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The Log - Issue five- Research activity: Use of mechanised felling systems in hard conditions

image of mechanised felling in hard conditions in Tasmania By Mauricio Acuna

The Tasmanian forest industry has been put on notice by Workplace Standards Tasmania (following a coroner’s report) to eliminate the practice of motor-manual felling of trees (in which harvesters fell trees using chainsaws), particularly in forests in which the trees are of small-to-medium diameter. This is a response to recent accidents and fatalities, but aims to provide a safer working environment for forest workers. The most obvious way to improve worker safety and still maintain timber production is to replace motor-manual tree felling with mechanical tree felling, in which the worker is enclosed in a protective cabin while felling trees.

Factors limiting implementation of mechanical felling

However, some known factors limit effectively implementing mechanical felling systems in Tasmanian native forests. Native forests in Tasmania are characterised by steep slopes, with rocky, rough and uneven terrain. They typically have very large diameter older trees interspersed among relatively uniform-sized even-aged regrowth trees of small-to-medium diameter. Introducing mechanical tree felling in such forests will require changing work methods, introducing new machines and/or combinations of machines, and will have implications for productivity, safety and associated costs.

Study details

To investigate the factors affecting the productivity and costs of mechanical (feller buncher) and manual felling systems, a detailed time and motion study was conducted on two different sites in southern Tasmania. Ground conditions on each site were assessed with a terrain classification system defined by the CRC for Forestry. Before collecting data, all trees within each plot were identified according to their diameter class with a painted colour code. Over a period of one or two weeks, the operation and work elements of each machine were recorded using a camcorder and timing software. Complementary information, such as operating delays, painted colour code, species, branchiness, number of logs per stem, and terrain classification assessment were recorded on data collection forms.

Preliminary results

The data is still being analysed, but preliminary results indicate that in hard conditions (rough and rocky ground, and big trees) the productivity of mechanised (feller buncher) systems is about 60% higher than motor-manual systems but comes at a considerably higher hourly cost. It was also noted during the study that there were areas that simply could not be accessed by the mechanical system and discussions with contractors and operators confirmed that the selection of felling system is dictated mainly by the presence of rocks and the ground conditions, and less by the tree. The results of this study will be published soon in an industry bulletin and will be used to propose recommendations to improve the productivity as well as the safety of the operations under those conditions.

The project is being undertaken by research fellows Mauricio Acuna, Damian Walsh and Mohammad Ghaffariyan in collaboration with Gunns Ltd and harvesting companies Eastern Tiers and Howell’s Logging.