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 tree stump, stump. CTL is typically a two-man, two-machine operation with a harvester (forestry), harvester felling, d ...

operations for

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

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

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 ...

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, e.g., including only woody plants with secondary growth, only p ...

. A forest harvester is typically employed together with a

skidder A skidder is any type of heavy vehicle used in a logging operation for pulling cut timber, trees out of a forest in a process called "skidding", in which the logs are transported from the cutting site to a landing. There they are loaded onto t ...

that hauls the logs to a roadside landing, or a

forwarder A forwarder is a forestry vehicle that carries big felling, felled Timber, logs cut by a Harvester (forestry), harvester from the stump to a roadside landing for later acquisition. Forwarders can use rubber tires or tracks. Unlike a skidder, a ...

to pick up and haul away. Feller buncher-2

History

Forest harvesters were mainly developed in

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

and

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

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 collecting plants, animals, or fish (as well as fungi) as food, especially the process of gathering mature crops, and "the harvest" also refers to the collected crops. Reaping is the cutting of grain or pulses fo ...

plantation Plantations are farms specializing in cash crops, usually mainly planting a single crop, with perhaps ancillary areas for vegetables for eating and so on. Plantations, centered on a plantation house, grow crops including cotton, cannabis, tob ...

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 Clearcutting, clearfelling or clearcut logging is a forestry/logging practice in which most or all trees in an area are uniformly cut down. Along with Shelterwood cutting, shelterwood and Seed tree, seed tree harvests, it is used by foresters t ...

areas of forest. For very steep hills or for removing individual trees, ground crews working with

chain saw A chainsaw (or chain saw) is a portable handheld power saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. Modern chainsaws are typically gasoline or electric and are used in activities such as tree fell ...

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

thinning In agricultural sciences, thinning is 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''. In forestry ...

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 The forest floor, also called detritus or wikt:duff#Noun 2, duff, is the part of a forest ecosystem that mediates between the living, aboveground portion of the forest and the mineral soil, principally composed of dead and decaying plant matter ...

", and the harvester and forwarder allow this to be achieved. Keeping workers 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

wheel A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machin ...

ed, tracked, or on a

walking excavator The term walking excavator may apply to two different forms of heavy equipment, the historic walking power shovel or dragline excavator that began to appear already early in the 20th century, or the contemporary version of all-terrain excavator ...

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

diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...

provides power for both the vehicle and the harvesting mechanism through hydraulic drive. An extensible, articulated boom, similar to that on an

excavator Excavators are heavy equipment (construction), heavy construction equipment primarily consisting of a backhoe, boom, dipper (or stick), Bucket (machine part), bucket, and cab on a rotating platform known as the "house". The modern excavator's ...

, 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 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

, 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 systems are feller-bunchers.

Manufacturers

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

Caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...

* Komatsu Forest * Ponsse *SP Maskiner *Tigercat * Timberjack (owned by

John Deere Deere & Company, Trade name, doing business as John Deere (), is an American corporation that manufactures agricultural machinery, heavy equipment, forestry machinery, diesel engines, drivetrains (axles, Transmission (mechanical device), transmi ...

) * Kesla Oyj *Prosilva *Sampo-Rosenlew

References

External links

Harvesters specs
{{Authority control Engineering vehicles Logging Forestry equipment