Finding the ‘Sweet-Spot’ of Mechanised Felling Machines

Understanding how stand and terrain parameters impact the productivity of harvesting machines is important for determining their optimum use. Productivity studies in forest operations are often carried out on new equipment, or on equipment being used in new conditions. Such information is normally presented as a productivity or efficiency function; that is, a regression equation that best represents the data. Most studies establish that piece size is the dominant predictor that impacts overall productivity. A common concept, know as the ‘piece-size law’, is that productivity increases at a decreasing rate with increasing piece size. What is not well understood is the upper limit to this piece-size law. That is, as the trees get ‘too’ large, the machine starts to struggle and we can expect a decrease in productivity. Four different mechanised felling machines were studied in New Zealand radiata pine plantations. Using more complex non-linear equations it was possible to identify an ‘optimum’ piece-size for maximum productivity, whereby this ‘sweet-spot’ piece size for all machines is considerably smaller than their maximum. Unexpectedly, productivity tended to decrease gradually, not drop off suddenly beyond the optimum. Using more complex statistical functions when correlating piece size to productivity will help identifying the ‘sweet-spot’.

[1]  Jori Uusitalo,et al.  Characteristics and Significance of a Harvester Operators’ Working Technique in Thinnings , 2004 .

[2]  Jingxin Wang,et al.  Production analysis of an excavator-based harvester: A case study in Finnish forest operations , 2002 .

[3]  Karl Stampfer,et al.  Tree-length system evaluation of second thinning in a loblolly pine plantation , 2003 .

[4]  Raffaele Spinelli,et al.  Analyzing and Estimating Delays in Harvester Operations , 2008 .

[5]  Metsäteho Oy,et al.  Productivity and Cutting Costs of Thinning Harvesters , 2004 .

[6]  Matthew A. Holtzscher,et al.  Tree diameter effects on cost and productivity of cut-to-length systems , 1997 .

[7]  Dag Fjeld,et al.  Single-tree and Group Selection in Montane Norway Spruce Stands: Factors Influencing Operational Efficiency , 2001 .

[8]  Raffaele Spinelli,et al.  Productivity and cost of CTL harvesting of Eucalyptus globulus stands using excavator-based harvesters , 2002 .

[9]  Han-Sup Han,et al.  Productivity and cost of cut-to-length and whole-tree harvesting in a mixed-conifer stand , 2007 .

[10]  Matti Sirén,et al.  Productivity and Costs of Thinning Harvesters and Harvester-Forwarders , 2003 .

[11]  T. Evanson,et al.  Productivity Measurements of Two Waratah 234 Hydraulic Tree Harvesters in Radiata Pine in New Zealand , 1996 .

[12]  Masahiko Nakagawa,et al.  Effect of Tree Size on Productivity and Time Required for Work Elements in Selective Thinning by a Harvester , 2007 .

[14]  Lars Eliasson,et al.  Simulation of thinning with a single-grip harvester , 1999 .

[15]  W. D. Greene,et al.  Productivity and cost of sawhead feller-bunchers in the South , 1991 .

[16]  Kalle Kärhä,et al.  Productivity and Cutting Costs of Thinning Harvesters , 2004 .

[17]  Lars Eliasson,et al.  Simulation study of a single-grip harvester in thinning from below and thinning from above , 1999 .

[18]  B. Brunberg,et al.  Basic data for productivity standards for single-grip harvesters in thinning , 1989 .

[19]  Jori Uusitalo,et al.  Time consumption analysis of the mechanized cut-to-length harvesting system , 2006 .