Assessing the Utility of Two Integrated Harvester-Forwarder Machine Concepts Through Stand-Level Simulation

The relative performance of two integrated machine concepts (combined harvesting / forwarding capabilities) was assessed against a conventional harvester / forwarder CTL system in a simulated thinning regime. Multiple-regression based on the simulation output was used in deriving time-consumption functions at the systems and machine level. Descriptive stand variables could be reduced to; harvest volume (m3/ha), stem volume (m3), lead distance (m) and object volume (m3/ stand) while maintaining acceptable statistical rigour (R2 > 0.95). The ability of one of the integrated machines to process logs directly onto the bunk provided it with an advantage that more than compensated for its reduced harvesting efficiency. Both integrated machine systems show a competitive advantage in forest structures with low object volumes and long or frequent relocations. Factors negatively affecting forwarding productivity (e.g. long lead distances) favour the conventional two-machine system. A break-even economic analysis showed that integrated machines could present a feasible alternative to contemporary mechanised CTL systems

Fuel Consumption In Forwarders

Forwarder fuel consumption was studied by examining a total of 27 forwarders under field conditions. Three datasets, representing different data acquisition methods, were used. In a field study, time and fuel consumption by work-element of two 20-21 tonne forwarders in final felling were recorded. In a questionnaire survey, daily data concerning fuel consumption, productivity and average extraction distance was provided on 18 forwarders, divided between final felling and thinning. Finally, accounting data on fuel consumption for 11 forwarders were obtained. In the field study, the fuel consumption varied between 8.3 to 15.7 l/PMH (productive machine hour) for different work elements. The total fuel consumption was 0.28-0.36 l/m3sub (solid under bark) at average extraction distances on 360-412 m for loads of sawlogs and 0.43-0.66 l/m3sub (458-514 m) for loads of pulpwood. 61-62% of that fuel was consumed during loading and driving during loading. The forwarders consumed 0.23-0.38 l/100 m driving and the difference was only 10% with and without load. In the questionnaire survey, the fuel consumption averaged 0.62 l/m3sub (sawlogs and pulpwood, 318 m average extraction distance) for final felling (16-20 tonne forwarders) and 0.92 l/m3sub (644 m) for thinning (11-14 tonnes). An exception was 2.5 tonne forwarders that consumed only 0.35-0.37 l/m3sub (120-180 m). 89% of the extracted volume in the accounting data was from thinnings and the fuel consumption was in average 0.67 l/m3sub (100-200 m) for 9 to11 tonne forwarders. More difficult terrain conditions, the use of tracks and wheel-chains and one more assortment in the questionnaire survey are the most probable reasons for higher fuel consumption than in the field study. At long extraction distances it is especially important to utilize the maximum load capacity to benefit low fuel consumption on m3 basis

New Techniques For Pre-Commercial Thinning -- Time Consumption and Tree Damage Parameters

High costs, increasing density and height of young stands at the time of pre-commercial thinning, and difficulty in attracting personnel to do motor-manual work have called for the development of new techniques for pre-commercial thinning. In the study reported here a new motor-manual and mechanized pre-commercial thinning technique was compared to the conventional brush saw technique in terms of time requirements and damage caused to crop trees. The motor-manual tools tested were a hacksaw and two pole saws with modified chainsaw blades. The mechanized machine prototype was built especially for pre-commercial thinning, and was equipped with a new type of crane tip-mounted device based on a cutting-squeezing technique. Our expectations were that, compared to the brush saw, themechanized approach would be less time-demanding in dense and/or large diameter stands, but more main stems would be damaged. Furthermore, a motor-manual device with a larger cutting area than the conventional brush saw blade should allow faster operation in dense and large diameter stands, without damaging higher numbers of main stems. To test these beliefs, a rig was built that enabled the tools to be compared in experimental stands with different densities and diameters of secondary stems. One of the pole saws and the mechanized prototype machine were competitive with the conventional brush saw in terms of both time requirements and frequency of damage to main stems, especially in dense (i.e. >15000 stems ha-1) and large diameter (>4 cm) stands. The pole saw was competitive despite having a less powerful engine. The mechanized prototype showed more homogenous time consumption, with lower variation than the other tools. Further field studies are needed to compare the tools in economic terms

Distribution, characteristics and potential of biomass-dense thinning forests in Sweden

Understanding the characteristics of unutilized biomass resources, such as small-diameter trees from biomass-dense thinning forests (BDTF) (non-commercially-thinned forests), can provide important information for developing a bio-based economy. The aim of this study was to describe the areal distribution, characteristics (biomass of growing stock, tree height, etc.) and harvesting potential of BDTF in Sweden. A national forest inventory plot dataset was imported into a geographical information system and plots containing BDTF were selected by applying increasingly stringent constraints. Results show that, depending on the constraints applied, BDTF covers 9-44% (2.1-9.8 M ha) of the productive forest land area, and contains 7-34% of the total growing stock (119-564 M OD t), with an average biomass density of 57 OD t ha^-1. Of the total BDTF area, 65% is located in northern Sweden and 2% corresponds to set-aside farmlands. Comparisons with a study from 2008 indicate that BDTF area has increased by at least 4% (about 102 000 ha), in line with general trends for Sweden and Europe. Analyses revealed that the technical harvesting potential of delimbed stemwood (over bark, including tops) from BDTF ranges from 3.0 to 6.1 M OD t yr^-1 (7.5 to 15.1 M m^3 yr^-1), while the potential of whole-tree harvesting ranges from 4.3 to 8.7 M OD t yr^-1 (10.2 to 20.6 M m3 yr^-1) depending on the scenario considered. However, further technological developments of the harvest and supply systems are needed to utilize the full potential of BDTF

Changes in technical performance, mechanical availability and prices of machines used in forest operations in Sweden from 1985 to 2010

This study describes developments in large-scale logging technology in Sweden from 1985 to 2010. Data were collected from manufacturers' sales material and from large forest enterprises. On average, forwarders manufactured in 2010 had 27–33% higher boom lifting torque than those manufactured in 1985–1989. The inflation-adjusted prices of medium-sized single-grip harvesters remained the same, but prices of forwarders increased by 30–50% in this period. The mechanical availability of various classes of machinery used increased from 70–80% to 85–88% between 1985 and 2008. The harvesting costs of thinning decreased between 1990 and 1998, while those of final fellings decreased from 1985 to 2006. However, in 2008 costs of both thinning and final felling tended to increase. The productivity of logging by the Swedish forest enterprise SCA increased almost three-fold in the period 1985–2010. However, since 2003 there have been signs of declining productivity. Currently, there is considerable interest in harvesting forest biomass for energy production. The new work tasks involved will affect the configuration of forest machines. A possible trend is that a new generation of forest machines and methods will be developed to facilitate integrated handling of roundwood and forest biomass for energy generation

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