In the Republic of Croatia (RC) forests and forest land cover 2.5 million of hectares or 44% of t... more In the Republic of Croatia (RC) forests and forest land cover 2.5 million of hectares or 44% of the total area of RC. 81% of forests are owned by the state, and the remaining 19% are privately owned forests. The annual allowable cut in state-owned forests is up to 4.9 million m3. In accordance with the Forest Act the company „ Hrvatske sume“ ltd. Zagreb (Croatian Forests – CF) manage the state-owned forests. CF mostly rely on their own capacities for felling, processing, skidding/forwarding and transportation of wood, as well as for the construction of forest roads. These capacities are organised in 13 mechanisation working units (MWUs). The efficiency of MWUs was estimated by the application of ‘ Data Envelopment Analysis’ (DEA). DEA is a well-known non-parametric method for the assessment of relative efficiency of comparable decision making units with different inputs and outputs. By linear programming, DEA models determine empiric efficiency frontier based on data of used inputs ...
This paper presents the research of possibilities of use of wheel numeric, as a satisfying parame... more This paper presents the research of possibilities of use of wheel numeric, as a satisfying parameter that describes the environmental acceptability of interaction between vehicle wheels and soil in timber extraction. The wheel numeric is a non-dimensional parameter, which describes the interaction between the loaded wheel and soil. This parameter can be easily measured/calculated by simple on-site measurement of soil cone index and by use of semi-empiric expressions for contact pressure. The analysis of the ratio between wheel numeric and rut depth, which can be easily measured and represents the most conspicuous consequence of the vehicle’ s adverse effects on soil, showed that the wheel numeric is a sufficiently good parameter for its assessment and therefore also for the assessment of the environmental acceptability. In order to get a better understanding of this problem, the basic components of the wheel numeric as well as models of different authors for their calculation are ex...
U radu je istražen novi sustav za mjerenje osovinskih opterecenja sumskih kamiona i ostalih vozil... more U radu je istražen novi sustav za mjerenje osovinskih opterecenja sumskih kamiona i ostalih vozila, prijenosna mjerna platforma. Razvoj ovog sustava je potaknut sve vecom potražnjom za sumskom biomasom za energiju, te potrebnom za sto preciznijim i jednostavnijim nacinom za određivanje proizvedenih kolicina prvo neusitnjenog drva zatim, nakon prirodnog prosusivanja i usitnjenog drva za energiju. Nadalje potreba za ovakvim sustavom proizlazi i iz potrebe za normiranjem sumskih radova primarnog transporta te za potrebe izrade planova proizvodnje. Mjerna platforma se sastoji od cetiri mjerna pretvornika postavljena u kutovima. Mjerni pretvornici mjere pojedinacno opterecenje do 30 tona. Umjeravanje vage vrseno je pomocu atestiranih utega od 500 kg. Prilikom provođenja testova opterecenja i rasterecenja zabilježene su greske mjerenja koje su iznosile od -2 kg do 20 kg. Sve pogreske su u okviru prihvatljivih vrijednosti za prakticnu uporabu mjerne platforme. Zbog svoje robusne konstrukci...
Cilj je rada istražiti ucinkovitost drobilice kamena Vermeer T 855 pri pripremi buduce trase sums... more Cilj je rada istražiti ucinkovitost drobilice kamena Vermeer T 855 pri pripremi buduce trase sumske protupožarne ceste kao i pri melioraciji krskog zemljista obraslog makijom. Istraživanje je provedeno na podrucju sumarije Zadar i sumarije Buzet tijekom 22 radna dana, pri cemu su se dnevno prikupljali slijedeci parametri: ukupno utroseno vrijeme rada, efektivno (pogonsko) vrijeme stroja, potrosnja goriva, broj potrosenih noževa bubnja, duljina izrađene trase, dubina rada i vrsta podloge. Osnovna se podjela radnih dana odnosi na dubinu rada i vrstu podloge. Iz mjerenih podataka je za svaki radni dan izracunat ucinak stroja, izražen u duljini izrađene trase u jedinici vremena, potrosnja goriva po jedinici vremena i duljini izrađene trase te potrosnja noževa po duljini izrađene trase. Na osnovu se rezultata mjerenja prvenstevno želi naglasiti mogucnosti primjene pokretne drobilice kamena Vermeer T855 pri gradnji sumskih protupožarnih cesta. Prednost pokretne drobilice se ogleda u moguc...
