Merjenje mejnih sposobnosti pri spravilu lesa navzgor z gozdarskim traktorjem WOODY 110

The paper deals with the test results of uphill skidding of wood with a WOODY 110 cable skidder. The aim of the study was to find the limits of uphill skidding in relation to load size, log orientation and the slope. The trial was prepared on a test track of concave shape in the forest and with pre-designed loads of different sizes. The loads were skidded uphill once withbutt-end and then with top-end forward, until the tractor stopped because of the slope. The results show that butt-end forward skidding is more efficient. The difference between maximum loads at specific maximum slopes is almost constant (0.53 t). Proper load formation (butt-end forward if possible)is more important when skidding on steeper slopes.V članku obravnavamo spravilo lesa navzgor s traktorjem zgibnikom WOODY 110. Cilj študije je bil iskanje mej spravila lesa navzgor v odvisnosti od velikosti kosa lesa, orientacije bremena in naklona terena. Poskus smo pripravili v gozdu na testni vlaki konkavne oblike in z vnaprej pripravljenimibremeni. Bremena smo vlačili enkrat z debelim, enkrat s tankim koncem naprej, dokler se traktor ni zaustavil zaradi prevelikega naklona. Rezultati so pokazali, da je spravilo z debelim koncem naprej učinkovitejše. Razlika med maksimalnimi bremeni pri nekem naklonu je bila skoraj konstantna (0,53 t). Pravilno oblikovanje bremena (debeli konec naprej) je pomembnejše, kadar spravljamo les navzgor na večjih naklonih terena

Ugotavljanje maksimalnih bremen pri spravilu lesa s traktorji navzgor

The results of measuring maximum loads on different slopes when skidding uphill with WOO DY 110 cable skidder and adapted 4WD agricultural tractor AGT 835 are described in the article. Both tractors are very different and were chosen for the purpose of finding the limits of uphill skidding. Besides the slope, the pre-designated loads of different sizes and log orientation (butt-end or top-end forward) have been main variables. The trial was conducted on two concave shaped test skid trails in the forest. On the lower altitudes, the skid trails had small inclination, which slowly increased to 42% on the track where WOODY 110 was tested, and 27% where AGT 835 was measured. First the loads were skidded uphill with butt-end and then with top-end forward. The purpose was to choose too heavy loads, as we wished to stop tractors due to overload, but on different slopes. The proper load formation (butt-end forward if possible) in uphill skidding is most important on steeper skid trails. The dependency between maximum load and slope is linear. The calculated theoretical maximum load on horizontal surface enables us to make similar assessment for any other tractor weighing between 2 and 7 tons. For this purpose, John Deere 6220 and LIMB 80 LUXS adapted agricultural tractors for forest use were chosen and compared. The ratio between the tractor load on different slopes and tractor weight was calculated for all four tractors included in our comparison. Apart from the weight, tractor\u27s engine torque (power) has the decisive influence on the load size. Maximum loads on different slope categories were calculated according to different engine powers.Članek obravnava rezultate meritev spravila navzgor z gozdarskim traktorjem WOODY 110 in prilagojenim kmetijskim traktorjem s pogonom na štiri kolesa AGT 835 z mehanskim in hidrostatsko-mehanskim pogonom. Namen analize je bilo ugotavljanje maksimalnih bremen. Oba traktorja sta zelo različna in sta bila izbrana zato, da bi ocenili zmogljivosti traktorjev pri spravilu lesa navzgor. Poleg naklona vlake so bile spremenljivke še vnaprej določene velikosti bremen in njihove orientacije (z debelim oz. tanjšim koncem naprej). Meritve so bile opravljene v gozdu na dveh testnih vlakah konkavne oblike. Vlake so imele v spodnjem delu majhen naklon, ki se je pri vlaki za WOODY 110 povzpel na 42 % in na 27 % na vlaki, kjer je bil merjen AGT 835. Bremena so bila vlečena navzgor z debelim in v drugem poskusu s tankim koncem pri traktorju. Namen je bil izbrati pretežka bremena za takšne naklone, da bi se traktor zaradi preobremenitve zaustavil pri nekem naklonu vlake. Pokazalo se je, da je pri spravilu navzgor pravilno oblikovanje bremena (če je mogoče, z debelim koncem naprej) najpomembnejše na zelo strmih vlakah. Odvisnost največjega bremena in naklona vlake je linearna. Izračunano teoretično, največje breme na horizontalni podlagi omogoča oceno za katerikoli traktor, ki tehta med 2 in 7 tonami. V ta namen smo izbrali za spravilo lesa prilagojena kmetijska traktorja John Deere 6220 in LIMB 80 LUXS. Za vse štiri traktorje smo izračunali razmerje med največjim bremenom in težo traktorja. Na velikost največjega bremena poleg teže traktorja odločilno vpliva navor (in moč) motorja, zato je za različne kategorije terena izračunana odvisnost med največjim bremenom in močjo motorja

