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

Košir, Boštjan

Marenče, Jurij

Digital repository of Slovenian research organizations

Zbornik gozdarstva in lesarstva 83 (2007), s. 59–62GDK: 377.44(045)=111Prispelo / Received: 30.01.2007               Kratki znanstveni članekSprejeto / Accepted: 04.06.2007                                  Short communicationMeasuring the limits of uphill timber skidding with a WOODY 110 forestry tractorBoštjan KOŠIR1, Jurij MARENČE2AbstractThe 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 thelimits 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 with butt-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 differencebetween 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.Key words: forestry, tractor, skidding, maximum slope, maximum loadMerjenje mejnih sposobnosti pri spravilu lesa navzgor z gozdarskim traktorjem WOODY 110IzvlečekV 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 pripravljenimi bremeni. 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. Ključne besede: gozdarstvo, traktor, spravilo, maksimalni naklon, maksimalno breme1 Prof. Dr. B. K., University of Ljubljana, Biotechnical Faculty, Department of Forestry and Forest Resources, Večna pot 83, 1000 Ljubljana, Slovenia, bostjan.kosir@bf.uni-lj.si2 Dr. J. M., University of Ljubljana, Biotechnical Faculty, Department of Forestry and Forest Resources, Večna pot 83, 1000 Ljubljana, Slovenia,  jure.marence@bf.uni-lj.si1 Introduction1 UvodIn Slovenian forestry, tractor skidding prevails. In addition to adapted wheeled agricultural tractors, adapted tracked tractors and special forestry tractors are used. Special forestry tractors – cable skidders – are used only by various kinds of forestry enterprise, while private forest owners use only agricultural tractors of different sizes and adaptations for forest work. Among the various types of skidder, the WOODY tractor is important, since it was designed and made by the Slovenian Slovenj Gradec forestry enterprise in the eighties (KOŠIR 1997), and later reconstructed and further developed by the VILPO enterprise (KOŠIR 1999, KOŠIR / KRČ 2000). The tractor is hydrostatically driven and remote controlled (KOŠIR 2000). The latest model is the WOODY 110, and it comes in various attachment and size options. There are many in use in Switzerland, Germany and Austria, as well as nine already in use in Slovenia. The tractor was tested in 2000 and later under controlled conditions. This paper gives some of the results, which can be used for estimating the skidder's capabilities when skidding heavy loads uphill.2 Methods2 MetodeThe purpose of the trial was to determine the limits of uphill skidding in relation to load size, log orientation and slope, under conditions as near as possible to average conditions in forestry. The basic features of the tractor are shown in Table 1. The tractor was equipped with a remote controlled winch with a pulling force of 70 kN. The whole tractor was remote controlled, but neither of these options was relevant to the trial. For test purposes, we chose a skid road of concave shape. The skid road was divided into 60            Zbornik gozdarstva in lesarstva 8314 segments on the basis of the changing slope (Table 2). In addition to other variables (JEJČIČ et. al. 2001, 2003, MARENČE 2000, ŠUŠNJAR 2005) we also measured the time and recorded the whole operation with a video camera. The loads were composed of four 8 m long spruce logs of different sizes (Table 3) and orientations (butt-end of logs on tractor and top-end forward) - (MARENČE 2005). The loads were prepared before the trial in such a manner that the volumes, measured as usual in forestry, were as close as possible to 2, 3, 4, 5 and 6 m3 under bark. The loads were weighed at the roadside after the trial. The tractor dragged the load in an uphill direction until it stopped because of slip or choked transmission.Table 1: Basic features of the