RC servos are used to control the movable surfaces of a radio-controlled device. The amount of movement, commonly known as throw, needed varies between applications. A 3D aeroplane requires a large amount of throw, whereas a trainer benefits from a much smaller amount. The need to adjust the amount of throw from an RC servo is not limited to aeroplanes. The procedures for adjusting RC servo throw is common to all applications.
- Skill level:
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Things you need
- Plywood (optional)
- Thread (optional)
- CA glue (optional)
- Computerised transmitter (preferred)
Select a servo arm that will fit your application. Servo arms come in several sizes and shapes. Sometimes it is necessary to trim one side of the servo arm to give the other side full movement. Servo arms usually have several pre-drilled holes in them; this is where you attach the pushrods.
Select a hole, and attach the pushrod. Select a hole near the centre of the servo to have less throw and farther out to have more throw. It may be necessary to try several holes before finding one that works well for your application.
Extend the arm with some light plywood if your servo arm is not long enough to provide the amount of throw desired. Drill two holes in the plywood extension; use a screw to attach the extension to the servo arm and the second hole for the pushrod. Another way to mount an extension is to wrap thread around the servo arm and the extension, and glue it in place with a drop of CA glue.
Make adjustments on the transmitter if more are necessary. Use the end point adjustment feature of a computerised transmitter to change the throw. End point adjustment limits or extends the servo arm travel. Most servos can be programmed to travel from 0 to 120 per cent of their normal range.
Tips and warnings
- Most aeroplanes will have a recommendation for the amount of throw needed for each surface; follow these recommendations to get the best flight performance.
- If you have a computerised transmitter, look at features such as dual rates and exponential for greater servo control.