AN ABSTRACT OF THE THESIS OF
Dennis Albert Neilson
Forest Enqineering
in
Title:
for the degree of
presented on
Master of Forestry
December 9, 1977
The Production Potential of the Iqland-Jones Trailer Alp
Yarder in Thinninq Younq Growth Northwest Conifers:
A Case
Study
Abstract Approved:
Dean Edward Aulerich
Results of a recent production study indicate that a four man
crew thinning young growth Douglas-fir [Pseudotsuga mensiezii (Mirb.)
Franco] with an Iglarid-Jones Trailer Alp can produce 1360 to 1460
cubic feet (38 to 41 cubic metres; 8160 to 8750 bd. ft.,) per eight
hour day on slopes of 10 to 50 percent with average slooe distances
of 150 to 300 feet (46 to 91 metres) and average lateral yarding
distances of 30 to 50 feet (10 to 15 metres).
The stand studied was
thinned from 226 stems per acre (558 stems per hectare) to 130 stems
per acre (321 stems per hectare).
The average tree size removed was
19.4 cubic feet (0.55 cubic metres) and the average log size yarded
was 12.9 cubic feet (0.36 cubic metres).
A standing skyline system
was used with a haulback line attached to hold the carriage in
position during lateral yarding.
The cost of a four man crew felling, bucking, and yarding this
material with an average slope distance of 250 feet (76 metres) and
an average lateral yarding distance of 35 feet (11 metres) is
estimated at $36.63 per cunit ($12.93 per cubic metre; $61 .04 per
Mbf.).
A three man crew operating under the same conditions would
produce only 1160 cubic feet (33
cubic metres; 6950 bd. ft.) per day
but the unit cost of production would be lower at $35.30 per cunit
($12.46 per
cubic
metre; $58.83 per Mbf.).
During the study,
operating delays accounted for 26 percent 0f total study time and
skyline road changes accounted for 10 percent of total study time.
The use of intermediate supports can successfully extend yarding
distance on unfavorable slopes and can facilitate efficient decking
if placed within 100 feet (30 metres) of the landing.
The Production Potential of the Igland-Jones
Trailer Alp Yarder in Thinning Young Growth
Northwest Conifers: A Case Study
by
Dennis Albert Neilson
A PAPER
submitted to
Oregon State Univerty
in partial fulfillnient o.f
the requirements for the
degree of
Master of Forestry
Completed December 9, 1977
Commencement June, 1978
Approved:
Professor of Forest Engineering
Head of the Department of Forest Engineering
Dean of the Graduate School
Date thesis is presented
Typed by C. Joy Martin for
December 9, 1977
Dennis Albert Neilson
TABLE OF CONTENTS
Page
INTRODUCTION
1
OBJECTIVES OF STUDY
3
OPERATING CONDITIONS
4
Area and Stand Description
:4
Stand Assessment Data -
4
Selection for Thinning
10
Yarding System
11
STUDY METHOD -
19
Elements of Yarding Cycle
Variables
of
Yarding Cycle
--
19
--
21
Delays
22
Road Changes -
-
Rigging Intermediate Supports
DATA ANALYSIS -
2.
25
26
Sumary of Yarding Cycle -
26
Regression Analysis
28
Delays -
37
Road Changes
41
Intermediate Supports
43
Potential Producticn
46
Casts
52
DISCUSSION OF RESULTS
Productivity
Sensitivity
53
53
of
Production
55
Table of Contents (continued)
Lateral Yarding
55
Intermediate Supports
55
Crew Size
61
Stand Damage
63
FUTURE STUDIES
65
CONCLUSION
66
BIBLIOGRAPHY
68
APPENDICES
69
Appendix 1
70
Appendix Z
71
Appendix 3
72
Appendix 3a
73
Appendix 4 Appendix 5
75
Appendix
76
6
Appendix 7 -
77
Appendix 8
78
Appendix 9
79
Appendix 10
8
Appendix 11
82
LIST OF FIGURES
Figure
Page
1
Blodgett Tract, Columbia County
5
2
Trailer Alp Study Area
6
3
Diameter distribution pre-and post-thinning
12
4
Distribution of log lengths yarded
12
5
Igland-Jones Trailer Alp
14
6
Igland-Jones Trailer Alp Trailer
15
7
Single span carriage
16
8
Multispari carriage
16
9
Alp .jack and support line
18
10
Example of a maintained and neglected deck
36
11
Distribution of turn volumes-thinning
40
12
Distribution of turn volumes-clearfelling
40
13
Line tightener
44
14
Swedish climbing ladder - Virginia study
47
15
Production per hour as a function of lateral
and slope distance (standard units)
50
15a
Production per hour as a function of lateral
and slope distances (metric units)
61
16
Production per hour as a function of slope
56
distance and volume per piece (standard units)
16a
Production per hour as a function of slope
distance and volume per piece (metric units)
57
17
Production per hour as a function of slope
distance and percent delays (standard units)
58
17a
Production per hour as a function of slope
distance and percent delays (metric units)
59
18
Example of ringbark damage
64
LIST OF TABLES
Table
Page
1
Pre-Thinning Assessment Piot Data
8
2
Post-Thinning Assessment Plot Data
9
3
Stand Characteristics Pre- and Post- Thinning 10
4
Trailer Alp Drum Specifications
13
5
Summary of Yarding Cycle Times
26
6
Summary of Production Variables
27
7
Delays
38
8
Road Changes
42
9
Sumary of Time Usage
43
10
Rig Support Times
45
U
Support Tree Limbing Times
45
12
Dafly Operating Costs
52
LIST OF APPENDICES
Appendix
Page
Profiles of Skyline Roads Studied
70
2
Hewlett Packard 9830 Used to Calculate
Estimated Producti on per Hour
TI
3
Line Pulling Forces - Standard Units
72
3a
Line Pulling Farces - Metric Units
73
4
Daily Cost - Trailer Alp Yarder
74
5
Dafly Cost - John Deere 2640 Tractor
75
6
Daily Cost - Crew Transportation
76
7
Daily Cost - Chainsaws
77
8
Dafly Cost - Radio
78
9
Determination of Production and Cost Data
for Three Man Logging Crew
79
10
Net Production Rate for Four Man Crew
81
11
Falling and Bucking Productivity
82
1
THE PRODUCTION POTENTIAL OF THE IGLAND-JONES
TRAILER ALP YARDER IN THINNING YOUNG GROWTH
NORTHWEST CONIFERS: A CASE STUDY
INTRODUCTION
Approximately 3.3 million acres (1.3 million hectares) of
commercial forest land in the Douglas-fir sub-region of Oregon and
Washington conist
of stands between 20 and 70 years old, (Aulerich,
1975) and are considered young growth stands.
This amounts to about
24 percent of the total area in commercial forest.
Both the acreage
and the percentage of commercial forest in this age group will
increase significantly within the next. decade as old and second
growth forests are depleted or 'locked up" by conservation
legislation.
According to Aulerich (1975) most of the stands 20 to 70 years
old consist of trees under 20 inches (51 cm) dbh. or log volumes
averaging less than 25 cubic feet (0.7 metres).
Historically, the limited logging of this small piece size
material has been done with yarders which were designed to yard old
growth and second growth forests.
The high capital and operating
costs of these machines, the difficulty of setting up and yarding
with them in small wood (especially thinnings) and the adequata
supply of larger material has discouraged the utilization of many of
the smallwood stands.
This situation is changing rapidly, however.
The Forest Engineering Department of Oregon Stata University, anticipating the need to improve harvesting operations in small timber,
2
'embarked on a research project in 1972 to examine current harvesting
practices and develop and, test more efficient and economic techniques
to utilize small stands.
One result of this project has been the acquisition of an IglandJones Trailer Alp yarder to be tested in smallwood stands under
Northwestern conditions.
The purchase and research on this machine
has been funded on a cooperative basis by a number of private
companies.
The testing of the machine is the responsibility of the
Forest Engineering Department of Oregon State University.
The
Departrnent has contracted the operation of the yarder to a small,
independent logging organization.
During the summer of 1977, the Igland-Jones Trailer Alp was
used to thin a stand of Douglas-fir in the Blodgett Tract Forest in
Northwest Oregon (Figure 1).
During the tests, measurements were
made of the various facets of the operation and the data analyzed to
determine the production potential of the machine.
A description of
the study and the presentation of the results forms the basis for
this paper.
I,
3
OBJECTIVES
The objectives of the study were:
To evaluate the perforinance of the Igland-3ones Trailer
Alp yarding smallwood thinnings with external yarding
distances of less than 1000 feet (300 metres).
To investigate the use of intermediate supports as an
aid to extending the yarding distance on unfavorable
slopes.
To develop production equations for the major elements
of the yarding cycle and ue these to predict the
production potential of the machine over a range of
conditions.
