Games - Chainsaw

	Games - Chainsaw

A chainsaw (also spelled chain saw) is a portable mechanical, motorized saw. It is most commonly used in forestry activities such as logging and tree thinning; by tree surgeons to fell trees and remove branches and foliage; and to harvest firewood. Chainsaws with specially designed blades have been developed as tools for use in chainsaw art.

Construction

Chainsaws consist of a small two-stroke gasoline (petrol) internal combustion engine (although smaller versions sometimes use electric motors), the "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 saws the teeth are not straight blades; they have a forward section which 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. The underside of each link features a small metal finger which keeps the tooth centred 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 at a high speed, providing an effective (if rather rough) cutting action.

Maintenance

Chainsaws usually 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. Since this mixture is highly flammable, a completely separate oil reservoir is used for the external lubrication of the blade and chain. This latter oil is depleted quickly because it tends to be thrown off the chain by centrifugal force. Failing to keep this reservoir topped up, or using an oil of incorrect viscosity, is a common source of damage to saws and tends to lead in the chain coming off of 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.

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 it with petrol: use fuel that has not yet had oil added—otherwise the residual oil on the filter will make it clog up again faster.

Chains must occasionally be removed from the saw for sharpening. This may be done lightly in the field with a round file, or more thoroughly with a specialised electric sharpening jig. The jig helps ensure that each cutting face is kept at the correct angles, which are carefully balanced to maximise the saw's efficiency. A common error is to reassemble the saw with the teeth facing back-to-front, which naturally considerably reduces its cutting power. Carbide chainsaw blades cannot be sharpened by conventional sharpeners and must be sharpened by a certified chainsaw repairman.

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 near the bar tip cuts into wood without cutting through it. The chain cannot continue moving, and the bar is driven in an upward arc towards 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 as a large tree can weigh much more than an automobile. 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 are generally worn while operating them, and many jurisdictions require that operators be certified or licensed to work with chainsaws.

A fuller 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.

Accessories

Some saws can have the blade replaced by other attachments, using the saw's "power head" as their motor. The most common such attachments are augers and circular saws.

History

The origin is debated, but two important contributors to the chainsaw as we know it 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 , developed the world´s first gasoline-powered chainsaw and mass-produced them.

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