Abstract
Skidders are one of the most used machines in harvesting operations, especially when dealing with large timber. Their use is still widespread around the world, a fact reflected by numerous efficiency studies. Since 95% of logging operations in Romania are done by means of skidders and farm tractors, this study aimed to assess timber skidding efficiency in a mixed fir-beech stand undergoing group shelterwood cuttings. Following a time study performed on 100 winching replications which corresponded to 31 on-trail skidding replications, it was found that a winching replication was most affected by winching distance and log volume whereas an on-trail skidding replication was affected by skidding distance. However, in case of all skidding operations, winching distance, skidding distance and number of logs forming a load were the most significant independent variables for the time consumption estimation. Delays (technical, operational and personal) accounted for 28% of the total skidding time, whereas in a delay-free skidding work cycle, winching and on-trail skidding accounted for 30 and 70% respectively of skidding time. If mean conditions are considered (winching distance of 23.02 m, on-trail skidding distance of 1037.32 m, volume of load of 7.12 m3 and 3 logs per load), the net production rate was of 12.65 m3h-1. The results of this study may be useful for an improved organization of harvesting operations in similar conditions.
Key words: Skidding, efficiency, group shelterwood system, time prediction, production rates.