WOODY 110 skidderPreglednica 1: Osnovne značilnosti WOODY 110Weight / Teža 5500 daNLength / Dolžina 5400 mmHeight / Višina 2750 mmWidth / Širina 1940 (2000)mm with tyres / s pnevmatikami 14.9/13-28Motor / Motor PERKINS 1004-40T, 4 cyl. cil. Power / Moč 76.5kW - 2200 rev/min o/min Tyres / Pnevmatike 14.9/13-28 PR12Drive / Pogon Hydrostatic – mechanical, processor control / Hidrostatični – mehanski, procesorska kontrola Winch / Vitel IGLAND 2H, 2x7000 daNVelocity / Hitrosti 0 - 17 , 0 - 30 km/hTable 2: Skid road characteristicsPreglednica 2: Značilnosti traktorske vlakeTable 3: Load sizesPreglednica 3: Velikosti bremenLoad orientation Lega bremena Under bark Brez skorje m3WeightTeža kNButt-end forward  Debeli konec naprej 1.66 17.683.11 24.304.07 31.695.12 39.586.10 45.37Top-end forward  Tanki konec naprej 2.37 17.892.89 23.834.13 33.535.15 36.336.14 47.29For the purposes of further research and possible comparisons, we also deﬁned the friction coefﬁcient bydragging a known load parallel to the typical surface of the skid road.3 Results3 RezultatiThe friction coefﬁcient was shown to be an average of0.54, which is comparable with other studies (MARENČE 2005, SAMSET 1979). We measured the moisture of the soil surface over the course of the experiment, but the results showed very low variability due to the sunny weather during all measurements. The low variability of the friction coefﬁcient means that the results of the trialcan be fairly well trusted. Basic data of the trial are shown in Table 4. The ﬁrstpoint to be made is that the tractor failed to reach the top of the skid road in all cases, but it must be stressed that the maximum slope at the top was chosen on the basis of experience as a maximum for any kind of uphill skidding ProﬁleProﬁlSlope NaklonHorizontal distance Horizontalna razdaljaHeight difference Višinska razlikaCumulative slope distance Kumulativna poševna razdaljaCumulative horizontal distance Kumulativna horizontalna razdaljaCumulative height difference Kumulativna višinska razlika% m m m m m1 - 2 10 14.2 1.4 14.3 14.2 1.42 - 3 19 17.4 3.3 32.0 31.6 4.73 - 4 10 15.1 1.5 47.2 46.7 6.24 - 5 14 16.4 2.3 63.8 63.2 8.55 - 6 17 14.8 2.5 78.8 78.0 11.16 - 7 12 15.8 1.9 94.7 93.8 13.07 - 8 24 16.1 3.9 111.3 109.9 16.88 - 9 20 17.6 3.5 129.2 127.5 20.39 - 10 25 14.5 3.6 144.1 141.9 24.010 - 11 32 17.1 5.5 162.1 159.0 29.411 - 12 31 12.6 3.9 175.3 171.7 33.312 - 13 42 12.3 5.2 188.6 183.9 38.513 - 14 42 12.7 5.3 202.4 196.6 43.8Košir,, B., Marenče, J.: Measuring the limits of uphill timber skidding with a WOODY 110 forestry tractor 61with tractors. The results are shown in Figure 1, and can be brieﬂy summarised. Skidding with the butt-end to thefront is more successful (HORVAT 1996) with the given physical properties of the skid road.Table 4: Stopping points of different load orientations and sizes Preglednica 4: Točke zaustavitve pri različnih legah bremena in naklonih vlake For practical purposes, it is essential to evaluate the difference between the two load orientations. A calculation of linear regression (Figure 1) shows that the curves are practically parallel within statistical signiﬁcance. Thismeans that the tractor is capable on average of hauling uphill 0.53 t more when the orientation is butt-end forward (0.45 t on horizontal ground, 0.61 t on very steep slope). The explanation is clear – when the butt-end is oriented toward the tractor and lifted from the ground, the vertical load of the tractor is greater, and the required horizontal force when moving is smaller. The distribution of the weight between the front and rear axles of the tractor on the horizontal surface when empty is 57%:43%. When lifting the load on the rear axle, this proportion reaches around 50%:50% (horizontal ground) or 39%:61% (on slope) - (KOŠIR / MARENČE 2005), which enable very good exploitation of the driving forces.The relative proportion between the orientation of the maximum loads driven uphill under