A log-by-log productivity analysis of two Valmet 475EX harvesters

Productivity of a mechanized harvesting system is influenced by stand and terrain conditions, operator performance, and machinery limitations or design. The purpose of the study was to compare the productivity of two near-identical single-grip harvesters in similar Australian Pinus radiata clearfell harvesting operations on a log-by-log basis. The study first compared the productivity of each harvester against tree volume for cycle times and for tree processing times only. Significant differences in productivity between the harvesters were found to be largely due to significant differences in tree processing times. Comparisons between each component of processing time (dragging-out time, disc-cutting time, cross-cutting time, harvester head travel time and delimbing time) for a subset of 6.1 m sawlogs at each study site found operator working technique differences to be the main driver of productivity differences between the harvesters. In particular, the operator of the less productive harvester dragged out most trees after felling and cut discs on most trees to reset the length-measuring device, whereas the operator of the other, more productive harvester rarely carried out these activities