Single- and Double-Grip Harvesters – Productive Measurements in Final Cutting of Shelterwood

Abstract

To compare the performance and cost of two machine types, a time study of single-grip harvesters (SGH) and double-grip harvesters (DGH)| was conducted in the final cutting of three shelterwood stands in central parts of Sweden. A randomized block design was used with one block in each stand and the treatments SGH and DGH, respectively. The stands were characterized by dense to relatively dense advanced regeneration under approximately 200 trees/ha. No significant differences were found in mean harvesting time between SGH and DGH or between stands. Fewer trees, but approximately the same volume per hour, were harvested when shelterwood stands were cut as compared with clear-cutting of ordinary stands. Despite few stems per hectare and the dense regeneration hindering the operator’s field of view, final cutting was done with fairly high productivity (15.9–34.0 m³/E15-h)| and a low harvesting cost (2.7 –|6.0 USD/m³). It was concluded that both machine types gave acceptable results regarding cost and productivity. The SGH could be recommended as a good choice in general due to the low cost per machine hour as compared with the DGH, while the properties of the DGH would be beneficial in shelterwood stands with a large proportion of trees with large diameter (e.g. >7| cm) branches.

Keywords:

• Time study
• harvesting time
• normative time
• productivity
• cost