Payload analysis for the North Bend, South Bend, and modified North Bend skyline logging systems

Graduation date: 1985The North Bend skyline system was first introduced into the Pacific Northwest in 1912 by the North Bend Lumber Company, North Bend, Washington. The system was able to raise the front end of logs over obstacles while yarding large payloads uphill. Yarding efficiency was improved since hangups were minimized. The Modified North Bend System was developed at the same time, and was used\ud to yard timber downhill. The South Bend System was introduced as a second variation of the North Bend System. The three systems are currently used throughout the world to yard or swing timber over broken terrain where access is limited. The minimum system uses a two drum yarder, for the main and haulback lines, and a standing skyline. The systems are best utilized on clear cuts where tail holds are limited. Greatest production is realized when turns are dragged. However, logs can be fully suspended over streams and other sensitive areas. The payload capacity of a yarding system is one component of its productivity. Payload analysis techniques have been developed for a variety of skyline systems.\ud Modern computers and programmable calculators have increased the speed and accuracy of these techniques. No program has yet been reported which analyzes the payload\ud capability of the North Bend System and its variations. This paper presents a mathematical algorithm for determining payload capabilities of the North Bend, the\ud South Bend, and the Modified North Bend skyline systems. The formulations utilize catenary and log drag geometry to represent static loadings of the systems. Full and\ud partial log suspension are considered. The algorithms were implemented on an IBM Personal Computer. The computer code, written in BASIC, for an interactive payload analysis routine is included. Operating instructions are provided. Sample analyses are presented. Field verification was outside the scope of this study