Productivity in Final Felling and Thinning for a Combined Harvester-Forwarder (Harwarder)
Authors
Fredrik Wester
Martinsson AB
Lars Eliasson
Swedish University of Agricultural Sciences
Abstract
During the last decade, the interest for a combined harvester forwarder (Harwarder) has increased and a quite rapid machine development has taken place in the Nordic countries. In 2000 a new prototype equipped with a rotatable and tiltable load carrier was built in order to enhance the possibilities for processing logs directly into the load carrier. A time study was done to test the hypotheses that 1) the rotatable and tiltable load carrier decreases total time consumption, and thus increases productivity, compared to a fixed load carrier, and that 2) the difference in time consumption between the two harwarder configurations is larger in final felling than in thinning. Results showed that harwarder productivity was increased by 6 per cent in final felling and 20 per cent in thinning by the introduction of a rotatable load carrier. In final felling with the fixed load carrier, the operator changed work method in order to process as many trees directly into the load carrier. It is suggested that this explains why the difference between machine configurations was lower for final felling than for thinning. Calculated harvesting costs for the harwarder were higher than the expected harvesting costs for a harvester and a forwarder in the studied stands. However, there is a large potential to increase harwarder productivity by both further development of the machine and the work methods used.