A methodological study of forest opening has been made, which in its final phase of work and conf... more A methodological study of forest opening has been made, which in its final phase of work and confirmation of quality was tested in two mountain management units. The model was made for two levels of building the primary forest road infrastructure: for the present openness level and for the zero openness level. According to all indicators of the forest road network efficiency, much better results were obtained by the model than the present condition of openness. Testing of the theoretical computer model of forest road network optimisation, on the terrain, was carried out for the present condition of openness and for the first opening variant. Deviations by a computer model of certain routes and their projection on the terrain from the designed forest roads were within acceptable limits and did not deviate much from the general route trend. Made project documents of forest roads showed the correspondence of designed forest roads to the prescribed technical features and the cost analys...
This paper presents the way and measuring problems of assesing environmental suitability of timbe... more This paper presents the way and measuring problems of assesing environmental suitability of timber skidding. Research results are based on uphill and downhill skidding on two skid trails with a slope of 15 % and 30 %. Measurement of wheel loads was performed by tensiometric method. Distribution of wheel loads during timber skidding is shown in dependence of the slope, load volume and skidding direction. Dynamic load of wheels exerts pressure on the soil. Depending on the soil bearing strength at the moment of wheel load, soil is compacted and wheel rut is formed. Wheel contact pressure was determined for each wheel. The ratio between soil cone index (measured by cone penetrometer) and wheel contact pressure is recommended for the evaluation of environmental acceptability of skidder work. By knowing the contact pressures of the skidder’ s wheel under exploitation conditions and by simple determining the soil bearing strength during work operations, it is possible to anticipate and av...
The forces required for pulling out a winch steel cable are essential for evaluating the effect o... more The forces required for pulling out a winch steel cable are essential for evaluating the effect on physical load of choker man. The following parameters have the greatest impact on the size of these forces: diameter and unit weight of steel cable, resistance forces in the winch that occur due to friction in the drum bearings, improper adjustment of winch brake and clutch and also the terrain slope where the rope is pulled. This paper presents the results of in situ measurements: • pulling force of steel cable, • velocity of steel cable pulling, • power consumed in pulling, carried out on a Hittner 2 x 80 winch mounted on a skidder Ecotrac 120V. Changes of measurement values are analyzed as a function of: • length of the pulled steel cable, and • terrain slope (5 different inclinations ranging between -19 ˚ and +19 ˚). Based on the research results, physical load of choker-man is classified as work under heavy load according to the Directive 90/269/EEC, including the possibility of e...
This paper presents the results of measuring wheel loads of skidder during timber extraction. Res... more This paper presents the results of measuring wheel loads of skidder during timber extraction. Research results are based on uphill and downhill skidding on two skid trails with continuous slope of 15 % and 30 %. Measurement of wheel loads was performed by tensiometric method and remote transferring of measurement signal. Distribution of wheel loads during timber skidding is shown in dependence of slope, load volume and skidding direction. Nominal ground pressure based on tyre size was determined for each wheel. The ratio between soil cone index (measured by cone penetrometer) and nominal ground pressure was used for the evaluation of environmental acceptability of skidder work. Due to winter period during investigation, frozen soil on skid trails had a very high capability to bear wheel pressures of skidders.
Istraživanje dinamickih opterecenja skidera pri privlacenju provedeno je na dvije traktorske vlak... more Istraživanje dinamickih opterecenja skidera pri privlacenju provedeno je na dvije traktorske vlake jednolikog nagiba 15 % i 30 %. Rezultati se istraživanja temelje na 19 vucnih pokusa uz nagib i niz nagib. Ustanovljene su velicine vertikalne i horizontalne sastavnice sile u užetu, adhezijskim skidera pri privlacenju drva, zakretnih momenata i opterecenja na kotacima u svakom vucnom pokusu. Mehanicke su velicine mjerene tenzometrijskom metodom pretvorbom dijelova skidera u mjerila uz daljinski prijenos mjernih signala. Rezultati pokazuju da najveci utjecaj na opterecenje kotaca ima vertikalna sastavnica sile u užetu, koja punim iznosom opterecuje skider. Raspodjela je zakretnih momenata u ovisnosti o vertikalnom opterecenju na kotacima skidera. Pri privlacenju niz nagib ne može se govoriti o ostvarivanju prave vuce jer skider vuce tovare svojom težinom, a prijenos snage s pogonskog motora na kotace se ne koristi za ostvarivanje vucne sile vec za kocenje skidera.
