Volume utilization and value of timber assortmets of dried silver fir (Abies alba Mill.) trees

Zdravstveno se stanje jele obične u preborno gospodarenim sastojinama utvrđuje praćenjem stanja krošnje pojedinih stabala, odnosno osutosti iglica. Republika Hrvatska je od 1992. godine uključena u praćenje zdravstvenog stanja šuma u okviru Međunarodnog programa za procjenu i motrenje zračnog onečišćenja na šume. Motrenje se ponavlja na stalnim plohama posrednom (vizualnom) procjenom osutosti krošanja pojedinih stabala. U 1999. godini bilo je 63,8 % značajno oštećenih, a 2004. godine zabilježeno je visokih 88,4 % značajno oštećenih stabala. Istraživanjem je obuhvaćeno 200 stabala jele srednjeg prsnog promjera 48 cm i prosječne visine 29,4 m u odsjeku od 36,00 ha, a od toga 44 stabla u "3b" i 156 stabala u "4" stupnju posušenosti. Ukupni obujam doznačenih stabala prema Schumacher-Hall-u iznosi 570,95 m3, a srednji obujam stabla 2,85 m3. Postotak iskorištenja kretao se od 35,79 % do 87,10 % s prosjekom od 71,97 %, a otpad je u prosjeku iznosio 28,03 %. Prema neto izrađenom obujmu stabla u "3b" stupnju bilo je 66,18 % tehničke oblovine, a višemetarskog prostornog drva 33,82 %. Kod stabala u "4" stupnju posušenosti na tehničku oblovinu otpada svega 37,69 %, a na višemetarsko drvo 62,31 % izrađenoga neto obujma. Relativna vrijednost jediničnog drvnog obujma u razredu oštećenja krošnje "3b" manja je za 10 % do 30 % od jedinične vrijednosti neoštećenih stabala. Kod razreda oštećenja krošnje "4" vrijednosti jediničnog obujma smanjene su za iznose od 30 % do 45 % u odnosu na neoštećena stabla.Silver fir (Abies alba Mill.) is naturally distributed in mountainous regions of central, southern and parts of western Europe (Figure 1). Ecologically, commercially and traditionally, silver fir is the most important Croatian conifer species, participating in the total conifer growing stock with about 35 % (Prpić and Seletković 2001). It occurs in selection forests, which represent an important ecological stronghold of the most forested region in the Republic of Croatia. The stand´s health status is assessed by monitoring the crown condition of individual trees. Dobbertin and Brang (2001) showed that mortality rates increase exponentially with increasing defoliation. Crown damage can be monitored indirectly and directly, but neither of these methods is completely objective (Redfern and Boswell 2004). The health status of forests in Europe is monitored on an annual level within the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests, ICP FORESTS. The programme was launched in 1985, and the Republic of Croatia joined in 1992. Monitoring is repeated in permanent plots by indirect (visual) assessment of crown defoliation of freely grown trees. According to the assessment of forest condition in Croatia (ICP FORESTS) for the year 1999, undamaged fir trees accounted for only 14.3 %, whereas severely damaged trees accounted for as much as 63.8 %. Severe damage denotes crown needle loss ranging from 26 % to 99 % (Potočić and Seletković 2000). Particularly high participation of damaged fir trees of 81.6 % was recorded in Gorski Kotar in 1999, while only 3.8 % were healthy fir trees. The results of field research suggest that the portion of damaged fir trees is constantly increasing. Thus, as much as 88.4 % of severely damaged trees were recorded in 2004 (Vrbek et al. 2008). The value of wood assortments of dead trees from salvage cuts is lower compared to those obtained from regular silvicultural treatments in healthy selection stands. The goal of this research is to analyze the quantity, quality and value of wood volume obtained from salvage cuts of silver fir in a selection forest. The research was conducted in the area of Gomirje forest administration within the management unit of "Potočine - Crna Kosa". The management unit extends over northern and north-eastern slopes of Mt. Velika Kapela at altitudes between 339 and 1,200 m. The compartment covers an area of 36.00 ha. The management class is a managed forest of silver fir and common beech with a total growing stock of 339 m?/ha. The growing stock of fir is 112 m?/ha. There are 304 trees per hectare, of which 157 are silver firs. To investigate fir trees during salvage cuts, breast diameters and heights were measured on every blazed tree and crown damage was directly assessed using the ICP FORESTS methodology. Trees marked for cutting were divided into two classes (degrees) of crown damage ("3b" and "4"). Crown damage for class "3b" ranges between 81 % and 99 %, while class "4" represents completely dry trees (Figure 3). The volume of each marked tree was calculated according to the Schumacher-Hall expression. Values of wood and timber assortments change in accordance with changes in the society, on the market and in economic relations, and in accordance with the application of new technologies and impacts of other factors (Rebula 1996). Value analysis of the obtained wood volume is made by determining the price of every single timber assortment. The price of every single piece of roundwood corresponds to the valid pricelist of the main forest products. The pricelist is used to calculate the price of roundwood from forests owned by the Republic