Systems that may be used for highlead yarding in the eastern United States have power requirements that differ according to the mechanical characteristics of the yarder and rigging arrangement. A study compared the conventional highlead system with two running skylines employing chokers, the Grabinski and the Purdue traction-cable. Both of these skyline systems have a rider block on the haul-back line to increase lifting capabilities. In the conventional and Grabinski systems, running-line tension to lift the lead end of the log was controlled with drum brakes. In the Purdue system, which was used to simulate a yarder having a drum interlocking mechanism for regulating running-line tension without the use of brakes, lift was controlled by installing, at the yarder, a sheave through which the haulback line had been threaded. With running-line tension controlled by brakes, input energy efficiency of the Grabinski increased with size of load; the maximum load tested required 36 percent less power than the conventional system. When the two rider-block systems were compared, the drum interlock was the more efficient as the load increased. For the maximum test load, power requirements were 24 and 51 percent less than for the Grabinski and conventional. These percentages would be expected to vary with load size and terrain.
Document Type: Journal Article
Associate Professor of Forestry, Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana
Publication date: October 1, 1980
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