Zbornik gozdarstva in lesarstva, 46, 1995, s. 97 - 116 
FDC 377.2 : 301 : (497.12) 
A STUDY OF DAMAGE TO HAULING STEEL WIRE ROPES ON THE 
EXAMPLE OF TRACTOR WOOD EXTRACTION 
Dr. Boštjan KOŠIR* 
Abstract 
The method and partial results of the survey of mechanical damage to steel wire 
ropes (torn wires and rope deformations), used in tractor wood extraction in the 
Republic of Slovenia, is described in the article. Ten ropes of three different 
types were examined in the investigation. It was found out that the number of 
torn wires increased significantly towards the end of a wire rope (that is towards 
the load fastening point), while other deformations are more frequent at the first 
half of the rope. 
Key words: steel wire ropes, wood extraction, tractors, skidders 
POŠKODBE VLAČILNIH JEKLENIH VRVI 
Izvleček 
V prispevku je opisana metoda in delni rezultati meritev mehanskih poškodb 
(raztrgane žice in deformacije) jeklenih vrvi, ki jih uporabljamo pri traktorskem 
spravilu lesa v R. Sloveniji. Izmerili smo spremembe pri treh različnih tipih vrvi 
na desetih premerih vrvi. Ugotovili smo, da število raztrganih žic močno narašča 
proti koncu vrvi (na mestu pripenjanja bremena), medtem ko so ostale 
deformacije pogostejše in večje v prvi polovici vrvi. 
Ključne besede: jeklene žične vrvi, spravilo lesa, traktorji, Slovenija 
Docent, dr., dipl. ing. gozd., Gozdarski inštitut Slovenjje, 61000 Ljubljana, Večna pot 2, SLO 
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Zbornik gozdarstva in lesarstva, 46 
TABLE OF CONTENTS 
1 INTRODUCTION .................................................................................. 99 
2 WIRE ROPES IN TIMBER EXTRACTION ........................................ 99 
3 METHODS OF MEASUREMENT .................................................... 100 
4 RESUL TS OF THE TRIAL ............................................................... 104 
5 DISCUSSION ..................................................................................... 112 
6 SUMMARY ......................................................................................... 113 
7 REFERENCES .................................................................................. 114 
8 APPENDICES .................................................................................... 115 
1 INTRODUCTION 
99 
Košir B.: A study of damage to hauling steel wire ropes ... 
Wire ropes are constituent parts of the majority of devices used for wood 
extraction in forestry. They are destined either for the gathering of timber (by 
winches) or for the hauling, bunching and transport of timber (by cableways; 
KOŠIR 1990). By cableway wood extraction, different wire ropes are used for 
different purposes - one for the hauling and transport and another for bunching 
of timber. Yet there are also devices, by which the same rope is used for the 
hauling as well as for bunching of timber. By tractor wood extraction, the same 
rope is actively used only for the gathering of timber. 
lf used, the ropes wear out rather quickly. In the case of cableway wood 
extraction, the skylines have to be replaced every 2000 working hours and the 
main lines every 1200 working hours. By tractor wood extraction, wearing of the 
ropes is much faster and the winch ropes have to be exchanged every 200 - 300 
working hours. 
The wearing of a rope depends on severa! factors: the construction of a device, 
working conditions (the quantity of rocks, the slope), the load size and the usage 
(KOŠIR, 1993a). 
2 WIRE ROPES IN TIMBER EXTRACTION 
Too fast wearing of the ropes is a serious economic problem for foresters. lf only 
the ropes of wood extraction devices that are used in the state forests of 
Slovenia are taken into consideration (Table 1), it is quite clear that the costs of 
such rope quantity of represent a great financial burden for forestry enterprises. 
Steel wire ropes cost 5 - 1 O DM per running metre on the average, depending 
on their thickness and other characteristics. 
Therefore, it is important to find out the factors which have influence on the 
wearing of ropes and - connected to that - on the necessity of their replacing -
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Zbornik gozdarstva in lesarstva, 46 
because only once these factors are known, the prevention of their damaging 
effects is possible. For this reason an investigation was started in 1991 to reveal 
the factors responsible for the shortening of the life of steel wire ropes used for 
wood extraction. As tractors are most frequently used for extraction of timber -
by their number as well as by the quantity of extracted timber (KOŠIR et ali. 
