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