Torques from Manual Tools for Directional Tree Felling

Motor-manual tree felling is commonly practiced in many regions of the world. Trees falling in unwanted directions cause severe accidents and extra work in motor-manual logging. Different kinds of manual tools can help force trees to fall in the desired direction, but their capacity are uncertain due to a lack of suitable evaluation methods. Reliable recommendations of felling tools’ limits could help reduce human injuries and damage to property. The objective of this study was, therefore, to develop and evaluate a realistic and convenient method for studying felling tools’ capacity in terms of the potential torque they can generate. A theoretical model of torque components was constructed and the mechanics of the falling tree and of the studied equipment were explained. The developed method uses real trees, which were cut at 1.65 m above stump height to create trial stems. Trial stems were anchored to a neighboring tree and then cut as if they were to be felled. Standardized forces were applied to a forestry jack, felling lever, and wedge, and their effects on the trial stem were recorded by a load cell in the anchoring line. The method proved suitable for the evaluation of forestry jacks, while it needs improvements to evaluate felling levers and wedges thoroughly. Methodological improvements are suggested and practical applications are discussed and demonstrated in terms of the forestry jack’s capacity to deal with trees with unfavorable angles of inclination.