1991, 1993b) - the investigation started with a study of tractor wood extraction. 
Table 1 The length of wire ropes, used tor wood extraction in the stale 
forests of Slovenia (approx. 300 000ha) - an estimation 
Type of a device Length of Length of Length of Tota! 
hauling skylines auxiliary/ 
lines main lines 
Adapted farm tractors 20.500 - - 20.500 
Steering trame skidders 7.000 - - 7.000 
Adapted caterpillars 5.500 - - 5.500 
Tractors together 33.000 - - 33.000 
Single drum gravity cable cranes 20.500 20.500 2.500 43.500 
Mobile tower yarders 12.500 12.500 13.500 38.500 
Tota! 66.000 33.000 16.000 115.000 
In the last years the number of tractors and cable cranes owned by forestry 
enterprises has significantly dropped. Despite this fact those machines have 
remained in forestry and are involved in forest operations, both in private and in 
the state forests and are managed by contractors. 
3 METHODS OF MEASUREMENT 
The mechanical damage and changes to steel wire ropes used in tractor wood 
extraction were studied - among the other goals there was also the intention to 
test the method with which it would also be possible to evaluate the wearing out 
and the damage to ropes by diverse wood extraction devices in the further 
101 
Košir 8.: A study of damage to hauling steel wire ropes ... 
studies. A special record sheet was prepared for the measured data to be filled 
in. The list of variables, evaluated for each rope separately, is presented in 
Table 2 and Figure 1. 
By counting of the torn wires it was not possible to know whether the same wire 
was torn severa! times. 
The measurements were carried out in the region of Celje in May and June 
1991. The damage was evaluated on three wire ropes (total measured = 1 O 
ropes). Adapted farm tractors and steering frame skidders were included in the 
investigation (LKT 80, Timberjack, Belt). 
The rope no.1 was examined by adapted farm tractors IMT 560 (manufactured 
by Pančevo - Serbia), the rope no.2 by steering frame skidders Belt 
(manufactured by Belt Črnomelj - Slovenia) and the rope no.3 by steering frame 
skidders Timberjack (Table 3 and Table 4). In most cases conifer wood (length 
8m) was extracted, either on soft or on hard ground surface. 
The results of the measurements were treated according to the normal 
procedures. Our major interest was to establish, how the deformations and other 
changes were distributed along the whole length of the rope. Therefore, the most 
important independent variable was the rope distance (in metres) from the winch 
drum, on which the changes were evaluated. Because the ropes' lengths were 
different, this variable was expressed in per cents of the whole length of a rope 
(0% = by the winch, 100% = by the load). The other independent variables, as 
for example the ground surface, the age and quantity of extracted timber, were 
taken into consideration too, yet there were not enough measurements done for 
the influence of these latter variables to be statistically reliably defined. 
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Zbornik gozdarstva in lesarstva, 46 
Table 2 The list of variables by measurements ot damage to steel wire ropes 
La bel of the variable Description 
STA Duration of the rope usage (days) 
KUB Quantity of timber extracted by a single rope (m3) 
POD Ground surface (O = soft, 1 = hard); soft surface = smooth, even 
terrain, deep soils; hard surface = rocky, uneven terrain 
MET Distance in metres (1 = by the drum) 
NSTRGA Number of torn wires by non-deformed wire rope (torn wires by 
deformed wire rope are not included); in case of ovalness, the torn 
wires are taken into consideration as well 
NTOCKA Number of local defects (folded wire ropes) 
NZICA1 Number of torn wires by CDEFOB 
NZICA2 Number of torn wires by CDEFOD 
COVALN Length of ovalness (cm); the ovalress of rope was taken into 
consideration if the difference in diameters was more than 15% 
CBREZB Length of deformed - flattened - rope (cm); the rope's core is not 
deformed (no wires are torn) 
CBREZD Length of deformed - flattened - rope (cm); the core is visibly 
deformed, but no wires are torn 
CDEFOB Length of deformed - flattened - rope (cm); the core is not 
deformed, some wires are torn 
CDEFOD Length of deformed - flattened - rope (cm); the core is visibly 
deformed, some wires are torn 
CVTISN Length of the segment (cm) on which the rope's core is replaced 
by a pressed-in rope strand 
Figure 1 
Table 3 
NSTRGA NTOCKA 
CBREZB CBREZD 
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Košir B.: A study of damage to hauling steel wire ropes ... 
