Efficiency of timber skidding on the slopes

The aim of the study is to characterise the working time structure of an operator of the LKT 82 skidder performing timber skidding on the sloping area, and to develop models of efficiency and time−consumption of the work depending on selected factors characteristic of the described transport process. The research was performed in the Sucha Forest District (S Poland). We considered two treatments: late thinning and felling performed in stands with the dominating share of beech. Logs obtained with chainsaws were initially extracted with horses and laid at the slope road. Later on the additional skidding with skidder tractor was done. Continuous timing of individual operations was performed with the use of a microcomputer equipped with time measurement software (accuracy of 1 second). We also determined skidding distance using a GPS device, the number of extracted logs in the load, and the volume of the logs. The total timing measurements lasted for a total of 70 h 24 min 27 s. During that time, the tractor made 72 cycles, transporting 998 logs with a total volume of 493.3 m3. In the mature stand, the average skidding distance amounted to approximately 1,160 m, a single load consisted of 3−4 logs with a volume of 7.7 m3. The operational efficiency of the skidding was 9.1 m3/h. In the thinning stand, the skidding distance was 1,230 m, the average load consisted of 22 logs with a volume of 5.8 m3. The operational efficiency amounted to 7.8 m3/h, on average. The working time structure was dominated by auxiliary (over 60%) and effective (nearly 30%) times. The obtained regression models of the duration of activities from the group of operational times were characterised by high correlation coefficient (about 0.75 for skidding time and driving without a load). Relatively strong relationships (r > 0.5) were also found between the times of collecting cable pulling and load attachment, and the volume of the extracted loads, and in the case of the times of collecting cable pulling also the type of treatment performed. The regression models for the times of log stacking, pulling the loads up with the winch and detaching them, despite the fact that they were statistically significant, characterised by relatively low correlation coefficients. The relationship between skidding efficiency and skidding distance was also determined (fig.). The duration of skidding cycles was described using the multiple regression with the volume of single loads and the skidding distance as the determinants. The regression models of skidding efficiency and time−consumption of skidding cycles may find practical application in estimating the efficiency of the tasks performed in stands and under conditions similar to those analysed in the present research