Analyzing Slack-pulling Forces in Manually Operated Skyline Logging Systems

Publisher： Society of American Foresters

ISSN： 0015-749X

Source： Forest Science, Vol.25, Iss.3, 1979-09, pp. : 475-484

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Abstract

A model is developed to calculate the main-line tension produced by line resistance caused by ground drag when pulling a cable main line through a clamped skyline carriage by hand. Slack-pulling effort was found to increase linearly with increasing slope along the skyline corridor. An increase in line weight, coefficient of friction, or horizontal distance from the landing to the carriage produced a linear rise in slack-pulling effort. The effect of carriage height is nonlinear but nearly constant with respect to main-line tension at the carriage. Assuming constant main-line tension at the carriage, the main-line tension encountered by a choker setter at the ground decreases linearly with increasing carriage height. Using the model it is possible to establish bounds on feasible distances for hand-pulling slack as a function of crew size. In addition, the determination of main-line tension at the carriage provides a useful parameter for the design of carriages that use mechanical means for pulling slack. Forest Sci. 25:475-484.