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Gewählte Doctoral Thesis:

Thomas Holzfeind (2020): Timber Extraction with Winch-Assisted Forwarders — Economic, Safety and Ecological Aspects.
Doctoral Thesis - Institut für Forsttechnik (FT), BOKU-Universität für Bodenkultur, pp 81. UB BOKU obvsg

Data Source: ZID Abstracts
Increasing costs for timber harvesting and low contribution margins at the same time require continuous development of fully mechanized timber harvesting systems. Ground-based winch-assisted systems can be considered as one of the major innovations in steep terrain harvesting in the last decade. Besides steep terrain, its operating range might also expand to gentle terrain, where soils are wet or unstable and where timber harvesting faces challenges with shortening periods of frozen soil conditions due to climate change. Field studies were carried out to get better insights into the economic, safety and ecological aspects of winch-assisted forwarders. The studies showed that influencing factors on forwarding productivity are piece volume, slope gradient, driven distance during loading and extraction distance. A developed productivity model showed an average productivity of 13.7 m³/PSH15 leading to forwarding costs of 8.06 €/m³. In downhill operations, the setting up of the cable for the winch-assisted forwarder took on average 21.6 min. This results in total costs for the forwarding operation of 9.1 €/m³, including the setup costs of about 1 €/m³. Tensile force measurements of about 15 h without delays of two different winch-assisted forwarders showed that peaks with an amplitude of up to 50 kN can occur within a few cs. A detailed analysis revealed that 90 % of the amplitudes of peaks ≥20 kN occurred during driving activities although they took only 40.5 % of productive time. Amplitudes of peaks are significantly higher during driving activities than during loading activities. As shown during a field trial on a sensitive site in flat terrain with a winch-assisted forwarder, increasing tensile force decreases wheel slippage significantly. Average slippage without using winch-assist was 5.3 % and went down to an average of 0.4 % if using winch-assist. In addition, a literature review showed that winch-assist harvesting is considered to be more productive compared to conventional steep terrain harvesting. Furthermore, it increases work safety on steep terrain and reduces soil disturbances from ground-based equipment.

Betreuer: Stampfer Karl
1. Berater: Gronauer Andreas
2. Berater: Kanzian Christian

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