Based on the knowledge of the dimensional and mass features of a forwarder, a model was developed to assess its mobility during timber forwarding uphill in a safe and eco-efficient way. The model is ...based on knowledge of the position of the forwarder’s centre of gravity, its declared payload and the length of the loaded timber, as well as the gradeability for uphill timber forwarding based on the traction characteristics of the vehicle. The model connects two research approaches, (1) vehicle–terrain approach (distribution of axle loads depending on the longitudinal terrain slope) and (2) wheel–soil approach (estimation of the traction characteristics of the forwarder based on the wheel numeric), concerning previous research: (i) underload on the front axle of the vehicle, (ii) overload on the rear axle of the vehicle, (iii) permissible tire load, (iv) minimal soil bearing capacity, (v) wheel slip. Simulation modelling for the assessment of the forwarders’ mobility range during timber forwarding uphill was conducted on an example of an eight-wheel Komatsu 875 forwarder, with a declared payload of 16,000 kg, equipped with 710/45-26.5 tires, for which the position of the centre of gravity was determined by the method of lifting the axle. The results of the distribution of the adhesion load on the front and rear axles of the forwarder indicated that, during timber forwarding of 16,000 kg and 4.82 m long hardwood logs on a terrain slope below 68%, there is no critical unloading on the front bogie axle, nor overloading on the rear bogie axle, i.e., wheel tire overload that could limit forwarder mobility. For the specified range of longitudinal terrain slope, a minimal cone index of 950 kPa for an exemplary forwarder is an environmental factor and was calculated based on the nominal ground pressure of the reference (heavier loaded) rear wheels of the vehicle. The forwarders’ mobility range was determined by the intersection curves of the gradeability (based on forwarders’ traction characteristics at wheel slip of 25% vs. cone index) and the curve of the minimal soil cone index.
This study compared oak butt-log volume estimations gained through terrestrial measurements in the forest stand with a remote approach using an unmanned aerial system (UAS) and photogrammetric ...post-processing. Terrestrial measurements were conducted in the lowland part of Croatia after a completed motor–manual final felling of a 140-year-old even-aged oak stand. Butt-logs’ volumes were estimated with four methods: the sectioning method and Huber’s, Smailan’s and Riecke–Newton’s methods. Measuring diameters and lengths and estimating volumes remotely were based on orthophotos using four different software: ArcGIS, QGIS, AutoCAD and Pix4D. Riecke–Newton’s method for volume estimation had the smallest relative bias of +1.74%, while for Huber’s method it was −8.07% and with Smailan’s method it was +21.23%. Log volume estimations gained remotely via ArcGIS and QGIS were, in the case of Huber’s method, at +3.63% relative bias, and in the case of Riecke–Newton’s method at +1.39% relative bias. Volume estimation using the sectioning method resulted in a total of 51.334 m3 for the whole sample, while the sectioning method performed with the help of AutoCAD resulted in 55.151 m3, i.e., +7.43% relative bias. Volume estimation of thirty oak butt-logs given by Pix4D software (version 4.8.4) resulted in +9.34% relative bias (56.134 m3). Comparing terrestrial measurements and the volume estimations based on them to those gained remotely showed a very high correlation in all cases. This study showed that using a UAS for log volume estimation surveys has the potential for broader use, especially after final felling in even-aged forests where the remaining trees in the stand would not block photogrammetric analysis.
During the seven-year research period, the average annual removal was by 3274 m3 higher than the average annual removal prescribed by the existing management plan (MP). The main reason lies in the ...high amount of salvage felling volume at 55,238 m3 (38.3%) in both the main and the intermediate felling due to oak dieback. The analysis of forest accessibility took into account the spatial distribution of cutblocks (with ongoing felling operations) and the volume of felled timber for two proposed factors: (1) the position of the cutblock and (2) the position of the removal. Cutblock position factor took into account the spatial position of the felling areas/sites, while removal position factor besides the spatial reference took into account the amount of felled timber (i.e., volume) both concerning forest infrastructure network and forest operations. The analysed relative forest openness by using geo-processing workflows in GIS environment showed four types of opening areas in the studied management unit (MU): single-opened, multiple-opened, unopened and opened areas outside of the management unit. Negative effects of the piece-volume law and low harvesting densities on forest operations are highlighted in this research due to high amount of salvage felling particularly in the intermediate felling by replacing timber volume that should have come from thinnings.
