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6-wheeled Valmet harvester

Small 4-wheeled Rottne harvester

Timberjack harvester

John Deere harvester in Sweden

A harvester is a type of heavy forestry vehicle employed in cut-to-length logging operations for felling, delimbing and bucking trees. A forest harvester is typically employed together with a forwarder that hauls the logs to a roadside landing.

History[link]

Forest harvesters were mainly developed in Sweden and Finland 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 1973^[1] by Finnish systems engineer Sakari Pinomäki 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 of plantation 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 30 inches in diameter was developed in the US called The Mammoth Tree Shears. The operator after shearing off the tree could with the movement of his controls cause it to fall either to the right of left. Unlike a harvester, it did not delimb the tree after felling it.^[2]

Uses[link]

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

The leading manufacturers of harvesters are Timberjack (owned by John Deere), Valmet (owned by Komatsu) and Ponsse.

Harvesters are built on a robust all terrain vehicle, either wheeled or tracked. The vehicle may be articulated to provide tight turning capability around obstacles. A diesel engine 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[link]

Harvester head

Harvester head, chainsaw visible

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

• a chain saw to cut the tree at its base, and also cut it to length. The saw is hydraulically powered, rather than using the 2-stroke engine of a portable version. It has a more robust chain, and a higher power output than any saw that can be carried by a human.
• 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 tree to be embraced by the harvester head, 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.

All of this can be controlled by one operator sitting in the cab of the vehicle. 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 900 mm in diameter, built on vehicles weighing up to 20 t, with a boom reaching up to 10 m radius. Larger, heavier vehicles do more damage to the forest floor, but a longer reach helps by allowing more trees to be harvested with fewer vehicle movements.

The approximate equivalent type of vehicle in full-tree logging systems are feller-bunchers.

External links[link]

Media related to Harvesters (forestry) at Wikimedia Commons

• Harvester on the Ritchiewiki

References[link]

1. ^ Rihko Haarlaa: Organization and technology of wood harvesting in Finland. Department of Forest Resource Management, University of Helsinki, Finland. 1992.
2. ^ "Paul Bunyan Scissors." Popular Science, July 1946, p. 83.

Look up harvester in Wiktionary, the free dictionary.

Harvester can refer to:

Agriculture and forestry[link]

• a person involved in the process of harvesting crops, either manually or with the help of machines
• different agricultural machinery
  • Combine harvester, a machine commonly used to harvest grain crops
  • Forage harvester, a machine used to harvest forage
  • Other harvesting machines - see List of harvesters
• Harvester (forestry), a type of heavy vehicle employed in cut-to-length logging of trees

Biology[link]

• Miletinae, a subfamily of butterflies commonly called the harvesters
• Feniseca tarquinius, a species of butterflies commonly called the harvesters

Arts[link]

• Harvester (publisher), a book publisher dealing in literary criticism and cultural studies based in Brighton, Sussex
• The Harvesters (painting), a wood painting by Pieter Bruegel in 1565
• The Harvesters (band), Swedish alternative country band

Information technology[link]

• Bioinformatic Harvester, a bioinformatic meta search engine
• Harvester (web), or web harvesting, a tool to download websites
• Harvester (video game), a computer adventure game

Places[link]

• Harvester, Missouri an unincorporated community in St. Charles County
• Burr Ridge, Illinois, by former name

Companies[link]

• International Harvester, a former agricultural machinery company
• Harvester (restaurant), a British restaurant chain

Other[link]

• Harvester, a fictional large machine in the 1965 novel Dune by Frank Herbert - see Dune terminology
• Träd, Gräs och Stenar, formerly International Harvester and Harvester, a Swedish progg band
• Harvester Judgment, a 1908 Australian High Court case that established the concept of a minimum wage
• HMS Harvester (H19), a destroyer
• Harvester (metal band), a melodic black metal band from Singapore
• Harvester (horse), winner of the 1884 Epsom Derby

See also[link]

• Theristai, a lost satyr play by Euripides, aka as Reapers or Harvesters

See also[link]

• All pages beginning with "Harvester"
• All pages with titles containing "Harvester"

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