Slope effect on costs and productivity of single-grip purpose-built and excavator based harvesters

[摘要] ENGLISH ABSTRACT: In this study a mechanised Eucalyptus pulpwood cut-to-length harvesting operation comprising felling, debarking, debranching and cross cutting of assortments, was observed using time studies to determine the effect of slope on harvester productivity and cost of wood production. Time studies and data analysis was done according to the South African Forestry time study standard and machine costs according to the South African Harvesting and Transport Costing Model. Two different types of harvesting machines were studied; an excavator based machine, Volvo EC210BF, and a purpose built levelling machine, TimberPro TL725B, both fitted with Maskiner SP 591 LX harvester heads. A single operator with significant experience and training on both machines was used throughout the duration of the study. The machines were observed harvesting on a range of slopes, from level to 50% in two separate work corridors with relatively similar trees in terms of individual tree volume and form. The species studied was a Eucalyptus grandis x camaldulensis clone. Continuous slope data, as opposed to slope categories, for each position at which the harvesters would position themselves to undertake harvesting and processing, was derived using large footprint LiDAR data of the area. The purpose built harvester was levelling enabled as opposed to the Volvo which was not.Apart from differences in mass, the Volvo was not modified for forestry work and the booms were on different sides of the particular machine. Cost calculations were carried out on each machine to determine which machine was more cost effective. The study design was a 2 x 2 factorial design with two treatments (machine type) against slope and individual tree volume as factors.The results indicate that the productivity of the excavator based machine decreased by 0.048m3.PMH-1 for every 1% increase in slope. The purpose built machine was not significantly affected by slope in this study and maintained an average productivity regardless of extreme slope. The purposed built machine was found to have a higher mean productivity (16.24 m3.PMH-1) than the excavator based machine (13.00 m3.PMH-1), but this extra productivity came at a price, as the excavator based machine was more economical per cubic metre. The mean harvest cost for the purpose built machine was found to be R122.67.m-3 whilst the excavator based machine achieved a mean cost of R94.46.m-3.

[发布机构] Stellenbosch University