Dinamika tehničnih parametrov traktorja WOODY 110 v območju zaustavljanja zaradi preobremenitve pri vlačenju lesa navzgor

The article deals with uphill wood skidding with WOODY 110 skidder and the changes taking place in technical parameters: slip, torque, tractive forces, and weight distribution of a loaded tractor in the last three meters of skidding, which is defined as a range of stopping due to overload. The test was performed on a concave skid trail, where tractor loaded with 8 meter long fir logs stopped at the 32% incline. It stopped somewhat later when skidding with butt-end forward in comparison to skidding with top-end forward. The loadweight with butt-end forward was 31.69 kN, whereas with top-end forward itweighed 33.53 kN. The measured speeds showed minute changes until the last meter, but decreased swiftly after stopping. Regarding some technical parameters, there were almost no changes at the end of stopping, two exceptions being the slip, which increased in the range of stopping, and the forward torque, which decreased in this range. The results showed that the hydrostatic transmission was efficient, considering that in a relatively well-controlled slip (the slip values increase only in the last three meters, which approximately equals the half of tractor\u27s length) there was less grounddamage.Članek obravnava vlačenje lesa z zgibnim traktorjem WOODY 110 navzgor, in sicer spremembe tehničnih parametrov: zdrsa, navora, vlečne sile in razporeditve teže traktorja z bremenom v zadnjih treh metrih vlačenja, ki smo ga imenovali območje ustavljanja zaradi preobremenitve. Poskus je potekal na konkavni vlaki, kjer se je traktor, ki je bil obremenjen s štirimi osemmetrskimi jelovimi hlodi, zaustavil pri naklonu 32 %, ko je vlačil les z debelim koncem naprej, in nekaj prej, ko je vlačil les s tankim koncem naprej.Breme je pri vlačenju z debelim koncem naprej tehtalo 31,69 kN, pri tankem koncu naprej pa 33,53 kN. Merjene hitrosti so skoraj do zadnjega metra pokazale majhne spremembe, nato pa so ob zaustavitvi hitro upadle. Pri nekaterih tehničnih parametrih prav tako skoraj do konca zaustavitve ne prihaja do bistvenih sprememb. Izjema je zdrs, ki v območju ustavljanja naraste, in navor spredaj, ki v tem območju upade. Rezultati kažejo, da je hidrostatski prenos učinkovit, saj z razmeroma dobro kontroliranim zdrsom (vrednosti zdrsa narastejo šele v zadnjih treh metrih, kar je enako približno polovici dolžine traktorja) prispevajo k manjšim poškodbam tal

The suitability evaluation of cut-to-length in Slovenia in view of terrain and stand

The paper presents the method and results of the study of cut-to length suitability in Slovenia. The study was carried out with the aid of a computer model. Decisive variables and all the available digital forest inventory data were used with then most important cut-to-length limiting factors. The variation of decisive variables was analysed and compared with basic values inorder to determine areas suitable for cut-to-length. The results show great variations as far as the selected areas are concerned, with terrain slope and share of conifers in growing stock as the most important factors in them

Labour costs in diverse forest work conditions and utilization of wood harvesters

Sodobne tehnologije v procesu pridobivanja lesa zahtevajo skrbno analizo stroškov dela. V ta namen so analizirani nekateri tuji modeli računanja stroškov za strojno sečnjo. Predstavljamo program za analizo stroškov strojne sečnje, ki omogoča izdelavo kalkulacij za stroje za sečnjo in nadaljnjo analizo učinkov in stroškov pri različnih pogojih dela. Predvidene so različice za majhne in velike stroje ter za sestoje iglavcev in listavcev. Program omogoča analizo vplivnih dejavnikov na višino stroškov, med katerimi so najpomembnejši operativna stopnja izkoriščenosti strojev, analizirana v odvisnosti od učinkov in premikov stroja med delovišči, velikost delovišč, koncentracija sečenj in povprečno drevo poseka. Poleg navedenih vplivnih dejavnikov je mogoče analizirati tudi vpliv letne stopnje izkoriščenosti stroja na višino stroškov strojnega dela. Analize so pokazale, da se v splošnem pojavijo največje razlike v stroških dela pri kombinaciji koncentracije 30-40 m3/ha in 0,3 m3 povprečnega drevesa poseka.In contemporary wood production technologies, there is an urgent demand for precise forest operation cost analyses. Some examples of cost calculation for mechanized cutting are analyzed. A new computer procedure for cost calculationis presented. The procedure enables forest operation cost calculation and analyses of productivity in different work conditions. Forest operation productivity for small and big harvesters in coniferous and deciduous stands can be selected. The program also enables analyses of influential factors which affect mechanized cutting costs. The most important influential factor is the operational degree of utilization, which is influenced by transfer of machines between work fields, size of work fields, cutting and tree volume. It is also possible to conduct sensitivity analyses of machine utilization expressed in working hours per year. Generally, sensitivity analyses showed that the labour cost differences are highest at the cutting volume of 40-50m3/ha and 0.3 m3 mean tree volume

