Productivity of TIMBERJACK 240A and LKT 81T Skidders at Selective Cutting and Longer Distances

The extraction of wood from forests is a difficult, risky, expensive, and time-consuming operation, especially in mountainous areas and selective forests. In the forestry of Bosnia and Herzegovina (BIH), winching and skidding of wood assortments is most often done with cable skidders. They are the most applicable because they can handle hilly, mountainous and inaccessible terrain in the compartments that are most common in local forestry. In addition, selective and group-selective forest management systems are dominant, where the manoeuvring of any type of machinery is strictly limited to the skid trails and skid roads. It is a matter of legal and sub-legal regulations and environmental standards. Striving for higher productivity and economy of skidding is ultimately one of the objectives of forest management. Different Timberjack and LKT models of skidders are widely used in BIH. The study was conducted in the area of two public forest enterprises, in compartments 32 (Forest management unit "Vrbanja") and 99 (Forest management unit ““Lješljanica-Maglajska”) with similar stand and relief conditions. The research objects were two skidders, which are used very often in the forestry of BIH, LKT 81T and Timberjack 240A. Skidder LKT 81T was used in compartment 32, where 29 cycles were recorded, during which 212 logs were skidded. Total volume of skidded wood was 159.98 m3 with average volume of 5.52 m3·load-1. Timberjack 240A was used in compartment 99, where 84 cycles were recorded, with 398 logs. Total skidded wood with Timberjack 240A was 657.34 m3, with average volume of 7.83 m3·load-1. Relative share of work operations showed that loaded and unloaded drive had the largest share, onsie In case of LKT 81T loaded drive was 31% and unloaded drive 25%, while for Timberjack 240A skidder loaded drive accounted for 44% and unloaded drive for 37% of productive work time. Average skidding distance for loaded drive was 1080.34 m for LKT 81T and 727.98 for Timberjack 240A. Unloaded drive, manoeuvring drive and loaded drive showed dependence on corresponding distances. With the increase of the distance and volume of the load, the time required for skidding per unit of product increases. In comparable range (up to 900 m), for the same load size, Timberjack 240A achieved lower standard time, i.e., higher productivity than LKT 81T. Using a skidder at longer distances significantly reduces productivity and increases costs. However, planners often decide in such cases to use a cable skidder for wood skidding, knowing that the costs will be higher, which is again a better option than not harvesting parts of the compartment.