Resistance from the Load

Abstract

The cable cranes in forestry are used for uphill or downhill transport of logs, stems or full trees. The total weight to be carried by the cable crane consist of the payload, the carriage as well as the vertical components of the main line, the haul-back line, hoist line etc. The rolling resistance between the carriage wheels and the skyline is approximately f_r = 0.02 – 0.05 while the frictions coefficient between the load and the forest floor is approximately f_gu = 0.5 – 0.8. It is an advantage to lift the load free from the terrain during the transport. Often the height difference between the skyline and the terrain is too little to allow the load to be lifted from the ground. Sometimes intermediate supports may be used. They lead to longer rig up time for the cable crane. In addidition, the transport speed is heigher on a single span than when intermediate supports have to be passed.