This paper shows the results of measurement of daily exposure of five cutters to respirable parti... more This paper shows the results of measurement of daily exposure of five cutters to respirable particles, i.e. to total wood dust during felling and processing of beech trees. The research was carried out in a mixed stand (beech 56%, oak 28%, hornbeam 16%), 109-year old in the central mountainous region of the Republic of Croatia at an altitude ranging between 170 and 210 m. The operations of felling and processing were carried out by use of chain saw Stihl 044. For determining the mass concentration of wood dust by the method of personal collectors, the separators (cyclons) were used, which operate in a way that imitates the worker's respiratory system, i.e. the separation of non-respirable fraction and respirable particles with a medium efficiency (50%) with aerodynamic diameter of 5 μ m. During the research only beech trees were cut. The measurements were carried out of the factors affecting the dustiness of the cutter's working environment (tree diameter at breast height, t...
Kod privlacenja (izvoženja) obloga drva od mjesta sjece do pomocnoga stovarista pri pridobivanju ... more Kod privlacenja (izvoženja) obloga drva od mjesta sjece do pomocnoga stovarista pri pridobivanju drva iz nizinskih suma Hrvatske cesta je primjena specijalnih sumskih vozila – forvardera. U radu je prikazana ocjena pogodnosti primjene teskog 17-tonskog forvardera Timberjack 1710B (6WD) određenjem njihova položaja unutar obitelji forvardera temeljem morfoloske rasclambe vozila. Morfoloska rasclamba provedena je na temelju geometrijskih, masenih i drugih velicina, pomocu kojih se izražavaju ovisnosti i donosi sud o valjanosti primjene, odnosno odabira stroja. Utvrđene su i granicne vrijednosti kod kojih prestaje rast najvecih dimenzija forvardera, unatoc porastu snage motora forvardera, te moguce ovisnosti između imaginarne tlocrtne plostine forvardera i stvarnoga tlaka forvardera na mjestu dodira stroja s tlom. Uporaba teskoga forvardera Timberjack 1710B u uvjetima hrvatskoga sumarstva predstavlja suboptimalno rjesenje zbog nemogucnosti konstrukcije lakseg forvardera sa zadovoljavaju...
Utjecaj mineralnog i biorazgradivoga ulja na rasadnicku klijavost i rast sadnica hrasta lužnjaka ... more Utjecaj mineralnog i biorazgradivoga ulja na rasadnicku klijavost i rast sadnica hrasta lužnjaka (Quercus robur L.) HR EN Sažetak: Svrha je ovoga
In the Republic of Croatia (RC) forests and forest land cover 2.5 million of hectares or 44% of t... more In the Republic of Croatia (RC) forests and forest land cover 2.5 million of hectares or 44% of the total area of RC. 81% of forests are owned by the state, and the remaining 19% are privately owned forests. The annual allowable cut in state-owned forests is up to 4.9 million m3. In accordance with the Forest Act the company „ Hrvatske sume“ ltd. Zagreb (Croatian Forests – CF) manage the state-owned forests. CF mostly rely on their own capacities for felling, processing, skidding/forwarding and transportation of wood, as well as for the construction of forest roads. These capacities are organised in 13 mechanisation working units (MWUs). The efficiency of MWUs was estimated by the application of ‘ Data Envelopment Analysis’ (DEA). DEA is a well-known non-parametric method for the assessment of relative efficiency of comparable decision making units with different inputs and outputs. By linear programming, DEA models determine empiric efficiency frontier based on data of used inputs ...
This paper presents the research of possibilities of use of wheel numeric, as a satisfying parame... more This paper presents the research of possibilities of use of wheel numeric, as a satisfying parameter that describes the environmental acceptability of interaction between vehicle wheels and soil in timber extraction. The wheel numeric is a non-dimensional parameter, which describes the interaction between the loaded wheel and soil. This parameter can be easily measured/calculated by simple on-site measurement of soil cone index and by use of semi-empiric expressions for contact pressure. The analysis of the ratio between wheel numeric and rut depth, which can be easily measured and represents the most conspicuous consequence of the vehicle’ s adverse effects on soil, showed that the wheel numeric is a sufficiently good parameter for its assessment and therefore also for the assessment of the environmental acceptability. In order to get a better understanding of this problem, the basic components of the wheel numeric as well as models of different authors for their calculation are ex...
