The Human Influence on Productivity in Harvester Operations

It is well-known that machine operators vary in their performance when undertaking mechanized forestry harvesting operations. Nevertheless, the human factor is still largely disregarded in productivity calculations. In the present study, operator performance is evaluated by analysing archived production data collected automatically by computers on-board single grip harvesters driven by 32 operators working in 3,351 stands over a period of three years. The experimental conditions were all approximately the same. The effect of the operators is modelled by a multilinear regression analysis. Seventeen operators were found to have performance levels that differed significantly from the mean model. Together, ‘tree volume’ and ‘operator’ explained 84% of the overall variance. However, since 37.3% of the variance in productivity is explained by the operator, the influence of the operator on productivity is quite large. The minimum and maximum significant mean productivity values for all the operators differed by a factor of 2.2, which reduced to a factor of 1.8 if only data from experienced operators were analysed, although this still demonstrates that the best operators are nearly twice as productive as the worst. The operator, therefore, has an important influence on productivity and should be considered a key factor in productivity models

Transfer System to Adapt Timber Harvesting Operations to Local Conditions

Sustainable management requires equal consideration of economic, ecological and social criteria. The science looks back on more than 50 years, in which different multi-criteria decisionmaking models have been developed and refined. They are well suited for the solution of complex tasks, but are dependent on case studies und limited to them. Due to this high complexity, it is not possible to transfer the results of such case studies into practice. It is, therefore, necessary to prepare a transfer model that gives the opportunity to the practice to translate the scientific findings into their local multi-criteria decisions. Such a transfer model should provide a fixed basic structure, with which the complexity is reliably depicted. However, it should be open for individual additions and adaptations in order to adapt to the locality. In the process of finding the action options, it should support the user to enlarge the search space as far as possible. The criteria and attributes should be largely fostered by scientific if-then rules, in order to meet the transfer task. In this context, uncertainties, risks and side effects must be pointed out. In the selection of the scales, in contrast, it is recommended to dispense with scientific objectivity in favor of simpler applicability in practice. On the basis of these demands, a model is developed for finding optimal wood harvesting methods. In phases Develop – Assess – Evaluate, the user is guided through the decision-making process. Initially, he is commissioned to develop concrete action options for his individual task and to predict their results. After that, he has to check six criteria with attributes and assess the options. Several methodological concepts are offered for the final evaluation. The model has proven its worth in various teaching environments. Therefore, it is recommended to develop it into an online tool for a wider target group as a continuing education module

Tree Felling with a Drill Cone

Motor-manual timber felling is one of the most dangerous operations in the forest and cannot be completely replaced by fully mechanized timber harvesting by a harvester when dealing with large and deciduous trees. Shifting the center of gravity of tree ready to be felled beyond its tipping line using conventional felling wedges is dangerous because the forest worker is directly behind the stem and under the tree crown until just before the tree falls. The worker can be hit by the trunk itself, but also by falling parts of the crown. In a preliminary study for the development of a new type of felling head, felling with a drill cone that can open the felling cut with the help of an applied torque was investigated. A drill cone does not require any special cutting technique, no counter forces to the tree, works without impulses, it is self-retaining and can be unscrewed again. In order to determine the torque required for felling the tree as a function of the tree parameters, the mathematical equation framework was established and practical experiments were used to determine the friction parameters and verify the calculations. The torque of the drill cone is used to bend the intact fibers of the hinge, shift the center of gravity of the tree in the direction of fall, and to overcome the friction of the drill cone on the felling cut. The effects of forward or backward leaning trees on the required torque can also be quantified. It has been shown that the efficiency of a drill cone is low, but this is compensated for by the high internal torque to lift ratio. The maximum measured input torque for felling trees with a felling diameter up to 55 centimeter was 100 Nm

Development and Evaluation of a Felling Head for a Light Forest Crawler

With motor-manual wood harvesting (by a forest worker with a chainsaw) fatal accidents happen every year when the tree is felled or when parts of the crown fall down. The alternative is to fell trees mechanically using a timber harvester head, which, however, must be brought up to the trees in the forest by means of its crane. With the usual crane reach of 10 m, the harvester needs a system of parallel strip roads with a spacing of 20 m. Furthermore, the harvester needs a dead weight of around 20 tons that compacts the soil. Both consequences increasingly evoke critics. The requirement to fell trees mechanically and to enlarge the distance between the strip roads calls for a solution to fell trees with a small, light machine that can apply its felling tool to the tree in close proximity. Together Pfanzelt Maschinenbau GmbH and the Professorship for Forest Technology of Technische Universität Dresden have run a project for developing a compact, new type of felling head, which is attached to the existing forest crawler »Moritz FR70/75« by means of a short manipulation arm. This head imitates the felling technique, which is applied by a forest worker, in a mechanical way with a high grade of automatization. Even though this machine works with higher system costs, it is significantly faster and more precise than the motor-manual version. The functional principle of the felling head was developed, patented, conceptualized and optimized with the help of prototypes and individual tests at the TU Dresden, Professorship for Forest Technology. After that, it was completely designed, manufactured and automated in terms of control technology by the Pfanzelt company. More than 100 conifers with a felling diameter of up to 50 cm were felled safely and without any problems with the prototype. The possible integration into harvesting processes as well as the effects on the use in the forest stands were analyzed in detail. The project has shown that it is possible to fell trees in a fully mechanized way without danger for the forest worker with a machine that weights roughly a tenth of the dead weight of a conventional harvester

Technodiversity—An E-Learning Tool as an Additional Offer for the Master’s Degree and In-Company Training

