Stańczykiewicz Arkadiusz, PhD.

Farm tractors are very popular in Poland and other European countries. When coupled with trailers equipped with a crane with a grapple, they are also used, especially in easily accessible, flat terrain, for timber forwarding in the CTL (Cut-to-Length) method. A comparative analysis of working time and productivity was performed on two forwarding units, consisting of a farm tractor Ursus and a Farma trailer with the load capacity of 6 tons, as well as a farm tractor Valtra Valmet and a Palms trailer with the capacity of 9 tons, which forwarded wood in a mature pine stand. An analysis was done for 64 work cycles with an average load volume of 2.1 m3 for the former unit, and 36 cycles with an average load volume of 7.9 m3 for the latter. The working time structure of both units was similar. During work, tractor operators spent most time, i.e. over 35%, loading the timber, then travelling with the load and unloading. The lowest share in the work cycle, around 5%, belonged to travelling without a load and forwarding. The average forwarding time for the Farma unit amounted to 33 minutes and was about twice shorter than that for the Palms unit, amounting to 64 minutes. The distance covered during loaded travel was the only factor that had a significant influence on the duration of forwarding cycles. The coefficients of correlation between these variables were 0.56–0.76. The net productivity obtained in the operating time of the Palms unit was 7.5 m3×PMH-1 and was almost twice as high as that of the Farma unit, i.e. 3.8 m3×PMH-1. For both units multiple regression models were developed, in which forwarding cycles productivity is calculated based on the volume of the transported load and the distance of loaded travel.