U radu je istražen novi sustav za mjerenje osovinskih opterecenja sumskih kamiona i ostalih vozil... more U radu je istražen novi sustav za mjerenje osovinskih opterecenja sumskih kamiona i ostalih vozila, prijenosna mjerna platforma. Razvoj ovog sustava je potaknut sve vecom potražnjom za sumskom biomasom za energiju, te potrebnom za sto preciznijim i jednostavnijim nacinom za određivanje proizvedenih kolicina prvo neusitnjenog drva zatim, nakon prirodnog prosusivanja i usitnjenog drva za energiju. Nadalje potreba za ovakvim sustavom proizlazi i iz potrebe za normiranjem sumskih radova primarnog transporta te za potrebe izrade planova proizvodnje. Mjerna platforma se sastoji od cetiri mjerna pretvornika postavljena u kutovima. Mjerni pretvornici mjere pojedinacno opterecenje do 30 tona. Umjeravanje vage vrseno je pomocu atestiranih utega od 500 kg. Prilikom provođenja testova opterecenja i rasterecenja zabilježene su greske mjerenja koje su iznosile od -2 kg do 20 kg. Sve pogreske su u okviru prihvatljivih vrijednosti za prakticnu uporabu mjerne platforme. Zbog svoje robusne konstrukci...
Cilj je rada istražiti ucinkovitost drobilice kamena Vermeer T 855 pri pripremi buduce trase sums... more Cilj je rada istražiti ucinkovitost drobilice kamena Vermeer T 855 pri pripremi buduce trase sumske protupožarne ceste kao i pri melioraciji krskog zemljista obraslog makijom. Istraživanje je provedeno na podrucju sumarije Zadar i sumarije Buzet tijekom 22 radna dana, pri cemu su se dnevno prikupljali slijedeci parametri: ukupno utroseno vrijeme rada, efektivno (pogonsko) vrijeme stroja, potrosnja goriva, broj potrosenih noževa bubnja, duljina izrađene trase, dubina rada i vrsta podloge. Osnovna se podjela radnih dana odnosi na dubinu rada i vrstu podloge. Iz mjerenih podataka je za svaki radni dan izracunat ucinak stroja, izražen u duljini izrađene trase u jedinici vremena, potrosnja goriva po jedinici vremena i duljini izrađene trase te potrosnja noževa po duljini izrađene trase. Na osnovu se rezultata mjerenja prvenstevno želi naglasiti mogucnosti primjene pokretne drobilice kamena Vermeer T855 pri gradnji sumskih protupožarnih cesta. Prednost pokretne drobilice se ogleda u moguc...
A methodological study of forest opening has been made, which in its final phase of work and conf... more A methodological study of forest opening has been made, which in its final phase of work and confirmation of quality was tested in two mountain management units. The model was made for two levels of building the primary forest road infrastructure: for the present openness level and for the zero openness level. According to all indicators of the forest road network efficiency, much better results were obtained by the model than the present condition of openness. Testing of the theoretical computer model of forest road network optimisation, on the terrain, was carried out for the present condition of openness and for the first opening variant. Deviations by a computer model of certain routes and their projection on the terrain from the designed forest roads were within acceptable limits and did not deviate much from the general route trend. Made project documents of forest roads showed the correspondence of designed forest roads to the prescribed technical features and the cost analys...
This paper presents the way and measuring problems of assesing environmental suitability of timbe... more This paper presents the way and measuring problems of assesing environmental suitability of timber skidding. Research results are based on uphill and downhill skidding on two skid trails with a slope of 15 % and 30 %. Measurement of wheel loads was performed by tensiometric method. Distribution of wheel loads during timber skidding is shown in dependence of the slope, load volume and skidding direction. Dynamic load of wheels exerts pressure on the soil. Depending on the soil bearing strength at the moment of wheel load, soil is compacted and wheel rut is formed. Wheel contact pressure was determined for each wheel. The ratio between soil cone index (measured by cone penetrometer) and wheel contact pressure is recommended for the evaluation of environmental acceptability of skidder work. By knowing the contact pressures of the skidder’ s wheel under exploitation conditions and by simple determining the soil bearing strength during work operations, it is possible to anticipate and av...
The forces required for pulling out a winch steel cable are essential for evaluating the effect o... more The forces required for pulling out a winch steel cable are essential for evaluating the effect on physical load of choker man. The following parameters have the greatest impact on the size of these forces: diameter and unit weight of steel cable, resistance forces in the winch that occur due to friction in the drum bearings, improper adjustment of winch brake and clutch and also the terrain slope where the rope is pulled. This paper presents the results of in situ measurements: • pulling force of steel cable, • velocity of steel cable pulling, • power consumed in pulling, carried out on a Hittner 2 x 80 winch mounted on a skidder Ecotrac 120V. Changes of measurement values are analyzed as a function of: • length of the pulled steel cable, and • terrain slope (5 different inclinations ranging between -19 ˚ and +19 ˚). Based on the research results, physical load of choker-man is classified as work under heavy load according to the Directive 90/269/EEC, including the possibility of e...