In November 2021, a project proposal submitted by the TU Dresden and in which seven other partner institutions are involved was approved in the ERASMUS+ program Action Type KA220-HED. The aim of the project is to develop an e-learning tool that can be used to teach forest technology at the Master’s level. Project work develops along four main tasks: (1) Facts and methods (theoretical contents), (2) Scientific audiovisuals (descriptive contents), (3) E-learning platform (structure) and (4) Didactics (implementation). In this article, the advantages and disadvantages of e learning are discussed and the development of the course contents (facts and methods) is presented in detail

Technodiversity—An E-Learning Tool as an Additional Offer for the Master’s Degree and In-Company Training

In November 2021, a project proposal submitted by the TU Dresden and in which seven other partner institutions are involved was approved in the ERASMUS+ program Action Type KA220-HED. The aim of the project is to develop an e-learning tool that can be used to teach forest technology at the Master’s level. Project work develops along four main tasks: (1) Facts and methods (theoretical contents), (2) Scientific audiovisuals (descriptive contents), (3) E-learning platform (structure) and (4) Didactics (implementation). In this article, the advantages and disadvantages of e learning are discussed and the development of the course contents (facts and methods) is presented in detail

Cost evaluation of three ground-logging methods in a mixed broadleaved mountainous forest

Aim of study: To compare cost and productivity of three ground-based logging methods by skidder: 1, tree length method (TLM), 2, long length method (LLM) and 3, short length method (SLM). Area of study: A mixed broadleaved mountainous forest stand in the Hyrcanian forests in northern Iran. Material and methods: To develop time prediction models, all measurements of time were replaced by their decadic logarithms, and on the basis of the developed models, we simulated cost of 11 skidding turns depending on the diameter of the log (DL), skidding distance (SD), and the winching distance (WD) for TLM, LLM, and SLM. Main results: Our results demonstrated that on average the net costs per extraction of one cubic meter wood (m3) were 3.06, 5.69, and 6.81 €/m3 in TLM, LLM, and SLM, respectively, and the most economical alternative depending on DL, SD and WD was a TLM. Furthermore, the results of simulated models suggest that as long as the diameter of the felled trees is less than 40 cm, the cut-to-length system is not an economical alternative. The cut-to-length method can be applied for trees with larger diameter (more than 40 cm), and in short skidding distance SLM is preferable to LLM but in cases of long skidding distance, LLM is more economical than SLM. Research highlights: DLand SD were the main causes which influenced the productivity and cost of ground-based logging methods

Cost evaluation of three ground-logging methods in a mixed broadleaved mountainous forest

Aim of study: To compare cost and productivity of three ground-based logging methods by skidder: 1, tree length method (TLM), 2, long length method (LLM) and 3, short length method (SLM).Area of study: A mixed broadleaved mountainous forest stand in the Hyrcanian forests in northern Iran.Material and methods: To develop time prediction models, all measurements of time were replaced by their decadic logarithms, and on the basis of the developed models, we simulated cost of 11 skidding turns depending on the diameter of the log (DL), skidding distance (SD), and the winching distance (WD) for TLM, LLM, and SLM.Main results: Our results demonstrated that on average the net costs per extraction of one cubic meter wood (m3) were 3.06, 5.69, and 6.81 €/m3 in TLM, LLM, and SLM, respectively, and the most economical alternative depending on DL, SD and WD was a TLM. Furthermore, the results of simulated models suggest that as long as the diameter of the felled trees is less than 40 cm, the cut-to-length system is not an economical alternative. The cut-to-length method can be applied for trees with larger diameter (more than 40 cm), and in short skidding distance SLM is preferable to LLM but in cases of long skidding distance, LLM is more economical than SLM.Research highlights: DLand SD were the main causes which influenced the productivity and cost of ground-based logging methods

Medienos ruošos technologijų analizė atskirose Europos šalyse

Straipsnyje pateikta medienos ruošos technologijų studija atskirose Europos šalyse. Vakarų Europoje dominuoja pilnai mechanizuotos technologijos, o Lietuvoje, Lenkijoje, Čekijoje ir Vengrijoje, dažniausiai, naudojamos dalinai mechanizuotos medienos ruošos technologijos. Arkliai medienos ruošos darbuose naudojami retai, tik atskirose šalyse (pvz., Vokietijoje, sunkiai pravažiuojamose kirtavietėse ir kai atstumas tarp valksmų didesnis kaip 40 m). Pagal medienos apdirbimo laipsnį, įvairiose Europos Sąjungos šalyse naudojamos ir stiebinės, ir sortimentinės medienos ruošos technologijos. Pagrindinės problemos yra medienos ruoša šlapiose augavietėse ir didelio skersmens stiebų transportavimas. Miško dirvos apsaugos nurodymai ruošiant medieną įstatymuose numatyti Austrijoje, Lietuvoje, Lenkijoje, Vengrijoje ir Vokietijoje. Tik Lietuvoje ir Vokietijoje medienos ruoša vykdoma naudojant valksmų sistemą. Austrijoje, Didžiojoje Britanijoje, Prancūzijoje ir VengrijojeThe study of wood preparation technologies in different European countries is presented in the paper. Fully mechanized technologies dominate in Western Europe, and in Lithuania, Poland, Czechia, and Hungary commonly usable partially mechanized technologies of wood preparation. According to the degree of wood processing, in different European countries there are usable caulescent as well as assortment wood preparation technologies. Main problems are wood preparation in the wet places and transportation stems of big diameter. In the laws of Austria, Lithuania, Poland, Hungary and Germany there are unlooked-for guidelines of forest soil protection while wood preparation. Only in Lithuania and Germany wood preparation is operating according the haul system. In Austria, Great Britain, France and Hungary it is allowable to drive wood preparation machines in all stallVytauto Didžiojo universitetasŽemės ūkio akademij