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Lawn mower

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A lawn mower, or alternatively spelt lawnmower, is a type of mower, used to cut grass or other plants to an even length.

A late 19th century reel mower.

History

The idea of a machine to cut grass was conceived in Gloucestershire, England around 1830 by freelance engineer Edwin Beard Budding. Formerly a carpenter at Chalford, he was possibly inspired by a rotary cutter designed to cut the nap off wool cloth at the Brinscomb Mill. Budding's mower was designed primarily to cut the lawn on sports grounds and expansive gardens as a superior alternative to the scythe. His patent of 25 October, 1830 described "a new combination and application of machinery for the purpose of cropping or shearing the vegetable surfaces of lawns, grass-plats and pleasure grounds." The patent went on to state, "country gentlemen may find in using my machine themselves an amusing, useful and healthy exercise."

In an agreement between John Ferrebee and Budding dated May 18, 1830, Ferrebee paid the costs of development, obtained letters of patent and acquired rights to manufacture, sell and license other manufacturers in the production of lawnmowers. (The agreement is housed in the Stroud Museum).

One of the first Budding and Ferrabee machines was used in Regent's Park, Zoological Gardens England, in 1831. It took ten years and further inovations to create a machine that could be worked by donkey or horse power and sixty years before a steam powered lawnmower was built.

Manufacture of lawn mowers began in the 1850s. By 1862, Farrabee's company was making eight models in various roller sizes up to 900 mm, (36 inches). He manufactured over five thousand machines until production ceased in 1863. Thomas Green produced the first chain driven mower in 1859, named the Silens Messor. Around 1900, one of the best known English machines was the Ransomes' Automaton, available as chain or gear driven. JP Engineering of Leicester, founded after World War One, produced a range of very popular chain driven mowers. About this time, an operator could ride behind animals that pulled the large machines. These were the first riding mowers.

The rise in popularity of sports such as lawn tennis, croquet, cricket, football and rugby helped prompt the spread of the invention. Lawn mowers became a more efficient alternative to simply relying on gardeners wielding the scythe (which left unsightly circular scars) or bare spaces caused by domesticated grazing animals

Steam powered lawnmowers were patented in 1893 by James Sumner of Lancashire, England. His machine burned petrol and/or parrafin oil as a fuel. After numerous advances, the machines were sold by the Stott Fertilizer and Insecticide company of Manchester and later, the Sumner's took over sales. The company they controlled was called the Leyland Steam Motor Company. Numerous manufacturers entered the field with gasoline driven mowers after the turn of the century. The roller-drive lawnmower has changed very little since around 1930. The first grass boxes were flat trays but took their present shape in the 1860s.

Gang mowers, those with multiple sets of blades, were built in the United States in 1919 by a Mister Worthington. His company was taken over by the Jacobsen corporation but his name is still cast on the frames of their gang units.

Rotary mowers were not developed until engines were small and powerful enough to run the blades at a high speed. In the 1930s, Power Specialties Ltd. introduced a gas powered rotary mower. One company that produced rotary mowers commercially was the Australian Victa company, starting in 1947.

Operation

Two cutting mechanisms are in common use:

  • reel mowers, those with a set of spiral-cylindrical blades spinning on a horizontal axis. Cutting is by a scissor-like action between the moving spiral blades and a single stationary horizontal blade. The axle is attached to a gear that is then mounted on one of the wheels in order to spin the blades rapidly for good grass cutting action even when the mower is moving slowly.
  • rotary mowers, those whose blades spin horizontally on a vertical driveshaft. Cutting is due to a horizontal blade striking the grass at a high speed.
    Gasoline-powered push rotary mower.

The two cutting mechanisms can lead to different results. On rotary mowers, the blade is usually not sharp enough to cut the grass cleanly. The speed of the blade simply tears the grass resulting in ragged tips. By contrast, the cylinder-type reel lawn mowers and manual lawn mowers usually work by scissor action on the blades and a cleaner cut is achieved.

Lawn mowers often allow the height of the lawn mower to be adjusted to control the height of the cut grass. On older or less expensive lawn mowers, this is accomplished by manually moving each wheel to a different slot on the chassis. A more recent innovation in rotary mowers is a "one-touch" height-adjust mechanism where the blades are mounted on a frame separate from the rest of the lawn mower and the frame can be raised and lowered.

Lawn mowers need power for two purposes: to cut and to move. The act of pushing or pulling a reel mower provides power for cutting and moving at the same time. For rotary mowers, the power sources may vary: grass-cutting may be powered by either an internal combustion engine or an electric motor, while propulsion may share that power source or be supplied by the user or another external source such as a tractor. Wheel-driven gear systems allow for cutting to be powered by the same external source as that used to propel the mower.