NZICA1 NZICA2 COVALN 
CDEFOB CDEFOD CVTISN 
Schematic disp/ay of the measured variab/es 
Characteristics of the examined wire ropes 
Wire Diameter Construction Manufacturer Supplier Dale of Weight Breaking Twist-
rope (mm) delivery (kg/m) force (kN) ing 
1 12 6x37+FC NFK,YU UNIOR, 1,1988 0,498 91, 1 sZ 
ŠMARJE 
2 14 6x19+FC NFK,YU RUDAR, 7,1987 0,730 134,0 sZ 
Seale ZAGREB 9,1989 
3 16 6x37+FC NFK,YU RUDAR, 7,1987 0,886 162,0 sZ 
ZAGREB 
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Table 4 The data about the examined ropes and the tractors 
Type of a tractor Type of a winch Pulling force (kN) Safety factor Rope no. 
IMT 560 lgland Compact 2 X 50 1,8 1 
GV 50 2H 2 X 50 
Belt GV 70 lgland 2 X 80 1,7 2 
LKT 81 Original 2 X 60 2,2 2 
Timberjack Hercules original 80 2,0 3 
Among the dependent variables, the sum of ali torn wires (NSUM) and the sum 
of ali deformations in cm per 1 m (CSUM) were the most important . The length 
of non-deformed rope per rope segments of 1 m was expressed as the difference 
between the CSUM value and 100cm. 
4 RESUL TS OF THE TRIAL 
One of the purposes of the investigation was also the testing of the method of 
rope damage evaluation. Because of this, the amount of various ropes used in 
different working conditions was not great enough for a reliable evaluation of the 
influence of ground surface on rope damage (Appendix 2). A special problem is 
the relation of the duration of rope use, which is in high correlation with the 
quantity of extracted timber (Appendix 2), to damage to ropes. 
This relation could be the most accurately evaluated if the same rope was obseNed 
and examined for a longer period of tirne or a sufficient amount of ropes of different 
ages were measured. The second possibility was chosen but not enough data were 
gathered for the rope no.3. The results tor the ropes no. 1 and no. 2 were well 
comparable - considering the age of the ropes and the quantity of transported timber 
(Table 5). Anyway, the results of the measurements for the rope no. 3 are presented 
too - although only one measurement was done. 
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Košir B.: A study of damage to hauling steel wire ropes ... 
Table 5 Average values of some variables 
Variable Label Unit Rope no.1 Rope no.2 Rope no.3 
Quantity of wood KUB m3 505 644 35 
Duration of use STA day 144 145 62 
Rope length MAX m 57,58 53,74 62,87 
Number of examined ropes 4 5 1 
The dependent variables have been classified into two groups (see also 
Appendix 1 ). In the first group, the variables representing the number of torn 
wires and in the second one there are those related to the various rope 
deformations. The mean values for both groups are presented in Table 6 and 
Table 7. In the first group (torn wires), the number of torn wires where rope is not 
significantly deformed (only the ovalness is possible) is ttie most frequent rope 
damage. The torn wires in the segments of badly deformed rope represent less 
than a fifth of the whole amount of torn wires. 