Na osnovi poznavanja dimenzijskih i masenih značajki forvardera, razvijen je model raspodjele osovinskih opterećenja te procjene kretnosti forvardera pri izvoženju drva uz i niz nagib terena. Model ...je zasnovan na poznavanju položaja točke težišta forvardera, deklariranoj nosivosti forvardera i duljini utovarene oblovine, graničnom nagibu kretnosti forvardera temeljem vučne značajke vozila pri izvoženju drva uz nagib terena te graničnom nagibu terena pri izvoženju drva niz nagib, kod kojega obodna sila poprima vrijednost nula, uz poštivanje ograničenja proisteklih iz prethodnih istraživanja.Simulacijsko modeliranje procjene kretnosti pri izvoženju drva uz i niz nagib terena prikazano je na primjeru osmokotačnoga forvardera Komatsu 875, deklarirane nosivosti 16.000 kg, opremljenoga pneumaticima 710/45-26.5 za koji je metodom podizanja osovine određen položaj točke težišta. Rezultati raspodjele adhezijskog opterećenja prednje i stražnje osovine forvardera ukazali su da pri izvoženju drva tvrdih listača mase 16.000 kg te duljine 4,82 m, uz i niz nagib terena u granicama ±70 % ne dolazi do prekoračenja zbroja dopuštenih opterećenja guma kotača po osovinama te dopuštenog opterećenja prednje i stražnje bogi osovine. Pri izvoženju drva uz nagib terena, do rasterećenja prednje bogi osovine dolazi kod nagiba terena >68 %. Za navedeni raspon uzdužnih nagiba terena, najmanji konusni indeks od 950 kPa za primjerni forvarder predstavlja mjeru okolišne pogodnosti, a izračunat je na osnovi nominalnog tlaka na podlogu referentnih (opterećenijih) kotača stražnje bogi osovine vozila.Granični nagib kretnosti nominalno natovarenoga forvardera uz nagib terena značajno ovisi o nosivosti šumskog tla iskazanoga konusnim indeksom, ali i o klizanju kotača vozila. Za iste vrijednosti konusnoga indeksa tla, pri vrijednostima klizanja kotača (10 – 15 %) koje odgovaraju najvećoj vučnoj korisnosti, granični nagib kretnosti forvardera ima niže vrijednosti, u odnosu na klizanje kotača (20 – 25 %) koje odgovara okolišnom ograničenju, odnosno početku erozionih procesa na nagnutim terenima.Granični nagib terena pri izvoženju drva forvarderom niz nagib terena kod kojeg obodna sila poprima vrijednost nula, značajno ovisi samo o nosivosti šumskog tla te se nije pokazao kao dobar pokazatelj ograničenja izvoženja drva. Određivanje ograničenja kretnosti forvardera pri izvoženju drva niz nagib terena u budućnosti će predstavljati istraživački izazov.
In the example of an eight-wheeled forwarder, a simulation model is presented for assessing the mobility of the forwarder when transporting timber uphill and downhill. The presented model shows the changes in forces during timber forwarding by a nominally loaded forwarder due to a wide range of changes in influencing factors: 1) the slope of the terrain, 2) the direction of timber forwarding, and 3) the soil bearing capacity expressed by the cone index. By incorporating the criteria/limitations of timber forwarding derived from previous research, the forwarder mobility model gains practical meaning; that is, the theoretical approach brings the reality of timber forwarding closer. The mobility model shown is based on easily measurable or available data but also on the position of the centre of gravity, which is relatively easy to determine by the shown method of lifting the forwarders’ axle with the use of portable scales and is usually unavailable to read in the manufacturers’ catalogue. All known criteria/restrictions of mobility of forest vehicles are primarily related to their movement uphill. The limitation of the skidder’s mobility when skidding timber downhill has been firmly determined, while there are no limitations in the literature for forwarding timber downhill. Gradeability of a nominally loaded forwarder downhill, where the thrust force takes the value of zero, did not prove to be a good indicator or a limitation of timber forwarding. Determining the mobility limitations of the forwarder during timber forwarding downhill will be a research challenge in the future.
Soil Characteristics in Oak Lowland Stand Đuka, Andreja; Popović, Maja; Poršinsky, Tomislav ...
Croatian Journal of Forest Engineering,
01/2024, Letnik:
45, Številka:
1
Journal Article, Paper
Recenzirano
Odprti dostop
The behavior of the vehicle-soil interaction and reduction of the possible soil damage to an acceptable level is one of the goals of forest engineering. This study aimed to analyze the impact of a ...6-wheeled forwarder on water-physical soil characteristics on lowland soil – pseudogley. The research was conducted using a 17-ton Timberjack 1710B forwarder, which forwarded 694.1 m3 volume of oak (Quercus robur L.) assortments. Soil characteristics were measured after each of the eight passes of the loaded forwarder. Bulk density measured on the surface layer ranged from 1.01–1.23 (Me=1.10) g/cm3 (undisturbed soil); 1.14–1.70 g/cm3 (multiple passes of the loaded forwarder). The highest soil density increase was observed after the first pass of the loaded forwarder (16%). Soil solid phase ranged from 2.49 to 2.73 g/cm3 with no statistically significant difference between undisturbed soil and soil after multiple passes of the vehicle. The highest porosity decrease was observed after the first pass of the loaded forwarder (10%). The highest soil water retention capacity decrease was observed after the first pass of the loaded forwarder (3%). The highest soil air capacity decrease was observed after the first pass of the loaded forwarder (30%) compared to the undisturbed soil of the forest stand.