Reel mowers

Reel mowers have between three and seven blades depending on the model type. Reel mowers are usually powered by people pushing them or tractors pulling them. Golf courses are most often cut with reel mowers which are pulled by a tractor.

Presently several companies are producing cordless electric reel mowers. The performance of the batteries vary in terms of how long the batteries can power mowers and the recharging cycles. An hour and a quarter (75 minutes) to half an hour (30 minutes) is the range of running time. Six hours to twenty-four hours is the range of time required to fully recharge batteries. Most batteries can be recharged several hundred times. Cordless electric reel mowers weigh 30 – 35 pounds.

Polish-Canadian inventor, Andrzej Piprek, is largely credited with the revolutionary development of the Bratzen-Derwitz method of mower blade propulsion in which 17 different kind of blades "intermingle" to create a grass-eating monster. The first mower to be marketed in Poland employed the Bratzen-Derwitz blade but was immediately adopted by the invading Nazis in late 1939 as a choice of perverse weaponry. Opposing the Germans' disruption of his genius, Piprek went forward in time to Canada in 1994 at which point he appeared as a 16-year-old "dude", ready for action. The plan for the Bratzen-Derwitz was lost in a fire in Poland in 1946 and to this day, Andrzej Piprek refuses to reveal his secret plans for a utopian mower-society.

Rotary mowers

Rotary mowers are often powered by internal combustion engines. Such engines can be either two-stroke or four-stroke cycle engines, running on gasoline or other liquid fuels. Internal combustion engines used with lawn mowers normally have only one cylinder. Power generally ranges from two to seven horsepower (1.5 to 5.25 kW). The engines are usually carbureted and require a manual pull crank to start them, although an electric start is becoming a sales feature in some countries.

Electric rotary lawn mower with rear grass catcher.

Rotary mowers powered by electric motors are increasingly popular. Usually, these mowers are moved by manual motive power— the on-board engine or motor only spins the blades. These have the disadvantage of requiring a trailing power cord that limits its range and so these are only useful for relatively small lawns, close to a power socket. There is the obvious hazard with these machines of mowing over the power cable, which stops the mower and may put users at risk of electrocution. Installing a residual-current device (GFCI) on the outlet can reduce the risk of electrocution. Cordless (battery powered) electric lawn mowers are also available for small lawns. Electric rotary mowers weigh 45-50 pounds.

Rotary mowers typically have an opening in the side or rear of the housing where the cut grass is expelled. Some have a grass catcher attachment at the opening to bag the grass clippings.

A mulching blade.

Special mulching blades are available for rotary mowers. The blade is designed to keep the clippings circulating underneath the mower until the clippings are chopped quite small. Other designs have twin blades to mulch the clippings to small pieces. This avoids the need for bagging the clippings or raking the clippings. Not only does this save labor, as no organics are removed from the lawn, less fertilizer is needed.

A dead man's switch is required in some places so that the operator must hold a switch to keep the engine running. Typically, this is an extra bar that is held against the handle. Should the operator lose control of, or contact with, the lawn mower and release the bar, either the engine is turned off or the blade is disconnected by disengaging a clutch.

Riding mowers

A riding mower on the campus of Harvard Business School.

A popular alternative for larger lawns is the riding (or ride-on) mower. These often resemble small tractors, with the cutting deck mounted amidships between the front and rear axles. An alternative layout for a ride-on is a rear-mounted engine with rear-wheel steering, and a front-mounted deck. These mowers are generally more maneuverable around tight corners than the tractor type, but are generally more expensive. Most of these machines cut using the horizontal rotating blade system, though usually with multiple blades.

Hover mowers

Hover mowers are powered rotary push mowers that use a turbine above the spinning blades to drive air downwards, thereby creating an air cushion that lifts the mower off the ground like a hovercraft. The operator can then easily move the mower as it floats over the grass. Hover mowers are necessarily light in order to achieve the air cushion and typically have plastic bodies with an electric motor, although small petrol engines have been used. A different style of movement is often employed with hover mowers whereby operators swing the mower in an arc around themselves because there are no wheels touching the ground to impede movement in sideways directions.

Hover mowers can also be applied to very long grass and even light scrub, since their lightness permits most operators to lift the mower up and then let it sink slowly down while the blades progressively chop up the vegetation. The lifting action is made even easier when the mower is swung around with the handle held against the operator's mid-body to provide leverage.

