Assessing Cable Tensile Forces and Machine Tilt of Winch-Assisted Forwarders on Steep Terrain under Real Working Conditions

Winch-assisted forwarders are now commonly accepted as an innovative alternative for extracting wood on challenging terrain. In order to assess safety risks, it is necessary to know the tensile forces in the steel wire rope and their interaction with the machine tilt under real working conditions. In this study, the tensile force and the machine tilt of two winch-assisted forwarders (John Deere 1210E and Komatsu 840TX) were observed for about 15 work hours without delays on two different stands in Austria. The tensile force data and the machine tilt data were separated by work elements. The mean tensile force ranged from 18.1 kN for unloading up to 56.8 kN for loading activities. During the measurements, the cable tensile force exceeded 50% of the minimum breaking strength (MBS) only twice. The maximum observed tensile force was 174.5 kN or 82.7% of the MBS, respectively, which led to a failure of the steel cable. For the machine tilt, a maximum of 80% was measured during loading and driving during loading. John Deere 1210E was operated 31% of the productive work time above the manufacturers tilt limit. For Komatsu 840TX, the manufacturers’ maximum tilt limit was exceeded only twice. The study also showed that peaks with an amplitude of up to 50 kN can occur within a few centiseconds, which highlights the need of high measurement rates, when measuring cable tensile force of winch-assisted machinery. The detailed analysis of the peaks showed that 90% of the pit-to-peak amplitudes ≥20 kN occurred during driving activities. Only 10% of pit-to-peak amplitudes ≥20 kN were measured during loading activities, although loading took about 43.5% of the productive work time. As such, the study results confirm that amplitudes of peaks in tensile force, and hence safety risks, are significantly higher during driving than during loading.

[1]  Boone Y. Richardson,et al.  Feasibility study of self-contained tether cable system for operating equipment on slopes of 20 to 75% , 1978 .

[2]  J. Uusitalo,et al.  Impact and productivity of harvesting while retaining young understorey spruces in final cutting of downy birch. , 2012 .

[3]  D. Neary,et al.  Proceedings of the Sixth Biennial Southern Silvicultural Research Conference , 1991 .

[4]  Jennifer L Bell,et al.  Changes in logging injury rates associated with use of feller-bunchers in West Virginia. , 2002, Journal of safety research.

[5]  Rien Visser,et al.  Effect of terrain steepness on machine slope when harvesting , 2015 .

[6]  Bruce R. Hartsough,et al.  Control of a cable-towed vehicle to minimize slip , 1993 .

[7]  N. Magagnotti,et al.  The effects of introducing modern technology on the financial, labour and energy performance of forest operations in the Italian Alps , 2011 .

[8]  Bruce R. Hartsough,et al.  Harvester-Forwarder and Harvester-Yarder Systems for Fuel Reduction Treatments , 2001 .

[9]  Marco Giglio,et al.  Life prediction of a wire rope subjected to axial and bending loads , 2005 .

[10]  R. Cavalli,et al.  Steep terrain forest operations – challenges, technology development, current implementation, and future opportunities , 2019, International Journal of Forest Engineering.

[11]  Karl Stampfer,et al.  Productivity, setup time and costs of a winch-assisted forwarder , 2018, Journal of Forest Research.

[12]  Karl Stampfer,et al.  Cable Corridor Installation Times for European Yarders , 2006 .

[13]  Sven-Ăke Axelsson,et al.  The Mechanization of Logging Operations in Sweden and its Effect on Occupational Safety and Health , 2013 .

[14]  Ola Lindroos,et al.  Drivers of Advances in Mechanized Timber Harvesting – a Selective Review of Technological Innovation , 2017 .

[15]  J. Sessions,et al.  Theoretical Stability and Traction of Steep Slope Tethered Feller-Bunchers , 2017 .

[16]  A.R.T. de Silva,et al.  Effect of abrasive wear on the tensile strength of steel wire rope , 2002 .

[17]  S. Grigolato,et al.  Tensile Force Monitoring on Large Winch-Assist Forwarders Operating in British Columbia , 2018 .

[18]  Mohammed Raoof,et al.  Behaviour of cables under dynamic or repeated loading , 1996 .

[19]  Karl Stampfer,et al.  Expanding Ground-based Harvesting onto Steep Terrain: A Review , 2015 .

[20]  Karl Stampfer,et al.  Monitoring Cable Tensile Forces of Winch-Assist Harvester and Forwarder Operations in Steep Terrain , 2018 .