4
OPERATING CONDITIONS
Area and Stand Description
The area chosen for the study was a stand of 35 to 40 year old
Douglas-fir in the University owned Blodget Tract Forest in Columbia
County, Oregon; 17N, R514, WM (Figure 1).
The stand sloped away from a logging spur road at slopes
ranging from 10 tQ 70 percent.
Along much of the stand, a prominent
convex break in slope occurred 200 to 300 feet (60 to 90 iTietres)
from the road which would have made single span yarding difficult for
four of the seven skyline roads studies.
Western hemlock
Tsuga heterophylla (Raf.) Sarg.] stems were
dispersed throughout the western section of the stand and a pocket
of red alder [Alnus rubra (Bong)] was established within the stand
along an intermittent water course (Figure 2).
The alder was
clearfelled and yarded during the study period, but the data analysis
and discussion presented in this paper is restricted to the thinning
operation only, unless otherwise stated.
Stand Assessment Data
Pre-Thinning Assessment
A total of eight 0.2 acre (0.08 hectare) circular plots were
randomly selected and measured prior to logging.
measured included species and diameter.
Parameters
A random selection of 23
trees through the existing height range were measured for height and
5
.
'S
\
P.ckRoas
irP.as
1d P.i1z
Graas
Ses
Tyce U.te -.
ip.,.
Trailer Alp Study
Area (section 30)
,,
Figure 1.
Columbia County T7M, R5W, WM
80 Foot Contour Interval
mile (3.8 cm = 1 Km)
Scale: 2.4" =
Blodget Tract.
1
Leqend
-I--I
i-i--h
6.
Old Railway Grade
1nterrneiate Support
Skyline Road
Road
Ridge
- Draw
Not Logged During
Study Period.
" Pocket of
red alder
Road to
Mist, Oregon
Prepared by:
D.E. AuleriCh.
.June,1977.
Figure 2.
Trailer Alp Study Area
SCALE: 12OO'
(1 cm = 24 m)
S
7
diameter, and this information was used to calculate a tariff
number (Little, 1972).
Individual tree volumes [to a six inch (15 cm)
top] were obtained from Douglas-fir tree volume tables (Turnbull et
al., 1972).
For the purpose of this assessment, western hemlock
stems were identified separat&y from Douglas-fir, but individual
tree volumes were selected from tree volume tables of the latter
species using the single derived tarif-F number.
Post-Thi nni ng Assessment
Eight 0.2. acre (0.08 hectare) circular plots were randomly
se1ectd after the thinning operation was complete.
Individual tree
volumes were selected using the same tariff number derived from the
pre-thinning assessment.
8
Table 1.
All Plots 0.2 Acre
Plot
No.
No. of
Stems
1
Pre-Thinning Assessment Plot Data
(0.08 hectare)
Tariff Number = 29
Volume to 6" (15 cm)
Volume per Tree
(cu.ft)
(cu.m)
54
990.4
27.98
18.3
0.52
2
45
997.8
27.62
al.7
0.61
3
47
1252.0
35.37
26.6
0.75
4
4g
1232.5
34.82
25.1
0.71
5
38
1042.7
29.45
27.4
0.77
50
957.2
27.04
lg.1.
0.54
7
34
796.6
22.50
23.4
0.66
8
46
851.8
24.06
18.5
0.52
45
1012.6
28.60
22.5
0.64
1.30
(5.8%)
0.04
Mean
(cu.ft)
(cu.m)
SE.
of
2.17
Mean
(4.8%)
57.29
(5.6%)
1.62
9
Table 2.
AU P1ot
PTht
No.
Post-Thinning A.seszment Plat Data
0.2 Acre (0.08 hectare)
Na.
Stems
Tariff Number = 29
Volume to 6" (15 cm.)
(cu.ft)
(cu.m)
Volume per Tree
(cu.ft)
(cu.m)
1
28
723.3
20.43
25.8
0.73
2
32
667.7
18.86
20.9
0.59
3
21
703.5
19.87
33.5
0.95
4
28
648.8
19.34
24.5
0.69
6
30
732.1
20.68
24.4
0.69
6
26
555J
15.68
2L3
0.60
7
26
481.1
13.59
18.5
0.52
8
17
589.0
16.64
34.6
0.98
Mean
26
642.0
18.19
25.4
0.72
1.72
32.10
0.9
2.06
(8.1%)
0.58
S,E.
of
Mean
(6.6%)
(5.0%)
10
Table 3.
Stand Characteristics:
Pre and Post Thinning
Pre-Thinning
Number of stems per acre
per hectare
Post-Thinning
226
558
130
Volume (cu.ft. per acre)
(cu.m per hectare)
5060
354
3210
225
Average D.B.H. (inches)
14.1
36
14.7
190.5
43.7
118.6
27.2
(cm)
Average basal area
(sq.ft. per acre)
(sg.m. per hectare)
Height (feet)
(metres)
321
37
85
26
The thinning operation removed 42 percent of the fir-hemlock
stems and 37 percent of their volume.
Selection for Thinning
Tree selection for thinning was performed by the fallers.
They
were instructed to thin approximately 50 percent of the existing
stems but to use their judgnent with regard to spacing, tree form,
and size.
Many of the well-formed trees in the stand were removed
because of bear damage to the cambial layer.
The fallers were instructed to cut peeler length logs and
utilize each tree to a five inch (13 cm) top if possible, although
many final bucking cuts were made closer to six inches (15 cm).
11
(175) 7
(75)3
0
(50)2
E
0
(inches)
(cm)
Figure 3.
7
9
11
18
23
28
13
33
Diametar distribution:
15
38
17
43
19
21
23+
48
53
5B
Pre and Post-Thinning
1 00
75 -
50
25 -
0
1O'O'
3.05m
1718U
27b01t
348"
4210"
5.39ni
8.23ni
1O.57m
13.06m
-
Figure 4.
Log Lengths
Distribution of log lengths yarded
12
Figure 3 details the diameter distribution pre- and postthinning and Figure 4 illustrates the percentage of each log length
cut during the study.
Yarding System
The Igland-Jones Trailer Alp yarder is of Scottish-Norwegian
design.
It consists of a single-.axled trailer with skyline, mainline,
haulback and utility drums, two winches, a tower and carriage
(Lisland, 1975).
The machine studied was transported between skyline roads and
powered during yarding by a John Deer 2640, 70 h.p. farm tractor
(Figure 5).
Power for the winches is transmitted to the trailer by
a transmission shaft driven from the tractor and by chain drive to
the winches.
An Igland 5000 compact double drum winch is. mounted on the front
of the trailer (A),
ropes.
which is used for strawline and other spare
On one side is a chain drive for powering the skyline drum.
Behind this winch, is the skyline drum (B).
This is split into
two parts, one for storing the skyline and one for tightening it
(Figure 6).
The skyline brake is sufficient to keep full tension
on the skyline without extra anchoring of the cable.
Unloaded
skyline tensions of up to 12,000 lbs. (5450 Kg) were measured during
the study.
At the back of the trailer, an Igland special 3000/2H winch is
mounted (C).
This winch drives the mainline and haulback drums.
13
Clutches and brakes are mechanical, but hydraulically operated.
controls are mounted on a movable arm CD).
The
Hydraulic guages are
installed to measure the pressure on the clutches and brake system.
Table 4.
Drum Type
Trailer Alp Drum Specifications
Rope Capacity
(ft)
(metres)
Diameter
(ins)
Line Speed
(cm)
(ft/mm)
(rn/mm)
Skyline
2600
800
6/8
1.6
400-1000
l20300
Mainline
1800
650
3/8
1.0
400-1000
120-300
Haulback
1800
550
3/8
1.0
400-1000
120-300
The tower is 23.7 feet (7.21 metres) high.
The skyline, mainline,
and haulback lines pass through blocks on swivel fairleads at the top
of the tower.
Three guylines ar
attached to the top of the tower
and anchored so as to stabilize the machine during yarding.
A standing skyline configuration was used during the study.
A
haulback line was used to help move the carriage from the landing to
the chokeretter, and to hold the carriage in place during lateral
inhaul.
Two different carriages were operated during the study period:
a simple carriage for single span logging (Figure 7) and a second
carriage (Figure 8) designed to pass over a support jack was used for
yarding on multispan roads.
.4
)
3
-
I.UIrn
Figure 5.
/9/ ft
g-._ - ---- - 2.13"
--
-- -_-.4- -
-
Igland-Jones Trailer Alp
--
-.
'ii ..
-
-!
control Levers
I
,,
Figure 6
Igland-Jones Trailer Alp Trailer
16
i
Figure 7.
Single span carriage
Ewt = 35 lbs. (16 Kg.)]
41
*:
k
Figure 8.
Multispan carriage
Ewt = 80 lbs. (36 Kg.)]
