Annals of Warsaw University of Life Sciences – SGGW Agriculture No 64 (Agricultural and Forest Engineering) 2014: 89–96 (Ann. Warsaw Univ. Life Sci. – SGGW, Agricult. 64, 2014) Effect of kerf execution correctness during felling with internal combustion chain saw on direction of tree fall KRZYSZTOF WÓJCIK Department of Agricultural and Forest Engineering, Warsaw University of Life Sciences – SGGW Abstract: Effect of kerf execution correctness dur- combustion chain saw with has been still ing felling with internal combustion chain saw on commonly used in felling, branching and direction of tree fall. To maintain proper direction of tree fall as well as from the viewpoint of sawman cross-cutting; with its use over 90% of safety, proper execution of kerfs during tree felling timber mass is annually harvested in Po- is very important. This refers to both the under-cut land. Therefore, it will be for a long time (that determines direction of tree fall) and the fell- a basic implement used in timber har- ing cut with properly formed hinge and mainte- vesting on hand-machine operation level nance of safety threshold. Parameters of particular kerfs depend mainly on tree diameter in the place [Wójcik 2005, 2007a]. of felling kerf execution, while the proper form of It is well known that internal combus- kerfs depends also on assumed direction of felling, tion chain saw is a machine regarded as inclination and height of tree, size and shape of its particularly dangerous and most danger- crown, tree habit, shape of trunk and of adjacent ous in the group of hand-operated work- trees. Basing on carried out investigations, the obtained results and their later analysis there was ing tools. Apart from dangers connected found a signi¿ cant dependence between the way directly with the chain saw as a device of execution of particular kerfs (under-cut kerf and itself (vibrations, noise, rebound, con- felling kerf with properly formed hinge and main- tact with sharp edges, contact with hot tenance of safety threshold), with consideration to surfaces etc.), the hazard during its uti- suitable parameters of a tree subjected to felling (diameter, inclination and height, shape and size of lization results also from speci¿ c and crown, tree habit and shape of trunk), and direction hard conditions of work and the speci- of the tree fall (felling). It was assumed during in- ¿ ed technological limitations of timber vestigations, that 20° deÀ ection of lying tree to the harvesting process [Sowa 1989, Wójcik left or right from the expected felling direction is 2007b]. These include, ¿ rst of all, the not regarded as discordant with the expected one, and can be caused by such factors like: rebounding speci¿ ed requirements that should be tree from the ground or the remaining stump, roll- considered by chain saw operator in or- ing of tree, turning round of tree on branches etc. ganization of work on the cutting area. Key words: internal combustion chain saw, timber For that matter it is the selection of suit- harvesting, kerf, tree felling able method for timber harvesting (e.g. entire stem method, long wood method, INTRODUCTION short wood method etc.), as well as as- suring of maximal productivity of log- In spite of constantly increasing share ging means (clambunks, skidders, for- of highly-productive machines in the warders etc.), by proper determination of process of timber harvesting, an internal tree fall direction and, more important, 90 K. Wójcik proper felling of harvested trees. One MATERIAL AND METHODS should also take into consideration the site con¿ guration, inclination of major- The investigations were carried out in ity of trees, course of operation roads, August/September 2011 on the ground direction of skidding, type of skidding of Forest Inspectorate Wipsowo (forest means, but also necessity of protecting district Borek). The felling area was situ- natural regenerations, and also protect- ated in a pure pine stand (90%) of age ing trees from damage (trees on the fell- 110–120 years, with addition of spruce ing site and adjacent); in the case of clear and birch (10%). Felling area was di- felling it is fairly easy, but in the case of vided into two plots (felling pockets), pocket felling or thinning it is rather dif- surrounded from three sides with forest ¿ cult [Laurow 1999, WiĊsik et al. 2005, walls, and from one side with an im- Nurek 2013]. proved forest road. Part of trees of the To maintain proper direction of tree main stand (¿ rst story) and the whole of fall as well as from the viewpoint of saw- shrub layer (second story) were removed man safety, proper execution of kerfs from felling pockets the year previous to