Abstract

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.

Highlights

  • Ground-based harvesting has significantly benefited from mechanization (Spinelli and Magagnotti 2011, Lindroos et al 2017) but is often restricted by terrain conditions

  • 3.1 Cable Tensile Force In total, the two machines were observed for about 15 work hours without delays

  • The maximum values for Komatsu 840TX did not exceed 50% of minimum breaking strength (MBS) (SF=2), but for John Deere 1210E the tensile force was above 50% of MBS (SF=2) for 2.09 sec

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Summary

Introduction

Ground-based harvesting has significantly benefited from mechanization (Spinelli and Magagnotti 2011, Lindroos et al 2017) but is often restricted by terrain conditions. Trafficability can be restricted because of obstacles in skid trails (stumps, stones, etc.), partially steeper terrain (embankments, etc.) or potentially high soil disturbances caused by driving. To solve these problems and expand the application of ground-based vehicles, the idea came up to use winches for assistance in order to reduce site damage and harvesting costs on steep, soft or wet terrain

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