17
A total of seven skyline roadz were studied, four o-F which used at
leazt one intermediate support.
Each support consisted of an Alp Jack
(42 lbs., 19 Kg.) hung from a block which in turn was suspended on a
one-ialf inch support line (Figure 9). This line pazzed through
blockz strapped on two support trees situated perpendicular or near
perpendicular to the skyline road and was tied down to stumps or
trees on either side of the support treez.
A single chokersetter operated for 75 percent of the turns
observed.
He pulled line nianually for lateral yarding.
A second
chokersetter aszisted with line pulling and chokersetting at slope
distances greater than 500 feet (150 nietres) on slopes of 10 to 40
percnt, and greater than 300 to 400 feet (90 to 120 nietres) on slopes
lesz than 10 percent.
acted as a chaser.
A third crew niember operated the yarder and also
Logs were cold decked to be loaded out at a later
date by a self-loading truck.
18
-
J
Figure 9.
Alp jack and support line
19
STUDY METHOD
Yarding cycle element times (in centiminutes) were taken with a
stopwatch.
A wristwatch was used to time the elements of road changes
and delays lasting longer than one hour.
One tinier observed the woods
operations, and, when available, a second timer observed the landing
operation.
Elements of Yarding Cycle
The following elements of the yarding cycle were identified and
measured.
Outhaul empty - began when the operator was ready to move
the carriage out to the chokersetter and ended when the chokersetter touched the chokers.
Sort rigging (chokersetter) - began at the end of the
outhaul empty element and ended when the chokeretter was ready
to move latera.11y.
This element 'involved untangling the chokr
if necessary and occurred on 32 percent of the turns observed.
Lateral out - began at the end of the sort rigging element
and ended when the chokersetter was ready to hook a turn.
Hook - began at the end of lateral out and ended when the
chokersetter had completed hooking and signaled the yarder
operator to begin the 'inhaul process.
Lateral in - beQan at the end of the hook element and ended
when the turn was pulled up to the carriage and began to move up
the skyline corridor.
a
20
Reset - an element which occurred when a turn became hung
up and one or more logs had to be rechokered.
It began when
the chokersetter signaled for the turn to be stopped and ended
when the turn began moving again, after being reset.
This element
occurred on 23 percent of the turns studied.
Inhaul - began at the end of the lateral in element and
ended when the turn had reached the position on the deck where
it could be directly unhooked.
Unhook
began at the end of the inhaul element and included
the operator walking into the choker(s), unhooking and walking
back to the machine to begin the outhaul element.
Position
an element which began at the end of inhaul and
It
ended when the operator was ready to move in to unhook.
occurred when a turn had to be positioned on the deck before it
could be unhooked and was observed on 16 percent of the turns
studied.
Sort rigging (operator)
an element which was isolated
from the unhook sequence if the operator had to untangle the
rigging before sending the carriage out to the woods.
This
element occurred on seven percent of the turns observed.
Sort deck - an element which involved the operator flatten-
ing down the deck or moving logs so that further logs could be
landed safely.
turns observed.
This element occurred on
21
percent of the
21
Variables of the Yarding Cycle
These variables included:
Slope distance.
The slope distance from the yarder to the
tail tree was measured with a tape before yarding commenced and
marked every 50 feet (15 metres) with paint.
The lateral yarding distance was normally
Lateral distance.
paced to the nearest 10 feet (3 metres) during yarding operations.
However, this distance was measured with a tape if the position
of the lateral corridor could be determined before yarding
commenced.
This distance was measured as the slope distance from
the skyline corridor to the hook point.
Volume.
Each log was premeasured and tagged before yarding
so individual piece volumes could be later identified.
The
large end and small end diameters (inside bark) and the length of
each log were measured.
Log volumes were calculated using the
equati on:
V = 0.001818 * L * (012 + 022 + 01 * 02) (Wood Handbook, 1974)
where:
V =
L =
D1=
D2=
volume in
length in
large end
small end
Skyline height.
cubic feet
feet
diametar inside bark in inches
diameter inside bark in inches
The height of the skyline above the ground
at the carriage was visually estimated.
In addition, the number of chokers used, the number of chokersetters operating, the number of logs per turn and the number of intermediate suppor-t
used were recorded by the observer in the woods.
The
22
landing observer measured the deck height to the nearest foot using
a premarked measuring stick.
The average groundslope of each corridor in percent was calculated from data collected during the field survey of the skyline roads.
Groundslope was chosen as a variable rather than chordslope as the
skyline tends to more closely follow the ground than the chord when
intermediate supports are used.
Delays
The cause of each delay was noted during the study but during
the analysis eleven delay codes were identified, and each delay was
placed into one of these codes.
It was noted during the analysis that
delay times could be separated into two distinct categories.
These
categories have been defined as operating delays and experimental
delays.
Operating delays were those considered to be part of the normal
yarding operation.
Experimental delays were those considered to be
atypical o-F a normal operation.
Examples include downtime caused by
visitors, crew un-Familiarity with the equipment, and the experimental
nature of the logging system.
The latter delays have been excluded when calculating machine
utilization and production potential.
The breakdown of the delays
into the above categories within delay codes is detailed in Table 7.
The delay codes included:
Prepare - this time was spent in personal and yarding
preparation each day, and was the elapsed time between arriving
23
on the job and the commencement of yarding operations.
Fell and buck - this involved felling and bucking trees
hung up during falling, and also removing trees badly damaged
during logging.
Snag problems - the Trailer Alp did not have the power to
drag logs through old snags which were scattered throughout the
stand.
Often snags had to be "rigging cut" to enable yarding to
continue and this time was considered a snag problem delay.
Ropes and Carriage - this time included splicing broken
rope and replacing bolts and plates on the carriage.
It also
included the time spent respooling the mainline, which occasionally rapidly unwound from the drum and tangled.
Supports - the time spent rehanging the skyline in the jack
or ad,juting the height of the jack was considered support delay.
Mechanical - any time spent repairing the yarder was
considered mechanical delay.
Deck problems - on one occasion, the deck became so
cluttered that turns cüuld not be landed, and the operator was
forced to pull a number of logs off the deck using the utility
drum.
This time was considered a deck problem delay.
Personal - this included time taken by the operator and
chokersetter.
Radio - the downtime caused by the need to repair faulty
transmitters, receivers, and aerial.
Other - these delays included downtime caused by visits
and waiting for a truck which loaded out during yarding on two
24
occasions.
Unspecified - those delays which could not be identified
by the observer.
Road Changes
The following elements in the road change sequence were identified
and measured:
Rigging in - this element began upon completion of yard and
ended when all the rigging lines and carriage were at the yarder.
Guylines in - this element began when one or more crew
members moved towards the guyline stumps and ended when the
guylines were ready for the machine to move.
Move machine - this element began when the operator started
to remove the transmission shaft from the tractor power take off
unit and ended when the machine was in position at the new site
and attached to the power source.
Guylines out - this element started when the guylines were
moved towards the new anchor stumps and ended when they were
tightened.
Rigging out - this element started when the first rigging
line was moved and ended when all the lines, and carriage, were
in position.
Raise supports - this element included the time taken to
place the skyline in the jack, raise the jack to the required
height, and anchor the support line.
It did not include the
time to hang the clocks and support line because they were
25
prerigged.
The variables measured during the road change cycle included
the slope distance of the skyline road, the distance between
skyline roads, the number of supports used and the crew size.
Rigging Intermediate Supports
Two rigup times for intermediate supports were measured and the
results are presented in Table 10.
During the study, most of the
support trees were prelimbed before being rigged and two supports were
prehung by the faller while yarding corrtinued.
The elements of
intermiediate support rigup identified included:
Move in rigging - the time taken to carry the support
rigging, jack, and climbing gear to the support trees.
Hang rigging - the time taken to climb, limb, and hang
support blocks in both support trees.
Anchor support line - the time taken to anchor the support
line to nearby trees or stumps.
p
26
DATA ANALYSIS
Summary 0f the Yarding Cycle
The average element times for the thinning study are presented in
Table 5, together with the maximum and minimum times recorded for each
element.
Table 6 presents similar values for the variables which
influenced these times.
Table 5.
El ement.
Summary of Yarding Cycle Times
No. of
Obs.
Max.
Time
(mm)
Mm.
Avg.
Time
Time
(rain)
(mm)
Percent
Outhaul
549
2.5
0
0.70
15.6
Sort Rigging
(chokersetter)
549
2.00
0
0.10
2.2
Lateral Out
549
2.27
0
0.42
9.4
Hook
549
6.30
0.65
14.5
Lateral In
549
4.29
0
0.42
9.4
Reset
549
6.98
0
0.35
7.8
Inhaul
549
2.38
0
0.69
15.4
Position,
549
2.22
0
0.12
2.7
Unhook
549
6.30
0.60
13.4
Sort Rigging
(Operator)
549
2.00
0
0.07
1 .6
Deck
549
9.12
0
0.36
8.0
4.48
100.0
Total Turntime
Without Delay
0.05
0.05
f
27
Table 6.
