A harvester is a type of heavy forestry vehicle employed in

cut-to-length logging Cut-to-length logging (CTL) is a mechanized harvesting system in which trees are delimbed and ''cut to length'' directly at the stump. CTL is typically a two-man, two-machine operation with a harvester felling, delimbing, and bucking trees and ...

operations for

felling Felling is the process of cutting down trees,"Feller" def. 2. and "Felling", def. 1. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) © Oxford University Press 2009 an element of the task of logging. The person cutting the trees ...

delimbing Limbing or delimbing is the process of removing branches from a standing or fallen tree trunk. In logging, limbing follows felling. Limbing plays a role in fire prevention by removing branches from live trees that can otherwise serve as part ...

and

bucking Bucking is a movement performed by an animal in which it lowers its head and raises its hindquarters into the air while kicking out with the hind legs. It is most commonly seen in herbivores such as equines, cattle, deer, goats, and sheep. Most r ...

trees In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are u ...

. A forest harvester is typically employed together with a

forwarder A forwarder is a forestry vehicle that carries big felled logs from the stump to a roadside landing. Unlike a skidder, a forwarder carries logs clear of the ground, which can reduce soil impacts but tends to limit the size of the logs it c ...

that hauls the logs to a roadside landing.

History

Forest harvesters were mainly developed in Sweden and

Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...

and today do practically all of the commercial felling in these countries. The first fully mobile timber "harvester", the PIKA model 75, was introduced in 1973Rihko Haarlaa:
Organization and technology of wood harvesting in Finland.
' Department of Forest Resource Management, University of Helsinki, Finland. 1992. by Finnish systems engineer

Sakari Pinomäki Sakari Pinomäki (1933–2011) was a Finnish systems engineer and an inventor, who pioneered the mechanized forestry industry. He was the founder of PIKA Forest Machines which produced the first purpose-built forest machine in 1964 in Ylöjärvi ...

and his company PIKA Forest Machines. The first single grip harvester head was introduced in the early 1980s by Swedish company SP Maskiner. Their use has become widespread throughout the rest of Northern Europe, particularly in the

harvesting Harvesting is the process of gathering a ripe crop from the fields. Reaping is the cutting of grain or pulse for harvest, typically using a scythe, sickle, or reaper. On smaller farms with minimal mechanization, harvesting is the most labor- ...

plantation A plantation is an agricultural estate, generally centered on a plantation house, meant for farming that specializes in cash crops, usually mainly planted with a single crop, with perhaps ancillary areas for vegetables for eating and so on. The ...

forests. Before modern harvesters were developed in Finland and Sweden, two inventors from Texas developed a crude tracked unit that sheared off trees at the base up to in diameter was developed in the US called The Mammoth Tree Shears. After shearing off the tree, the operator could use his controls to cause the tree to fall either to the right or left. Unlike a harvester, it did not delimb the tree after felling it."Paul Bunyan Scissors."
''Popular Science'', July 1946, p. 83.

Uses

Harvesters are employed effectively in level to moderately steep terrain for clearcutting areas of forest. For very steep hills or for removing individual trees, humans working with

chain saw A chainsaw (or chain saw) is a portable gasoline-, electric-, or battery-powered saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. It is used in activities such as tree felling, limbing, bucking, pruning, ...

s are still preferred in some countries. In northern Europe small and manoeuvrable harvesters are used for

thinning Thinning is a term used in agricultural sciences to mean the removal of some plants, or parts of plants, to make room for the growth of others. Selective removal of parts of a plant such as branches, buds, or roots is typically known as pruning. ...

operations, manual felling is typically only used in extreme conditions, where tree size exceeds the capacity of the harvester head or by small woodlot owners. The principle aimed for in mechanised logging is "no feet on the forest floor", and the harvester and forwarder allow this to be achieved. Keeping humans inside the driving cab of the machine provides a safer and more comfortable working environment for industrial scale logging. Harvesters are built on a robust all terrain vehicle, either wheeled, tracked, or on a

walking excavator A walking excavator or popularly spider excavator is a special type of all-terrain excavator. Like the regular excavator it consists of a boom, stick, bucket and cab on a rotating platform known as the "house". However, its house sits atop an u ...

. The vehicle may be articulated to provide tight turning capability around obstacles. A

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-ca ...

provides power for both the vehicle and the harvesting mechanism through hydraulic drive. An extensible, articulated boom, similar to that on an excavator, reaches out from the vehicle to carry the harvester head. Some harvesters are adaptations of excavators with a new harvester head, while others are purpose-built vehicles. "Combi" machines are available which combine the felling capability of a harvester with the load-carrying capability of a forwarder, allowing a single operator and machine to fell, process and transport trees. These novel type of vehicles are only competitive in operations with short distances to the landing.

Felling head

A typical harvester head consists of (from bottom to top, with head in vertical position) * a

to cut the tree at its base, and cut it to length. The saw is hydraulically powered, rather than using the

2-stroke engine A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...

of a portable version. It has a stronger chain and a higher power output than any saw a person can carry. * two or more curved delimbing knives which reach around the trunk to remove branches. * two feed rollers to grasp the tree. The wheels pivot apart to allow the harvester head to grasp the tree and pivot together to hug the tree tightly. The wheels are driven in rotation to force the cut tree stem through the delimbing knives. * diameter sensors to calculate the volume of timber harvested in conjunction with * a measuring wheel which measures the length of the stem as it is fed through the head. One operator in the vehicle's cab can control all of these functions. A control computer can simplify mechanical movements and can keep records of the length and diameter of trees cut. Length is computed by either counting the rotations of the gripping wheels or, more commonly, using the measuring wheel. Diameter is computed from the pivot angle of the gripping wheels or delimbing knives when hugging the tree. Length measurement also can be used for automated cutting of the tree into predefined lengths. Computer software can predict the volume of each stem based on analysing stems harvested previously. This information when used in conjunction with price lists for each specific log specification enables the optimisation of log recovery from the stem. Harvesters are routinely available for cutting trees up to in diameter, built on vehicles weighing up to , with a boom reaching up to radius. Larger, heavier vehicles do more damage to the forest floor, but a longer reach helps by allowing harvesting of more trees with fewer vehicle movements. The approximate equivalent type of vehicle in

full-tree logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...

systems are

feller-buncher A feller buncher is a type of harvester used in logging. It is a motorized vehicle with an attachment that can rapidly gather and cut a tree before felling it. ''Feller'' is a traditional name for someone who cuts down trees, and ''bunching'' ...

Manufacturers

*NEUSON Forest * Rottne * Logset *EcoLog *Kone Ketonen *AFM-Forest *Barko Hydraulics * Caterpillar * Komatsu Forest *

Ponsse Ponsse Plc ( fi, Ponsse Oyj) is a company domiciled in Vieremä, Finland, a forest machine manufacturer run by the Vidgrén family. Ponsse manufactures, sells and maintains cut-to-length forest machines such as forwarders and harvesters and a ...

*SP Maskiner *Tigercat * Timberjack (owned by John Deere) * Kesla Oyj *Prosilva *Sampo-Rosenlew

References

External links

Harvesters specs
{{Authority control Engineering vehicles Logging Forestry equipment