of Croatia during the sale of standing trees ("on the stump") to contractual buyers. Value coefficients were established in accordance with mutual relations of price classes in relation to the most represented price class, which was taken as 1.00. The results were expressed by the relative value ratio of timber assortments produced from trees in crown damage classes "3b" and "4". Figure 3 shows distribution of dead silver fir trees in compartment 7b with regard to crown damage degree. Diameter classes range from 17.5 cm to 77.5 cm. The lowest number of trees, i.e. only one tree, was in the largest diameter class, while the majority of the trees were in the diameter class of 47.5 cm. A total of 200 trees with average breast diameter of 48 cm and average height of 29.4 m were marked and processed. A comparison of the total marked volume determined with the Schumacher-Hall form and the volume taken from the mentioned tables is given in Figure 5. The comparison was made on the basis of individual and total tree volume. According to Šurić, the total volume of marked trees was 491.93 m?, according to Schuberg it was 570.32 m?, and according to Schumaher-Hall it was 570.95 m?. Statistically significant differences (for p<0.05) were found in Šurić - Schuberg and Šurić - Schumacher - Hall relations, whereas insignificant difference was found in the comparison of volume of Schuberg - Schumacher-Hall. The utilization percentage of wood volume is determined as the ratio of the produced wood volume and the volume of large wood over bark according to Schumacher-Hall (Table 2). In the sample, the utilization percentage ranged from 35.79 % to 87.10 % with an average of 71.97 %, or 73.54 % (Median). Wood waste amounted to 28.03 % (26.46 %) on average. In the "3b" damage class the average breast diameter was 53 cm and height was 31 metre. Overall marked volume was 157.31 m?, the volume of processed wood over bark was 137.07 m?, and that under bark was 120.42 m?. The average percentage participation of bark was 12.69% and was lower by 0.6 % than that in the "4" damage class. With regard to the net structure of 116.54 m? of roundwood, technical roundwood accounted for 77.13 m? (66.18 %), and pulpwood for 39.41 m? (33.82 %). Within overall utilization, 49.03 % related to technical roundwood and 25.05 % to pulpwood. With regard to the quality of felled trees, only logs in class I, II and III were produced, while the remaining volume related to pulpwood. In the structure of produced wood assortments, class I accounted for 19.85 %, class II for 43.78 %, and class III for 36.37 %. Of the total number in the sample, 156 trees were in the crown damage class "4". These trees had an average breast diameter of 46 cm and a height of 29 m. The total volume of marked trees was 413.64 m?. The volume of processed wood over bark was 356.60 m? and volume under bark was 312.56 m?, which shows that bark participates with 13.31% in the total wood volume. A quantity of 302.51 m? of wood assortments was produced, of which technical roundwood accounted for 114.01 m? and pulpwood for 188.51 m?. The percentage share of wood waste was 26.86 %. Overall utilization was lower than in class "3b" and amounted to 73.14 %. Within total utilization, 27.56 % related to technical roundwood and 45.57 to stacked wood. In terms of structure, technical roundwood accounted for only 37.69 % and pulpwood for 62.31 % of the net volume. Only logs in class I, II and III were produced. In the structure of produced wood assortments, only 5.02 % related to class I, 30.39 % to class II and as much as 64.59 % to class III. Monetary value of trees is determined on the basis of volume of a particular diameter class and the price of principal forest products. The price of forest assortments made from standing trees ("stump price") was used to calculate monetary value of wood volume. According to the pricelist, monetary value of assortments was divided into three price classes based on the mean saw log diameter. The largest number of assortments was in the price class of pulpwood, for which an index of 1.00 was determined. Value indices given in Table 3 were established on the basis of the price ratio of other price classes and the mentioned one. Multiplying the price class index with assortment volume resulted in the assortment value index. The sum of all assortment value indices of individual trees is the relative value of the produced wood volume, i.e. relative tree value. Stem value rises with an increase in breast diameter. The value of damaged trees (Figure 7) in crown damage class "3b" is lower by more than 20 %, and the value of trees in class "4" is lower by more than 35 % in relation to the value of undamaged trees from regular selection cuts. Value increases per wood volume unit (Figure 8) in accordance with an increase in tree breast diameter. The reason is the absence of certain quality classes in the thinnest trees and division of monetary value according to the prescribed assortment diameter. The relative value of wood volume unit in crown damage class "3b" is lower by 10 % to 30 % than the value unit of undamaged trees. In crown damage class "4", the values of volume unit are lower by 30 % to 45 % in relation to undamaged trees

