Volume 18, numéro 2, june 2007

EN :

The workspace around machines in forest operations is commonly illuminated by either halogen lamps or xenon (HID) lamps. Informal claims have been made that there is a large difference in subjective experience between using halogen lamps and xenon lamps. To obtain an objective quantification, human visual abilities were measured when illumination was provided by either xenon or halogen lamps with the same physical illumination as measured in Lux. Performance was measured as the number of correct identifications of test figures which depended on the color of test displays used, but the difference between lamp types was small. Overall, when differences could be measured between lamp conditions, somewhat better performance was obtained with the xenon lamps than with the halogen lamps. Furthermore, xenon lamps required much less energy: three halogen lamps (3 • 70 W) had an illuminance equal to one xenon lamp (35 W).

EN :

Road grading is the most common maintenance activity performed on forest roads. Reducing grading cost could release resources for other maintenance needs, ideally resulting in a better maintained road system. A combinatorial optimization method, tabu search, is combined with two local search procedures to generate efficient grading routes. Determining the optimal grading route is modeled as an extension of the Mixed Rural Postman Problem (MRPP), adapted to include a daily operating time limit and different traversal/service times. The objective was to minimize total operating time, a proxy for grading cost. The heuristic was tested on both artificial and actual forest road networks, and computational results are presented. The heuristic demonstrates the ability to generate efficient and feasible grader routes.

EN :

This paper examines the forwarding productivity of energy wood thinnings. The objectives of the study were to: compare the forwarding productivity following either manual or mechanized felling of whole trees and create productivity models for forwarding. The time consumption of the work phases in forwarding, following manual and mechanized cutting, was formulated by applying a regression analysis, in which the independent variables were cutting removal (m3/ha) and forwarding distance (m). The final calculation unit for time consumption in each of the work elements was second (s) per solid cubic meter (m3). Time studies were carried out using two Timberjack 810B forwarders. According to these results, forwarding productivity following mechanized energy wood cutting was significantly higher compared to productivity after manual cutting. Mechanized cutting by the harvester enables the felling and bunching of whole trees into large grapple loads close to the side of the strip road, which clearly improves the output of forwarding thereby helping to reduce costs. When the forwarding distance was 250 m, accumulation of energy wood was 60 m3/ha, and load size was 6 m3, the forwarding productivity following mechanized cutting was 11.9 m3/E0h and 7.1 m3/E0h after manual cutting.

EN :

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.

EN :

Mechanical failure rates associated with logging vehicle accidents in Georgia are dramatically lower today than they were in 1988–1991 before these trucks became subject to random roadside inspections. Mechanical failure dropped by half for logging tractor-trailers (from 10.9% to 4.8%) and by two-thirds for logging trucks (from 12.9% to 4.2%). Mechanical failure is now the seventh most cited contributing factor in logging tractor-trailer accidents instead of first as it was prior to 1991. Specific types of mechanical failures have also declined sharply. Three potential failure items that are visually checked during roadside inspections – brakes, slick tires, and lights – have seen the most dramatic declines. Brake failure has dropped by two-thirds and improper lights as a factor have almost disappeared. Driver impairment due to use of alcohol or drugs today occurs in less than 0.5 percent of accidents. Factors associated with logging vehicle accidents today in Georgia closely resemble those associated with all trucking accidents generally. Accidents per million tons of wood consumed, however, has increased steadily from 11 in 1991 to 19 per million tons in 2003.