Equipment Specs
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Forestry Equipment
Equipment Specifications - RitchieSpecs
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Harvester with chained wheels
A harvester is a portable, multi-functional mechanized felling machine used in the forestry industry that cuts, delimbs, and bucks trees. It is more commonly used in cut-to-length logging operations and works in conjunction with a forwarder that transports logs from the felling site to a landing. In recent years, there has been a tendency to move away from whole-tree harvesting towards cut-to–length harvesting. While cut-to-length harvesting is more expensive, it has a reputation for being a more environmentally friendly practice.[1]

Harvesters are used on a wide scale for the harvesting of plantation forests and clearcutting forests and in thinning operations. The are predominant fixtures in Europe’s forestry sector, particularly in Sweden and Finland, where they handle the majority of both those countries' commercial felling.


[edit] History

[edit] Rudy Vit’s Bomardier Harvester

The development of harvesters started in 1957 when Rudy Vit, a young engineering student in Czechoslovakia, was engaged in a project with Bombardier and the North Shore Paper Co. to design a mechanized timber-harvesting machine. His machine made creative use of two recent inventions at the time—hydraulics and chainsaws. The unit consisted of a compact unit mounted on a Bombardier HDW coupled with two chain saws mounted on the front. One saw made an undercut and the other severed the tree held by a hydraulic power-driven head. The tree was then lowered over the machine and placed on rear rack that could hold several trees at once. Approximately 11 units were built over nine years and showcased the potential for a machine that could fall, accumulate and skid a whole turn of trees to the roadside. As a full-tree harvester, his machine was a decade ahead of its time.[2]

Over the next decade, the development of harvesters focused primarily on shortwood harvesters that could fall, delimb, and buck trees into short lengths in order to meet the demands of a growing pulpwood industry.

[edit] John Pope’s Crawler Tractor Harvester

A year after Vit built his first harvesting machine, John Pope designed another harvester at North Western Pulp & Power’s Hinton, Alberta operations. He chose to mount a hydraulic-powered falling head to a crawler tractor. The head was very similar to Vit’s. It grasped the tree while a chainsaw cut it off. The machine then rotated the tree into a horizontal position to be delimbed before pushing the tree back through the falling head to be bucked. One drawback of both Vit and Pope’s machines was that they both had to drive right up to the tree in order to fall it, resulting in poor production rates.

[edit] The Timberbuncher

In 1959, Jack Boyd of Timberland Machines designed a harvesting machine that inherently addressed this problem. The Timberbuncher was a turntable mounted on a tracked undercarriage and used a knuckleboom with a grapple and a saw to fall and pile the trees into bunches. The falling device was of particular interest as it utilized a hydraulic cylinder to force wire rope through the tree. Despite this, no forest companies wanted to finance the development of his harvester. Eventually the knuckleboom concept for a harvesting machine would be introduced to market in later years. Boyd’s machine was simply introduced a decade too early for the industry.

[edit] The Beloit Harvester

In 1963 Bob Larson, on behalf of the Ontario-based Marathon Paper Mills, developed the Beloit Harvester. His machine also addressed the weaknesses presented in Vit and Pope’s machines. Larson’s version of a harvester was also mounted on a crawler tractor but it displayed one unique concept—a knuckleboom capable of reaching out from the tractor and delimbing the tree with knives, essentially topping and falling it with a shear, and then piling the tree to one side. Since the harvester was being built to handle larger timber, over time it grew to a size that made it too bulky, eventually rendering it useless. It did however garner a lot if interest at the onset. Over a span of 10 years, 40 units were built.

[edit] The Busch Combine

Designed by Tom Busch in 1959, the Busch Combine was a harvester built to work in drier southern pine forests. This machine was built on an articulated, rubber-tired tractor. It drove directly up to tree and cut it with shears before placing the tree in a carriage to be delimbed and bucked. The cut logs descended into a cradle and tied into one-cord bundles that were then ejected from the machine and picked up by a forwarder. He even designed a forwarder called a Busch Loader to complement his harvester. Busch’s machine had many amicable features and qualities. It was affordable to maintain, could travel on public roads, was highly mobile, and cost less to manufacture than tracked machines. It also possessed the most efficient set of shears on the market at that time. The harvester generated a great deal of interest amongst loggers and spurred the development of number of other harvesters.[3]