Ecoefficient Timber Forwarding Based on Nominal Ground Pressure Analysis

U radu se prikazuje istraživanje mogućnosti izvoženja drva forvarderima na djelotvoran i okolišno prihvatljiv način u uvjetima ograničene nosivosti glejnih tala hrvatskih nizinskih šuma zbog njihove povećane vlažnosti tijekom cijele godine. Analiza je provedena na primjeru srednje teškoga šestokotačnoga forvardera Valmet 840.2, a obuhvatila je: 1) utjecaj smanjenja tereta na djelotvornost forvardera, 2) okolišnu pogodnost forvardera u uvjetima ograničene nosivosti tla temeljem nominalnoga tlaka na podlogu (Mellgren 1980) prednjih i stražnjih kotača vozila ovisno o masi utovarenoga drva, opremljenosti vozila užim (600 mm) i širim (710 mm) gumama, odnosno opremljenosti kotača stražnje (bogi) osovine gusjenicama. Granica je okolišne pogodnosti bilo dopušteno opterećenje tla ograničene nosivosti < 60 kPa (Owende i dr. 2002). Rezultati analize djelotvornosti izvoženja drva forvarderom pokazali su da je smanjenje tereta u uvjetima ograničene nosivosti glejnih tala, kao mjera koja osigurava kretnost vozila, ali i smanjenje razine oštećivanja šumskoga tla, izrazito neprihvatljiva zbog pada proizvodnosti i rasta jediničnih troškova. Iz analize je nominalnoga tlaka na podlogu ispod kotača prednje i kotača (gusjenica) stražnje osovine vidljivo da se u uvjetima ograničene nosivosti tla: 1) može iskoristiti nominalna nosivost forvardera te djelotvorno izvoziti drvo, 2) pri čemu će okolišnu pogodnost osigurati primjena četveroosovinskih (osmokotačnih) forvardera opremljenih širim gumama te polugusjenicama na kotačima prednje i stražnje bogi osovine vozila.This paper presents the research of possibilities of forwarding timber in an efficient and environmentally friendly way, under conditions of limited bearing capacity of gley soils of Croatian lowland forests due to their increased moisture all the year round. Reduced soil bearing capacity causes restricted mobility and decreases the forwarder productivity, and also increases the level of damage caused to forest soil, reflected in its compaction and rutting (Fig. 1). In lowland even-aged forests of Croatia, main felling is mostly carried out based on wood cutting and processing by chain saws and forwarding of timber, processed by cut-to-length method, by six-wheel forwarders, usually not equipped with semitracks on rear wheels of bogie axle (Fig. 1). The analysis was carried out on the example of a medium-weight six-wheel forwarder Valmet 840.2 (nominal load capacity of 12 t, whose dimensions and load distribution of empty vehicle are shown in Fig. 4), and this analysis involved as follows: 1) the effect of load reduction on forwarder efficiency, 2) forwarder environmental soundness under conditions of limited soil strength based on nominal ground pressure (Mellgren 1980) of front and rear wheels of the vehicle depending on the mass of loaded timber, vehicle with narrower (600 mm) and wider (710 mm) tires, or with tracks on wheels of the rear (bogie) axle. The limit value of environmental soundness would be the allowed ground pressure of limited bearing capacity <60 kPa (Owende et al. 2002). The effect of load reduction (4 t, 8 t with respect to 12 t of the vehicle nominal load capacity) on forwarder efficiency with respect to the distance of timber forwarding, is expressed according to the multicriteria calculation model of productivity of these vehicles (Stankić 2010), which takes into account: 1) forwarder class 2) soil strength, 3) use of tracks, 4) felling density, 5) volume of the average felling tree and 6) distance of timber forwarding. The unit cost of timber forwarding was calculated according to machine rate made by the company »Hrvatske šume» d.o.o Zagreb for the forwarder Valmet 840.2 (433.19 kn/h). For calculating the nominal ground pressure (Fig. 3), a theoretical model of axle load distribution was used, the case of vehicle at standstill on level ground, depending on mass and length of loaded logs in the bunk area of the forwarder (Poršinsky and Horvat 2005). The analysis of axle load distribution was based on an average length of logs (4 m) made by cut-to-length method in the area of the Croatian lowland forests, and the mass of 1800 kg of a pair of semitracks. The wheel load assumed even load distribution of axle load by pertaining wheels. The contact area between wheels (tracks) and soil was calculated according to Mellgren (1980), for narrower (front – 600/65-34, rear – 600/55-26.5) and wider (front – 710/55-34, rear – 710/45-26.5) tires recommended by the manufacturer of forwarder. The analysis of the forwarder environmental soundness was based on: 1) values of nominal ground pressure of front and rear wheels of the vehicle depending on the mass of loaded timber, and use of narrower and wider tires, i.e. or use of tracks, and 2) the upper limit value of the allowed ground pressure (<60 kPa) of limited bearing capacity (class 3 – Fig. 2), which prevails at the time of main felling in the Croatian lowland forests. The results of efficiency analysis of timber forwarding (Fig. 5) showed that the reduction of load under conditions of limited bearing capacity of gley soils, as a measure for providing vehicle mobility as well as for diminishing the level of damage caused to forest soil, is highly unacceptable due to the decrease of productivity and increase of unit costs. The analysis of nominal ground pressure (Fig. 7) under wheels of the front axle and wheels (tracks) of the rear axle, showed that under conditions of limited soil bearing capacity: 1) the forwarder nominal load capacity may be used and that efficient timber forwarding may be performed, 2) the environmental soundness can be provided by the application of four-axle (eight-wheel) forwarders equipped with wider tires and half-tracks on wheels of front and rear bogie axle of the vehicle. These results should be used as guidelines for purchasing forwarders, and such approach would provide in future ecoefficient timber forwarding under conditions of limited bearing capacity of gley soils in main felling sites of lowland forests

