Bending a wire rope over a small diameter sheave decreases its effective strength by what percentage?

• A. 25%
• B. 50%
• C. 10%
• D. 40%

Answer: (B)

Bending a wire rope over a small diameter sheave affects its effective strength primarily due to the resulting stress and strain on the fibers of the rope. When the rope is bent sharply, the outer wires experience greater tension and compression compared to the inner wires. This uneven load distribution can lead to a decrease in the overall strength of the wire rope.

Research and industry standards indicate that bending a wire rope around a sheave, particularly if the sheave is small relative to the rope’s diameter, can reduce its effective strength significantly. The generally accepted decrease in strength for such scenarios is around 50%. This substantial reduction reflects the mechanical disadvantage that bending creates, as compared to straight or gently curved runs of rope where the load is distributed more evenly.

Understanding this principle is essential for safe rigging practices and helps prevent accidents related to overloading or equipment failure in the field. Properly assessing the dimensions of sheaves in relation to wire rope is crucial in ensuring safe operation and maintaining the integrity of the system being used.