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This article was originally published on the web at cranbrookengineering.co.uk however that website is defunct at April 2013. The copyright is with the original owners of cranbrookengineering.co.uk

Choosing a lawn mower

The Main Types of Mower are:
  • Wheeled
  • Rear Roller
  • Hover
  • Cylinder

It's not always easy to choose the right type of lawn mower because you might want it to do several different tasks. For example you may have a classic, closely trimmed lawn as well as some steep grassy banks and a paddock or orchard. Clearly one machine is not ideal for all of those, so there are choices to be made.

Wheeled

Probably the most versatile type is the four-wheeled rotary mower. It can cut reasonably close, though it doesn't leave stripes, and it can be set higher for long or rough areas. Most of them will tackle reasonable slopes, but beware of over-doing the gradient because four-stroke engines, with oil in a sump, can lose lubrication if tipped too much. Two-stroke engines are a solution to this but they are rare on mowers, except on hover mowers. If you have much sloping ground, a self-propelled machine is pretty well essential.

Rear Roller

Rotary lawn mowers with a rear roller are also quite versatile in that they do cut close and leave a nice stripe on the lawn while at the same time being capable of cutting fairly (but not very) long grass.

Hover

Hover mowers are easy to manoeuvre round complex obstacles like beds, paths and stumps; but they are not all that good on large areas of open ground. Having said that, they do not leave wheel marks as four-wheelers do. The other strengths of hover lawn mowers are that they are designed for grassy banks and that they can be hung up in the shed.

Cylinder lawn mower

The fourth main type is the traditional cylinder lawn mower, which is ideal for a true British striped sward. This sort, of course, contains a horizontal cylinder consisting of several blades with their cutting edges on the circumference of the cylinder. Because these blades nip the grass tips between themselves and a fixed bottom blade, they cut very cleanly, just like scissors. This cutting action contrasts with rotary lawn mowers, which slash at the grass and cut it mainly by virtue of their speed. This is why cylinder mowers need less powerful engines and are usually quieter.

Propulsion

  • Push
  • Self-propelled (or power-drive, autodrive, or similar name)
  • Petrol engine
  • Mains electric motor
  • Cordless (battery) electric motor

Our view is that pushed lawn mowers are most suitable in reasonably level, small gardens. It depends how fit you are. Below there's a table giving suggested propulsion and cutting widths.

GUIDELINES TO LAWN MOWER PROPULSION AND SIZE

Lawn size: Suggested cutting width: Propulsion:
Compact lawn (area up to half a tennis court) Up to 19inch (48cm approx).

Any
Medium sized lawns (area of about one tennis court) 19inch (48cm approx) to 21inch (53cm approx). Usually self-propelled. Petrol. Possibly mains electric.
Large lawns (larger than a tennis court)

21inch (53cm approx) upwards. Consider a 'professional' machine. Self-propelled petrol.

Self-propelled lawn mowers often have a variable forward speed. This raises the question of ideal speed for efficiency. Many people want to get their mowing over with as soon as possible but, if you go too fast, the blade doesn't have time to cut properly and you get a poor quality of trim. The point is that there is a best speed for a blade to strike the grass (dependent on how wet or tough the grass is) and it may not be compatible with the best or most desired forward speed of the machine. The solution to this, in more expensive lawn mowers, is to be able to vary forward speed while independently varying blade speed to the optimum. This is automatically achieved with hydrostatic drive or other equivalent mechanisms.

Petrol engines these days start well and are a bit quieter than they used to be. They are powerful and their noise and emissions are regulated by law. They beat electric in not needing a trailing lead or a battery with a finite life. Mains electric lawn mowers are cheaper and their design is now much better than the early days, so that the better ones can cut really quite long grass without overheating. Cordless garden machines have advanced tremendously but you're still pushing your luck if you use them on medium or large lawns. Batteries now tend to be lead-acid or Lithium-Polymer, which last well and which do not have the 'memory' problem of Nickel-Cadmium.