Analiza životnoga ciklusa – izazov za šumarstvo

U radu je opisana analiza životnoga ciklusa kao metoda koja proučava utjecaj proizvoda na okoliš u svim razdobljima njegova života. Posebno je dan osvrt na primjenjivost analize životnoga ciklusa u šumarstvu, odnosno kao jednu od metoda utvrđivanja okolišne prihvatljivosti pri izvođenju šumskih radova radi odabira okolišno prihvatljivije inačice. Za šumarstvo je analiza životnoga ciklusa posebno teška zbog dugoga vremenskoga procesa proizvodnje sirovina, u prvom redu drva (duljina ophodnje), te zbog velikoga prostorno-vremenskoga utjecaja koji šume imaju na okoliš. Da bi se uspješno izradila, potrebni su kvalitetni izvori podataka koji će sadržavati sve ulaze i izlaze materijala, utrošaka energije i količine onečišćavala nastalih tijekom: 1) pridobivanja sirovina, 2) postupaka nastajanja proizvoda, 3) vremena korištenja proizvoda, 4) moguće oporabe i ponovnoga korištenja, 5) konačnoga odlaganja otpada na deponije. Zbog manjka kvalitetnih izvora podataka, ali i pretvorbe statičkoga karaktera analize životnoga ciklusa u dinamički, potrebna su daljnja istraživanja i unaprjeđenja ovoga, inače korisnoga, ali i vrlo složenoga alata procjene okolišne prihvatljivosti

Vučne značajke skidera pri privlačenju drva niz nagib

Kretnost je vozila određena: 1) dimenzijskim značajkama, 2) sposobnošću svladavanja terenskih čimbenika pri kretanju, 3) vučnim značajkama, 4) okolišnom pogodnošću. Vučna se značajka vozila najčešće prikazuje krivuljom klizanja ( – ) te ona ovisi o stanju podloge (nosivosti tla) i ukupnom djelovanju svih sila na vozilo. S obzirom na način prihvata tereta vučna je značajka skidera vrlo kompleksna. Cilj je ovoga rada istražiti: 1) vučnu značajku skidera – faktore bruto i neto vuče, 2) klizanje kotača te 3) korisnost kotača pri kretanju niz nagibe od 15 % i 30 %. Poznavanjem vučnih značajki skidera omogućilo bi se modeliranje njegove kretnosti pri privlačenju drva. Pri kretanju skidera niz nagib uočene su negativne vrijednosti vučnih sila zato što skider vuče teret svojom masom te se i prijenos snage s motora na kotače vozila ne koristi za vuču tereta (drva) već radi stalnoga kočenja vozila motorom. Faktori bruto i neto vuče iz istoga su razloga negativnoga predznaka kao i klizanje kotača. Pri privlačenju drva niz nagib najvažnije je izbjegavanje blokiranja kotača, što dovodi do potpunoga proklizavanje vozila uz narušavanje upravljivosti, o čemu vozač mora stalno voditi računa