Summary of Production Variables
Average
Value
Variable
Slope Distance (ft)
(iii)
Lateral Distance (ft)
(rn)
Skyline 1-leight (ft)
(rn)
Logs Per Cycle
650
0
224
200
0
68
140
0
41
42
0
12
48
6
17.5
15
2
6.3
1
1.62
4
Volume Per Cycle (cu.ft)
(cu.rn)
60.0
2.1
1.69
0.06
21.0
0.59
2
1
1.25
Chokes per Cycle
2
1
1.68
Logs Preset per Cycle
1
0
0.14
Chokersetter
per Cycle
28
Regression Ana]ysis
Regression equations were generated which relate element times to
one or more of the variables measured.
The stepwise regression proce-
dure was used with the SIPS statistical package program for the
Control Data Corporation 3300 computer (OS-3 operating system) to
test hypotheses, determine regression coefficients and coefficients
of determination.
The acceptance or rejection of variables in each regression was
determined using a combination of required confidence interval of 95
percent and the marginal increase in the coefficient of determination
value (R2) obtained by adding each new variable.
If the addition of
new variables to a regression did not improve the R2 value by more
than one percent, even though they were significant at 95 percent,
they have been rejected.
In the regression equations that follow:
SLPDST = slope distance in feet or metres
SKYHT
GRDSLP
NOSUP
= skyline height in feet or metres
groundslope in percent
= the number of intermediate supports
LATDST = lateral distance in feet or metres
NOCS
= the number of chokersetters used
NCLGS
= the number of logs per turn
VOL
= volume in cubic feet or cubic metres
PRST
= the number of preset logs
29
1)
Outhaul time (in minutes)
H0:
Outhaul = f(SLPDST, SKYHT, GRDSLP, NOSUP)
Outhaul = 0.25T1
n = 549
+ 0.00198 * SLPDST
(standard units)
Outhaul
R2= 0.685
0.25T1
+ 0.00649 * SLPDST
(metric units)
The addition of the other three variables increased the
by only 1.5 percent and so the above equations are accepted.
value
Ground-
slope is not a significant variable, probably because the operator
held the mainline tight during outhaul and pulled the carriage out
with the haulback line.
By doing this, he did not take advantage of
increasing groundslope returning the carriage more quickly.
Sort Rigging (Chokersetter) (in minutes)
Average time per turn
= 0.10 minutes
Standard deviation
= 0.233 minutes
Standard error of mean
= 0.010 minutes
n
549
Because of the random nature of this element, no significant
regression equation could be generated.
Lateral Out Time (in minutes)
H0:
Lateral Out = f(LTDST, LATDST2, SLPDST, SKYHT, NOCS,
GRDSLP)
Lateral Out = 0.116
+ 0.00G260 * SLPDST
n = 549
0.553
30
+ 0.00756 * LATDST
- 0.05067 * NOCS
(standard units)
Lateral Out = 0.1161
+ 0.000853 * SLPDST
+ 0.0248
* LATDST
- 0.05067
* NOCS
(nietric units)
Addition of the other three variables added less than 0.01 to
the R2 value and so the above equations are accepted.
The lateral
distance was the most significant variable, as expected; but the
slope distance was also a factor as it reflects the force required
to pull line to any given lateral distance.
Groundslope also affects
the force required to pull line but it was not a significant variable
in the equation.
4)
Hook Time (in minutes)
H0:
Hook = f(NOLG, VOL, GRDSLP, NOCS, PRST)
Hook = 0.4133
+ 0.1653 * NOLGS
n = 549
R2=0. 081
- 0.2121 * PRST
(standard and metric units)
Even with all five variables included, the R2 value increased by
only 0.003.
None of the above variables is significant at 96 percent.
As 92 percent of the variation in hooktime was caused by factors
other than the above variables, little reliance can be placed on it
and an average hooktime is presented here.
31
Average time per turn
=
0.65 minutes
Standard deviation
=
0.521 minutes
Standard error of mean = 0.0197 minutes
5)
H
:
Lateral
In Time (in minutes)
Lateral
In =
.0
Lateral In
f(LATDST, LATDST2, VOL. NOLGS, SKYHT,
LATDST * NOLOGS)
= 0.1080
n
0.00987
*
- 0.03501
*
LADST
= 549
R2= 0.253
LATDST2
1000
(standard unitz)
Lateral In = 0.1080
+ 0.032
-
*
0.3765 *
LATDST
L.ATDST2
1000
(metric unitz)
Addition of the four other variables increased the R2 value by
less than 0.01 and so the above equations are accepted.
As expected,
the lateral distance was the dominant influence in the time taken to
yard logs to the skyline corridor.
The relatively low
value
obtained may be attributed to the variation in number and effectiveness of obstructions along the lateral corridors.
If no trees, snags
or other obstructions blocked the path of a turn, the chokersetter
signaled the yarder operator to yard the logs in at full speed.
however,
If
any obstructions threatened to block the path of a turn, the
chokersetter would signal to pull the turn in slowly to the skyline
corridor.
32
6)
Reset (in minutes)
Average time per turn
= 0.35 minutes
Standard deviation
= 0.793 minutes
Standard error of mean = 0.038 minutes
Because of the. infrequent nature of this &ement, no significant
regression equation can be generated.
The impact of this element can
be minimized by the chokeretter anticipating probable hangups and
stopping the turn before it becomes jammed and requires considerable
time to reorganize the logs in the turn.
minimize damage to residual trees.
Rapid action will also
The probability of resetting being
necessary tended to increase as the number of logs per turn increased.
Of the one-log turns observed, 21 percent required resetting,
while
24 percent of the two-log turns and 26 percent of the three-log turns
required resetting.
7)
Inhaul Time (in minutes)
H0:
Inhaul
f(SLPDST, SKYHT, GRDSLP, NOSUP, VOL)
Inhaul
0.0841
n =
0.00201
*
SLPDST
0.01178
*
SKYHT
- 0.0754 * NOSUP
(standard units)
Inhaul
= 0.0841
0.00659
*
SLPDST
0.03863
*
SKYHT
- 0.0754 * NOSUP
(metric units)
549
R2= 0.S6
33
Addition of the other two variables increased the R2 value by
less than 0.01 and so the above equations were accepted.
Position Time (in minutes)
Average time per turn
Standard deviation
n = 549
0.12 minutes
= 0.330 minutes
Standard error of mean= 0.015 minutes
Because of the random nature of this element, no significant
regression equation could be generated.
Unhook Time (in minutes)
H0: Unhook = f(DKHT, NOCKS)
Unhook = 0.1512
n = 549
R2= 0.197
+ 0.02657 * DKHT
+ 0.1116 * NOCKS
(standard units)
Unhook = 0.1512
+ 0.08715 * DKHT
+ 0.1116 * NOCKS
(metric units)
Deck height, in turn, may be described by the equation:
Deck height = 2.467
+ 0.0588 * NOLGS
(standard units)
Deck height = 0.752
+ 0.0179 * NOLGS
(metric units)
= 505
R2=0. 714
34
The relatively high R2 obtained indicates that the deck height
required to stockpile a given number of Togs may be predicted with
some confidence and may be used as an aid to layout design in stands
with similar piece size material to the one studied, if cold decking
will be necessary.
Sort Rigging (Operator) Time (in minutes)
Average time per turn
= 0.07 minutes
Standard deviation
= 0.294 minutes
Standard error of mean
n
549
0.013 minutes
Because of the random nature of this element, no significant
regression equation could be generated.
Decking Time (in minutes)
Average time per turn
Standard deviation
= 0.36 minutes
n
549
0.939 minutes
Standard error of mean = 0.042 minutes
Because of the random nature of this element, no significant
regression equation could be generated.
The maximum number of logs cold decked during the study was
210, and the maximum deck height measured was 16 feet (5 metres).
With regular flattening to maintain a safe deck,
may be decked without serious problems.
200-220 logs
The major problem encoun
tered with cold decking during the study was the lack of operator
vision when the deck became higher than 10 feet (3 metres).
35
Figure 10 illustrates two adjacent deckz, each with approximately
the same number of logs.
One haz been flattened regularly by the
yarder operator with a peavy, while the other has not been maintained
at all.
12)
Total Time per Turn (in minutes)
The estimated time per turn (without delays) can be derived in
two ways:
by combining the individual element times discussed above
for a given set of variable values; or
by deriving a single regression equation with the total
time per turn as the dependent variable and one or more of
the measured independent variables as the independent
variable(s).
