In a setup using a 1-inch wire rope eye sling around a 1-inch shackle, the efficiency is approximately what percentage?

In a setup using a 1-inch wire rope eye sling around a 1-inch shackle, the efficiency is approximately what percentage?

• A. 25 percent
• B. 75 percent
• C. 100 percent
• D. 50 percent

Answer: (D)

When a wire rope eye sling is used around a shackle pin, the rope has to bend around that pin, creating contact friction that reduces how much of the sling’s nominal capacity is actually transmitted to the load. With a single wrap around a shackle pin that is similar in size to the rope, this friction is enough to roughly cut the usable capacity in half. That’s why about 50 percent is used as the practical efficiency for this arrangement. The other values would imply less loss (approaching full capacity) or more loss than is typical for a single wrap around a 1-inch shackle.

When a wire rope eye sling is used around a shackle pin, the rope has to bend around that pin, creating contact friction that reduces how much of the sling’s nominal capacity is actually transmitted to the load. With a single wrap around a shackle pin that is similar in size to the rope, this friction is enough to roughly cut the usable capacity in half. That’s why about 50 percent is used as the practical efficiency for this arrangement. The other values would imply less loss (approaching full capacity) or more loss than is typical for a single wrap around a 1-inch shackle.