Table 6 The average number of torn wires per 1 m of rope 
Variable Label Rope no.1 Rope no.2 Rope no.3 
Number of torn wires by non-deformed NSTRGA 6,43 7,59 2,97 
wire rope perm 
Number of torn wires by length of NZICA1 0,69 0,48 0,02 
deformed - flattened - rope (cm); the 
core is not deformed, some wires are 
torn perm 
Number of torn wires by length of NZICA2 0,53 0,72 O, 14 
deformed - flattened - rope (cm); the 
core is visibly deformed, some wires 
are torn perm 
Total number of torn wires perm NSUM 7,66 8,79 3, 13 
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Among deformations, ovalness is the most frequent form, and the second one is 
the flatness of rope without the deformation of its core. lf damage was expressed 
in per cents, ovalness would represent 18% - 34% of deformations and diverse 
flatness the additional 6% - 12%. It is evident from Table 7, that on the average 
only 54% - 76% of rope remain non-deformed. 
Table 7 The average length of deformations (cm) per 1m of rope 
Variable Label Rope Rope Rope 
no.1 no.2 no.3 
Length of deformed - flattened - rope (cm/m); CBREZB 3,55 5,21 7,43 
the rope's core is not deformed (no wires are torn) 
Length of deformed - flattened - rope (cm/m); CBREZD 1,28 3,99 1,90 
the core is visibly deformed, but no wires are torn 
Length of deformed - flattened - rope (cm/m); CDEFOB 1,21 1,32 0,16 
the core is not deformed, some wires are torn 
Length of deformed - flattened - rope (cm/m); CDEFOD 0,36 2,13 1,03 
the core is visibly deformed, some wires are torn 
Length of ovalness (cm/m); COVALN 17,66 18,24 33,62 
the ovalness of rope was taken into consideration 
if the difference in diameters was more than 15% 
Length of the segment ( cm/m) in which the rope's core CVTISN O, 18 1,30 1,52 
is replaced by a pressed-in rope strand 
Total deformations (cm/m) CSUM 24,24 32,19 45,67 
107 
Košir B.: A study of damage to hauling steel wire ropes ... 
An analysis of local deformations (Table 8), among which the restraightened 
slings are the most frequent, shows that local deformations are more numerous 
in the closer parts of the ropes. This can well be undrestood since slings emerge, 
when there is too much rope unwound, so that it curves and twists 
uncontrollably. As the rope no. 3 had only been used for a short period, the 
mentioned characteristic had not been evident with it yet . lf the ropes no.1 and 
no. 2 are compared, it could be establish, that the thicker rope no. 2 has less 
local deformations. Most probably that is due to the fact that the thicker rope 
does not twist so easily as the thinner ropes do. 
Table 8 The average number of local deformations (NTOCKA) per meter of 
a rope with regard to the position in the rope (% of the rope length) 
Position in the rope Comment Rope no.1 Rope no.2 Rope no.3 
0% - 20% Near the winch O, 19 0,36 o 
21 o/o - 40% 0,50 0,29 0,08 
41 o/o - 60% 0,43 0,27 o 
61 o/o - 80% Use of chokers 0,39 0,20 o 
81 % - 100% Near the load 0,24 O, 13 o 
Average value 0,35 0,25 0,02 
The dependencies of the number of torn wires (NSUM) and the sum of lengths 
of all deformations (CSUM) were also treated by regression equations to 
evaluate the shares of explained variability (Table 9). 
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Zbornik gozdarstva in lesarstva, 46 
Table 9 
lndependent 
variable 
M(%) 
M 
M2 
M3 
M4 
M5 
M8 
M10 
M12 
1/M 
1/M2 
Constant 
Explained var. 
N of cases 
Regression dependence of rope damage on the distance from the 
winch (M - %) 
Regression Dependent variable 
coefficient 
Rope no.1 Rope no.2 Rope no.3 
b; Tota! Tota! Tota! Tota! Tota! Tota! 