different slopes can also be expected to increase according to the slope, since the absolute difference remains almost constant (Figure 2).This would in practice mean that when skidding close to maximum skid road inclinations, greater attention needs to be paid to the load orientation (SAMSET 1985). This could be achieved by proper felling of the trees, and in certain cases also through the process of wood bunching. We would suggest that when skidding uphill, the fellers should fell the trees with the top away from the skid road whenever possible. Such a practice would increase the bunching distance. On the other hand, it would increase the tractors' loads. Over short skidding distances, it would not greatly affect the overall skidding efﬁciency, but onextreme slopes or over greater skidding distances, this practice would obviously show better results. Proper time studies (SAMSET 1985) of actual production need to be carried out to compute the marginal distances and slopes where the load orientation is crucial.A practical conclusion from Figure 2 is that the importance of the load orientation increases with slope when skidding uphill. This has important consequences for instructions related to directional felling performed by woodcutters. Butt-end forward can only be done when the cutter fells the tree at the proper angle away from the skid road. On the other hand, this means that the bunching distance is greater than when the cutter fells the tree toward the skid road. Which of the two is better economically, still needs to be calculated. Load orientation Lega bremenaLoadBremeMaximal slope distance Največja poševna razdaljaMaximal slope Največji naklon vlakeHeight difference Višinska razlikakN m % mButt-end forward Debelikonec naprej 17.68 194.7 36.50 40.8524.30 184.3 31.50 36.0131.69 164.1 28.50 30.0439.58 153.8 22.50 26.3045.37 118.0 22.00 20.65Top-end forward Tanki konec naprej 17.89 188.8 31.50 37.3423.83 183.1 31.50 35.6533.53 154.6 22.50 26.4936.33 154.1 22.50 26.3747.29 88.0 18.00 14.13�������������������� ��������������������������������������������������� �� �� �� �� ������ �����������Maksimalni naklon����������������Maksimalno breme����������������������Debeli konec naprej������������������Tanki konec naprej������������������������Debeli konec naprej�����������������������Tanki konec naprejFigure 1: Maximum loads in kN when skidding uphillSlika 1: Maksimalna bremena v kN pri vlačenju navzgor ����������������������� �� �� �� �� ������ �����������Maksimalni naklon���������������������������Povečanje maksimalnega bremena��Figure 2: Relative proportion between the orientation of the loads Slika 2: Relativna razmerja med legama kosov lesa v bremenu 62            Zbornik gozdarstva in lesarstva 83As already mentioned, we also measured the time of each journey. The differences between trials were not great, but when we calculated how much time was spent dragging separate loads, it was shown that load orientation had no impact on skidding speed. Larger loads need less time, and vice versa, but larger loads cannot be dragged up such steep slopes and the slope distance is similarly smaller. That also means that the dragging speed was slower with larger loads. Computed relations between speed, slope and loads of different load orientations are shown in Figure 3. Maximum speeds when skidding different load orientations are the same, but when skidding top-end forward, the maximum speed is achieved with a smaller maximum load than with butt-end forward. The speed increasingly lessens with load sizes over 30 kN. Differences between the speeds of skidding different load orientations also increase, which affects the overall performance of tractor skidding and its economy.Figure 3: Speed of skidding loads uphill according to load size and corresponding maximum slopeSlika 3: Hitrost vlačenja bremen navzgor glede na velikost bremena in odgovarjajoči največji naklon vlake 4 Discussion4 RazpravaMeasuring