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.
Highlights
When harvesting large timber, mechanized logging means are required in order to match tractive power with the logs dimensions
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
In post-socialist Romania, skidders represent one of the most used machines in timber harvesting operations (Sbera, 2007) a fact which relates to their mobility and productivity (Oprea, 2008), despite the fact that most of the Romanian forests are located in steep terrain (Report on Forest State, 2010) where cable yarders would be a better choice
Summary
When harvesting large timber, mechanized logging means are required in order to match tractive power with the logs dimensions. In post-socialist Romania, skidders represent one of the most used machines in timber harvesting operations (Sbera, 2007) a fact which relates to their mobility and productivity (Oprea, 2008), despite the fact that most of the Romanian forests are located in steep terrain (Report on Forest State, 2010) where cable yarders would be a better choice. Another reason which promoted the use of skidders in Romania for the last two decades is the poor developed forest transport infrastructure (Bereziuc et al, 2011) which generates impossible harvesting conditions due to reduced accessibility and the lack of trained personnel. This has not been the case of other countries which have tried and succeeded to develop efficiency studies for several skidding machines (Kluender et al, 1997; Kluender et al, 1998; Wang et al, 2004; Sabo and Poršinsky, 2005; Zečić et al, 2005; Horvat et al, 2007; Behjou et al, 2008; Naghdi and Mohammadi, 2009; Behjou, 2010; Özturk, 2010a, b; Spinelli and Magagnotti, 2012; Ghaffarian et al, 2013; Mousavi, 2012)
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