Cutting Corners with a New Crane Concept

Abstract

It is only possible to pivot (horizontally rotate) conventional harvester cranes at the crane pillar. A new type of harvester crane has an extra pivoting point on the outer boom, which makes it possible to reach behind residual trees and thus probably ease thinning work. This paper quantifies differences in harvester time consumption in thinning between a conventional crane and a pivoting outer boom (POB) crane by the use of a simulation study and a field study. Simulations were made in two mapped stands. A harvester equipped with a POB crane was used in the field study. The work of a conventional crane was performed with the same machine by not using the pivoting function. Six blocks were created with densities ranging from 1,230 to 3,100 trees per hectare and tree choice was restricted. The POB crane required 4 to 8 percent less time compared to the conventional crane in the simulation study and 7 to 15 percent less time in the field study. In the field study, the mean time consumption of the POB crane was significantly lower for the work elements machine movement backwards and crane out. The number of machine movements backwards was significantly lower for the POB crane, and 17 percent more trees could be cut per machine position by the POB crane. The pivoting function was used on 29 percent of the cut trees. Based on the consistent results from the simulation and the field study, it was concluded that the pivoting function significantly increased productivity in thinning.