque rod to the rudder, the other end is short and has a crank attached in which the upright end has a fork in it. In the middle of the fork is the end of a rod that runs into the wing.

This rod ends in the middle of a fork on a horizontal bellcrank that has rod on each end going out to an aileron.

A less involved method would have the servo mounted on the floor of the fusealage for a mid or shoulder wing plane. One side of the servo arm would connect to the rudder and the other side would use a rod going up into the wing ending in the fork of a bellcrank to a push / pull rod for controling the ailerons.

A CAR system can also be setup with the single servo mounted in the wing. In this configuration the servo arm is attached to a vertical rod which extends down into the fusealage ending in the fork of a bellcrank. The other end of this bellcrank has a rod going back to the rudder horn.

A second single 2 piece rod soldered at the center or two individual rods are attached to the servo arm and extend out towards each end of the wing. Each rod end is attached to a bellcrank which in turn is attached to each of the 2 aileron horns.