Wood extraction performance with a farm tractor in a mountainous region of Brazil: cycle time, productivity and costs of two different work crews

Abstract

Harvesting is a complex and expensive step within forestry operations. In mountainous terrain timber harvesting is complex due to the risks and limitations that the terrain imposes on traditional forms of wood extraction. The objective of this study was to evaluate the effective time of work cycle, productivity, operational costs, and production costs of tree extraction by means of a farm tractor with winch, in two work crew compositions: Crew A: one tractor operator and a choker setter; and Crew B: one tractor operator and two choker setters. The study was implemented in the Vale do Ribeira region of south-eastern Brazil, using a full tree-harvesting system through a time and motion study under different conditions of extraction distance (6–135 m), log yard (5–241 m), and ground slope (7–37°). To evaluate the cycles, a regression analysis was conducted for each treatment, and subsequently compared using the Graybill F-test. Next, a regression with a dummy variable was performed. Crew B showed an average productivity of 13.54 m3; per productive machine hour (PMH), which was higher than the 9.50 m3; PMH−1 of Crew A. The operational costs were US$33.52 PMH−1 for Crew A, and US$44.24 PMH−1 for Crew B. Despite the higher operational cost with Crew B, the increase in productivity resulted in a lower production cost up until the scenario of 120 m of winching distance.