Monitoring Cable Tensile Forces of Winch-Assist Harvester and Forwarder Operations in Steep Terrain

Holzleitner, Franz; Kastner, Maximilian; Stampfer, Karl; Höller, Norbert; Kanzian, Christian

doi:10.3390/f9020053

Cited by 21 publications

(17 citation statements)

References 5 publications

(4 reference statements)

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“…In the present study, the observation time is not long enough, and it is suggested to derive the k factors from the literature. In the present study, as proposed by Holzleitner et al [35], a correction factor of 0.3 was used as indicated by Stampfer [40]. In order to estimate total time consumption per cycle (TTC), including delays less than 15 min and expressed in hours, the sum of TM, TL, and TU (Equations (1)-(3)), multiplied by k factor, were divided by 60 (Equation (4)).…”

supporting

confidence: 69%

“…The data collection was based on a time and motion study through video recording using on-board digital video cameras (Drift ® , Ghost-HD). The acquisition rate was set at 720 ppm with 30 frame/s and a field of view of 170 • , as also proposed in similar studies [24,[34][35][36]. As proposed by Mologni et al [34], in order to estimate forwarder load volume, high-resolution photos were taken of each load both from the back and laterally.…”

Section: Data Collectionmentioning

confidence: 99%

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Forwarder Productivity in Salvage Logging Operations in Difficult Terrain

Cadei

Mologni

Röser

et al. 2020

Forests

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Large scale windthrow salvage logging is increasing in Central Europe because of the growth of severe atmospheric events due to global heating. Sustainable forest operations in these conditions are challenging in terms of both productivity performances and safety of the operations. Fully mechanized harvesting systems are the preferred solution on trafficable terrains and proper slopes. However, different work methods and logistic organization of the operations could largely change the overall performances. The study observed three harvesting sites based on fully mechanized cut-to-length systems and located in areas affected by the Vaia storm, which hit north-eastern Italy in October 2018. The objectives were to estimate forwarder productivity in salvage logging in difficult terrain and to identify significant variables affecting this productivity under real working conditions. Time and motion studies were carried out and covered 59.9 PMH 15 , for a total of 101 working cycles, extracting a total volume of 1277 m 3 of timber. Average time consumption for each site was 38.7, 42.2, and 25.1 PMH 15 with average productivity of 22.5, 18.5, and 29.4 m 3 /PMH 15 , respectively, for Sites A, B, and C. A total of seven explanatory variables significantly affected forwarder productivity. Average load volume, maximum machine inclination during loading, and number of logs positively affected the productivity. On the contrary, travel distance, load volume, maximum ground slope during moving and loading have a negative influence. With an average travel distance of 500 m, the productivity resulted 20.52, 16.31, and 23.03 m 3 /PMH 15 , respectively, for Sites A, B, and C. An increase of 200 m of travel distance causes a decrease in productivity of 6%.Forests 2020, 11, 341 2 of 14 or on (ii) passive management [6]. Active intervention strategies focus on rapid post-disturbance harvest and recovery of the economic value of the forest [7] in order to decrease the risk of a rapid reduction of the timber value due to reductions in wood quality [8], the risk of wildfires [9], and insect outbreaks [10].A common post-disturbance management approach is salvage logging [11,12] which consists of the widespread removal of damaged trees. Salvage logging benefits and drawbacks are widely discussed as it can have a negative effect on forests in terms of reducing biodiversity, increasing erosion, and reducing soil fertility [11]. Some authors report that salvage logging interventions must be planned considering the site-specific characteristics [13,14]. When salvage logging is appropriate to be applied, the most suitable technological solutions are those based on fully mechanized systems as these guarantee high productivity and above all a lower risk for operators as they work exclusively on the machines [15,16].In complex terrain and in mountain areas, with a low density of forest roads, the use of fully mechanized systems in salvage logging operations is difficult. In these conditions, the main system remains the semi-mechanized system based ...

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supporting

confidence: 69%

Section: Data Collectionmentioning

confidence: 99%

Forwarder Productivity in Salvage Logging Operations in Difficult Terrain

Cadei

Mologni

Röser

et al. 2020

Forests

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“…There are no published international regulations on SWL for winch-assisted machinery, but the actual draft version of ISO 19472-2 has a SF of two. Different to the findings of Holzleitner et al (2018) and Mologni et al (2018), the tensile force in this study exceeded SWL (SF=2). As this was only for a really short time, a SF of two would be in practice well suitable for wheeled machines.…”

Section: Discussioncontrasting

confidence: 99%

“…The merging and analysis of the sensor data was done similarly to the approach of Holzleitner et al (2018). All data was preprocessed via R-Scripts and exported into a database in separate tables for tensile force, tilt and time and motion data.…”

Section: Data Analysingmentioning

confidence: 99%

“…For example, Schaare et al (2016) recorded cable tensile force for tracked feller bunchers in New Zealand and observed a peak tensile force of 412 kN (60.1% of MBS). For wheeled harvesters and forwarders, Holzleitner et al (2018) developed a specific survey protocol for monitoring tensile forces and during field tests they measured a peak of 75.5 kN (41.7% of MBS). In this study, safe working load (SWL) of the cable, considering a safety factor (SF) of two (actual draft version of ISO 19472-2), was not exceeded.…”

Section: Introductionmentioning

confidence: 99%

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

Holzfeind

Kanzian

Stampfer

et al. 2019

Croat. j. for. eng. (Online)

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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.

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