Which cable type should be used when pulleys change the direction of cable travel?

• A. Stiff steel cable.
• B. 7x7 cable.
• C. Extra-flexible cable (7x19).
• D. Fiber optic cable.

Answer: (C)

When a cable must change direction around pulleys, flexibility is essential. An extra-flexible construction, known as 7x19, uses many small wires that bend easily, allowing the cable to wrap around bends and pass smoothly over pulleys without kinking or taking a permanent set. This flexibility also helps distribute bending stress over many wires, reducing fatigue and wear where the cable changes direction. In contrast, a stiff steel cable resists bending and wears on pulleys quickly; a 7x7 construction is less flexible than 7x19 and won’t handle sharp bends as well; fiber optic cable isn’t suitable for bearing tensile loads or pulling mechanisms. Therefore, the extra-flexible 7x19 cable is the best choice for applications involving changing directions with pulleys.