Graduate Thesis Or Dissertation
 

Comparison of skyline carriages for smallwood harvesting

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  • Three skyline carriage types are analyzed on the basis of their operating characteristics and limitations. Their effect on productivity is expressed as cubic feet per hour yarded to the landing. These carriage types, tested as part of Oregon State University's School of Forestry Smallwood Harvesting Research Program represent those which are especially suited to thinning smallwood stands. The three types are distinguished by their clamping mechanisms: 1) skyline stop 2) self-clamping hydraulic and 3) self-clamping mechanical. The clamping mechanism is the means by which the carriage is secured to the skyline during the lateral inhaul element of the yarding cycle. Since data from the individual studies are not all comprehensive, five carriage studies are used for the analysis of the three carriage types. The Maki and Christy carriages represent the skyline stop carriages. The Koller 1.0 and 2.5 carriages represent the self-clamping hydraulic carriages and the Wyssen 2.5 represents the self-clamping - mechanical carriages. The operating characteristics which proved to be most important are the ability to throw slack in the mainline, adaptability for use with sliding chokers, spotting ability and carriage delays. The skyline stop carriages tend to throw slack in the mainline when they hit the skyline stop at the end of outhaul (which aids in the lateral outhaul of the mainline). The Koller carriages, representing the self-clamping hydraulic carriages, cannot be used with sliding chokers without modification, since the load hook is part of the release mechanism. This effect, along with the effect of throwing slack, was not quantified. The Wyssen carriage was observed as having a greater capacity to be spotted at an exact location on the skyline for the lateral yarding sequence than any of the other carriages. This resulted in a lead angle standard deviation of only 17.7 degrees. A similar standard deviation of 16 degrees was observed for the Koller 1.0. The Christy carriage resulted in a larger standard deviation of 24 degrees. Lead angle data was not available for the Maki and Koller 2.5 carriages. The importance of spotting is that either the logs can be yarded laterally to lead or the best extraction path can be choosen for a turn. Both of these advantages serve to reduce resets and minimize stand damage. Carriage delay analysis indicated very little difference between the time required to move the skyline stop calculated on a per turn basis and the time required for the self-clamping carriages to cycle every turn. With operational delays added in, the carriage delays for the skyline stop carriages is 0.2678 minutes per turn and for the self-clamp mechanical is 0.2625 minutes per turn. This information was not available for the self-clamping hydraulic carriages, but is probably greater than the self-clamping mechanical type and may be greater than the skyline stop type. The three carriage types were compared on a productivity basis. No conclusive differences were found since factors not accounted for in the individual studies tended to mask the affects of the different carriage types. The differences in productivity due to carriage types appear to be small in comparison to such factors as crew selection, stand conditions and site conditions.
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