Volume 11, numéro 1, january 2000

EN :

The paper presents the conditions in which forest production as well as forest road design and construction in Slovenia are going on. The most important influential factors and the limitations in the production process have been given special emphasis, among which there are also potential environmental disturbances and forest functions. A brief description of a method based on multi-criteria decision making, a model form of which was applied in the analysis of technologies and forest road network in the Jezersko forest region, is presented as well. The results indicate the suitability of terrain for the design and construction of forest roads and skidding tracks. An analysis of the present forest road and skidding track network as well as a comparison of terrain suitability with the suitability of all terrain have been made as well. It has been established that especially in the construction of forest roads and skidding tracks difficulties regarding construction have strongly been taken into consideration, because the existing network is situated on terrain which is easier than the average. Finally, the possibilities as to the further developments of the model have been indicated.

EN :

An increased use of shelterwoods in regeneration has generated a demand for knowledge of how single-grip harvester performance is affected by shelterwood treatments. Time consumption and productivity of a large single-grip harvester working in shelterwood establishment and thinning was studied using work sampling. Five treatments were studied, 1) shelterwood establishment, thinning of 2) sparse, 3) medium and 4) dense shelterwoods and 5) clear-cutting. Each treatment was replicated three times. Results shows that time consumption for the average harvested tree increased with tree volume and declining number of harvested trees per ha. Productivity was higher in clear-cutting than in any of the shelterwood treatments. Harvesting costs in the shelterwood system thus becomes higher than in the clear-cutting system. These costs must be carefully weighted against the ecological and silvicultural benefits of the shelterwood, including the possible reductions of the regeneration costs.

EN :

Two Madil 046 skyline yarders, rigged as slackline systems and equipped with Ballenger motorized carriages, were studied by field crews from the University of British Columbia - Forest Operations Group for approximately six months at sites on the west coast of Vancouver Island in British Columbia. A continuous turn element time study, using handheld data recorders was employed to collect data throughout the study. Mean cycle times for the two operations ranged from 11.5 to 13.5 minutes per cycle. Delays contributed at least 20 percent of the cycle time for both operations and were primarily caused by carriage related problems. Average piece size differed by more than 56 percent and created significant differences in overall system productivity. While average cycle time for the two systems differed by at least two minutes, the system with the longer cycle time had higher mean production due to the larger volume per piece and per cycle. The study results strongly suggest that maximizing volume per cycle is critical to maintaining productivity and minimizing costs, even though cycle time may be increased. In this case, one system was able to capitalize on larger average piece size to significantly improve hourly production, even though cycle times for this yarder were higher. More effort is needed during operations to monitor volume (or weight) per cycle and consistently maintain the maximum volume per cycle for existing conditions.

EN :

This study examines the role of forest operations strategies in sector development for Norway's fjord region. The paper starts with an examination of forest owner attitudes and perceptions in relation to their harvesting behaviour, use of contractor harvesting and road net extension. The influence of forest owner decisions, contractor mechanisation and road net extension standards on operational efficiency is examined in a simple deterministic model of the regional wood chain. Average wood procurement costs are calculated for increasing sector capacity. Direct and indirect harvesting costs are also followed throughout this development.

EN :

This report summarises findings of an ergonomic evaluation of manual planting under three different site conditions. Heart rate data were collected and analysed using several heart rate indices. The three sites did not differ greatly, producing mean working heart rates that ranged from 132.7 bt.min-1 (+ 16.2) to 134.9 bt.min-1 (+ 13.8). Results indicate that manually planting Pinus radiata seedlings on all three sites can be classified as hard continuous work or very heavy work. Planters maintained similar mean working heart rates for all three sites by decreasing productivity as planting conditions became more difficult. Body part discomfort was only experienced when planting on pasture, where slight to severe discomfort was reported 48% of the time. Hazard occurrence was low for all three site conditions.

EN :

Four sampling methods were compared for accuracy and ease of implementation in measuring residual stand damage. Data were collected from young Douglas-fir (Pseudotsuga menziesii) stands, which were commercially thinned using three different logging systems in western Oregon. Systematic plot sampling consistently provided damage estimates similar to the results of a 100% survey; there was no significant difference between their accuracies in measuring stand damage. This method also took the least amount of time and effort for map layout and field plot location. Because measuring stand damage requires considerable effort in sample planning and implementation, an easier, quick-survey method should be developed to monitor residual stand damage for in-progress and post-thinning operations.

EN :

Previously we published some results of the procedure for the improvement of intermediate technology and machinery performance criteria. The aim of the present paper is to describe the model of the middle level of hierarchy - the optimization of the hydraulic cylinder operating mechanisms. Drive and transmission mechanisms for forest machinery crane synthesis are discussed as optimizations for boom operating mechanisms and outboom operating mechanisms. Concentration is on the static part of this problem. Although the speed of movement of the crane elements affects productivity, it is not taken into account in this study. Future studies will take into consideration a dynamic analysis and output of machinery.

The results of this study show the necessity to separate the design of different types of forest machine cranes. For example, for the parallel crane type, a modification of the proposed algorithms is necessary.

This paper may be useful for forest machine designers as well as university students, who take courses in forest machine design.

EN :

Filling wood cell cavities or modifying walls with polymer improves mechanical properties and reduces influences of moisture and biodeterioration agents. Properties of untreated wood and wood polymer composites are presented in the paper.