number of lengths of number of lengths of number of lengths of 
torn wires deformed torn wires deformed torn wires deformed 
perm rope cm/m perm rope cm/m perm rope cm/m 
NSUM CSUM NSUM CSUM NSUM CSUM 
b1 0,253 
b2 -0,0142 
b3 -7,61 E-05 1,17E-05 
b4 -1,59E-06 
b5 1,50E-08 -1,68E-09 
b6 2,44E-15 
b7 6,54E-19 
b8 -6,70E-23 1,12E-22 
b9 -315,45 -70,78 -714,47 
b10 361,80 921,25 
a 0,40 63,57 -0,92 53,21 0,09 93,58 
R2 0,40 0,22 0,05 0,26 0,47 0,36 
229 229 258 258 63 63 
The equation: NSUM (or CSUM) = a + b1 *M + b2*M2 + b3*M3 + ... + b1 0/M2 
It was found out that the entire number of torn wires (NSUM) normally increases 
towards the end of the rope (M = % of rope length, O = near the winch). This is 
quite evident with the ropes no.1 and no.3, while in case of rope no.2 the 
maximum number of torn wires exists at 75% of the rope length. This maximum 
is obviously the consequence of too great wearing of the rope, which was most 
probably caused by incautious work (Figure 2). 
70 
E 60 .... ... 
CII 
0. 50 
III 
~ 
'i 40 
E ,s 30 
o ... 20 CII 
.o 
E 
10 ::i z 
o 
Figure 2 
Rope 1 - --Rope 2 
- -Rope3 
-- -
L..-- i---- ---- --·--
109 
Košir B.: A study of damage to hauling steel wire ropes ... 
- -- -- - -~ - --- ----- - --- --- --...._ 
O 5 1 O 15 20 25 30 35 40 45 50 55 60 65 70 7 5 80 85 90 95 1 O 
o 
M - % of the rope length (near the winch = 0%) 
Oependence of the number of torn wires upon the place of rope 
measurement 
Different longitudinal rope deformations (CSUM) show that ropes are most 
deformed somewhere between 20% and 40% of their length (the winch is 
considered the starting point = 0%) and the least deformed at the very beginning 
(where the rope is the least deformed in general) and at the very end of the rope 
(where normally torn wires are prevailing - Figure 3). 
The deformations most probably result from unsuitable rope winding on the 
drum, which is with the majority of tractors not properly solved. In Slovenia, 
tractors are mainly used for wood gathering at the distances of 1 Om - 30m. That 
corresponds to the position of rope deformations, resulting from its winding to a 
drum when it is heavily loaded by hauled timber. 
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Zbornik gozdarstva in lesarstva, 46 
E 80 .... ... 
70 Q) 
C. 
VI 60 C 
o .. 
50 CII 
E ... 
.E 40 
Q) ,, 
30 Q) 
.C .... 
20 .... o 
.C 
10 .... 
Cl 
C 
Q) o ...J 
Figure 3 
Rope 1 
~ I"""'-, 
-
_./ ' ~-Rope 2 1/ -........ '" -Rope3 ~ - r---- ------- ", / i--------
/ I, 
-------• r-----. "~ ) I ~ 
I J -----~ "I " ' I I ------ "I ~ ~ , .. -~ 1 I '--
!------------- ----- , 
O 5 1 O 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 1 O 
o 
M - % of the rope length (near the winch = 0%) 
Dependence of the /ength of rope deformation upon the position of 
rope measurement 
A further analysis of the total damages (NSUM + CSUM) of the rope per 1 m 
showed that the cumulative distribution could be divided into three parts (Figure 
4), The first part of the rope length lies near the winch drum (up to the 20% of 
the rope length) where the inclination of the cumulative curve is rather great with 
a digressive tendency, The structure of rope damage shows the prevailing share 
of longitudinal deformations over broken wires per 1 m, 
In the second part of the rope (say: between 20 and 80% of the rope length) the 
inclination of the cumulative curve is more or less zero and the total probability 
of damage is close to O, 1 o_ The structure in this part emphasizes the growing 
share of the number of torn wires per 1 m of the rope, with decreasing 
importance of longitudinal deformations, 
111 
Košir B.: A study of damage to hauling steel wire ropes ... 
The third part of the rope, which is near the load, represents the part where 
chokers are sliding along the rope during timber bunching. This is the cause of 
the rapidly growing share of torn wires with very little longitudinal deformations. 
The inclination of the cumulative curve in this part is similar as in the first part -
steep but with a progressive tendency. 
