Chainsaw
From Wikipedia, the free encyclopedia
A chainsaw (or chain saw) is a portable mechanical, motorized saw. It is most commonly used in logging activities such as felling, limbing, and bucking; by tree surgeons to fell trees and remove branches and foliage; to fell snags and assist in cutting firebreaks in wildland fire suppression, and to harvest firewood. Chainsaws with specially designed blades have been developed as tools for use in chainsaw art.
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[edit] Construction
A chainsaw consists of a small two-stroke gasoline (petrol) internal combustion engine (although smaller versions sometimes use electric motors), the "guide bar" (essentially a long metal frame of a very hard wearing alloy) and the cutting chain itself. Usually each segment in this chain (which is constructed from riveted metal sections similar to a bicycle chain, but without rollers) features a small sharp blade, called a "tooth." "Skip tooth" chain has a tooth only on every second link, and is used for reduced risk of the chain clogging when cutting very soft wood. In modern chainsaws the teeth are not straight blades; they have a forward section that first chips a piece of wood from the bottom of the cut, then another section, at a right angle to the first, which chips a piece from the wall of the cut. There are left and right-handed teeth, depending on which wall of the cut they will chip. Left and right teeth are alternated in the chain. Chains come in varying pitch and gauge; the pitch of a chain is defined as half of the length spanned by any three consecutive rivets (e.g., 0.325 inch), while the gauge is the thickness of drive link where it fits into the guide bar (e.g., 0.05 inch).
The underside of each link features a small metal finger that keeps the tooth centered between the rails of the bar, helps to carry lubricating oil around the bar, and engages with the engine's drive sprocket inside the body of the saw. The engine drives the chain around the track by a centrifugal clutch, engaging the chain at high speed but running free at lower speed. The chain on the lower side of the cutter bar is normally used for cutting, working towards the operator.
As chainsaws become more popular among home owners, chainsaw manufacturers are introducing features to make them easier to use. Stihl has developed an Easy2Start, or ErgoStart in Europe, system that uses a spring to overcome the engine's compression.[1] These saws usually start on one pull.
Women are increasingly becoming loggers and foresters. Husqvarna has developed a small saw easy to use for felling and bucking small trees and marketing it towards female foresters.[2] Stihl also sponsors and gives away saws to female chainsaw carvers to promote women in the forest industry.[3] Masters of the Chainsaw has an all-women carving demonstration team called the "Chainsaw Chix."[4]
As chainsaw carving has become more popular, chainsaw manufacturers are making special short, narrow-tipped bars for carving. These are called "quarter tipped," "nickel tipped" or "dime tipped" bars, based on the size of the round tip. Echo sponsors a carving series,[5] as well as carvers such as former Runaways singer Cherie Currie.[6] RedMax specifically built the G3200 CV chainsaw for carving applications.[7]
[edit] Maintenance
Most chainsaws require two sources of lubrication. Like most two-stroke engines, the engine is lubricated by its fuel, which contains about 2 – 5% (depending on model) oil dissolved in the fuel. Separate chain oil is used for the external lubrication of the bar and chain. The chain oil is depleted quickly because it tends to be thrown off the chain by centrifugal force, and it is soaked up by sawdust. The chain oil reservoir is usually topped at the same time as refuelling, and the reservoir is large enough so that the saw runs out of fuel and stops before the chain oil runs dry. Failing to keep the chain oil topped up, or using an oil of incorrect viscosity, is a common source of damage to saws, and tends to lead to rapid wear of the bar, or the chain jamming or coming off the bar. With some types of wood, the operator will need to occasionally stop and unplug the holes where the oil is dispensed to the chain and guide bar.
The air intake filter tends to clog up with sawdust. This must be cleaned from time to time, but is not a problem during normal operation. Many saw operators clean them with petrol, although manufacturers recommend using compressed air to blow the dust off the filter mesh from the inside, or washing in warm, soapy water, and then being left to air-dry. If these resources are not available, pure, clean gasoline should be used, otherwise the residual two-stroke oil on the filter will make it clog up again faster.
Chains must be kept very sharp to perform well, and become blunt very rapidly if they touch soil, metal or stones. When blunt, they tend to produce powdery sawdust, rather than the longer, clean shavings characteristic of a sharp chain; a sharp saw also needs very little force from the operator to push it into the cut. Sharpening[8] may be done with a round file or a sharpening jig (without removing the chain from the saw), or with a specialised electric jig with the chain removed from the saw. The jigs help ensure that the cutting faces are kept at the correct angles, which are carefully balanced to maximise the saw's efficiency. Proper hand-sharpening may produce a better result, but electric sharpeners are faster, particularly when sharpening very blunt chains. Carbide chains cannot be sharpened by conventional sharpeners and a diamond sharpener must be used.