Ecoefficient Timber Forwarding Based on Nominal Ground Pressure Analysis

U radu se prikazuje istraživanje mogućnosti izvoženja drva forvarderima na djelotvoran i okolišno prihvatljiv način u uvjetima ograničene nosivosti glejnih tala hrvatskih nizinskih šuma zbog njihove povećane vlažnosti tijekom cijele godine. Analiza je provedena na primjeru srednje teškoga šestokotačnoga forvardera Valmet 840.2, a obuhvatila je: 1) utjecaj smanjenja tereta na djelotvornost forvardera, 2) okolišnu pogodnost forvardera u uvjetima ograničene nosivosti tla temeljem nominalnoga tlaka na podlogu (Mellgren 1980) prednjih i stražnjih kotača vozila ovisno o masi utovarenoga drva, opremljenosti vozila užim (600 mm) i širim (710 mm) gumama, odnosno opremljenosti kotača stražnje (bogi) osovine gusjenicama. Granica je okolišne pogodnosti bilo dopušteno opterećenje tla ograničene nosivosti < 60 kPa (Owende i dr. 2002). Rezultati analize djelotvornosti izvoženja drva forvarderom pokazali su da je smanjenje tereta u uvjetima ograničene nosivosti glejnih tala, kao mjera koja osigurava kretnost vozila, ali i smanjenje razine oštećivanja šumskoga tla, izrazito neprihvatljiva zbog pada proizvodnosti i rasta jediničnih troškova. Iz analize je nominalnoga tlaka na podlogu ispod kotača prednje i kotača (gusjenica) stražnje osovine vidljivo da se u uvjetima ograničene nosivosti tla: 1) može iskoristiti nominalna nosivost forvardera te djelotvorno izvoziti drvo, 2) pri čemu će okolišnu pogodnost osigurati primjena četveroosovinskih (osmokotačnih) forvardera opremljenih širim gumama te polugusjenicama na kotačima prednje i stražnje bogi osovine vozila.This paper presents the research of possibilities of forwarding timber in an efficient and environmentally friendly way, under conditions of limited bearing capacity of gley soils of Croatian lowland forests due to their increased moisture all the year round. Reduced soil bearing capacity causes restricted mobility and decreases the forwarder productivity, and also increases the level of damage caused to forest soil, reflected in its compaction and rutting (Fig. 1). In lowland even-aged forests of Croatia, main felling is mostly carried out based on wood cutting and processing by chain saws and forwarding of timber, processed by cut-to-length method, by six-wheel forwarders, usually not equipped with semitracks on rear wheels of bogie axle (Fig. 1). The analysis was carried out on the example of a medium-weight six-wheel forwarder Valmet 840.2 (nominal load capacity of 12 t, whose dimensions and load distribution of empty vehicle are shown in Fig. 4), and this analysis involved as follows: 1) the effect of load reduction on forwarder efficiency, 2) forwarder environmental soundness under conditions of limited soil strength based on nominal ground pressure (Mellgren 1980) of front and rear wheels of the vehicle depending on the mass of loaded timber, vehicle with narrower (600 mm) and wider (710 mm) tires, or with tracks on wheels of the rear (bogie) axle. The limit value of environmental soundness