Resistance coefficients on ground-based winching of timber

This paper deals with the research of resistance differences in winching of logs with their thicker or thinner end turned forward.Winching represents traction of wood assortments on the ground from the felling site to the forest vehicle equipped with a forest winch. The winching coefficient is determined by the horizontal tractive force and weight of the traction load. The research of resistance in winching wood assortments was carried out for the purpose of determining the size of the forest winch designed for equipping the prototype of the thinning tractor assembly (adapted farming tractor, forest semi-trailer and hydraulic crane) and developing an environmentally and economically viable technology for timber production. The research was carried out on flat forestland in a pedunculate oak stand by winching three logs of different weight. The research results have shown that the winching coefficients depend on the weight of logs, shape of log and their direction. Higher weight causes higher traction resistance. In all cases, the winching coefficients were higher in winching of logs with their thicker end turned forward. In order to achieve lower ground-based traction resistance and, at the same time, cause less damage to forest soil, winching of logs should be carried out with their thinner end turned forward

Battery Technology – Use in Forestry

Technical development and system optimization during the last decades have targeted more efficient, socially acceptable and ecologically sustainable ways to use forestry machines and tools. This is supported by the development of electronics and electrical components, as well as battery technology, without which it is impossible to imagine doing some forestry work in forest areas with no permanent source of electricity. Today, we cannot imagine life without e.g. a cell phone, and also doing business in the forestry sector without a field computer. There are numerous examples in everyday life, but also in industry, where portable devices make life and business much easier, and the basis for the operation of these devices is battery technology. The importance of the development of battery technology is proven by the fact that in 2019 the Nobel Prize in Chemistry went into the hands of scientists who developed a lithium-ion battery - a lightweight, rechargeable and powerful battery that is used today in numerous products from mobile phones to laptops and electric vehicles. This paper will outline the historical development of battery technology and the use of battery powered devices, tools and machines with their advantages and disadvantages in forestry sector

Soil compaction in timber skidding in winter conditions

The research of soil compaction in timber skidding was carried out on two skid trails of uniform slope –15%and 30 %. The degree of soil compaction is shown by changes of water-air soil characteristics of the skid trail after a certain number of passes of a loaded skidder and by comparison between these values and the characteristics of untreaded soil during research. The research was carried out in winter conditions at low air and soil temperatures and with the research site covered with snow. Multiple passes of a loaded skidder affect the degree of soil compaction. The result of soil compaction is the decrease of momentary moisture content, porosity and soil water capacity, as well as the increase of native bulk density. Soil compaction is higher if the soil is not frozen. Due to low air temperatures and disappearance of snow from wheel ruts during skidding, the rut soil gets frozen more easily during the night than the untreaded soil. Soil compaction during the day does not cause squeezing out of water from soil micropores and consequently its freezing enlarges the volume of micropores and increases soil porosity and soil water capacity and decreases its native bulk density

