0 Chainsaws - what's new?

Chainsaws have become sophisticated machines with a range of specialist designs for large timber or climbing work. But, many of the developments have been geared towards improving the health and safety record of tree work and to making operation easier for occasional users.

Stihl.jpgStihl is now incorporating much of its advanced technology, first developed for foresters, into general purpose chainsaws such as the new MS 391, designed to tackle anything from fallen trees to fence posts. The company suggests that this would be an ideal choice for a golf course, with its 64.1cm3 engine and choice of 16-20in guide bars.

These include the 2-Mix engine designed to offer fuel consumption savings of up to 20 percent compared to a conventional two-stroke engine, lower emissions and improved performance.

The engine's four-port technology optimises fuel combustion to improve efficiency, while stratified scavenging reduces the scavenging losses typical of two-stroke engines, where unburned fuel emissions are emitted to the environment with the exhaust. The new technology injects a layer of clean air between the burned charge in the combustion chamber and fresh mix in the crankcase. What escapes as the scavenging loss with the exhaust emission is not fresh fuel mixture, but air. The exhaust, therefore, contains fewer pollutants.

A new long life air filter reduces maintenance by incorporating a pre-separation system that extends the service life of the air filter. The pre-separation system uses centrifugal force and a three-dimensional air flow to remove larger, heavier particles of dirt and route them away from the intake air, before they even get to the physical air filter. The largely particle-free air is then directed to the filter via a pre-separation channel.

Stihl's anti-vibration system uses a combination of Cellasto AV elements and special springs between the engine unit and handles to reduce the vibration caused by the engine and saw chain, even at high speeds. This is said to offer comfortable operation as well as improved guiding of the saw bar, enhanced by low vibration Stihl Comfort Saw chains fitted as standard.

An option is the Picco Duro (PD3) saw chain with a drive link thickness of 1.3mm and 3/8in pitch. This carbide tipped low profile saw chain is said to stay sharp up to four times longer than a standard saw chain while offering low vibration and low kickback properties. Stihl suggests that this chain is also ideal for the less experienced chainsaw user, or someone working with dirty wood such as fence posts or railway sleepers.

Husqvarna's latest developments include TrioBrake and AutoTune.

Husqvarna.jpgIn addition to the usual inertia mechanism and the front kickback guard, the chain brake can be triggered in a third way with Trio Brake. A new guard, which be activated by the user's right hand, has been added to the rear handle. Together, the three different modes form a brake system that can prevent injury in certain kickback and fall situations.

Trio Brake is said to be ideal for occasional users and those who have not used a saw before. It can also encourage a more ergonomic working posture, because if the user doesn't bend their knees when working and, instead, bends their back, the right hand is likely to trigger the chain brake.

The brake may be activated manually or automatically (during a kickback and during improper or dangerous use). Users have commented on benefits from improved safety, improved work techniques and efficiency, productivity and a reduction in physical strain, says Husqvarna.

AutoTune is a new technology that provides the saw with improved engine performance through an automatic engine setting function. This avoids wasting time on carburettor adjustments, as the saw automatically adjusts for different fuels, altitudes, humidity and temperature. It also compensates for clogged air filters, will regulate idle, low and high speed settings and comes with diagnostic technology.

The heavy duty 576XP AT chainsaw is the first of Husqvarna's chainsaws to feature Auto Tune, although it will be introduced as an option on other models in the future.

As well as AutoTune this saw features an X-Torq engine, designed to produce high torque over a wide rpm range, combined with low fuel consumption and reduced emission levels. Its low emissions technology is designed to use fuel more efficiently than a conventional two-stroke engine, the company suggests, with 20 per cent fuel savings and a 60 per cent reduction in emissions.

Makita.jpgMakita says that chainsaw safety is a fundamental element of the design and manufacturing its saws with three key safety factors: an efficient chain brake, a new easy-start system and low vibration levels.

Saws feature a forward finger guard and chain brake. When the operator shuts down the throttle completely, the clutch automatically slows the chain drive and stops the chain running. If the operator pushes the finger guard forward, the chain is mechanically halted immediately. The guard must be re-set before the chain will move again.

The new easy-start system featured on the latest DCS3501 and DCS4301 models provides a spring assisted cord action, said to reduce the cord effort by 50%. Coupled with a new variable ignition timing and push fuel pump, the new easy-start system is designed to ensure efficient first time starting which eliminates the risk of operator strain or accidental machine movement whilst starting.

In operation, Makita's 2-mass system effectively separates the grip handles from the body of the machine by mounting the handles on spring-fulcrums, designed to substantially reduce the transmission of vibration through the handles to the operator. For instance, the 50cc DCS5030 has tri-axial rating of 4.7m/sec2, reducing HAV risks.

PellencPolesaw.jpgAnother approach is the battery powered saws offered by Pellenc and distributed by Etesia. With a power output equivalent to 30cc, the Selion Pole and Telescopic chainsaws are fitted with an Oregon chain for accurate cutting. With a lightweight design and +90°/-45° angle adjustable head, the Selion Pole and Telescopic chainsaws allow vertical and horizontal cutting from the base of the tree. Pellenc chain guide bars are made from composite materials for torsional flexibility and to prevent breakage in case of accidental jamming.

Automatic chain tensioning features a simple 'click' from the spring when the guide bar is fitted, providing assurance that both the guide bar and chain are correctly tensioned. The chain can be removed and installed easily using a retractable spanner integrated in the head of the tool.

The retractable spanner is also used when the chain needs re-tensioning during cutting. Electronic oil flow control is said to give a 30 percent saving on oil compared with a typical petrol-engine chainsaw. Benefits of the Ultra lithium battery are odour and pollution free operation and a high working capacity.

Selion C15 and M12 electric chainsaws weigh in at 2kg and less than 1.7kg (excluding battery packs) with a power output equivalent to 35cc and 30cc respectively. An Oregon chain, composite guide bar, automatic chain tensioning and electronic oil flow control also feature on these saws. The Selion C15 and M12 have a direct drive chain sprocket rather than a clutch and gearbox for efficiency and reduced weight. An electronically-triggered kickback sensor instantaneously applies the electric chain brake in the event of a fall or kickback.

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