would be the allowed ground pressure of limited bearing capacity <60 kPa (Owende et al. 2002). The effect of load reduction (4 t, 8 t with respect to 12 t of the vehicle nominal load capacity) on forwarder efficiency with respect to the distance of timber forwarding, is expressed according to the multicriteria calculation model of productivity of these vehicles (Stankić 2010), which takes into account: 1) forwarder class 2) soil strength, 3) use of tracks, 4) felling density, 5) volume of the average felling tree and 6) distance of timber forwarding. The unit cost of timber forwarding was calculated according to machine rate made by the company »Hrvatske šume» d.o.o Zagreb for the forwarder Valmet 840.2 (433.19 kn/h). For calculating the nominal ground pressure (Fig. 3), a theoretical model of axle load distribution was used, the case of vehicle at standstill on level ground, depending on mass and length of loaded logs in the bunk area of the forwarder (Poršinsky and Horvat 2005). The analysis of axle load distribution was based on an average length of logs (4 m) made by cut-to-length method in the area of the Croatian lowland forests, and the mass of 1800 kg of a pair of semitracks. The wheel load assumed even load distribution of axle load by pertaining wheels. The contact area between wheels (tracks) and soil was calculated according to Mellgren (1980), for narrower (front – 600/65-34, rear – 600/55-26.5) and wider (front – 710/55-34, rear – 710/45-26.5) tires recommended by the manufacturer of forwarder. The analysis of the forwarder environmental soundness was based on: 1) values of nominal ground pressure of front and rear wheels of the vehicle depending on the mass of loaded timber, and use of narrower and wider tires, i.e. or use of tracks, and 2) the upper limit value of the allowed ground pressure (<60 kPa) of limited bearing capacity (class 3 – Fig. 2), which prevails at the time of main felling in the Croatian lowland forests. The results of efficiency analysis of timber forwarding (Fig. 5) showed that the reduction of load under conditions of limited bearing capacity of gley soils, as a measure for providing vehicle mobility as well as for diminishing the level of damage caused to forest soil, is highly unacceptable due to the decrease of productivity and increase of unit costs. The analysis of nominal ground pressure (Fig. 7) under wheels of the front axle and wheels (tracks) of the rear axle, showed that under conditions of limited soil bearing capacity: 1) the forwarder nominal load capacity may be used and that efficient timber forwarding may be performed, 2) the environmental soundness can be provided by the application of four-axle (eight-wheel) forwarders equipped with wider tires and half-tracks on wheels of front and rear bogie axle of the vehicle. These results should be used as guidelines for purchasing forwarders, and such approach would provide in future ecoefficient timber forwarding under conditions of limited bearing capacity of gley soils in main felling sites of lowland forests