Robotic mowers

Robotic lawn mowers represented the second largest category of household autonomous robots used by the end of 2003. A typical robotic lawn mower requires the user to set up a border wire around the lawn that defines the area to be mowed.

Pull mowers

A pull mower is essentially the same as a manually pushed mower but the propulsion unit pulls the mowing unit instead of pushing it. Thus it is the normal system when a tractor or animal-drawn mower is used.

Professional mowers

Professional grass-cutting equipment (used by large establishments such as universities, sports stadiums or local authorities and suchlike) usually take the form of much larger, dedicated, ride-on platforms or attachments that can be mounted on, or behind, a standard tractor unit (a "gang-mower"). Either type may use rotating-blade or cylindrical-blade type cutters, although good-quality mown surfaces demand the latter.

Other mowing tools

Edge trimmer

Edge trimmers (also called strimmers in the UK, line trimmers or whippersnippers in Australia, and weed eaters in New Zealand and in the United States) are specialized, electric or gasoline-engine powered, hand-held mowers for cutting grass near fences, under trees and other areas too small or rough for a mechanized lawn mower. The cutting device is either a monofilament nylon 1.6 to 3 mm diameter line, or a nylon or steel three-blade rotor.

Electric edge trimmers have the advantage of being very light, easy to manoeuver and easy to operate devices. However, the length of power cord that can be deployed across the ground limits them and they are usually less powerful and robust than the petrol-engine ones. Electric machines normally are limited to 2.5 mm (0.100 inch) maximum diameter nylon because of their lower power output (400 to about 1200 watts).

Gas-engine powered trimmers usually have a minimum of 25 cc displacement motors. At this size they can easily turn 2 mm (0.080 inch) line and some have nylon blades as accessories to the line-reel. A 32 cc engine can swing a 2.75 mm (0.110) line and often has metal-blade accessories.

While this type of trimmer is heavier, uses a gas-oil mix and vibrates significantly they are much more mobile (not attached to a power outlet) and are not very limited in maximum power for commercial use. Large trimmers, used for cutting roadside grass in large areas, may be quite heavy—being suspended from the body by a harness—and may be a two-hand-controlled device.

For trimming close to fences and other snagging features, petrol-trimmers can be throttled back to limit the chance of the line catching or breaking off. Speed-control is not possible with electric trimmers— they are essentially single-speed machines.

A line-trimmer works on the principle that a line that is turned fast enough is held out from its housing (the rotating reel) very stiffly by centrifugal force. The faster it turns the stiffer the line. Even round-section nylon line is able to cut grass and slight, woody, plants quite well. Some monofilament lines, designed for more powerful cutters, have an extruded shape—like a star—that helps the line slash the material being cut and thus it is able to cut quite large woody plants (small shrubs) or, at least, ring-bark them very effectively. These lines make disks less necessary for tough jobs.

The line is hand-wound onto a reel before the job is started, leaving both ends extending from the reel housing. The motor turns the reel and the line extends horizontally while the operator swings the trimmer about where the plants are to be trimmed. The operator controls the height at which cutting takes place and can trim down to ground level quite easily. As the line is worn, or breaks off, the operator knocks the reel on the ground so that a release mechanism allows some of the line in the reel to extend and replace the spent portion. A small cutter on the line-guard ensures that the line length exposed for cutting does not exceed the length that can be swung efficiently by the motor. Newly extended line operates more efficiently because of its heavier weight and surface effects (the star-shaped edges).

Trimmers that have nylon or metal blades usually have straight driveshafts because of the higher torque required to turn the disk and because of the shock loads that are passed back from the blade to the driveshaft and its gearbox(es). Smaller line trimmers have curved driveshafts to make holding the cutting-head at ground level much easier and with less strain on the operator.

Safety precautions, often ignored, with edge trimmers are that the operator should wear robust boots and clothing (especially trousers), goggles, hearing protection and gloves. The power should be disconnected (or the engine stopped) before the line is replaced or before any significant work is done in the line-reel area (such as removing grass stalks that have wound onto the reel). The line guard should not be removed because it stops material being flung back at the operator's legs and because it carries the cutter ensuring that the line length is not too long for the trimmer. When using a disk the operator can easily overload the driveshaft and damage the machine or strip the gearbox gears.

Clippers

Hand-powered or battery-powered grass clippers can used for the tightest spots, for example around flowers, however one has to be on their knees a lot. The simplest forms of these are shears, which are like scissors with long blades.

An early Victa Mower - National Museum

Resources

See also

External links

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