Production of Wood Chips from Logging Residue under Space-Constrained Conditions

A study was conducted on chip production from logging residue left after a cable yarder operation. The logistics were managed with tractor and trailer units (shuttles). The study specifically dealt with a very difficult case of space constrained operations, further expanding the knowledge about chip supply in extreme work conditions. The focus of the investigation was also extended to the shuttles. The study tested a production chain, in which only 3 machines (1 chipper, 2 shuttles) were used to minimize operational costs. The use of 2 shuttles was decisive, reducing shuttle delays. The chips produced had an average moisture content of 40.2 ±3.1%. Particle size distribution shows an unfavorable composition. The content of accepts is as low as 72%, while oversized particles get up to 5.4% and fines rise to a maximum of 24%. The estimated net productivity of the whole system was 11.5 t PMH-1, corresponding to a gross productivity of 11.1 t SMH-1. The cost of the whole operation amounted to 21.2 €t-1

Production of Wood Chips from Logging Residue under Space-Constrained Conditions

A study was conducted on chip production from logging residue left after a cable yarder operation. The logistics were managed with tractor and trailer units (shuttles). The study specifically dealt with a very difficult case of space constrained operations, further expanding the knowledge about chip supply in extreme work conditions. The focus of the investigation was also extended to the shuttles. The study tested a production chain, in which only 3 machines (1 chipper, 2 shuttles) were used to minimize operational costs. The use of 2 shuttles was decisive, reducing shuttle delays. The chips produced had an average moisture content of 40.2 ±3.1%. Particle size distribution shows an unfavorable composition. The content of accepts is as low as 72%, while oversized particles get up to 5.4% and fines rise to a maximum of 24%. The estimated net productivity of the whole system was 11.5 t PMH-1, corresponding to a gross productivity of 11.1 t SMH-1. The cost of the whole operation amounted to 21.2 €t-1

Evaluation of Different Modes for Yarding Windthrown Timber with a Double-Hitch Carriage

Yarding whole trees is the most efficient way of extracting timber in steep terrain and allows reaping the combined benefits of mechanization and biomass recovery. In downhill yarding, however, whole-tree extraction is associated with a greater risk of loosening rocks or debris by the incoming loads as they bounce around along the extraction corridor. That may also cause damage to the cables and anchors by corresponding shock loads, ultimately endangering the yarder and its crew. To avoid these risks, »double-hitch carriages« can be employed. They combine a conventional motorized dropline carriage with a secondary carriage (»trailer«), equipped with a further, independent dropline winch. Thus, loads can be attached at two points and transported fully suspended above the ground in a horizontal position. Operation of these carriages may not be limited to the »horizontal« mode: the main carriage could also be operated without trailer (»single« mode), or separate loads may be attached to the two droplines (»double« mode), but their impact on the efficiency and economy of yarding operations is yet unknown. Therefore, the present study investigated how these modes affect the productivity and cost of downhill whole tree yarding. To this end, a classic time and motion study was conducted during a salvage logging operation in Northern Italy under a strictly controlled experimental design. Average productivity (18.2±7.2 to 24.5±15.4 m³ PSH0-1 merchantable volume per productive system hour excluding delays) and extraction cost (18 to 20 Euro m-³) did not differ significantly between treatments, while load composition and time consumption by task did. More (2.2±0.5) pieces per load were yarded under the »double«, than under the »single« (1.4±0.5) and »horizontal« (1.1±0.3) treatments. Inhaul speed (3.1±0.6 m s-1) was significantly higher under the »horizontal« treatment, which compensated for increased loading time derived from attaching the load at least at one point outside the corridor. Unloading took significantly longer under the »double« treatment, as loads had to be dropped successively due to the confined conditions on the landing. Though slowest (2.5±0.9 m s-1) during inhaul, the »single« treatment exhibited none of the other treatments disadvantages and larger loads could be accumulated due to partial suspension. From an economic viewpoint, the »horizontal« mode may only be warranted over yarding distances substantially beyond average. On shorter ones, it must be justified by other reasons, such as minimizing product contamination, soil disturbance or excessive strain to the skyline when the terrain profile impedes sufficient ground clearance

Influence of chain sharpness, tension adjustment and type of electric chainsaw on energy consumption and cross-cutting time

Recently, electrical cordless chainsaws were introduced, which provide less harmful working conditions for the operators, and should therefore be deployed as much as possible in all non-professional and professional applications. The low power of the electric engines may result in lower efficiency and higher energy consumption in the case of over-tensioned chains, due to increased friction between the saw and the chain. Therefore, a partial factorial experiment with one factor on three levels (saw type) and two factors on two levels was designed, whereby a wooden beam was cross-cut at two levels of chain sharpness and tension. The time of cross-cutting and energy consumption were controlled. The chain tension does not have a significant effect onto time of cross cutting, or electricity consumption. Both have cross-cutting and energy consumption have been found to differ significantly when comparing the saws used in the experiment. The average efficiency of cross cutting using electrical chainsaws reported is 2.35 times lower than when using petrol powered saws. The lower efficiency is caused by the lower engine power of electrical saws, and lower speed of chain rotation. Energy consumption and time of cross cutting are significantly higher when using a blunt chain, with large differences in time of cross cutting and electricity consumption, making the chain sharpness the most important of all controlled factors. In the study, we did not find evidence that over tensioning of the chain increases the time of cross cutting or energy consumption, however the integration of such systems is recommended because of the worker’s safety

Analysis of Inclusion of Wood Forwarding into a Skidding Model

Mechanized felling was introduced in Slovenia at the beginning of this decade, and before that Slovenian forestry relied on motor manual felling and tractor skidding or cable crane yarding. In this research we are dealing with wood forwarding. Model skidding maps were built, using terrain classification and decision support systems for forwarders and tractor trailers. The purpose of this research is to establish how to plan in advance new individual skidding systems, which involves changing the skidding map. In the first phase, the criteria for the selection of skidding means were determined using multicriterial methodology, and then this model was applied to a study area. In the third stage we conducted a comparison between the reference map provided by the Slovenian Forest Service and the model map resulting from steps one and two. Afterwards it was determined which types of terrain were selected for forwarding and which forms of skidding would face the most serious competition from forwarding. It was determined that the terrain allows for more forwarding than suggested by the reference skidding map. In the research area most of the forest is privately-owned, making it very unlikely that large forwarders would be used, and so tractor trailers were included in the model. Including tractor trailers we have established, that tractor skidding increases marginally at the expense of forwarding, in particular in terrain with higher terrain gradient and more difficult working conditions

Morphological analysis of articulated forestry skidders from the archive database of forestry mechanization from 2015 to 2022

The database was preprared on the basis of systematic data gathering in the field of forest harvesting. The foundations for the database were initially established by Prof. dr. Boštjan Košri and colleagues in the mid 1970s in an effort to better understand the long-term dynamics of development of forest harvesting machinery. The data mechanization database contains data about forest machinery, and can be used to study the trends in machine development, facilitate research in the field of terramechanics, and influence onto forest soils. The current database includes 53 machines, from 9 producers, across 7 countries. It database provides critical infrastructure for research in the field of forest harvesting. This is the first attempt to publish the database, however continuous improvement is required, at first with expanding the database to years prior to 2015, and secondly by providing additional parameters. What is missing is control of manufacturer data by means of actually measuring parameters, and development of methods of machine-soil interaction