Machinery World: information on the mechanization
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Anno 2020 Numero 1-2

Focus
January - February 2020

Hand-held brushcutters

The landscape of brushcutters hand-held by the operator is very diverse, and many companies offer apparently similar products, but in reality they differ substantially, not only based on the power of the accessories, but also on the level of ergonomics and comfort, as well as polluting emissions

The brushcutter is a very useful tool not only to keep grass under control in the garden or in the areas near to the vegetable garden, but it can also be equipped with accessories that make it suitable for use in unexpected eclectic ways. In addition to different types of wires or blades for cutting also shrubs or brambles, it is often possible to replace the end part with small chain blades to use as telescopic chainsaws, or even with small hoes for the garden.

Last but not least there are also those offering the option to turn them into outboard engines for small boats. But apart from these digressions, and remaining in the classic areas of use connected to vegetation, it is good to know that in choosing the most suitable model for your needs, it is first of all beneficial to think about what you intend to do with this machine, identifying which will be its prevalent use. The first selection must be made based on the maximum power that the tool can supply. It is pointless to buy a large engine brushcutter to mow the grass on the edge of a small garden. It would not only prove too expensive to purchase, but also heavy (and therefore tiring) to handle and with higher fuel costs. In order to correctly guide your choice, you must take into account not only its main methods of use, but also the different technical characteristics, the quality of the machinery, as well as the reliability of the manufacturer and the retailer, i.e. those who will have to provide after-sales support and warranty service.

 

The engine and the power

The first feature that needs to be evaluated is the power and type of engine that will equip the machine. If up until 20 years ago the choice of a 2-stroke engine was almost inevitable, nowadays there are many alternatives. In addition to those solutions, several models equipped with 4-stroke engines have been introduced to the market. For the same power, they have the disadvantage of being a little heavier, but they have a lower fuel consumption, there is no need to prepare the mixture (except for the 4 mix models produced by Stihl), they are a little quieter, and they have much lower polluting emissions than their 2-stroke cousins. The only limit to the dissemination of these models is given by the fact that to date, 4-stroke engines do not deliver very much power (the Stihls reach almost 2 Hp, while Honda 35 cc engines top at 1.3 Hp and other engines with displacements between 25 and 31 cc provide powers of around 1 Hp).

At this point, it is worth emphasizing that, for example, many 2-stroke 25 cc engines supply power around 1 hp. With 2-stroke brushcutters with displacements in the order of 50-60 cc, the power involved is already in the order of 4-6 Hp, but there are some that go even further.

There are also electric brushcutters powered by the 220 V mains, which obviously require a connection cable to the socket, but many battery-powered models are now increasingly widespread. Electric wire brushcutters have drawbacks since they are connected by an electric cable. Moreover, they are generally not very powerful, and are recommended above all to maintain small trees near the house. The latest battery-powered models already offer interesting work capacities and good battery life, and also offer important advantages such as being much quieter than models with an endothermic engine, providing lower vibration levels, and above all having zero pollutant emissions due to on-site fuel combustion.

The only disadvantage of electric brushcutters at the moment is that there are no models on offer characterized by powers greater than 1-1.5 Hp, which are however more than sufficient both for the classic edges in domestic gardens and for mowing very tall grass in agriculture or in public parks, on the roadside etc. Another thing to consider is that it is useless to exaggerate with the power. During its operation, this tool will have to be controlled using your own muscular energy, so that tools that are too powerful, especially if used continuously for a long time, also become dangerous. Lastly, a more favourable torque curve compared to the endothermic cousins makes them more suitable for performing partial-load operations.

It is precisely for these reasons that more and more often, when choosing to buy a new professional machine, we turn to battery electric machines, relegating traditional propulsions to those uses where it is essential to operate often on large expanses and on very dense grass, for cutting brambles and small shrubs, or in any case when working in areas where the lack of electricity makes recharging the batteries difficult.

 

The transmission

For small trimmers equipped with low-power motors, the wire transmission may be sufficient, but for models intended for professional use it is undoubtedly safer and more reliable to look to the more widespread shaft drives with bevel gears near the cutting head. The situation is different for battery-powered machines, in which case there is no transmission since the brushless motor is not housed in the upper part of the machine, but near the ground and directly in the work head, being directly connected to the cutting device. In this case the batteries will be housed in the end part, also to act as a counterweight to the working head.

