Cable Yarding How it works…. Rien Visser, Virginia Tech.
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Transcript of Cable Yarding How it works…. Rien Visser, Virginia Tech.
Cable Yarding
How it works….
Rien Visser, Virginia Tech
Problem: Extraction of trees on steep terrain
stems
waterway
- suspend wire rope across the slope (skyline)
stems
skyline
Wire Rope (cable)Function: provides the elements of a rigging system to pull
the stems from the forest to the landing
Strand
Inner wire
Core
Rope
Steel Core
Strand
Right hand ordinary lay6 x 19
- Suspend cable from tailtree (or tailhold) and a yarder
stems
skylinetailhold
yarder
Yarder Types
Yarders
Mobile Stationary
IndependentSteel tower/spar,
wooden tower/spar, steel lattice work.
Integral SwingSteel lattice work.
Excavator type yarder.
IntegralSteel tube or steel lattice
work. Either vertical
or leaning.
TowerFunction: Keeps the cable off the ground and
provides lift to the stems, especially near the landing
• Independent or integrated
• Small (30ft), medium (60ft), large (90ft)
• Wooden spar, steel tower or lattice tower
• One-piece, folding or telescoping
CarrierFunction: support yarder equipment and allows transportation
• Tracked, tires or skid• Self-propelled, towed or carried/pulled• Mounting for power-train
- add a carriage, mainline and drums
stems
skylinetailhold
yarder
mainline and carriage
drums (winches)
CarriagesFunction: runs on the skyline to get the chokers out to the
cut-over and the logs back to the landing • simple single or double sheaves
(blocks)• slack-pulling capabilities
– hand, mechanical or motorized
Winches (drums) / BrakesFunction: transfers the power from the power-train to the cables to do the work
• Mechanical or hydraulic winches
• Water or air cooled brakes• Drum stores the cable• 1 – 5 working winches on
a yarder
- add chokers, choker-setter and operator
stems
skylinetailhold
yarder
mainline and carriage
choker-setter
operator
Cab / ControlsFunction: to safely ‘house’ the operator and control
the operation of the yarder
• Houses the operator– protection from external environment– clear vision of operating area
• Controls the yarder– ‘Old/simple’:
Mechanical levers– ‘New/modern’: Electronic
switches and hydraulic levers
- complete system, ready to work…..
stems
skylinetailhold
yarder
mainline and carriage
choker-setter
operator
- how does it work…..
stems
skylinetailhold
yarder
choker-setter
operator
- let carriage out…..
stems
skylinetailhold
yarder
choker-setter
operator
- stop carriage above stems…..
stems
skylinetailhold
yarder
choker-setter
operator
- choker-setter hooks up the stems…..
skylinetailhold
yarder
choker-setter
operator
- choker setter moves away…..
skylinetailhold
yarder
choker-setter
operator
- operator raises the stems…..
skylinetailhold
yarder
choker-setter
operator
- pulls towards landing…..
skylinetailhold
yarder
choker-setter
operator
- drop stems on landing…..and starts over again….
skylinetailhold
yarder
choker-setter
operator
Yarder on the landing
Yarder on Roadside
• Limited stacking area• Bell-logger or crane mounted on yarder• Self-loading trucks on regular schedule
Effective yarder operation
• Its one thing to run one,
another to operate it effectively….
• ‘D’eflection
• ‘D’eflection
• ‘D’eflection
Three D’s of productive cable logging
• More deflection: – more payload – same cable tension
skylinetailhold
yarder
choker-setter
operator
Planning !!!!
Unit 1
Unit 2Unit 3
Cable Landing
Unit 1
Unit 2Unit 3
Cable Landing
Landing Layout• Cable layout
– direction of pull
– guyline location and anchoring
• Machinery layout– yarder location on the landing
– other machinery on the landing
– location of timber stacks
– processing area
– loading out area
Felling pattern• ‘Headpulls’ reduces productivity by 15%• Fell trees at an angle to the skyline
= 30 + slope (degree)– 20 degree slope - fell at 50 degrees
– 40 degree slope – fell at 70 degrees
Yarder
Skyline Felling direction
Yarder Business Management– Daily production chart
0
50
100
150
200
1 3 5 7 9 11 13 15 17 19 21 23
Working Days
Target
Average
Number of Chokers?
More chokers means:• greater ave drag volume
• more tangled strops
• increased risk of overloading
0
10
20
30 Max
Min
• Direct and significant influence on:
Human Performance ?
• System implementation and use• Machine productivity• Mechanical and operational delays• Innovation
Learn-Curve Effect• Takes a new employee about 3 months to get to ‘100%’
– Training helps – also increases potential
– Basic cost of new employee estimated at $2500 - $7500
Learn Curve Effect
40
50
60
70
80
90
100
110
0 2 4 6 8 10 12 14
Weeks of Work
Ne
w E
mp
loy
ee
Pro
du
cti
vit
y (
%)
Value of human performance? Yarder operator = $12 / hrYarder costs = $110 / hrTimber Value = $1,000 / hr