[edit] Safety
Despite safety improvements, chainsaws can be dangerous, and injuries can arise from their use. The most common accident arises from "kickback", when a chain tooth at the upper quadrant of the guide bar tip cuts into wood without cutting through it. The chain cannot continue moving, and the bar is driven in an upward arc toward the operator. Kickback can result in serious injuries or death.
Another dangerous situation occurs when heavy timber begins to fall or shift when a cut is nearly complete - the chainsaw operator can be trapped or crushed.
Operation of chainsaws can also cause vibration white finger, tinnitus or industrial deafness. The risks associated with chainsaw use mean that protective clothing and hearing protectors should be worn while operating them, and many jurisdictions require that operators be certified or licensed to work with chainsaws. Injury can also result if the chain breaks during operation due to poor maintenance or attempting to cut inappropriate materials.
A more complete description of the design features built into chainsaws to enhance safety is given in the chainsaw safety features article. Personal protective equipment to be worn by chainsaw users is described at chainsaw safety clothing[9]
[edit] History
The origin is debated, but the first chainsaw was probably made around 1830 by the German orthopaedist Bernard Heine. This instrument, the osteotome, had links of a chain carrying small cutting teeth with the edges set at an angle; the chain was moved around a guiding blade by turning the handle of a sprocket wheel. As the name implies, this was used to cut bone.
Two important contributors to the modern chainsaw are Joseph Buford Cox and Andreas Stihl; the latter patented and developed a chainsaw in 1926 and a gasoline-powered chainsaw in 1929, and founded a company to mass-produce them. In 1927, Emil Lerp, the founder of Dolmar, developed the world's first gasoline-powered chainsaw and mass-produced them. McCulloch and Industrial Equipment Corp in North America started to produce chainsaws. The early models were heavy, two-person devices with long bars. Often chainsaws were so heavy that they had wheels like dragsaws. Other outfits used driven lines from a wheeled power unit to drive the cutting bar.
After World War II, improvements in aluminum and engine design lightened chainsaws to the point where one person could carry them. In some areas the skidder / chainsaw crews have been largely replaced by the feller buncher and harvester.
Chainsaws have almost entirely replaced simple man-powered saws in forestry. They come in many sizes, from small electric saws intended for home and garden use, to large "lumberjack" saws. Members of military engineer units are trained to use chainsaws.
[edit] Popular brands
- Echo
- Husqvarna AB
- Poulan
- Stihl
- homelite
[edit] In popular culture
In films and computer games, the chainsaw is used as a weapon or an instrument of murder or torture, most famously in The Texas Chain Saw Massacre and its sequels, as well as many subsequent films (such as Scarface, Deliria, and Halloween: Resurrection). Another major example is in the Evil Dead films, in which the protagonist (Ash Williams) wields a chainsaw attached in place of his severed hand to battle evil. The film Pulp Fiction features a character who considers using a chainsaw as a weapon. Video games that include a chainsaw as a weapon include the Doom series, the Xbox 360 game Gears of War (which features an assault rifle with a chainsaw bayonet), the Playstation 2 game Grand Theft Auto: Vice City, the GameCube and later released Playstation 2 game Resident Evil 4. Numerous bladed weapons in the Warhammer 40,000 universe have a chainsaw like variant such as the chainsword used prominently by the Space Marines. The chainsaw was also used by a boss in Dead Rising.
The chainsaw has also been used as a musical instrument by Jesse Dupree of the American rock band, Jackyl. In the recording of their song "The Lumberjack," Dupree would rev the chainsaw's motor either up or down to the beat. He would also perform this stunt live and the number would climax with Dupree slicing up a wooden stool onstage. Finnish punk rocker Maukka Perusjätkä used a Partner chainsaw as his instrument. In some concerts, rapper Eminem held a chainsaw while wearing a goalie mask reminiscent of Jason Voorhees in the Friday the 13th films.
A street performer in London's Covent Garden was banned in June 2007 for juggling live chainsaws.
[edit] See also
[edit] References
- ^ Stihl chainsaws
- ^ Husqvarna Outdoor Power Equipment
- ^ Example page of woman chainsaw carver
- ^ Masters of the Chainsaw - Chainsaw Competitions
- ^ ECHO Carving Series
- ^ Chainsaw carving page.
- ^ Masters of the Chainsaw - Chainsaw Competitions
- ^ Page describing need and methods for sharpening.
- ^ Chainsaw safety procedures.