The second method is uzed in this paper as the generation of a
single production equation enables statistical data to be calculated
and used in evaluating the usefulness of the equation.
Time per Cycle (in minutes)
H0: Time per cycle = f(SLPDST, SLPOST2, LATDST, LATDST2,
NOLGS, SKYHT, NOCS, GRDSLP)
Time per cycle = 1.6932
+ 0.005119 * SLPDST
+ 0.025653 * LATDST
+ 0.2783 * NOLGS
(standard units)
n = 549
0. 290
36
Figure 10.
Example of a maintained and a neglected deck.
V
37
Time per cycle = 1.6932
+ 0.01679 * SLPDST
+ 0.08414 * LATOST
+ 0.2783 * NOLGS
(metric unitz)
The above equation is used in the derivation of the potential
production rates presented in Figures 15 and iSa.
Delays
A summary of the delay times measured during the study, and the
percent of total study time is presented in Table 7.
The 8700 minutes of operations studied included both thinning
and clearfelling operations.
It is not poszible t
sort many of the
delays, especially those related to rapes, carriage and mechanical,
intQ those resulting frrn thinning and those resulting frrn clearfelling operations.
It is considered that the total operational
delays of 26.1 percent of working time is a high figure, and could
be reduced significantly by an experienced crew operating in smallwood.
Delays which might be reduced include:
Prepare
the crew spent almost 4 percent of the total
working time preparing for work.
This included refueling, hooking up
the signal system, and personal preparation.
If a signal system was
attached to the tractor permanently, some of this time could be
saved.
Fell and Buck Fallen Snags - a total of 4.3 percent of
operation time was spent removing hangups and snags.
Much of this
38
Table 7.
Delays
Operational
Code
Experimental
Time (mm.)
Percent
Time (mm.)
Percent
Prepare
334.1
3.8
61.1
0.7
Fell & Buck
191.6
2.2
Snags
177.8
2.1
Ropes and
Carriage
408.8
4.7
11.1
0.1
Supports
174.9
2.0
1106.0
12.7
Mechanical
767.1
8.8
693.8
8.0
Deck
120.2
1.4
Personal
34.4
0.4
Unspecified
60.6
0.7
Radio
98.7
1.1
Other
292.3
3.4
2263.0
26.0
Total
NB.
2269.5
Total Time Studied
26.1
=
8700 minutes
I
3.
work could be avoided by improved felling practices, and by the
fallers making bucking cuts in fallen snags which will cause yarding
problems.
Ropes and Carriage - the majority of the 409 minutes
recorded against this delay was spent resplicing broken rope.
The
mainline rope was not new when the operation commenced and it broke
on a number of occasions during the study.
It was observed that
breaks often occurred during or soon after yarding loads larger than
40 cubic feet (1.13 cubic metres).
The weight of these loads ranged
from 2500 lbs. to 3500 lbs. (1140 to 1640 Kgs).
Only 38 turns, or
5.6 percent of the total turns measured (including those from the
clearcut alder) exceeded the above volume but it would seem that
these turns contributed to excessive rope (and machine) wear.
Figures 11 and 12 present turn volume distribution for the thinning
and clearfelling operations.
Mditional rope wear was probably
caused by the yarder operator attempting to break out hung up turns
and also by attempting to pull logs through fallen snags.
Supports - if support configurations are designed before
layout, there should be no need to adjust the jack height to insure
the skyline sits in the jack.
Mechanical - most of the 770 minutes recorded as mechanical
downtime was the time taken to repair or replace the main winch
drive chain.
Again, it was observed that chain links broke during the
yarding of the larger turn volumes.
40
Average volume = 21.0 cubic feet
(0.59 cubic metres)
50
(1,
0
S.-
3O
C
20
0
0-10
1-1.3
11-20
0.3-0.6
21-30
0.6-0.8
31-40
0.8-1.1
41-50
5]+ (cubic feet)
1.1-1.3 1.4+ (cubic metres)
Volume Per Turn
Figure 11.
Distribution of turn volumes - thinning
Average volume
22.8 cubic feet
cubic metres)
(0.65
50
40
301
20!
10
'1,
0
0-10
0-0.3
11-20
0.3-0.6
21-30
0.6-0.8
31-40
0.8-1.1
41-50
1.1-1.4
51+
1.4+
Volume Per Turn
Figure 12.
Distribution of turn volumes - clearfelling
(cubic
(cubic
feet)
metres)
41
Reduction of these large volumes and the avoidance of breaking
out 'hung up
turns with the machine may reduce chain wear.
It has
been noted in a later study of the Alp (during which the drive chain
continued to cause downtime) that some bolts holding the winch to the
trailer franie were loose.
This caused the chain to stretch unneces-
sarily, and may have been the cause of so much chain wear in this
study.
Road Changes
With only seven observations, any regression equation which
correlates road change time with all four of the above variablez will
produce an artificially high R2 value.
However, it was apparent to
the obzerver that the slope distance was a major factor in road
change time, and so an equation has been generated which correlates
road change time slope distance (Table 8).
Road change time
-162.76
+ 46.5455 * ln SLPDST
n=7
R2= 0.305
This equation has been uzed in the derivation of the potential
production rates presented in Figures 15 and lSa.
The road change time, at nearly 10 percent of total working
time, is a significant non-productive operating element.
This time
might be reduced if:
Guy treez were selected and felled prior to a road change.
The rigging out element was better coordinated so that
maximum use was made of available man power.
Table 8.
Change
Rig
Guys
No.
In
In
Move
Yarder
Guys
Out
Road Changes (All times in minutes)
Rig
Out
Raise
Jacks
Total
Move
OST
No
Supj.
SIP
OST
(ft)
(m)
(ft)
(m)
Crew
Size
1
11
16
4
-
70-
18
119
275
84
27
8
1
3
2
13
3
8
- 123-
10
157
515
157
130
40
1
3
3
23
11
3
28
72
137
425
130
165
50
0
4
4
13
9
2
22
81
127
460
140
180
55
0
3
5
11
5
5
15
24
60
260
79
175
53
0
3
6
8
7
8
40
39
9
111
660
201
260
79
1
3
7
15
11
14
7
65
14
126
580
177
830
253
2
3
Total Time
Average Time
Percent of Total Time
837 minutes
119.6 minutes
9.6 minutes
43
During six road changes, guylines were tightened by using manual
pre-tightener
with the Alp utility winch used to hold the trailer
over towards the guytimps.
The winch brake was then released to
lower the trailer and tighten the guys.
During the last road change
studies, portable hand winches were used to tighten the guys (Figure
With crew familiarity, these winches may reduce road change
13).
times.
Guytrees were selected and prefelled before road changing on
this road, so the short (seven minute) guy out element could not
be attributed directly to the tighteners, but as the crew becomes
familiar with their use, they may reduce guy tightening time.
Table 9.
Surrnary of Time Usage
Operating
Delays
Percent of
Total Time
26.1
Road
Changes
Utilization
9.6
64.3
Niachine
Machine availability is calculated as 84.5 percent
Intermediate Supports
Details of the two rig support operations measured are located
in Table 10 on page 45.
The rigger recorded gross measurements on the trees he prelimbed.
Table 11 lists data for six trees.
These trees were limbed only, and
the support blocks were hung at a later time.
included climbing, limbing, and
The times listed
the rigger returninq to the ground.
44
4
Figure 13.
Line tightener for guylines
I
45
Table 10.
Rig Support Times
Element
(All times in minutes)
Support Number
2
1
Move in equipment
16
15
Climb, limb, and rig
12
15
17
14
3
2
Anchor support line
10
S
Total Time
58
51
tree 1
Climb, limb, and rig
tree 2
Move between trees
Number of limbs cut
#1
Not recorded
Not recorded
51
#2
Height of blocks
25
25
#1
#2
Table 11.
Tree No.
36
30
Support Tree Limbing Times
Height
No. Limbs
Time (mm.)
1
20
52
6
2
20
48
10
3
30
20
10
4
30
34
6
5
25
69
10
6
25
29
9
Average
25
42
8,5
46
During the study, most of the limbs removed were small and
generally dead.
The only reason for removing them was to allow the
rigger to climb the tree.
In a recent study (Gibson and Fisher, 1977)
which involved the use of supports, riggers used Swedish climbing
ladders to hang support blocks.
Their use in the Northwest for this
purpose may reduce the total rigging time as the number of limbs
require.d to be cut could be reduced, and the need to limb may even
be eliminated.
Some time was lost during the study adjusting the height of the
support jack so the skyline would sit on it when tensioned.
However,
the lateral placement of the jack in relation to the skyline corridor
seemed relatively flexible.
With the jackblock riding freely on the
support line, it could move laterally to compensate for any lack of
symetry in support block height or support tensions.
