Ola Lindroos 
,
Marina Henningsson,
Dimitris Athanassiadis,
Tomas Nordfjell
Forces required to vertically uproot tree stumps
Lindroos O., Henningsson M., Athanassiadis D., Nordfjell T. (2010). Forces required to vertically uproot tree stumps. Silva Fennica vol. 44 no. 4 article id 135. https://doi.org/10.14214/sf.135
Abstract
Stumpwood attracts renewed interest due to increased use of forest biomass for bioenergy. In Nordic countries stumps are generally uprooted with crawler excavators, which have strong cranes (ca. 400 kNm gross lift torque), but are not designed for moving in forest terrain. Their use is based on practical experience with available and tested machine types rather than thorough examinations of requirements, partly due to limited knowledge of force requirements for uprooting of stumps. Therefore, in this work mean and maximum forces required to vertically uproot stumps of Norway spruce (Picea abies) and birch (Betula spp.) were quantified together with the effects of various soil types and uprooting methods. The used excavator’s crane-mounted uprooting device enabled comparisons between usage of solely crane force, and a method in which preparatory loosening forces were applied prior to crane force. Uprooting stumps in single pieces proved difficult; 61% split unintentionally. Force requirements were similar across tree species, increasing curve-linearly with stump diameter, and stumps uprooted in a single piece required more force than split stumps. Preparatory loosening reduced crane force requirements and, surprisingly, less force was required to uproot stumps from a mesic, till soil than from a moist, finer-textured soil. No stump required more than 60 kN crane force and functions for maximum force requirements indicate that powerful harvesters and forwarders (gross crane lifting capacity of 273 and 155 kNm, respectively) should be able to uproot all stumps with ≤ 61 cm and ≤ 32 cm diameter, respectively, in one piece. Larger stumps could be managed if it is acceptable that stumps are split before uprooting.
Keywords
forest fuels;
Picea abies;
bioenergy;
stump harvesting;
machine development;
Betula spp.
-
Lindroos,
Department of Forest Resource Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
E-mail
ola.lindroos@srh.slu.se
- Henningsson, Komatsu Forest AB, Box 7124, SE-907 04 Umeå, Sweden E-mail mh@nn.se
- Athanassiadis, Department of Forest Resource Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden E-mail da@nn.se
- Nordfjell, Department of Forest Resource Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden E-mail tn@nn.se
Received 26 April 2010 Accepted 14 October 2010 Published 31 December 2010
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