Prostorski model oskrbe majhnih žag z lesom na območju Alp - študij primera

With wood logistics and forest operation modelling, we have connected a technologic chain of cutting, skidding and road wood transport operations. The goal of the paper is to present the possibilities of simulating forest operation activities including cost flow prediction. The case study regarding wood flow and forest operation cost modelling was conducted in four municipalities located in western Slovenia (bordering to Italy). Input data of forest inventory and basic forest data were used in order to predict the wood flow in the test area. We modelled the available cutting volumes with the capacities of local sinks - notably sawmills. Unbalanced hinterland areas of specific sinks that do not cover the local sink capacities were changed (reduced or enlarged) on account of the adjacent hinterland areas with surplus or shortage of wood volume. The hauling distances and wood volumes for covering the sawmillsć capacities of the adopted (balanced) hinterland areas were studied.S pomočjo modela za logistiko in pridobivanje lesa smo povezali tehnološko verigo oskrbe z lesom od sečnje in izdelave, spravila ter prevoza lesa. Cilj prispevka je predstavitev možnosti predvidevanja (simulacije) aktivnosti v procesu pridobivanja lesa, vključno z vidika njihovih stroškov. Raziskava je bila narejena na primeru štirih občin v zahodni Sloveniji na meji z Italijo. Na izbranem območju je bil uporabljen gozdarski informacijski sistem, vključno z osnovnimi podatki popisa gozdov z namenom napovedovanja pridobivanja in transporta lesa. Modelno smo primerjali razpoložljive količine možnih sečenj s kapacitetami lokalnih porabnikov - predvsem žag. Na osnovi neuravnoteženih razmerij med kapacitetami porabnikov in zaledjem gozdov smo posameznim porabnikom spremenili zaledja (pomanjšali ali povečali) na račun sosednjih zaledij s pribitkom ali pomanjkanjem lesa. Na osnovi sprememb so bili analizirani stroški prevoza lesa

Zdrs koles pri vlačenju lesa s prilagojenim kmetijskim traktorjem AGT 835 T

The paper presents a wheelslip measurement method for small farm tractors (AGT835 T) adapted for skidding, with mechanical and hydrostatic mechanical transmissions. The research focused on uphill skidding, as slip values measured in uphill skidding are higher than in downhill skidding. A comparisonwas made of the performance of tractors carrying equal load but equipped with mechanical and hydrostatic transmission systems. The hydrostaticdrive causes higher negative load values in downhill skidding, and slightly higher slippage. As for hydrostatic tractors, wheelslip is higher in uphill skidding than in downhill skidding. The increase in the sloping of the terrain causes wheelslip to rise progressively. When a tractor travels uphill,slip is linked to a loss of energy. Wheelslip measurements are therefore important for determining the optimum conditions for individual tractor types.Predstavljena je metoda merjenja zdrsa na majhnih prilagojenih kmetijskih traktorjih - AGT 835 T - za spravilo lesa z mehansko in hidrostatsko-mehansko transmisijo. Poudarek je na spravilu lesa navzgor, kjer je bil ugotovljen tudivečji zdrs kot pri vožnji navzdol. Narejena je primerjava med mehansko in hidrostatsko transmisijo traktorja pri enaki obremenitvi. Hidrostatski pogon povzroča večje negativne obremenitve pri spravilu navzdol, in tudi nekaj večjizdrs. Pri spravilu navzgor je zdrs pri hidrostatski izvedbi znatno manjši. Naklon terena z večanjem progresivno vpliva na večanje zdrsa. Zdrs privožnji traktorjev navzgor pomeni izgubo energije, zato je meritev zdrsa pomembna za določanje optimalnih razmer posameznih tipov traktorjev