Dealing with the cut grass

  • Collect
  • Mulch
  • Discharge

Most lawn mowers have a cloth bag or plastic box for the collection of clippings. Some are more convenient than others to remove, empty and refit. Some can be removed with one hand and lifted up between the handlebars. Obviously you want to stop as infrequently as possible to empty the collector, but size is not the only factor — packing the clippings in tightly also has an influence.

Many people like to buy mulching lawn mowers, or ones that can be converted as required. Mulchers are supposed to chop the grass extra small, but many are not very effective at it, often leaving a ridge of clippings. Mulching lawn mowers do save time and they do feed the turf and conserve moisture in dry weather. But some gardeners blame them for accumulating thatch at the base of the grass stems. Probably mulching sometimes and collecting at other times is the best answer.

When the grass is very long, perhaps at the first cut of the spring, it often pays to let the grass discharge without mulching: it uses less power and the mower is less likely to stall. One tip is to leave the long clippings for a day to wither then to come back and mow again, but this time with the collector fitted. Some lawn mowers have a side discharge facility, often by fitting a shaped baffle.

Judging quality

All the better garden machines have a good finish and a solid feel. Rotary lawn mowers come with steel, alloy and plastic decks. Thicker pressed steel ones are perfectly all right if you keep them clean to slow down rust. Avoid thin ones. If careful cleaning every time you mow does not appeal, buy a deck made in cast aluminium alloy: but even that is not everlasting, and a good clean now and then is advisable. Plastic, if not a cheapo, is now reliable and as near everlasting as you'll find.

Cutting height adjustment is easier if it's controlled by one lever and assisted by spring-loading. Four adjusters take longer. Ideally look for metal wheels, ball bearings on the wheel axles, a strong blade and sturdy control levers. The best cylinder lawn mowers have more and thicker blades on the cylinder than cheap ones. Most people prefer an overhead-valve engine to a side-valve model. The grass collector should look tough and durable as the corners of these are often the first part to fail.

The devices which automatically stop the blade when you let go are of two sorts. The most convenient one stops the blade but not the engine: this is often called a 'blade brake clutch'. The other stops both and is usually called an 'Operator Presence Control'. If you intend to use your mower a lot, it will be less tiring if you choose one with a quiet engine and anti-vibration features. The neighbours will be pleased too. Prices are higher for this sort of sophistication.

Maintenance

It's important to keep your lawn mower clean, as described above. All mowers come with maintenance instructions, but 'once a year' is a good rule for most people. Electric lawn mowers need hardly any maintenance and are therefore much cheaper to run than petrol models. Few petrol lawn mowers have oil filters to catch tiny abrasive particles, which is why regular oil changes are vital to long life. A dirty air filter also causes wear. A sharp blade always gives better results. The safety feature fitted to all lawn mowers, the one that stops the blade very rapidly when you let go of the handle, will need to be maintained to remain efficient. Cylinder lawn mowers are quite expensive to sharpen and set but the effect is marvellous.

It is a great mistake to keep old fuel as it goes stale within a few months, making starting difficult and gumming up your carburettor. This can be avoided by adding a little fuel preservative, such as Briggs & Stratton make.

The story of the lawn mower

Formal lawns were invented in France in the early 18th century, but soon caught on in the rest of Europe. One way to keep them trim was with sheep, but it wasn't very tidy from the point of view of ladies with long dresses and satin shoes. Another way was with hand shears. In 1830, Edwin Budding invented the cylinder lawn mower in Gloucestershire. Remarkably, the principle has survived to this day.

Many makers took up the idea. Quite often the machines were horse drawn — the animals wore soft boots to avoid marking the sward. In about 1890, steam-powered machines were introduced and in 1902 Ransomes began to sell lawn mowers with petrol engines.

Rotary lawn mowers only became a practical proposition when engines had been developed to a point where they were light and fast enough to give enough momentum to a blade. The first commercial ones appeared in the 1930's. Karl Dahlman invented the Flymo hover mower in 1964 inspired by Sir Christopher Cockerell's hovercraft.

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