Servo arms & horns

Control arms are a type of lever attachment on a servo. The???servo arm???may have one or more arms to allow for multiple positions and control rods. Some attachments that have multple positions are circular. It's the control arm that transfers leverage from the servo to the control rod.

A control horn is on the receiving end of the servo leverage, either being pushed or pulled. The control horn is simply a lever that is mounted onto a control surface, perpendicular to the edge of the control surface, that connects to the end of the control rod allowing the surface to pivot on a hinge point.

Control push rods

Control rods or wires can be made from various material such as plastic, metal, carbon fibre. What is used is often determined by the size and desired weight of the model, what is being controlled and the appropriate linkage types.

Control rods are often attached to the control horns and other levers by 2mm clevices, ball joints, or other specialized adapters. Small craft and park flyers often use a simple z-bend (bend in the wire the shape of a "Z", all angles being 90 degrees) to attach to a control horn, secured by swing-in-keepers. Larger models sometimes require a heavier duty solution, and in this case we can supply 3mm clevices or ball joints.

Closed Loop Systems

Closed loop systems are generally the reserve of the Radio control purist. It's true to say that they are a lightweight solution, and extremely precise if set-up correctly, but they can require specialist fitting and precise adjustment. Most systems comprise of nylon line, and specialist fittings, and are most suited to elevator, rudder or tail wheel control. They also give a scale appearance to classic aircraft.

Hinges

There are a number of different???products available???to hinge control surfaces. Some models utilise pre-made pinned hinges which give a great deal of strength, and if fitted correctly with pegs, cannot shift. For more lightweight solutions you could use Mylar hinges or hinge strip, which are generally???adhered with cyanoacrylate glues,???although this will not give the same degree of flexibility as a pinned hinge.

Assembly

Linkages are often made by soldering metal extenders on to 16swg piano wire,???this allows you to use the threaded end of the extender to give adjustment to the clevice or??????ball joints. A more professional solution is to use pre-manufactured plastic "snakes", like Sullivan golden rods. These are made from strong and durable plastic, and give ample strength to even large models.???Sullivan golden rods must be used with Sullivan branded clevices as they use a 2-56 thread pattern, as opposed to the 2mm standard fitting.

Control horns are usually bolted straight through the control surface provided strength and durability. Larger planes will often have retractable landing gear connected to one or more servos using the same kinds of linkages and components.

Throttle linkages are generally made with???threaded push rods, fitted with a metal clevice at one end, and secured from vibration with liquid threadlock. The other end is usually bent into a Z bend and pushed through the throttle arm on the engine. Making Z bends is best done with Z bend pliers.

Small planes and park flyers often have more restrictions. Materials must be lightweight (plastic, thin wire or cable) and as small as possible. Small tube wire guides are often used to encase the flexible wire or cable to its control surface destination. There are???also some moulded???fuselage opening components to allow the rods to neatly penetrate the covering.

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