This paper presents the results of measuring wheel loads of skidder during timber extraction. Res... more This paper presents the results of measuring wheel loads of skidder during timber extraction. Research results are based on uphill and downhill skidding on two skid trails with continuous slope of 15 % and 30 %. Measurement of wheel loads was performed by tensiometric method and remote transferring of measurement signal. Distribution of wheel loads during timber skidding is shown in dependence of slope, load volume and skidding direction. Nominal ground pressure based on tyre size was determined for each wheel. The ratio between soil cone index (measured by cone penetrometer) and nominal ground pressure was used for the evaluation of environmental acceptability of skidder work. Due to winter period during investigation, frozen soil on skid trails had a very high capability to bear wheel pressures of skidders.
Istraživanje dinamickih opterecenja skidera pri privlacenju provedeno je na dvije traktorske vlak... more Istraživanje dinamickih opterecenja skidera pri privlacenju provedeno je na dvije traktorske vlake jednolikog nagiba 15 % i 30 %. Rezultati se istraživanja temelje na 19 vucnih pokusa uz nagib i niz nagib. Ustanovljene su velicine vertikalne i horizontalne sastavnice sile u užetu, adhezijskim skidera pri privlacenju drva, zakretnih momenata i opterecenja na kotacima u svakom vucnom pokusu. Mehanicke su velicine mjerene tenzometrijskom metodom pretvorbom dijelova skidera u mjerila uz daljinski prijenos mjernih signala. Rezultati pokazuju da najveci utjecaj na opterecenje kotaca ima vertikalna sastavnica sile u užetu, koja punim iznosom opterecuje skider. Raspodjela je zakretnih momenata u ovisnosti o vertikalnom opterecenju na kotacima skidera. Pri privlacenju niz nagib ne može se govoriti o ostvarivanju prave vuce jer skider vuce tovare svojom težinom, a prijenos snage s pogonskog motora na kotace se ne koristi za ostvarivanje vucne sile vec za kocenje skidera.
This paper shows the results of measurement of daily exposure of five cutters to respirable parti... more This paper shows the results of measurement of daily exposure of five cutters to respirable particles, i.e. to total wood dust during felling and processing of beech trees. The research was carried out in a mixed stand (beech 56%, oak 28%, hornbeam 16%), 109-year old in the central mountainous region of the Republic of Croatia at an altitude ranging between 170 and 210 m. The operations of felling and processing were carried out by use of chain saw Stihl 044. For determining the mass concentration of wood dust by the method of personal collectors, the separators (cyclons) were used, which operate in a way that imitates the worker's respiratory system, i.e. the separation of non-respirable fraction and respirable particles with a medium efficiency (50%) with aerodynamic diameter of 5 μ m. During the research only beech trees were cut. The measurements were carried out of the factors affecting the dustiness of the cutter's working environment (tree diameter at breast height, t...
Kod privlacenja (izvoženja) obloga drva od mjesta sjece do pomocnoga stovarista pri pridobivanju ... more Kod privlacenja (izvoženja) obloga drva od mjesta sjece do pomocnoga stovarista pri pridobivanju drva iz nizinskih suma Hrvatske cesta je primjena specijalnih sumskih vozila – forvardera. U radu je prikazana ocjena pogodnosti primjene teskog 17-tonskog forvardera Timberjack 1710B (6WD) određenjem njihova položaja unutar obitelji forvardera temeljem morfoloske rasclambe vozila. Morfoloska rasclamba provedena je na temelju geometrijskih, masenih i drugih velicina, pomocu kojih se izražavaju ovisnosti i donosi sud o valjanosti primjene, odnosno odabira stroja. Utvrđene su i granicne vrijednosti kod kojih prestaje rast najvecih dimenzija forvardera, unatoc porastu snage motora forvardera, te moguce ovisnosti između imaginarne tlocrtne plostine forvardera i stvarnoga tlaka forvardera na mjestu dodira stroja s tlom. Uporaba teskoga forvardera Timberjack 1710B u uvjetima hrvatskoga sumarstva predstavlja suboptimalno rjesenje zbog nemogucnosti konstrukcije lakseg forvardera sa zadovoljavaju...
Utjecaj mineralnog i biorazgradivoga ulja na rasadnicku klijavost i rast sadnica hrasta lužnjaka ... more Utjecaj mineralnog i biorazgradivoga ulja na rasadnicku klijavost i rast sadnica hrasta lužnjaka (Quercus robur L.) HR EN Sažetak: Svrha je ovoga
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