Comparison of the Accuracy of Methods for Calculating the Volume of Standing European Beech Trees

The paper presents results of the analysis of the accuracy of calculating the volume of standing trees, calculated according to the method used in forestry practice, based on the principle of full calipering of all marked trees with the following calculation of mean height and standing volume according to the method of uniform volume curves. This volume was compared with the exact method for calculating the volume of actual removals including small wood in the beech stands of Little Carpathians in the territory of Lesy Slovenskej republiky, š.p. (Forests of the Slovak Republic, State Enterprise), branch establishment in Smolenice. The values of marked felling (standing trees) and the values of removals including logging residues left on the site will be compared and the difference expressed in percent. The difference between the values in percent is fitted with the accuracy of calculated standing volume (marked logging) established by the author of the method for calculating uniform volume curves, i.e. Halaj. A model curve is chosen by means of the directly detected value of mean stand quantity (mean height, mean diameter, age, site class etc.). The system of uniform volume curves links up with these quantities and gives volumes of individual trees for all diameter classes and corresponding heights. The method of uniform volume curves is used in Slovakia to calculate the volume of marked logging. Results of the analysis show that the volume of standing trees calculated according to the method of uniform volume curves is in reality underestimated by about 5% as compared with the actual volume of processed wood mass including logging residues left on the site. Thus, the calculation inaccuracy in forestry practice is exceeded by the above mentioned 5% as compared with the permitted deviation established through the method of uniform volume curves. Solution of this problem is a proposal submitted to the National Forest Centre in Zvolen for the elaboration of volume tables for the new ecotype of European beech.O

Analysis of Occupational Accidents in Tree Climbers

The work of tree climbers is a hazardous activity during which many risks of occupational accidents must be faced. Numerous injuries happen during the performance of this professional activity. This is why our research was conducted, and the principle of which was to gather and evaluate, on the basis of the questionnaire method, injuries occurring to tree climbers during their work. An anonymous online questionnaire was prepared in order to obtain data about the rate of accidents recorded amongst tree climbers working in the territory of the Czech Republic. There were 121 tree climbers participating in the collection of data. The questionnaire was divided into seven sections, each section including questions focused on possible injuries related to the work of tree climbers and first aid. Answers of respondents indicated that the highest number of injuries were caused by cutting with the manual saw. Burns caused by the power saw and damage to eyes by sawdust or dust during sawing followed. The results also showed that nearly 30% of tree climbers work alone, and 47% of tree climbers collaborate with a ground worker who is not able to rescue them from the tree in the case of an exceptional unexpected situation. The research also revealed surprising results as to carrying first aid kits. Only 62% of tree climbers have a personal first aid kit on them in the tree crown. However, a positive finding appears in the fact that 75% of tree climbers are graduates of some medical course.O

Dynamic Soil Pressures Caused by Travelling Forest Machines

Machines travelling in forest stands cause dynamic loading of soil, the size of which depends on a multitude of factors such as terrain ruggedness, machine speed, axle load and tyre inflation pressure. To decide on harvesting and transport machines suitable for specific field conditions, it is necessary to have at least some awareness about their dynamic effects on the soil, which sometimes considerably differ from static values measured on standing machines. The paper deals with the method of determining dynamic ground pressures according to the given parameters of vehicle weight and speed. At the same time, it compares dynamic pressures calculated by using this method with actually measured values

Comparative Time Study of Conventional Cut-To-Length and an Integrated Harvesting Method-A Case Study

Logging residues offer a significant contribution to the economical profitability and sustainability of forest-based resources. It is always desirable to optimise the harvesting and extraction method to improve the economy of the process along with ensuring sustainability from an environmental point of view. This study compares two harvesting methods, i.e., conventional cut-to-length (CTL) followed by harvesting residue extraction for energy and an integrated harvesting method combining CTL with harvesting residue pre-piling by the harvester followed by the extraction of both timber and logging residues for energy. The study was carried out in spruce stands (Picea abies (L.) Karst.) in South Moravia (Czech Republic) at Pozořice and Kuničky. Two methods utilized by harvesters and forwarders were compared. The first case was a conventional CTL method when trees are felled, delimbed, and cross-cut by the harvester. The resulting logs are pre-piled and then transported by the forwarder. In this case, the harvesting residues remain in the stand. The method does not involve utilizing harvesting residues such as brash mat on striproads but rather extracting them in an independent step as an energy source. In the second case, the resulting harvesting residues are piled up by the harvester to be later extracted by the forwarder. Such extracted harvesting residues are stored at the roadside for seasoning and future comminution. The aim was to obtain input data for internal analysis of a private entity contracting in a logging operation. The client demanded that the increase in time needed for the production of one timber unit with simultaneous harvesting residue preparation be measured. By our estimates, the integrated harvesting method required 33% more (harvester) and 16% less (forwarder) time compared to the alternate method for the extraction of harvesting residues, which in turn results in approximately 8% longer total operational time for the complete operation.O

Harvesting and forwarding of trees with harvestor technology on railway protection zone lines