Support blocks were hung 20 to 35 feet (6 to 10 metres) from
the ground in support trees 15 to 30 feet apart, and perpendicular to
the skyline road.
The jack was positioned 15 to 20 feet (4 to 6
metres) above the ground (Figure 9).
Potential Production
A computer program has been written in BASIC language for use on
the Hewlett Packard 9830 desk-top computer to derive potential daily
production rates for the Igland-Jones Trailer Alp thinning stands
similar to the one studied.
The program calculates production rates by:
47
Figure 14.
Swedish climbing ladder
- Virginia Study
48
accepting input data including the number of stems per acre
cut, the number of pieces per tree, the volume per piece, the
number of pieces per turn, and the total delays expected (as
a
decimal).
calculating the expected time per turn (without delays)
using the equation described on page 35.
calculating road change time for the slope distance being
considered.
calculating the total time to yard one road, by deriving the
area of the road and the total number of turns per road, and multiplying the number of turns by the time per turn.
Road change time
is added to this.
calculating an effective total time to thin one skyline
road including yarding, road changes, and delays.
The hourly priduction rate is derived by dividing the total
volume in a road by the time taken to yard the road.
Using this program, the production graphs presented in Figures
15 and lSa have been developed.
It can be seen that at an average slope distance of 250 feet
(75 metres) and with an average lateral yarding distance of 35 feet
(11 nietres), the anticipated hourly production is 175 cubic feet
(5 cubic metres) per hour.
This translates to a daily eight hour
priduction of 1400 cubic feet (40 cubic metres) or 109 pieces per
day if the average piece size equals 12.9 cubic feet (0.36 cubic
metres).
49
In a study of a Trailer Alp operating in British Columbia,
Maxwell and Oswald (1975) report that the machine yarded an average
of 190 logs per eight hour shift, with an average yarding distance of
270 feet (80 metres).
The operation thinned a western hemlock stand,
removing 177 stems per acre (437 stems per hectare).
This compares
with the study figure of 96 stems per acre (237 stems per hectare).
The average number of logs per turn in the Canadian operation was 2.1
compared with the present study average of 1.6; a difference probably
due to the large number of stems removed in the forTner operation.
The average turn time in Maxwell's study at 4.8 minutes, is similar
to the current study average of 4.5 minutes.
The higher daily piece
count is most likely explained by a combination of the higher number
of pieces per turn for the Canadian study and the lower operating
delay loss--less than 20 percent compared with an estimated 26.1
percent in this study.
50
Average Slope
Distance (ft)
182
L2
t72
L)
=
w
96
Trees per acre removed
L3
=
=
1.5
Logs per tree
=
Volume per log (cuft)
= 12.9
Logs per turn
=
LL12
26.1
Delays (percent)
L4
1 .6
7
VAE LTRRL DETRN(E (FT.)
Figure 15.
Production per hour as a function of lateral and slope
(standard units)
distances.
51
Average Slope
Distance
=
=
237
Trees per hectare removed
=
Logsper tree
= 1.5
Volume per log (cu.rn)
= 0.36
Logs per turr
= 1.6
Delays (percent)
= 26.1
-
12
RVERFE LTL ISTRN(E
Figure 15a.
t9
21
CM.)
Production per hour as a function of lateral and slope
distance (metric units).
52
Table 12.
Daily Operating Costs - 8 Hour Day
Trailer Alp
Tractor
Saws at $6.13 per day each
Transport (40 niles - 25 kilometres
one way)
Radio
Labor (including fringe benefit
factor of 39 percent) (USFS, Region 6
Lead Cutter @ $12.27 per hour
2
3man
4man
crew
crew
$92.93
$99.36
26.47
28.01
- 12.26
2 - 12.26
16.22
22.76
5.58
5.58
1976)
98.16
98.16
-
97.52
Second Cutter @ $12.19 per hour
Chokersetter (radio) $9.30 per hour
(a) 74.4.2
69.52
Yarder Operator @ $10.34 per hour
(a) 82.72
79.60
408.76
512.77
Total Daily Cost
Daily Production
Cubic Feet
Cubic Metres
Board Feet
Unit Cost on Ride
Per Cunit
Per Cubic Metre
Per Mbf.
(a)
Paid second cutter rates while falling.
1158
32.8
6950
1400
40.0
8400
$35 .30
1 2.46
$36.63
12.93
58.83
61 .04
53
DISCUSSION OF RESULTS
Productivity
The results of the production study, in conjunction with
personal observations would indicate that the Igland-Jones Trailer
Alp yarder has the ability to perform succe.ssfully thinning young
growth stands of Douglas-fir.
However, the operation of a small
yarder in smallwood requires different skills and different operating
techniques than the large machines which have been so effective in
the Pacific Northwest.
With limited power available, it is not desirable, and in many
instances not possible, to open the yarder throttle and expect hung
up turns to be pulled free of hang ups or pulled
obstacles.
through other
Although the Trailer Alp did not appear to be loaded to
its power capacity during this study, with heavier thinning intensities or larger piece material it will be important that the
chokersetter does not overload the machine--a situation difficult to
achieve with many of the large yarders currently being used.
It is very important that each crew member is familiar with all
facets of the thinning operation.
The financial viability of the
thinning operation may be determined by the skill of the fallers.
These fallers avoid hang ups while falling trees to lead and should
ensure that no immovable obstacles remain in the skyline or lateral
corridors.
The chokersetter must select his turns so that they will have
54
He should also
a relatively free path to the skyline corridor.
be ready to stop the inhaul cycle to reset the turn if it hangs up.
In turn, the yarder operator must appreciate the limits of his
machine and should not overwork it.
Because of the tighter limits placed on logging practices when
using such a small machine, it may be desirable that each crew
member rotate work positions so that he can appreciate the skills
involved in perfrrning each function efficiently.
It was noted in the analysis that the addition of a second
chokersetter had only a small
iiiipact (a saving of 0.10 minutes per
cycle) on the lateral out element and did not enter the hook
regression equation as a significant variable.
The number of
chokersetters was not a major variable in the total turn time regression.
This result would not be expected but may be explained by the
following reasons.
A second chokeretter was used at slope distances greater
than 300 feet (90 metres).
Because of the greater force required to
pull slack as slope distance increased, he did not speed up the
lateral out element, but did enable slack to be pulled at distances
where a single man would not have been able to operate by himself.
The hook element included the time taken for the chokersetter(s) to move to safety after setting the chokers.
When a
single chokersetter was operating, he often signaled for the beginning
of the inhaul elements before he was safely away from the turn,
relying on his agility to get out of the way before the turn moved.
4
55
When two chokeretters were working, however, the one with the
radio did not signal until both men were safely out of the path of
This delay tended to nullify the effect of the chorter
the turn.
hook time.
Sensitivity of Production
The sensitivity of the potential production rate to a change in
one or more of the variables used may be deteriiiined quickly by the
use of the Hewlett Packard 9830 program listed in Appendix 2.
The following figures indicate the variation in production
rates per hour expected by a change in important variables.
In
Figures 16 and 16a, the volume per piece is varied between 11 and 17
cubic feet, and 0.31 and 0.49 cubic metres, rspectvely.
The
derivation assumes:
Sterns removed
= 96 stems per acre (237 stems per hectare)
Pieces per tree
= 1.5
Pieces per turn
1.6
Operating delays = 26.1 percent
In figures 17 and 17a the expected operating delays are varied
between 17 and 26 percent.
The above assumptions hold (except for
No. 4) and the volume per turn = 12.9 cu.ft. (0.36 cu.m).
Lateral Yarding
Lateral yarding is a major work activity of the yarding cycle.
One man was able to pull mainline relatively easily out to 100 feet
Volume per piece
in cubic feet
17
I
-1
LU
IWU
1W
2UW
HVERHEE 5LUPE 1IiTHNCE (FT.)
Figure 16.
Production per hour as a function of slope, distance and vo'ume per piece
(standard time)
3UW
Voluiue per piece
in cubic metres
zEi
Dr
L12-.t
I!:
EL1
7
RYERRIE SLUPE 1I5TRN(E CM.)
Figure 16a.
Producti0r per hour as a function of slope distance and volume per piece
(metric units)
U1
F-
H
Percent Delays
Li
17
a:
r
I!1L1
a:
Li
ci
IIElkl
23
D
a:
25
17k1
R1L4
Figure 17.
2E
IL1
2LI
HVEFFIFiE SLIJFE LIiTHNCE (FT.)
Production per hour as a function of slope distance and percent delays.
(standard units)
31LI
-
.E1
=1
Percent Oelays
Et
LI
17
L4
P-r2I
23
9.F
7
HVEHFIIiE
Figure 17d.
LE1PE t?ITHNCE (M.)
Production per hour as a function of sope distance and percent delays.
(metric units)
60
(30 metres) laterally at a slope distance of 500 feet (150 metres) on
slopes greater than 20 to 25 percent.
