Control cable fabrication is one of those things that can feel beyond our capability as builders without very specialized tools. We have all seen premade push-pull cables with fancy swaged ends. These come in the form of rod ends, threads, eyelets, or sometimes even spherical or cylindrical fittings for carburetors.
Threaded ends come in familiar AN threads like 10-32 and 1/4-28 as well as coarse threads like 1/4-20. Attaching them is a matter of fitting a jam nut and a rod end for a bolted attachment. This arrangement allows for a few threads of length adjustment as well. These cables can be purchased in standard lengths in 1- or 2-foot increments. If your desired length sits in between two lengths, you’ll have to find some space to bunch up 6 inches and take a longer path, or custom-order one. Bunching up cables that are too long comes at the cost of friction in the final installation.
Friction not only wears out the cable faster, but it also takes away from the precise feel that pilots want, especially for throttle cables. The ideal routing is one with minimum curvature—basically the largest radius that doesn’t add additional twists and turns. Anything less than ideal routing can quickly add 2x, 3x, or even 5x the friction, which is largely determined by the number of pressure points between the inner wire and the jacket. Don’t underestimate the importance of proper cable routing and cable length.
(Note: If you’re building a modern kit and the manufacturer sells controls to the exact length for your aircraft, look no further—but always double-check for optimal routing.)
The second option is a solid-wire-end control, which ranges in inner wire and outer jacket diameter dimensions. Raw lengths of this material go by the name “Bowden cable.” The outer jacket diameter typically ranges from 3/16 to 5/16 inch and the inner wire diameter from 0.050 to 0.080 inch. These controls can also be purchased in 1-foot increments with the major difference that they can be cut to length. In tight quarters, there is often no other choice than a cut-to-length solid wire control. These controls are especially convenient for functions like parking brakes, heater controls, and cowl flaps when ordering a custom-length, threaded-end cable seems like overkill.
Solid-wire controls suffer when it comes to end fittings and attaching the wire. Most methods involve some way of squishing the inner wire, which often leads to damage and makes them difficult to remove and reinstall. Set screws are a particularly malicious example of this.
Read part 2, where we dive into different methods of attaching control cables and the associated pros and cons.