Předmětem monografie je technologický postup údržby dřevinných porostů v ochranných pásmech podél železničních dopravních cest a následný transport a úprava vytěžené dendromasy. Těžba dříví je dosud řešena na bázi použití přenosné motorové pily. Na strmých svazích pracovníci užívají poutací arboristické systémy. Je vyřešena nová technologie těžby náletových dřevin harvestorem umístěným na plošinovém železničním vozu, kterým je po železnici dopraven na pracoviště. Detailní postavení harvestoru ke kácenému stromu zajišťuje jeho pojezd po plošině železničního vozu. Soustřeďování a odvoz vytěžené dendromasy na úložné skládky pomocí forwarderu, umístěného a stabilizovaného na plošinovém železničním vozu, tvořícího součást zvláštní soupravy, do níž je zařazen minimálně ještě jeden železniční vůz s postranicemi. Vytěžená dendromasa je sbírána drapákem hydraulického jeřábu forwarderu a ukládána na jeho ložný prostor a do úložného prostoru sousedního vozu soupravy. Po naplnění ložných prostor souprava odjíždí na železniční stanici, kde je dendromasa desintegrována přistaveným štěpkovacím strojem a ukládána do ložného prostoru odvozní automobilové soupravy. Konečným produktem technologického postupu je energetická štěpka a v některých případech i výřezy pilařské, agregátové a vlákninové. Navrženým technologickým postupem je zkrácena doba uzavírky tratí, zvýšena bezpečnost pracovníků v těžbě náletových dřevin, požadováno vybavení pracovníků kvalifikačními osvědčeními pro dané práce. Dříví vytěžené z nárostů je zpeněženo se současným úklidem pracovišť a je zajištěna ekologická čistota prací.The monograph subject consists in the technological procedure of care of tree stands in protected zones along railway lines and the subsequent transport and adjustment of felled dendromass. So far, felling is carried out on the basis of portable power saws. On steep slopes, workers use arboristic equipment systems. A new technology has been worked out of self-seeding trees using a harvester placed on a plateau wagon, which is transported to a workplace by railway. The detailed position of the harvester to a felled tree is provided by its movement on the wagon plateau. Skidding and hauling the exploited dendromass to landings is carried out by means of a forwarder placed and stabilized on a plateau wagon creating the part of a special unit where another wagon with side boards was included. The felled dendromas s is collected by a grab of the forwarder hydraulic crane and placed on its loading space and into the stowage space of the unit neighbouring wagon. After filling the loading capacity the unit leaves for a railway station where the dedromass is disintegrated by a chipping machine and placed into the loading space of a logging truck-and-trailer unit. Final products of the technological procedure are fuel chips and in some cases also saw, aggregate and pulp logs. Through the proposed technological procedure, the time of the line closure is shortened, the safety of workers felling self-seeding trees is increased and the equipment of fellers by qualification certificates for given operations is required. Wood obtained from advance growth is realized together with cleaning the workplaces and the environmentally friendly operations are provided.Published Versio

Operating Characteristics of a Timber Trailer with a Hybrid Drive

This paper deals with the design and operational evaluation of a timber tractor-trailer unit with a hybrid trailer drive. The source of electrical energy for the two induction motors driving the front wheels of the tandem trailer axle is a battery, which is recharged by an induction machine operating as a generator during periods of a lower demand for power from the tractor diesel engine. An electric drive was designed for the defined working cycle of the tractor-trailer unit, and its loading characteristics were tested in the laboratory. The parameters measured on the field tests during timber forwarding were battery voltage and power, and the energy balance. Three adjustment levels of the potentiometer controlling the trailer hybrid drive (50, 75 and 100%) were tested at three different forwarding distances of 100, 500 and 1000 m. Additionally, any slippage of the prime mover wheels and trailer was measured. The maximum peak power taken from the battery was ca. 33 kW during the field tests, whilst the drive was able to deliver a peak output of up to 72 kW for 10 s and permanently up to ca. 50 kW. Even in harsh terrain conditions, the electric drive assisted the combustion engine only when the loaded tractor-trailer unit was travelling uphill. The hybrid drive operation was sustainable for the whole working shift, without the need for recharging when the potentiometer was set to 50%. This appropriate setting of the potentiometer controlling the trailer's hybrid drive reduced the slipping of the driven wheels of the tractor-trailer unit whilst travelling uphill.O

Impact on the Operation of a Forwarder with the Wheeled, Tracked-Wheel or Tracked Chassis on the Soil Surface

The impact of a small forwarder with the wheeled chassis, tracked-wheel chassis, and tracked chassis traveling on the soil profile was studied. The three chassis types were assessed for the influence of the loading of forwarder cargo space and the degree of tire inflation on induced specific and actual pressures of tires on the soil surface. Penetrometric resistances of soil profile and rut depths in the forwarder driving track were measured. The effect of a layer of logging residues in the forwarder driving track on the size of induced actual pressures was determined. The practice of determining the impact of forest machines on the soil surface by means of a specific tire pressure does not have a full informative value. In the forwarder wheeled chassis, maximum values of actual pressures exceeded specific pressures established numerically by up to 203%. Average values of actual pressures could be reduced by 45% by reducing the pressure of tire inflation, by 70% with the use of tracks, or by 49% by traveling on the layer of logging residues. As compared with the wheeled chassis type, the tracked type of the forwarder chassis induced actual pressures to lower by 81% and the rut depth after ten forwarder passes was smaller by 50%

Analysis of factors of the quality of logs produced by harvesters

Increasing demands of the present society lead to an effort to rationalize logging operations in fo­rest management. Therefore, multi-function logging machines are increasingly used in the course of timber harvesting. Nevertheless, the economic effectiveness of these machines is affected not only by their productivity or environmentally friendly operations but also the quality of performed work. It can be evaluated by the assessment of the quality of produced assortments. Decreasing quality of produced logs can result in the reduction of marketability and wood price. Thus, the aim of this paper is to determine some defects originating at the harvester production of assortments and specification of their potential causes