 

Reliability

Although electric motors are generally more reliable than endothermic ones, it is also essential to evaluate the useful life of the tool by choosing a tool with good mechanics. The reliability of the manufacturer brand is already an important guarantee in itself, but it is necessary to carefully evaluate the availability of spare parts over time and the availability of the support network, especially in a market increasingly inflated by the presence of imported products for which it is often very difficult to find even a trivial replacement.

 

The handle

The ideal brushcutter must be very comfortable to use, and must be equipped with a handle that is as ergonomic as possible. The light models can have a single handle, while the heavier ones require a double handle (commonly called "handlebar") to operate them better and more safely. We must also take into account the fact that it should offer both the option to adjust the working angle and to adjust the harness, adapting perfectly to your height and the way you work. The quality of the handle is assessed by testing the tool with the engine running, and it is essential that you feel little vibration while using it.

 

The backpack

If the choice should instead be directed towards backpack brushcutter, very comfortable for long tasks and working on slopes, in this case you will have the weight of the internal combustion engine conveniently allocated behind your back, so your arms won't need to support it; in any case, these are technical solutions for the more powerful models.

 

Weight

It is essential to take into account the weight of the equipment, unless the machine is intended for occasional use and for very short durations. Obviously the most powerful brushcutters will be heavier, so comparisons must be made on tools of equivalent power class.

 

Fuel consumption

Like any motorized machine, it is important to choose an engine that optimizes fuel consumption and performance, avoiding tools that are unnecessarily thirsty for fuel and therefore wasteful and polluting. If, on the other hand, you are leaning towards a battery operated tool, it is advisable to carefully evaluate not only the battery discharge time with the brushcutter used at maximum power, but also the charging time. For professional use it is advisable to have at least 2-3 batteries, so as to always have a charged battery ready as soon as the current one needs to be recharged.

 

Multi-function brushcutter

On the market there are also models with a shaft that can be split in half, allowing the end part to be modified by quickly installing other accessories instead of the grass cutting head, such as a telescopic chainsaw for trimming branches, a blower, a hedge trimmer, or some hoe blades. However, these are more useful solutions for hobbyists than for professional use, an area where it is more convenient and productive to have a specific tool for each activity.

 

Cutting tool

One of the strengths of brushcutters is the ease with which the cutting tool can be adapted to the type of vegetation. In general, brushcutters have several interchangeable heads or a hub on which the desired cutting tool can be adapted. In general, the classic wire heads are perfectly suited to cutting grass, while for brambles and undergrowth shrubs it is better to mount a blade.

The so-called "bump feed" heads are very comfortable for continuous work. They employ a spring mechanism that allows you to lengthen the wire without having to open the head or even turn off the engine, simply by bumping it on the ground. The contraindication to their use, however, lies in the fact that in the long term, the bumps needed to activate them also have a negative impact on the reliability of the machine and especially of the bevel gear. In any case, the heads with 2-wire nylon thread are perfect for finishing flower beds, soft grass and turf, while those with 4 wires are more comfortable to use on tall or thick grass and small bushes.

Blade heads are better suited to work on brambles and small bushes. In particular, the heads equipped with a number of blades ranging from 2 to 7 are normally used with the most powerful brushcutters, to cut large brambles, dense bushes and wild plants up to 3 cm in diameter, while the heads with a high number of teeth (over 30) can also (with due patience and attention) cut large branches and work easily on thick bushes and wild plants up to 5 cm in diameter. In this sector there are also specialized manufacturers who offer a multitude of variations on the theme to make the brushcutter adaptable to the most diverse needs.

The wire

The choice of nylon wire also depends on the use: thicker wires are stronger, square, hexagonal or star-shaped strings have edges and cut better, thus making it easier to cut even small brambles or small lignified suckers. However, they are noisier due to being less aerodynamics, which also negatively affects fuel consumption.

by Davide Facchinetti

Keywords: Brushcutters

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