[edit] Koehring-Waterous Harvester

Upon it’s entry into the logging industry into the 1960s, Koehring-Waterous obtained the rights to the Dowty rubber-tired forwarder and began working on a harvester using the Dowty chassis. The concept for the harvester was to be a unit that including a felling shear on a boom that reached out, severed a tree, and then held the tree upright for processing. The tree dropped into a processing head and was delimbed with the bucked-off logs being stored and then discarded from the machine in one-cord bundles. The machine was regarded one of the most successful harvesters of its kind.[4]

Throughout the 1960s, several other prototypes of harvesting machines would be developed and manufactured. These included the Windsor Tree Harvester, an Australian invention; an unsuccessful version of a harvester designed by Caterpillar that used a Model 950 front end loader to carry a falling, delimbing, and bucking attachment; the Woodsmobile harvester designed in 1966 by Bob Larson in cooperation with the Great Lakes Forest Industries; and a harvester developed by Timberjack in 1967.

[edit] Single-grip Harvester

The first single-grip harvester, the SP 21, was developed and manufactured by SP Maskiner in Sweden in 1983.[5]

[edit] How it Works

The capability of a harvester combines the functioning of a processor and feller buncher but without the ability to bunk or store logs and then forward the logs on to a roadside landing area. [6] A feller buncher fells and bunches up logs. A processor typically follows behind a feller buncher to pick up trees. The processor is a mobile machine that consists of a power plant, operator enclosure, and maneuverable articulating arm onto which a processing head is attached. Rollers on the processor pull the tree through to a clamp that removes tree branches. A saw in the processing head then cuts off the top of the tree. The machine pulls the delimbed tree through the processing head, halts at the desired length for cutting, cuts, and then repeats the entire process until all the trees in the pile left behind by the feller buncher are delimbed and cut to the appropriate lengths.

Harvesters are usually built on an all-terrain wheel or tracked vehicle that can maneuver on level ground and steep forest terrain. The vehicle may be articulated to provide tight turning capability around obstacles. A diesel engine typically powers the vehicle and the harvesting apparatus through hydraulic drive. An extensible articulated boom similar to that of an excavator carries the harvester head. In fact, some harvesters are adaptations of excavators with a new harvester head and others are built to be more multi-purpose machines.

[edit] Single-grip/ Double-grip Harvesters

There are currently two types of harvesters available on the market: single-grip harvesters and double-grip harvesters. Single-grip harvesters have tree-processing devices mounted on a single articulated boom. One of the drawbacks of single-grip harvesters is that the boom is not able to process another tree or be repositioned to process another tree after felling because the boom is also employed to delimb the tree.[7]
Double-grip harvesters, on the contrary, have only their tree felling mechanism mounted to the boom. This type of harvester consists of a tree delimbing assembly mounted in front of the vehicle and an articulated boom that includes a tree felling apparatus. After felling the tree, the boom moves the tree to the delimbing assembly. This enables the machine to immediately fell a second tree, while the first tree is being delimbed.[8]

[edit] Technological Advancements

Modern harvesters today are technologically advanced machines that employ the use high-speed saws and incorporate advanced hydraulic features in as much as 20 to 25 different functions including the crane, boom swing, grapple, stablizers, and harvesting heads. The use of hydrostatic drive is also the norm as opposed to mechanical drive. Harvester manufacturers are also developing machines with hi-tech computer control systems. More compact units are also in demand as a result of harvesters being used for more clearcutting and thinning operations.[9] On-the-job efficiency, increasing the machine’s productivity, and environmental concerns regarding soil erosion are spearheading these changes.

[edit] Common Manufacturers

[edit] References

  1. Korane, Kenneth. “Forest Machines Tread Lightly”. Machine Design. September 11, 1997. 59
  2. Drushka, Ken and Konttinen. Tracks in the Forest. Harbour Publishing: 1997. 117
  3. Drushka, Ken and Konttinen. Tracks in the Forest. Harbour Publishing: 1997. 118
  4. Drushka, Ken and Konttinen. Tracks in the Forest. Harbour Publishing: 1997. 119
  5. History. SP. 2008-09-28.
  6. Processor Harvester. OSHA. 2008-09-28.
  7. Tree Harvester. US Patent. 2008-09-28.
  8. Tree Harvester. US Patent. 2008-09-28.
  9. Korane, Kenneth. “Forest Machines Tread Lightly”. Machine Design. September 11, 1997. 59