DIGITALNA ARHIVA ŠUMARSKOG LISTA
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activity done by the same worker. The walking time stage was ignored since the timber to be debarked were located within very close distance to each other in the study area. Work stages like cleaning the surrounding area of the timber, starting the chainsaw or holding the axe were considered as preparation stage. The duration of time between the starting and ending of the debarking was considered as debarking time. During debarking, the workers turn the timber with their foot for enabling the side and back parts to be debarked. At this stage, the duration of time was considered as the timber turning time. For statistical analysis of the debarking activity, total of 120 measurements at the field were recorded; 60 of them were debarked by an axe, while other 60 were done by the debarking tool. Productivity Analysis – Analiza produktivnosti The effects of the timber volume on productivity of debarking were investigated. For this purpose, timber volumes were grouped under three classes (low: <0.08 m3, medium: 0.08 m3 – 0.12 m3, high: >0.12 m3) in order to investigate different volume classes within the debarking studies with axe and chainsaw mounted debarking tool. Total cycle time was determined as a dependent variable (y), while independent variables were determined as; timber diameter (x1), bark thickness (x2) and its volume (x3). „Huber’s Formula”, one of the most commonly preferred formula in technical forestry application, was used for calculating the volumes of the timber (Carus, 2002). It was calculated with the product volume (Vi), medium diameter and length as given below in Formula 1: (1) di = i medium diameter of the timber (cm) Li = i length of the timber (m) Then, using the data that were obtained with time measurement, hourly productivity (P in m3/hour) was investigated. „Formula 2” was used for productivity calculation as follows: P = (V / T)*60 (2) P = Productivity (m3/hour) V = Timber volume in a cycle (m3) T = Total time in a cycle (hour) 60 = Coefficient used for converting minute to hour The effect of different volume classes (low, medium, high) on productivity of debarking was investigated with One-Way Anova analysis (Akay et al., 2010). As the differences between the averages and number of samples were equal, Tukey multiple comparison test was used (Kayri, 2009). „Pearson Correlation” was applied to find out the relation of the variables that effects the time values of the debarking studies with the timber diameter, bark thickness, volume (independent variable) and total cycle time (dependent variable). „Linear Regression Analysis” was carried out to determine the mathematical models of the independent variables (diameter, bark thickness). When the volume variable was included to the regression analysis, the model did not give a confidence level of 95% sensible result (p>0,05); therefore, volume was not included in regression analysis of both methods. RESULTS AND DISCUSSION REZULTATI I RASPRAVA In debarking application, using a chainsaw mounted debarking tool, minimum and maximum timber diameter was determined as 13 cm and 30 cm (Table 1). Total average debarking cycle time was determined as 1.30 min/timber, with the average bark thickness of 1.40 cm. There were only two groups of timber lengths including 1.4 m and 2.0 m long timbers, therefore, timber length was excluded from statistical analysis to prevent contradictory interpretation. In debarking activity using an axe, minimum and maximum timber diameter was determined as 13 cm and 35 cm |