A second man was required at
slope distances greater than 500 feet (l0 metres) or, on flatter
ground, at shorter slope distances.
To estimate the amount of force required to pull line at
varying slopes and slope distances, the following equation may be
used (1ff, 1977).
F=W*L (rCosGtSinG)
where F = The force required to pull zlack (in lbs. or kg.)
W = The unit weight of mainline (in lbs/ft or kg/m)
L
Slope distance (in ft. or m.
r = Coefficient of kinetic friction between the mainline
and the ground
9 = Groundslope in degrees.
The value of r may vary depending on ground conditions.
wet conditions in this area, r = 0..
Under
Under wet conditions this
value has been measured to be 0.43 (1ff, 1977).
Some of the assumptions made in derivation of this equation may
not hold true for all yarding conditions, but field nieasurrnents have
confirmed its validity under a variety of conditions.
The use of this equation illustrates the effect of both
groundslope and slope distance on the amount of force required to
pull line.
For example, the amount of force required to pull a 3/8
inch (1 centimetre) mainline on a 40 percent downhill slope 500 feet
(150 metres) from the tower is 18 lbs.
(8 kg.).
On a 10 percent
I
61
downhill slope at the same distance, the force required is 58 lbs.
(26 kg.), and on a 20 percent uphill slope the force is 96 lbs.
(43 kg.).
The graph presented in Appendix 3 can be used to determine the
approximate line pulling effort required to pull mainline from the
carriage at varying slope distances and steepness.
Intermediate Supports
The use of intermediate supports solved two major problems in
the study area.
It enabled the yarder to extend 4.00 feet (20 metres)
further than it could have without supports on four of the skyline
roads.
When placed within 100 feet (30 metres) of the landing, it
facilitated efficient decking and enabled decks of more than 200
logs to be built up without excessive decking delays.
The crew bent three jacks while lateral yarding within 20
feet (6 metres) of the support line when the line was passed
directly through the yolk of the jack.
Following this experience,
the jack was hung from a block which enabled the jack to move freely
along the support line, and no further problems were observed,
although generally the Alp support jack and carriage worked
successfully during the study.
Crew Size
During the study three men were available for the yarding
62
operation.
All three men assisted with road changing and in one
change a fourth man assisted the regular crew.
The crew managed
to keep ahead with falling and bucking because of numerous mechanical
problems to the Trailer Alp which occurred before the study period
began.
However, in a production situation, the balance between
crew size and production would need to be analyzed.
A comparative
production and cost analysis for a three and four man crew has been
presented in this paper (see Appendices 9 and 10, and Table 12).
Gross measurements taken during the study indicated that an
average of 10 logs were felled, limbed, and bucked per man hour
(see Appendix 11).
The fallers were not under pressure to keep
ahead of the yarder, however, and so this figure has not been used
for analysis.
A recent study of felling and bucking in similar
material (Aulerich, 1975) reported that the average time per tree
taken to fell, buck, and limb was 7.52 minutes.
This translates to
eight trees per man hour or 96 logs in an eight hour day.
Using this figure, production and ccst estimates have been
calculated for a three and a four man crew yarding out to 500 feet
(150 metres) and lateral yarding out to 70 feet (21 metres) on each
side of the skyline corridor.
The results indicate that a three man
crew produces less than a four man crew because of the need for the
chokersetter and yarder operator to supplement falling production
but that the unit cost of logging with a three man crew is less than
with a four man crew (Table 12).
63
Stand Damage
A quantitative assessment of damage to the residual stand was
undertaken as part of the study.
It was observed, however, that the
damage to residual stems tended to be more prevalent and serious as
the number of stems per turn increased.
One of the three choker-
setters observed tended to 1bonus" as many turns as possible by the
use of sliders.
This practice may increase productivity, especially
in areas where logs are scattered, but this advantage should be
weighed against the extra stem damage which may result from the
reduced control the operator has over the turn.
Additional sources of stem damage were the straps used to hole
corner blocks, tail blocks, and those used to anchor intermediate
support ropes.
The half-inch straps used during the study ringbarked
the trees to which they were attached (Figure 15).
This damage would
be prevented by the use of protective rubber strips cut from auto
tires or similar material.
64
4
Figure 18.
Example of ringbark damage
65
FUTIJRE STUDIES
The Forest Engineering Department of Oregon State University has
already completed field data collection of the Trailer Alp yarding
clearfelled timber on a road right-of-way-out to 1000 feet (300
metres), using two intermediate supports and with haulback line.
Also, data has been gathered for a hardwood clearfelling operation
where a 150 lb.
(46 kg.)
gravity outhaul system.
'Mini Christy' carriage was used with a
These studies have yet to be evaluated,
but preliminary results of the Christy carriage study indicate that
the gravity outhaul system can significantly increase productivity
if intermediate supports are not required.
Two design modifications might be analysed:
The Trailer Alp, currently powered by a farm tracor, could
be adapted so that it is powered by a separate engine built onto
modified trailer.
a
The unit could be moved with a small skidder
which could also swing logs away from the deck.
Major production increased may be achieved if a gravity
outhaul clamping carriage can be modified so that it passes over
intermediate supports.
The combination of a clamping carriage with
a gravity outhaul system would probably generate a large amount of
interest in the Pacific Northwest.
66
CONCLUS ION
The Igand-Jones Trafler Alp has been tested thinning young
growth Douglas-fir in Western Oregon.
During the study period the
Trailer Alp was used with a standing skyUne configuration and inter-
mediate supports were used on four of the seven skyUne roads
observed to obtain additional deflection on unfavorable slopes.
The study was conducted only two weeks after the machine was
delivered to the yarding crew and many of the mechanical and
operating system delays measured were caused by crew unfamiUari]y
with the equipment and the experimental nature of the system.
Where possible, experimental delays have been removed from the
analysis, but their effect in disrupting the work patterns of the
crew effectively reduced the overafl productivity of the system
under study.
Because of this problem, the production estimates
presented in this paper wou]d represent a lower limit of what could
be expected from an experienced crew under similar operating conditions.
The niajor objective of the study--to develop production equations
which may be used to estimate production over a range of conditions--.
has been achieved.
It has also been demonstrated that intermediate
supports can be used successfully with the Trailer Alp to extend
yarding distance and permit yarding operations on long or convex
sI opes.
A detafled analysis of intermediate support design is currently
in progress at Oregon State University and the results from this
67
analysis should be valuable in determining the effective design
of and safe limits for intermediate supports in young Douglas-fir.
68
BIBLIOGRAPHY
Smallwood Harvesting Research at Oregon State
1975.
Aulerich, D.E.
Loggers Handbook, Vol. XXXV, 10-12, 84-88.
University.
Economics of Using a Small
1977.
ibson, H.F. and E. L. Fisher.
European Standing Skyline to Partial Cut Eastern U.S. Hardwoods.
U.S. Forest Service, Morgantown, West
Unpublished report.
35 p.
Virginia.
An Analysis of the Slack Pulling Forces Encountered
1977.
in Manually Operated Carriages. Masters Thesis, Oregon State
University.
65 p.
If-F, R. H.
A Case Study for Pre-bunching and Swinging.
1976.
Kellogg, L. D.
A Thinning System for Young Forests. Masters Thesis, Oregon
State University, 88 p.
Cable Logging in Norway, A Description
Lisland, Torstein. 1975.
A paper presented as
of Equipment and Methodz in Present Use.
a Visiting Scientist at Oregon State University, Forest
Forestry
Northwest Area Foundation.
Engineering Department.
Series.
47 p.
Tree Volume Tariff Access Tables for Pacific
1972.
Little, G. R.
Vol. 2, Major Coastal Species. State of
Northwest Species.
163 p.
Washington, Department of Natural Resourcez.
1975.
Maxwell, H. G. and D. Oswald.
Succezsful in British Columbia.
Vol. 49, 62-66.
Cable Yarder Thinning Proves
Canadian Forest Induztries,
Comprehensive
1972.
Turnbull, K. J., G. R. Little, and G. E. Hoyer.
State
of
Washington,
Department
of Natural
Tree Volume Tables.
Resources.
320 p.
Department of Agriculture, Forest
1974.
U.S. Forest Service.
Products Laboratory. Wood Handbook. Wood as an Engineering
Material, 356 p.
Department of Agriculture. Timber
1976.
U.S. Forest Service.
Appraisal Handbook, Region 6 Chapter. 416-482, 100 p.
69
APPENDICES
70
Appendix 1
Profiles of Skyline Roads Studied
Scale 1" = 130 feet (1 cm = 16 m)
2
1
a
7
a
I
a
9
(5)
7
(6)
2
I
2
3
1
* Intermediate supports used
71
Appendix 2
Hewlett Packard 9830 Computer Program
to Calculate Estimated Production per Hour (cubic feet)
Under Varying Conditions
3
.'i
4'
,:33,jL2)
11;iqr
:.::.:I
,7,:3...
