Assessment efficiency of HSM904 grapple skidder on Longitudal different levels of skid trail slope

In ground-base skidding operations several factors are influences on skidding time such as slope of skid trail, volume, number and length of logs per turn and direction of skidding by skidder machinery. To achieve this purpose, efficiency of skidder HSM904 in cut-to-length method was studied on district #2 (Arzanfun), Mazandaran wood and paper forests. We delineated six slope classes on a skid trail by 700 meters in length, before skidding operation which was running contrary to the slope (uphill skidding). During skidding operation 2 volume classes includes (3.5 m3 ) and number of logs per turn includes (up to 2 and more than 2 logs per turn) were selected. The results from 156 time cycles based on time study showed that in travels without load slope class (13-16%) has been significantly effect on skidder efficiency. The least speed’s skidder was recorded in slope class (22-25%). Speed of skidder decrease with increase slope skid trail, so that in travel with load, slope class (10-13%) has been more effect on skidder speed. So the least speed’s skidder was recorded in slope classes (19-28%) in combine. The results also firmed that the effects of load volume was significant on skidder efficiency, while number of logs was not significantly effect. The greatest efficiency skidder HSM904 was recorded in slopes (13-16%) in travel without load and (22-13%) as safe slope in uphill skidding by skidder HSM904 in the study area.