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New methods for manually falling trees using hydraulically powered flange spreaders

University of British Columbia

Safety in forestry and especially in manual tree falling has become increasingly important over the last decade. Manual tree falling is widely regarded as the most dangerous part of forestry work. This thesis reports the results from a project that used a remotely operated hydraulic flange spreader and a novel holding wood pattern, consisting of uncut strips (tension strips) to remove the faller from the base of the tree when it starts to displace, since this is when many accidents occur. The novel holding wood pattern uses uncut strips of wood on the backcut side of the tree to hold the tree in static equilibrium while the flange spreader is inserted. Field testing was conducted in three different trials and overall resulted in a 80% success rate. Success of the system was analyzed using logistic regression and multi linear regression. Success of the method used in the first trial was insensitive to tree species, diameter, and height; however, it was strongly affected by tree imbalance. In the second trial the distance between the backcut and the weakening cut was optimized to maximize success. In the third trial only one tension strip was used, as opposed to two in the previous trial, and it was found that this design was simpler for the faller to cut and performed similarly to the two strip design. In this project the weight of the flange spreader used to initiate falling was considered an important constraint; therefore, to limit the size of the flange spreader the separation force was limited to 44.5kN. The strength of the tension strips had to be designed so the flange spreader could initiate falling even when there was a small imbalance opposite to the direction of fall, while also preventing the tree from displacing if a tree had an imbalance in the falling direction. These competing constraints resulted in a design that sometimes failed because the tension strips could not hold the tree against a lean or wind, and sometimes failed because the flange spreader was not strong enough to initiate falling. The goal of future research is to design a tool with iii 89kN of separation force, and weighing only 4.5kg. This new tool will permit the use of stronger tension strips which will reduce the likelihood of trees falling before the faller is clear, while also providing a reserve force to initiate falling of trees with an imbalance opposite to the falling direction.

Text

2011-01-09

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/26368

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/