Browsing by Author "Wenhold, Roland Marius"
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- ItemSkills development of mechanised softwood sawtimber cut-to-length harvester operators(Stellenbosch : Stellenbosch University, 2018-03) Wenhold, Roland Marius; Ackerman, P. A.; Ackerman, Simon; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.ENGLISH ABSTRACT: In this study, a South African pine sawtimber mechanised cut-to-length harvesting operation – comprising felling, debarking, debranching and cross cutting of log assortments – was analysed using .stm-files from StanForD software. The objective of the analysis was to describe and model productivity development learning curves of beginner harvester operators in both clear-felling and thinning operations. A cohort of trainee operators were selected based on the results of a comprehensive battery of psychometric tests that assessed their aptitude for the complex array of decision-making required of harvester operators. These trainees subsequently completed several sequential tests on a harvester simulator. Following the simulator training, operators commenced with work on machines (harvesters) themselves until they were considered capable of working unsupervised. Within the framework of this progression of operator selection, simulator training and in-field operations, it was possible to model a potential learning curve of a typical beginner harvester operator in softwood sawtimber in both clear-felling and thinning operations. With regards to simulator training, the results of this study show that, on average, a trainee operator will start at a performance level (PL) of 60% lower than the population’s performance level (PPL) and end with a PL of 24% higher than the PPL. Furthermore, when the PL of an average simulator trainee was measured over a period of 9.2 days or 27 tests (three tests per day), it was evident that his PL improved with 269% following the efficient simulator training. Once in-field, thinning operators worked with an average tree size of 0.18m3 where they started at a productivity of 13.71 m3 ·PMH-1 (cubic meter per productive machine hour) at month one and managed to increase their productivity to 38.96 m3 ·PMH-1 (overall average = 28.8 m3 ·PMH-1 ) at the end of month 12. Clear-felling operators’ felling productivity level on an average tree volume of 0.54m3 started at 27.5 m3 ·PMH-1 in month one and increased to 43.75 m3 ·PMH-1 (overall average = 41.9 m3 ·PMH-1 ) at the end of month 12. Finally, on average, a thinning operator can reach the end of the learning phase after nine months. The two clear-fell operators reached the end of their learning curve after five and eight months respectively. On average, thinning operators increased their performances by 218%, while clear-fell operators increased theirs by 104%. These findings suggest acceptable learning periods and performance increases for beginner harvester operators.