~ 0.15 +---+---+-t--+---+---t-+--+--t----1r--+--+---+-t--+---+---t-+-
:c 
C1! 
.C 
e 0.1 +--+---+-+---+---+--a.. 
Figure 4 
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 
M - % of the rope length (near the winch = 0%) 
Probability of the /ongitudinal deformations and number of torn wires 
per 1 m along the rope /ength 
Related to this there is the question of the safety factor along the wire rope. It is 
obviously that the safety factor decreases from around 2 at the beginning of the 
rope toward 1 at a certain point where the rope is to be broken. It is also clear 
that the real distribution of safety factor values along the rope length is only 
possible to measure with mechanical testing of the breaking force at every meter 
of the rope. On the basis of the results of this paper however, the worst work 
safety could be expected in the last quarter of the rope, though we could expect 
breakage also in the first parts due to local deformations, whose influence on the 
safety factor is fully unknown. 
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Zbornik gozdarstva in lesarstva, 46 
5 DISCUSSION 
The survey of the wearing out of ropes by tractor wood extraction showed that 
ropes were most liable to mechanical deformations at the parts of load fastening 
and at the parts of slider gathering. These are the parts of the ropes that slide 
over the ground and different obstacles and are also at the same tirne through 
sliders burdened by heavy timber. Consequently due to the improperly solved 
rope winding, the rope deformations as ovalness, flatness and the like emerge. 
In these segments of ropes (between 20% and 40% from the drum), the number 
of torn wires is relatively srna II. 
There are several signs indicating that the ground surface on which the wood is 
gathered has a significant influence on the wearing out of ropes and damage to 
them. Yet in this - initial stage of the investigation, this influence could not be 
reliably evaluated yet. The situation as to the duration of rope usage, which has 
influence on the quantity of extracted timber, is rather similar. The loading of a 
rope within its life period is, without any doubt an important factor, which has 
great influence on the wearing out and the damage to ropes; yet up to now, the 
extent of this influence has not been studied yet. The wire ropes that are used in 
tractor skidding today are not resistant enough to such heavy wear because of 
mechanical influences. The wire ropes in the future will have to have strong steel 
core to be resistant against external forces, on the other hand thicker wires in the 
outside layer are an important characteristic too. 
In future, the method of measurement here introduced will also be used far the 
surveys of cableway wood extraction. There, the results will also help to 
elucidate the safety demands, which are much better defined for cableway wood 
extraction. Theoretical safety factors are very low in tractor skidding - below 2, 
while during practical work their values are completely unknown. This is also the 
field for further investigations, either under controlled conditions or during 
practical field operations. 
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Košir B.: A study of damage to hauling steel wire ropes ... 
6 SUMMARY 
The wearing out and damage to ropes by wood extraction are responsible for the 
frequent replacing of ropes, which is a great financial burden for foresters. In the 
tria!, a method of evaluation of damage to ropes by tractor wood extraction was 
tested. The rope changes were classified into two groups: torn wires and 
different deformations as for example ovalness and flatness of rope. Ten tractor 
ropes were examined; the results of measurements were later treated 
separately, with consideration to the characteristics of the ropes (rope no.1 = 
12mm, rope no.2 = 14mm, rope no.3 = 16mm). It was found out that the 
distance of the measured part of a rope from the drum expressed in per cents of 
the rope length (%) was the best indicator of the measured changes. The 
duration of rope usage and its loading, expressed by the quantity of extracted 
timber, was evaluated as well. In the analysis, it was not possible to define a 
reliable and comparable influence of these two factors on the rope wearing out. 
Most probably the ground surface also has significant influence on the variability 
of the rope deformations, yet that was not studied separately in this study. 
It was found out that the number of torn wires increased significantly towards the 
end of the rope (where the load is fastened), while the longitudinal deformations 
were most frequent between 20% and 40% of the rope length (nearer to the 
winch drum), that is at the section, where the loading of a rope by its winding is 
the greatest. 
The method, introduced in this study, will be further tested in the investigations 
of rope condition with cable cranes. 
