What is the D/d ratio for the relationship between sheave pitch diameter and wire rope diameter?

• A. 4:1
• B. 2:1
• C. 8:1
• D. 6:1

Answer: (D)

The D/d ratio compares the sheave pitch diameter (D) to the wire rope diameter (d) to indicate how tightly the rope is bent as it runs over the sheave. A larger ratio means the rope bends more gently, reducing bending stress, wear, and fatigue, which helps rope life and performance.

For wire rope, a minimum D/d of 6:1 is typically specified to keep bends from being too sharp. So the best choice is six to one. Smaller ratios—4:1 or 2:1—would bend the rope more tightly and shorten rope life, while a ratio like 8:1 is acceptable but represents a larger, less common minimum requirement.