'J
R:..:I3
LEL
F'
PLT
T
::::=1J T
i':'
TE
CLOT -i-2
Lt LtBEL
t
NE::1
ii
=
L21 PL31 i,
1
i43
-'U ,37P
1
L.5-3.3
CPLO
PLOY L:,It,t
i TGE .HTi_
t:E:i L9EL
L.2. L.79.3.i..'
t?i LCT L'L4.:
_tii _-i'_ fl rT I I1
l
11 ?SL
i
I
r
rtt.
L-
1
.i..:
T:i
24
h'CJT'
2$cj .t4PtJT '4
P
27
P
Z T!, JL
INF'JT PL1D
3ii FC..:!O
.J:3
291 FOP L.L
:21 ..1&d*F"
-
flil t -'-
i
2Ft'L1
"
'
:..
_
T1jPi
Z)
:T?
=4:4L)
..4:333
:
LI
9L
+
+
C=L... #4.
3
' F11AT 4
.1
4:
4t
- L
LT
LL
47Zi L.EL
5Li
L.
::r L
4i OF..OT :i.:. -cj..
49k)
4
t
i::i
LiTTP
1.
t.Th
.......2:
.
¶
F
r =
W
IWW
Appendix
3.
=
Percent slope
0.55
0.26 lbs/ft
IEL1
PJ1ø
2ø
'-tI1Ii
IL1
WI
L1JFE tITRr'ICE (FT.)
9SW
SWW
Ek1
Line Pulling Force as a Function of Slope Distance and Percent Slope
(standard units)
EiWkl
Percent slope2
r = 0.55
W
0.39 kgs/m.
LIIti
2L1
9LI
3t1
EiLl
7S
E114
12L1
tJ5
IEiE
IF11
5LEJPE DLTHNCE CM.)
Appendix 3a.
Line Pulling Force as a Function of Slope Distance and Percent Slope (metric unit)
74
Appendix 4
Daily Cost - TrailerAlp Yarder
New Cost
(NC)
$46,000
Resale (4 yrs, 25 percent) (S.V.)
Net Cost
11,500
$34,500
Average investment = (NC + Dep. + S.V.)
2
Fixed Costs
Depreciation (Dep.)
$ 8,625
Interest (12 perc2nt of average investment)
3,967
Insurance (2 percent of average investment)
66
Taxes, etc. (4 percent of average investment)
1,332
14, 585
Operating Costs
Repairs and Maintenance (50 percent of depreciation)
$ 4,312
Tires
50
Hydraulic Oil
200
Rigging
S/L 900' of 5/8
x $.667/ft.
600
M/L 1800' of 3/8h1 x $.392/ft.
706
H/B 1800' oq 3/8" x $.392/ft.
706
Chokers, 20 at $20
400
Tools and Miscellaneous
300
$ 7,274
Total Annual Cost
$21 ,859
Total Daily Cost (at 220 days per year)
$
99.36
75
Appendix 5
Daily Cost - John Deer 2640 Farm Tractor
New Cost
sis,000
Resale (8 yrs, 10 percent of NC)
1,800
$16,200
Average investment = $10,912
Fixed Costs
Depreciation
$ 2,025
Interest (12 percent of average investment)
1,309
Insurance (2 percent of average investment)
218
Taxes, etc. (4 percent of average investment)
437
$ 3,989
Operating Costs
Fuel - 220 days x 6 hrs, x 1 gal. x 5Ot
660
Oil and Lubrication
300
Repairs and Ma.intenanc
(50 percent of depreciation)
1 ,013
Tires
200
$ 2,173
Total Annual Cost
$ 6,162
Total Daily Cost
$
28.01
76
Appendix 6
Daily Cost - Crew Transportation
3Man
4Man
Crew
Crew
$5,000
$7,000
2,500
3,500
Net Cost
$2,500
$3,500
Average Investment
$4,166
$5,833
833
$1,167
Interest (12 percent of average investment)
500
700
Insurance (2 percent o-P average investment)
83
117
167
233
$1,583
$2,217
Fuel - 80 mls x 15 mpg x 220 dys x 65t/gal. $ 763
$1 ,144
New Cost
Resale
Fixed Cost
Depreciation
$
Taxes (4 percent of average investment)
Variable Costs
Repairs and Maintenance (50 percent of
depreciation)
833
1,167
Oil and Lubrication
150
200
Tires
240
280
$1 ,986
$2,791
Total Annual Cost
$3,569
$5,008
Dafly Cost
$
16.22
$
22,76
77
ADpendix 7
Daily Cost - Chainsaws
Each
$400
New Cost
Resale (1 yr)
$400
Net Cost
Average Investhient = $400
Fixed Costs
$400
Depreciation
Interest (12 percent of average investment)
48
Insurance (2 percent of average investment)
8
16
Taxes (4 percent of average investment)
$472
Operating Costs
$400
Repairs and Maintenance (100 percent of
depreci ati on)
Fuel
1
gal/dy x 220 dys x S5
121
011
1
pt/dy x 220 dys x 75t
165
Chain
9 chains x $20
180
$866
Total Annual Costs
$1 ,348
Daily Costs
$
6.13
78
Appendix 8
Daily Cost - Radio "Talkie Tooter'
New Cost
$3,500
Resale (5 yrs)
New Cost
Average Investment
$3 , 500
$2,100
Fixed Costs
$
Depreciation
700
252
Interest (12 percent of average investment)
42
Insurance (2 percent of average investment)
84
Taxes (4 percent of average investment)
$1 ,078
Variable Costs
Batteries, etc.
$
Repairs and Maintenance
5J
100
$
150
Total Annual Cost
$1 ,228
Daily Cost
$
5.58
79
Appendix 9
Determination of Production and Cost Data
for a Three Man Logging Crew
Assumptions
Average yarding distance
250 feet (76 metres)
Average lateral distance = 35 feet (11 metres)
Felling productivity = 12 logs per man hour
Faller assists chokersetter for final 10 percent of the road
One road in three requires a multispan
Multispans are pre-rigged by the faller with a total time
lost of 1 hour, 15 minutes
Net Productivity of Faller
Gross productivity (8 hour day) = 12 logs per hour
Yarder production per day = 1400 cubic feet (40 cubic metres)
= 109 flieces
= 13.6 pieces per hour
No. of pieces per road
231
A road change is required every 2.12 days
Time faller must spend chokeretting = 0.80 hours per day
Time faller must spend rigging
0.20 hours per day
Time faller must spend on road changing = 0.99 hours per day
Non-productive time
0.80 + O2O + 0.99
Production per day (8 hours) = 72 logs
- 1.99 hours per day
t
80
Net Daily Production of Yarder
Yarder will log above production in 5.3 hours
Time left = 8 - 5.3 - 2.7 hours
To balance this time between yarding and cutting:
Let x = no. a-P hours falling by machine operator and
chokers etter
Then 12 x
13.6 (2.7 - x)
x = 1.43 hours
i.e., the yarder operator and chokersetter must fall 1.43 hours per
day to provide logs for an additional 1.3 hours per day yarding.
Total yarding time = 5.3 + 1.3
6.60 hours
Net daily production = 1158 cubic feet (33 cubic metres)
Yarding Cozts
The fixed and variable costs for the yarder and tractor are
revised to reflect the reduced working time.
The resale value of the machines is increased by 15 percent and
the variable costs are reduced 1.5 percent.
-i
81
Appendix 10
Net Production Rate for a Four Man Crew
Gross Yarder Production = 109 pieces
Cutting Production =
1
man full time
1
man (as for 3 man crew)
12 x 8
96 pieces
72 pieces
169 pieces
i.e., felling capacity exceeds yarding capacity.
The net yarding
capacity can be derived directly using HP 9830 program.
82
Appendix 11
Table of Gross Time Measurements
of Felling and Bucking Productivity
Record No.
Time On
Time Off
No. of
Mins.
No. of
Logs
Logs per
Man Hour
1
7-10
11-30
260
54
12.5
2
7-30
11-30
240
41
10.3
3
3-15
11-30
255
37
8.7
4
3-15
11-20
245
42
10.3
5
3-00
4-30
90
9
6.0
6
3-30
4-46
196
42
12.9
7
12-36
4-46
250
41
9.8
8
9-00
11-30
150
24
9,6
9
7-45
11-30
225
28
7.5
1 0
1 2-15
5-00
285
51
1 0 7
11
7-15
11-30
465
55
7.1
12-00
3-30
12
8-00
11-25
205
46
13.5
13
3-15
5-50
135
17
7.6
n = 13
Mean logs/hr = 9.73
SE = 0.645
= 5.0% of mean