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Zbornik gozdarstva in lesarstva, 46 
7 REFERENCES 
KOŠIR, B., 1990. Ekonomsko-organizacijski vidiki razmejitve delovnega 
območja traktorjev in žičnih naprav pri spravilu lesa (Economical and 
organisational aspects of the limitation of the working domain of tractors and 
cable cranes in the extraction of wood). BF, Gozdarstvo. Doktorska 
disertacija, Ljubljana, p.350. 
KOŠIR, 8./ MEDVED, M./ DOBRE, A./ BITENC, B., 1991. Stanje mehanizacije 
in izkoriščanja delovnega časa delavcev v neposredni proizvodnji gozdarstva 
v R Sloveniji konec leta 1990 (The state of mechanisation and exploitation of 
the working tirne of workers in the direct forest production in the Republic of 
Slovenia at the end of 1990). Strokovna in znanstvena dela 107, IGLG, 
Ljubljana, 88p. 
KOŠIR, B., 1993a. Unterzuchungen uber Schaden an Drahtseilen am Beispiel 
der Holzruckung mit Schleppern. Proceedings of 2. lnternationaler Workshop 
Seilbringung im Gebirge in Ort/Gmunden, BOKU, p. 87-97. 
KOŠIR, 8./ MEDVED, M./ DOBRE, A./ BITENC, B., 1993b. Stanje mehanizacije 
in storilnost delavcev v gozdni proizvodnji v l. 1992 (The state of 
mechanisation and exploitation of the working tirne of workers in the direct 
forest production in the Republic of Slovenia at the end of 1992). Strokovna 
in znanstvena dela 114, IGLG, 86 p. 
115 
Košir B.: A study of damage to hauling steel wire ropes ... 
8 APPENDICES 
Appendix 1 Mean values of the measured variables 
Variable Mean Std Dev Variance Minimum Maximum 
KUB 516,37 401,83 161469,74 35 1140 
STA 135,07 89,73 8051,10 28 271 
CBREZB 4,77 11,36 129,13 o 80 
CBREZD 2,63 7,51 56,38 o 72 
CDEFOB 1, 14 4,65 21,65 o 48 
CDEFOD 1,27 5,02 25,24 o 43 
COVALN 19,76 24,61 605,58 o 99 
CVTISN 0,86 5,61 31,46 o 99 
CSUM 30,43 32,50 1056,14 0,00 110,00 
NSTRGA 6,58 20,01 400,60 o 182 
NZICA1 0,52 4,61 21,24 o 99 
NZICA2 0,58 4,72 22,28 o 99 
NSUM 7,67 21,77 474,03 0,00 192,00 
NTOCKA 0,27 0,55 0,30 o 3 
Number of valid observations = 550 
Appendix 2 Correlation matrix of the most important variables 
Correlation NSUM 
NSUM 
CSUM -0,1393* 
M(%) 0,2787** -0,3114** 
KUB 0,2142** 0,0725 
STA 0,1249* 0,1082 
POD -0,0938 -0,0441 
2 - tailed significance: * = 0,01, ** = 0,001, ..... = no significance 
Number of valid observations = 550 
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COMMENT This investigation was a pari of the research project, entitled 
"Extraction of wood in the forests with an emphasized protective role in Alpine 
conditions", which was financed by the Ministry of Science and Technology and 
the Ministry of Agricu/ture, Forestry and Nutrition of the Republic of Slovenia. 
The field measurements were with great personal endeavour and exactness 
executed by a forest engineer, Ms. Andreja RATAJC and colleagues (The 
Forestry Enterprise of Celje), during the training at the Institute of Forest and 
Wood Economy in Ljubljana (now cal/ed: Slovenian Forestry Institute), under the 
menthorship of Dr. B. KOSIR. The results of the measurements were furlher 
treated in the Oeparlment of Forestry Techniques and Economics. These results 
have already been presented at the 2. lnternationaler Workshop: Seilbringung im 
Gebirge in Orl/Gmunden, 1992 in Orl, Austria, and /afer published in the 
proceedings of the workshop. A s/ightly changed and revised text has been 
published here owing to the interest shown by production managers in forestry 
today.