Izvoženje drva forvarderima, obilježava kotrljanje drva na kotačima, prihvat i sakupljanje sortimentnom metodom izrađenoga drva hidrauličnom dizalicom, iz čega proizlazi i zahtjev za paralelnom ...mrežom sekundarnih šumskih prometnica međusobnoga razmaka dvostrukoga dosega dizalice.Rad se bavi prikazom: 1) dimenzijskih i masenih značajki forvardera u svijetlu norme ISO 13860 (2016) te 2) plana raspodjele tereta forvardera kojega je razvio njemački Kuratorij za šumski rad i šumsku tehniku (KWF), s ciljem pomoći šumarskim stručnjacima pri nabavci, odnosno korištenju ovih šumskih vozila.Za primjerni forvarder odabran je teški osmokotačni forvarder Komatsu 875, za koji su na osnovi mjerenja prikazane njegove dimenzijske i masene značajke, kao i plan raspodjele tereta s ciljem njegove ocjene.Kritički osvrt je dan i na normu ISO 13860 (2016) s obzirom na neobuhvaćanje nekih dimenzijskih (duljina i visina prednjeg te stražnjeg prepusta forvardera, kutovi i polumjeri prohodnosti vozila) i masenih (položaj točke težišta) pokazatelja forvardera, a koje opisuju i/ili služe modeliranju njegove kretnosti pri izvoženju drva s obzirom na smjer i uzdužni nagib terena. Isto tako, norma izrijekom ne spominje niti jedan pokazatelj okolišne pogodnosti (npr. nominalni tlak na podlogu).
Rad obrađuje dimenzijske značajke utovarnoga prostora forvardera, a koje norma ISO 13860 (2016) određuje trima dimenzijama zasnovanim na neposrednom mjerenju (duljina utovarnoga prostora, širina ...između držača tereta, visina držača tereta) te dvjema posrednim (računske) dimenzijama (površina poprečnoga presjeka utovarnoga prostora forvardera i visina težišta tereta). Iako za te pokazatelje utovarnoga prostora forvardera norma ISO 13860 (2016) daje definicije, za dva računska pokazatelja nije objašnjen način njihova izračuna te na kojim se dimenzijama utovarnoga prostora zasnivaju.Poticaji za pisanje ovoga rada jesu: 1) pojašnjenje važnosti poznavanja dimenzijskih pokazatelja utovarnoga prostora forvardera, 2) izrada prijedloga načina izračuna poprečnoga presjeka utovarnoga prostora forvardera i visine težišta tereta forvardera te 3) određivanje dodatnih potrebnih mjernih dimenzijskih značajki utovarnoga prostora.Na osnovi predloženih mjerenja prikazane su dimenzije, ali i računske značajke utovarnoga prostora osmokotačnoga forvardera Komatsu 875.
The paper deals with the dimensional characteristics of the forwarder loading space, which is determined by ISO 13860 (2016) through three dimensions based on direct measurement (distance of load bunk headboard to rearmost bunk, width across stakes, stake height) and two indirect (calculative) dimensions (cross-sectional area of load space and height of load centre). Although the ISO 13860 (2016) standard provides definitions for the listed indicators of the forwarder loading space, the method of their calculation, as well as the dimensions of the loading space, are not explained for the two calculative indicators. The aim of this paper was to: 1) clarify the importance of knowing the dimensional indicators of forwarder loading space; 2) draft a proposal for calculating the cross-sectional area of forwarder load space and height of load centre; and 3) determine additional (required) dimensional characteristics of loading space. Based on the proposed measurements, the dimensions and computational characteristics of the loading space of the eight-wheeled Komatsu 875 forwarder are presented.
Izvoženje drva forvarderima, obilježava kotrljanje drva na kotačima, prihvat i sakupljanje sortimentnom metodom izrađenoga drva hidrauličnom dizalicom, iz čega proizlazi i zahtjev za paralelnom ...mrežom sekundarnih šumskih prometnica međusobnoga razmaka dvostrukoga dosega dizalice.
