Tech-Info 09.4: Breaking strength
09.4 Efficiency of the rope
When running over a sheave, the wire rope must be transferred from the straight to the bent state at the run-up point and from the bent to the straight state at the run-down point. The bearing of the sheave must also be rotated. Here, the frictional forces in the rope and the bearing must be overcome. This leads to a change in the rope force. The ratio of the rope forces on both sides of the sheave is called the rope efficiency, taking into account that this numerical value also includes the friction losses of the bearing. When measuring rope efficiency, the loss of line pull when running over sheaves is measured. Generally, an efficiency of 0.98 is assumed for wire ropes, i.e. a force loss of 2% per sheave.