tractor technical performance when skidding wood is new in Slovenian forestry. The ﬁrst testsshow signiﬁcant differences between usual methods ofskidding. The test track was chosen in a real forest and the whole experiment was oriented toward simulation of real skidding conditions. This may also have affected the results, with rather greater variability of the measured parameters. On the other hand, the experiment was designed in such a way as to achieve results that can be more easily understood by average users in forestry. Similar tests will have to be carried out in the future on other types of tractor and on different substrates in order to achieve more reliable results. It is also important to connect the results described in this article with the behaviour of other measurable variables, such as axle load, torque, slip and pulling forces (KOŠIR / MARENČE 2005, MARENČE 2005, ŠUŠNJAR 2005).5 References5 ViriHORVAT, D., 1996. Proračun nekih veličina vučnih značajki četiriju vozila za privlačenje drva u proredama brdsko-planinskih sastojina = Calculations of some tractive parameters for four vehicles used for wood transportation in mountain thinning. V: Zaštita šuma i pridobivanje drva, Hrvatsko šumarsko društvo, Vol. 2, Zagreb, p. 243–252.JEJČIČ, V. / POJE, J. / MARENČE, J. / KOŠIR, B., 2001. Razvoj mjerne opreme za šumarski traktor Woody 110.- Proceedings, 29. International Symposium on Agricultural Engineering, Opatija, Croatia, Zavod za mehanizaciju poljoprivrede, p.111–118. JEJČIČ, V. / POJE, J. / MARENČE, J. / KOŠIR, B., 2003. Razvoj mjerne opreme za šumarski traktor AGT 835 s mehaničkom i hidromehaničkom transmisijom V: Proceedings, 31. International Symposium on Agricultural Engineering, Opatija, Croatia, Zavod za mehanizaciju poljoprivrede, p. 65–74. KOŠIR, B., 1997. Razvoj traktorja WOODY se nadaljuje.- Gozd.V., 7–8 (97) 55. Ljubljana, p. 365–369.KOŠIR, B., 1999. Maly przeglad europejskiego rynku skiderow - VILPO.- Las Polski, 9(1999), Warszawa, p.22–23.KOŠIR, B., 2000. Lastnosti prenosa sil na podlago pri traktorju WOODY 110.- Gozd.V., 3 (200) 58. Ljubljana, p. 139–145. KOŠIR, B. / KRČ, J., 2000. Študij časa pri spravilu lesa z WOODY 110.- XX Gozd.štud.dnevi, Zb. referatov, Kranjska gora, maj 2000. Univerza v Ljubljani , Biotehniška fakulteta Oddelek za gozdarstvo in obnovljive gozdne vire , Ljubljana, p. 151–168.KOŠIR, B. / MARENČE, J., 2005. Determining Technical Parameters in Tractor Skidding – Basis for the Choice of Tractor, Proceedings: FORMEC 2005, Ljubljana, p. 43–55. MARENČE, J., 2000. Ugotavljanje tehničnih parametrov traktorja Woody 110 (metodologija in merilni inštrumenti), Zb. referatov, Kranjska gora, maj 2000. Univerza v Ljubljani, Biotehniška fakulteta Oddelek za gozdarstvo in obnovljive gozdne vire , Ljubljana, p. 208–228.MARENČE, J., 2005. Spreminjanje tehničnih parametrov traktorja pri vlačenju lesa - kriterij pri izbiri delovnega sredstva : doktorska disertacija = Changes in technical parameters of tractors in timber skidding - a criterion for selecting work equipment : dissertation thesis. Ljubljana, 271 p.SAMSET, I., 1979. Forces and Powers in Winch and Cable Systems, Norwegian Forest Research Institute, Rep. 35.2, 211 p.SAMSET, I., 1985. Winch and cable systems, Martinus Nijhoff / Dr. W. Junk Publ., Dordrecht, p. 518–519.ŠUŠNJAR, M., 2005. Istraživanje međusobne ovisnosti značajki tla traktorske vlake i vučne značajke skidera. Doktorska disertacija = Interaction between soil characteristics of skid road and tractive characteristics of skidder: dissertation thesis. Zagreb, 271 p.������������ �� �� �� �� �� ���������Breme�������������������Maksimalni naklon����������������������������������Hitrost�����������������������Naklon : Debeli konec������������������Naklon : Tanki konec�������������������Hitrost : Debeli konec������������������Hitrost : Tanki konec

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

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