Leaf Blowers and How They Work

by:Jiali     2020-08-10
When you operate the new leaf blower that you have in your hand or slung over your back, what you are toting is nothing more or less than a miniature jet engine. Thinking of it this way may help you to appreciate not only its power for getting the work done but also its potential to create damage if you misuse it.
For, as in a jet, the air is drawn into the blower body by the centrifugal force of a motor (protected by an air filter) that rotates a multi-bladed impeller. This sucks the air into a reducing-diameter tube, thus accelerating it through increasing pressure and pushing it out through the exhaust: the blower nozzle.
The resulting force can be as fast as 320 km/hr. The whole process may be reversed at the flick of a switch in the case of a blower-vac machine, which sucks up waste from the normal exhaust end and diverts it via a chopping or 'mulching' shredder blade into the collection sack.
This acceleration of the mulching process is a very useful feature, and one which was unheard of in the days when all leaves were collected with rakes and shovels. Leaves always created large bulky mounds. Now, they can be reduced by a factor of 10 in the case of most machines, with some like the Ryobi electric model reducing them in volume terms by 15:1.
In addition to reducing the size they occupy, this kick-starts valuable composting. Chopped leaves may be used directly on flowerbeds between the plants, or can be put into composting bins for use in future seasons.
Power Plants Every machine needs a power source, and in the case of the leaf blower this may be electric or petrol-fuelled.
Batteries have not until recent years featured, because blowers require a lot of power, but they are now appearing as battery technology improves and outputs rise. Lithium-ion is a battery type that does not suffer from 'memory effect' and can be fully or partially discharged before recharging: Li-ion batteries recharge more quickly and are powerful, however they do require more careful handling than the older (and still popular) NiCad types. Once again, Ryobi offer a good model using their standard power packs and chargers that are compatible with many other power tools and machines. Bosch is also leading this cross-machine power plant approach and their clever 36V battery packs have built-in charging condition lights.
Corded (mains) power is the way to go for most electric blower users. The flexibility of the electric motor and its ability to reverse almost immediately makes it a natural choice for vacuum blowers. It is also a dry, clean technology that suits this application very well.
Power outputs are now very great: even budget machines like the Silverline boast outputs of 2400W which gives serious blowing or sucking power: while Flymo offer a 2700W machine with a 'Jet Vac' feature that boosts power to suck up wet leaves. And Flymo's flagship Scirocco has a mighty 3000W power plant. Perhaps wisely in view of the need to manage this amount of oomph, it comes with a wheel on the end of its telescopic tube. This is a feature on some machines that allows handheld machines to be controlled better: it rolls when on firm ground and when blowing it limits the spillage of air (important in terms of protecting plants) as well as concentrating the power to shift soggy leaves. When sucking, the partial vacuum can be created more easily so as to pick up efficiently.
Normally leaf blowers are hand-held nowadays but originally they were walk-behind machines or backpacks. They are lighter now but 4 to 6 kg is still a lot to carry on one shoulder, even with a strap support. In the electric arena there is at least one machine, the GMC, which has wheels and is designed for you to push it along as you go. A good option for those with limited mobility or for longer spells of operation.
Petrol engines have until recently all been 2-stroke (or '2-cycle') models in this market. Why? Well the 2-stroke, based on modifications to the original Otto Cycle engines, is a natural choice for a compact, relatively lightweight single-cylinder machine that can operate at any angle, even if it is upside down. It is air-cooled, does not require a separate oil tank and does not have oil being pumped around the system to lubricate the pistons. That is because oil is mixed at one part per 50 parts of petrol (nowadays unleaded fuel) to make a mix that is burnt in the piston.
To avoid further weight and complication, the engine is started manually by the operator pulling a cord to get the engine spinning and kick off the ignition cycle.
Specialist engine manufacturers like Briggs & Stratton make various models for use in these machines. They are innovating to bring out quieter engines, ones that pollute less (2-strokes do tend to emit more unburnt hydrocarbons) and ones that start more easily with less effort.
The 4-stroke may also be entering the market in force, particularly at the higher end: Makita are now offering (blower-only) models with this form of engine, having seemingly overcome the problems formerly associated with making 4-strokes that are lightweight and able to work when being shaken about and generally harshly treated.
Also at the top end are large wheeled models that are for push-along use or are self-powered: the Warrior comes with settings for 4 different suction heights plus a 'wander hose' for the same sort of flexibility as when using a backpack.
Future trends What of the working future for leaf blowers? It is likely to involve a continuing search for flexibility of operation, efficiency, lower noise, reduced pollution from petrol models, and increasing use of blower-vacs that are more versatile and which keep down the dust levels in operation. They will be kinder on the neighbors: and even easier to use for the owner.
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