Rad se bavi prikazom: 1) dimenzijskih i masenih značajki forvardera u svijetlu norme ISO 13860 (2016) te 2) plana raspodjele tereta forvardera kojega je razvio njemački Kuratorij za šumski rad i šumsku tehniku (KWF), s ciljem pomoći šumarskim stručnjacima pri nabavci, odnosno korištenju ovih šumskih vozila.
Za primjerni forvarder odabran je teški osmokotačni forvarder Komatsu 875, za koji su na osnovi mjerenja prikazane njegove dimenzijske i masene značajke, kao i plan raspodjele tereta s ciljem njegove ocjene.
Kritički osvrt je dan i na normu ISO 13860 (2016) s obzirom na neobuhvaćanje nekih dimenzijskih (duljina i visina prednjeg te stražnjeg prepusta forvardera, kutovi i polumjeri prohodnosti vozila) i masenih (položaj točke težišta) pokazatelja forvardera, a koje opisuju i/ili služe modeliranju njegove kretnosti pri izvoženju drva s obzirom na smjer i uzdužni nagib terena. Isto tako, norma izrijekom ne spominje niti jedan pokazatelj okolišne pogodnosti (npr. nominalni tlak na podlogu).
Timber forwarding is characterised by carrying timber clear of the ground and loading timber assortments by a hydraulic crane, which results in the requirement for a parallel network of secondary forest infrastructure network where the distance between trails equals to double span of the hydraulic crane.
The paper presents 1) dimensional and mass characteristics of forwarders considering ISO 13860 (2016) standard and 2) forwarder load distribution plan developed by the German Kuratorium für Wadarbeit und Forsttechnik (KWF) to assist forestry experts in the purchase and use of these forest vehicles.
The heavy eight-wheel forwarder Komatsu 875 was selected as an example. Its dimensional and mass characteristics are shown based on measurements and the load distribution plan, aiming to evaluate the vehicle.
A critical comment is also given regarding the ISO 13860 (2016) standard due to the lack of some dimensional (length and height of the front and rear overhangs of forwarders, approach and departure angles and clearance radii) and mass (position of the centre of gravity point) of forwarders. These characteristics describe and serve to model its mobility during timber forwarding concerning the direction and longitudinal slope of the terrain. In addition, the ISO 13860 (2016) standard does not explicitly mention any indicator of environmental suitability (e.g. nominal ground pressure).
Pri svakom je planiranju, pa tako i pri planiranju mreže šumskih prometnica, vrlo važno poznavati postojeće stanje, odnosno imati detaljan i točan uvid u postojeću mrežu šumskih prometnica područja ...zahvata otvaranja šuma, što omogućuje registar šumske prometne infrastrukture. Želi li se valjano procijeniti kvantiteta postojeće šumske prometne infrastrukture (gustoća šumskih prometnica), potrebno je jasno i nedvosmisleno definirati kriterije određivanja gustoće postojeće šumske prometne infrastrukture.U hrvatskome šumarstvu, trenutno važeće kriterije za određivanja gustoće primarne šumske prometne infrastrukture definiraju »Tehnički uvjeti za gospodarske ceste« (Šikić i dr. 1989), koji su u sažetom obliku uključeni u Pravilnike o uređivanju šuma (NN 111/06, NN 141/08) te (NN 79/15). Spomenuti su kriteriji nedovoljno precizni i nejasni te šumarskim stručnjacima prepuštaju donošenje niza subjektivnih odluka.Kako bi se izbjegla/smanjila svaka subjektivnost, dobili objektivni podaci te omogućila usporedivost izračunate gustoće primarne šumske prometne infrastrukture različitih gospodarskih jedinica, prišlo se izradi potpuno novih kriterija koji će poslužiti za precizno, objektivno i transparentno određivanje gustoće primarne šumske prometne infrastrukture. Kriteriji su razvijeni i detaljno opisani u okviru Obrasca za izradu Elaborata učinkovitosti mreže šumskih prometnica – primarne šumske prometne infrastrukture, koji je sastavni dio Pravilnika o provedbi mjere M04 »Ulaganja u fizičku imovinu«, podmjere 4.3. »Potpora za ulaganja u infrastrukturu vezano uz razvoj, modernizaciju i prilagodbu poljoprivrede i šumarstva«, tipa operacije 4.3.3. »Ulaganje u šumsku infrastrukturu« iz Programa ruralnog razvoja Republike Hrvatske za razdoblje 2014. – 2020. (NN 106/15, 65/17).U radu su na ortosnimkama prikazani te združeni sa fotografijom (slikovni dio registra primarne šumske prometne infrastrukture iz studije slučaja) najčešći/karakteristični primjeri primjene kriterija pri određivanju gustoće primarne šumske prometne infrastrukture.
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