Razvoj i umjeravanje prijenosnoga sustava za mjerenje osovinskih opterećenja vozila – mjerenja na forvarderu

U radu je istražen prijenosni sustav vaga WLS 101/R2K korišten za izmjeru osovinskih optereć enja forvardera Valmet 840.2 radi što preciznijega utvrđivanja količine šumske biomase. Zbog uočenih odstupanja u izmjerenoj masi tereta prijenosnoga sustava vaga i kontrolnoga mjerenja (kolna vaga) istraženo je kako značajke tovara (zakrivljenost oblovine i količina drva), niveliranje osovina vozila te značajke podloge utječu na izmjeru mase vaganjem. Mjerenja su provedena u tri serije: 1) mjerenja iste vrste tovara na neravnoj i ravnoj podlozi, 2) mjerenja pet različitih vrsta tovara uz istodobno istraživanje utjecaja horizontalnosti osovina, 3) mjerenja iste vrste tovara uz korištenje metalnoga okvira za umetanje para prijenosnih vaga radi centriranja kotača forvardera na mjernu površinu vage. Najmanja odstupanja mjernih vrijednosti (<2% u odnosu na kontrolno mjerenje mase kolnom vagom) postignuta su korištenjem metalnoga okvira za umetanje para prijenosnih vaga. Također je utvrđeno da je neprecizno postavljanje kotača vozila na površinu vaga uzrok najvećih pogrešaka u mjerenju mase tereta

Razvoj i umjeravanje prijenosnoga sustava za mjerenje osovinskih opterećenja vozila – mjerenja na forvarderu

U radu je istražen prijenosni sustav vaga WLS 101/R2K korišten za izmjeru osovinskih optereć enja forvardera Valmet 840.2 radi što preciznijega utvrđivanja količine šumske biomase. Zbog uočenih odstupanja u izmjerenoj masi tereta prijenosnoga sustava vaga i kontrolnoga mjerenja (kolna vaga) istraženo je kako značajke tovara (zakrivljenost oblovine i količina drva), niveliranje osovina vozila te značajke podloge utječu na izmjeru mase vaganjem. Mjerenja su provedena u tri serije: 1) mjerenja iste vrste tovara na neravnoj i ravnoj podlozi, 2) mjerenja pet različitih vrsta tovara uz istodobno istraživanje utjecaja horizontalnosti osovina, 3) mjerenja iste vrste tovara uz korištenje metalnoga okvira za umetanje para prijenosnih vaga radi centriranja kotača forvardera na mjernu površinu vage. Najmanja odstupanja mjernih vrijednosti (<2% u odnosu na kontrolno mjerenje mase kolnom vagom) postignuta su korištenjem metalnoga okvira za umetanje para prijenosnih vaga. Također je utvrđeno da je neprecizno postavljanje kotača vozila na površinu vaga uzrok najvećih pogrešaka u mjerenju mase tereta