As a rule of thumb, the friction loss for each sheave is approximately what percent of the load?

• A. 5%
• B. 10%
• C. 15%
• D. 20%

Answer: (B)

Friction from rope sliding over a pulley wastes part of the effort, so you use a simple rule of thumb: each sheave adds about 10% friction loss relative to the load. That means for every pulley in the rope path, you should expect roughly 10% more force (or tension) than the load itself to overcome that friction. So if the load is 1000 lb and there’s one sheave, you’re looking at about 1100 lb of rope tension equivalent, with the extra friction stacking if more sheaves are in the path. This 10% per sheave is a handy, common estimate used in quickSizing and planning, though the exact loss varies with pulley quality, lubrication, rope type, load angle, and wear.