Limiting forces and load masses during timber winching

Stabilnost traktora osim uzdužnog i poprečnog kuta stabilnosti podrazumijeva i sigurnost sidrenja traktora pri privitlavanju drva. Privitlavanje predstavlja vuču drvnih sortimenta po tlu od mjesta izrade u sječini do šumskog vozila za privlačenje drva opremljenog sa šumskim vitlom. Kod određenog graničnog tovara i nagiba terena dolazi do narušavanja uzdužne stabilnosti šumskog vozila s vitlom. Pri tome je faktor prijanjanja skidera i traktora sa podlogom važan pokazatelj mogućnosti sigurnog i pravilnog privitlavanja drva.Na osnovi općeg izraza za faktor prijanjaja skidera na ravnom terenu određen je faktor prijanjanja pri privitlavanju drva na nagibu te prikazan dinamički model opterećenja šumskog vozila pri privitlavanju drva.U rezultatima su prikazane granične horizontalne komponente sile u užetu i granične mase tovara u slučaju privitlavanja drva skiderom Ecotrac 120 V. Prema dobivenim vrijednostima graničnih horizontalnih komponenti sila u užetu može se zaključiti da je upravo stabilnost vozila definirana pomakom vozila u nazad granični uvjet privitlavanja drva. Prikazani model privitlavanja drva na nagibu prikazuje temeljni princip za određivanje graničnih tovara i nagiba terena, a koji se može lako prilagoditi ostalim uvjetima privitlavanja drva pri različitim položajima vozila i pravcima privitlavanja drva s obzirom na stvarne eksploatacijske uvjete.The stability of a forest vehicle apart from the longitudinal and transversal stability angle implies the safety of tractor anchoring during timber winching. Timber winching is a dragging of timber assortmens on the ground from the stump to a forest vehicle equipped with the forest winch. At a certain limiting load and slope of the terrain, disturbance of the longitudinal stability of the forest vehicle with the winch is occured. In this case, the adhesion factor of skidder and tractor on the ground is an important indicator of the possibility of safe and proper timber winching.The adhesion factor of the skidder during timber winching on the slope is detremined on the basis of the general expression of the adhesion factor on the skidder on the flat ground. Also, determined the dynamic model of the loading of the forest vehicle is presented during timber winching on the slope.The results show the horizontal components of forces in the rope and the limiting masses of the loads during timber winching by skidder Ecotrac 120 V. According to the obtained values of the horizontal components of forces in the rope, it can be concluded that the stability of the vehicle, defined by the displacement of the vehicle backwards is the limitation of the timber winching.The presented model of timber winching on the slope shows the basic principle for determining the limiting load masses and slope of the terrain, which can applied to all types of forest vehicles equipped with winch as well as easily be adapted to other conditions of timber winching at different positions of the vehicle and the direction of timber winching

LCA Studies in Forestry – Stagnation or Progress?

Today, LCA is one of the leading and most used tools for environmental management, but the application of LCA in forestry is still in an initial phase. Due to a high amount of different wood products which can be produced in forestry sector, production of raw material itself is not included enough in the whole LCA process. Raw wood products and biomass used to be widely declared as »carbon neutral« and renewable, but production steps have a significant influence on the environmental impact depending on machinery used, opening forest with new roads, management type (clear-cut, even-aged management or selective cut), etc. This paper gives a review of LCA studies in forestry based on three segments: harvesting operations biomass for energy road construction and maintenance

Energy Return on Investment (EROI) of Different Wood Products

Energy cannot be produced without consumption of some part of the energy, and the proportions in which this occurs are a key indicator of the efficiency of the production process. Energy return on investment (EROI) of energy production shows the relationship between obtained and invested energy in the production process. This relationship is a key factor in sustainable global energy supply. Wood chips and one-metre firewood are used to produce thermal energy. Amount of energy obtained by burning depends on the moisture content and the features of the energy plant. This chapter deals with the issue of the amount of energy required to produce in the process of wood chips and one-metre firewood production and its transport to the heating plant. When calculating the energy balance, it is important to include as many input parameters as possible (parameters of energy consumption), which represents an almost impossible task because one parameter directly binds several others. According to several authors, the relationship between obtained and invested energy or EROI for energy wood is 30:1 which is a better ratio than the production of oil, for which relationship between obtained and invested energy is about 20:1. The results of study show that most of the energy during the production and supply of energy wood products from final felling of oak stands is used for fuel for machinery and vehicles in the production process. Ultimately, the relationship between obtained and invested energy is approximately 25:1 in the case of moisture content in the wood chips in the limit (market) value of 35% and the mean distance truck transportation of wood chips of 50 km. The relationship of obtained and invested energy used for one-metre firewood is bigger than 25:1 because of less invested energy which does not include machines like wood chipper. This is a satisfactory relationship, but it decreases with a greater transport distance. Such is the case when chips manufactured in Croatia, due to the lack of heat plants, are transported over long distances to neighbouring countries