during tree felling is very important. investigations; it allowed for free deter- This refers to both the under-cut (that mination of tree fall direction, with no determines direction of tree fall) and the possibility of suspending cut trees during felling cut with properly formed hinge carried out measurements. and maintenance of safety threshold. Majority of investigated trees were Parameters of particular kerfs depend straight and of small branching (from 12 mainly on tree diameter in the place of to 34 branches) and of uniform distribu- felling kerf execution (Fig. 1), while the tion of branches on the trunk; this made proper form of kerfs depends also on as- easier carrying out measurements due to sumed direction of felling, inclination small effects of branch distribution and and height of tree, size and shape of its crown shape on expected felling direc- crown, tree habit, shape of trunk and of tion, it enabled to use the classical tech- adjacent trees [Wójcik 2013]. nique of felling trees (Fig. 2). under-cut 1 felling cut angle of safety threshold approx. under-cut 1/10 of diameter min 45° stump height under-cut 2 max. 1/4 of diameter depth of under-cut 1/4–1/3 of diameter hinge 1/10 of diameter FIGURE 1. Rules of proper kerfs’ execution in felling trees [WiĊsik et al. 2005] Effect of kerf execution correctness during felling with internal... 91 direction of tree fall FIGURE 2. Sequence of operations in felling of straight tree, thicker than guide length: 1 – under-cut with possible shortening of hinge, 2 – boring felling cut, beginning of hinge forming, 3 – boring fell- ing cut, hinge forming on right side of tree, 4 – execution of felling kerf (around tree), 5 – inserting wedges into slit of felling kerf, 6 – completing of felling kerf and ¿ nal hinge forming on left side of tree, 7 – possible striking of wedges to fall the tree [WiĊsik et al. 2005] Some of trees on research sites were Stihl MS 440 of engine displacement 3 slightly inclined in direction of tree fall Vs = 70.7 cm , power Ns = 4.0 kW, – deÀ ection of tree tip in vertical projec- weight m = 6.3 kg, guide length l = 18 in. tion (measured from the trunk) did not and chain saw pitch t = 3/8 in. exceed 3 m; this resulted in the need of Height of tree was measured after its tree felling with so-called supporting slat felling with the use of 30-meters-long (Fig. 3). measuring tape, with accuracy of 1 cm. During measurements the weather The same accuracy was used in measure- was windless (it did not call for a change ments on breast height diameter of tree in expected direction of tree fall), with and diameter of cut (prior to felling), moderate cloudiness and temperature while half-length diameter (and again 18qC. During measurements over 100 diameter of cut) on a lying tree with the pine trees were harvested; 60 of them use of a tree caliper of measuring range were selected (their parameters are pre- of 1 m. Volume of a single tree was cal- sented in Table 1). culated with Newton (Riecki) formula with consideration to previous measure- direction of tree fall ments and was compared to the volume of recording device, determined during timber acceptance procedure. direction of inclination Angle of cut wedge, created during making of under-cuts (oblique and hori- zontal), was measured after its complete cutting out from the cut tree (in the cen- FIGURE 3. Felling of tree inclined in direction of ter of meeting the oblique and horizontal tree fall – method with supporting slat: 1 – under- -cut, 2 – parts of kerf made by boring cut, 3 – cut- kerfs edges) with the use of bevel pro- ting of supporting slat [WiĊsik et al. 2005] tractor with accuracy of 1q. Measurement on deÀ ection from ex- Timber harvesting was executed with pected tree fall direction was executed the use of internal combustion chain saw in the ways presented in Figure 4. At 92 K. Wójcik TABLE 1. Characteristic parameters of harvested trees Tree parameter Minimum value Maximum value Mean value Breast height diameter, d1,3 [cm] 30.0 60.0 42.0 Diameter of cut, ds [cm] 38.0 68.0 49.3 Half-length diameter, d1/2 [cm] 20.0 39.0 30.0 Height, h [m] 18.8 30.8 26.9 3 Volume, Vd [m ] 0.76 3.67 1.91 direction of tree fall FIGURE 4. Measurement on lying tree deÀ ection from expected direction of tree fall: 1 – stump of cut tree, 2 – cut tree, 3 – measuring slat, Į – angle of cut tree deÀ ection from expected direction of tree fall distance of 15 m from the cut tree a of tree fall would not be regarded as dis- measuring slat 1.5 m long was set in the cordant with the expected felling direc- place determined by the sawman as the tion, and can be caused by such factors expected tree fall direction.