Skyline tension, shock loading, payload and performance for a European cable yarder using two different carriage types

The authors describe a study conducted under controlled conditions, with the goal of analysing the dynamic tension in the skyline of a yarder resulting from hauling known loads. The rigging was a classic three-cable configuration common to European yarder operations; with a single-span standing skyline and the mainline and haulback used to move the carriage back and forth along the span. Two carriage types were used to gauge tension differences between clamped (Hochleitner BW4000) and unclamped (SEIK Skybull 30/60) carriages. Tension was recorded at 0.5-s intervals through a measuring device with a nominal measuring range of 200 kN. Results showed that: (1) The recommended safe working load (safety factor = 3) was often exceeded by peak loads during lateral skidding and inhaul; (2) the endurance limit of the skyline was never reached; and (3) the Skyline XL software used for payload calculation grossly overestimated payload potential. Since study conditions could be considered representative of some commercial yarding operations in the European Alps, this finding suggests that local loggers may operate within safe limits considering the engineering properties of wire rope, while formally exceeding legal requirements.