Lawn mower

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A late 19th century reel mower.

A lawn mower, alternately spelled lawnmower, is a device which by means of one or more revolving blades is used to cut grass or other plants to an even length.


Environmental issues

Cars, trucks and other vehicles get most of the attention when it comes to air pollution, but a single gas-powered lawn mower used 45 minutes each week for a year is equal to driving 22,000 miles in a new passenger car, according to the Air Quality Management District, the air pollution control agency for Orange County and major portions of the L.A. area.[1]


File:Early victa mower.jpg
An early Victa rotary Mower - National Museum

The first Lawn mower was invented by English engineer Edwin Beard Budding in 1827. 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 Ferrabee and Edwin Budding dated May 18 1830, Ferrabee 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 in London, in 1831. It took ten years and further innovations 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 in chain- or gear-driven models. JP Engineering of Leicester, founded after World War I, 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, when placed in incompetent hands, left unsightly scars on and in the ground) or bare spaces caused by domesticated grazing animals.

James Sumner of Lancashire patented the first steam-powered lawnmower in 1893. His machine burned petrol and/or paraffin oil (kerosene) 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 first grass boxes were flat trays but took their present shape in the 1860s. The roller-drive lawnmower has changed very little since around 1930. 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. Early in the 1930s, experiments in design of rotary mowing equipment were conducted by a farmer in the Midwest region of the United States, by the name of C.C Stacy. His concept was the use of a toothed circular saw blade mounted horizontally on a vertical shaf t, which would be suspended at a height of approximately 2" and moved across a lawn to cut grass and other lawn vegetation at a uniform height. The power for his experimental mower was an electric motor. The success of Stacy's design was limited by 2 factors: the relatively small diameter of the saw blades he used for his experiments, which were about 8"; and the fact that toothed circular saw blades were not really an optimum cutting tool for free standing grass and other plants. Stacy did not come up with any idea for a cutter similar to modern rotary mower straight blades, and soon dropped his experiments with rotary mowing. He never submitted any of his ideas for patent, although drawings of his ideas still exist and are in the possession of family members. Late in life, Stacy, deceased in 1993, asserted that his ideas for rotary mowing equipment originated with him, and he had never seen or heard of any mowing equipment other than cylinder or reel type mowers prior to formulating his ideas. He lamented jokingly that if he had pursued and patented the concept, his family name might have become as well known as Jacobson, that of a prominent mower manufacturer in the first half of the 20th century.

On May 9, 1899, John Albert Burr, an African American inventor, patented [patent 624,749] an improved rotary blade lawn mower. Burr designed a lawn mower with traction wheels and a rotary blade that was designed to not easily get plugged up from lawn clippings. John Albert Burr also improved the design of lawn mowers by making it possible to mow closer to building and wall edges.


File:MTD Lawn Mower.jpg
A typical modern gasoline-powered mower.

Two cutting mechanisms are in common use:

  • reel or cylinder 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, or "bed knife". 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.

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.

Rotary 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

There are four major types of reel mower: push, walk behind power, riding power, and tow behind gang mower.

Rear quarter view of push mower mechanism showing fixed cutting blade above roller and wheel-driven (through gears) rotary blades

Push mowers are powered by people pushing them and are usually used on very small lawns. The walk power reel mower can be divided into two types: a (largely obsolete) powered version of the push mower, used for residential lawns and a 'greens mower' used for the precision cutting of golf greens. Riding power reel mowers can also be divided into two types: the 'triplex' which has three hydraulically driven independent cutting heads and is used for golf greens, and the larger 'fairway' machine that has five or seven hydraulically driven cutting heads. Gang reel mowers are towed behind a tractor in sets (gangs) of three, five, or seven. They are 'ground-powered' that is, the tires of each cutting unit are geared to drive the reel. Gang mowers are used to mow large areas of turf such as sports fields or parks.

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.

The cutting action of the reel mower requires contact between the spinning reel and the stationary bed knife. The reel is first adjusted until it spins free. It is then adjusted back until it barely touches the bed knife on one side. The other side is then adjusted until it too makes contact with the bed knife. Contact is judged by cutting strips of slick magazine paper. The machine should be gradually adjusted until it is able to cut paper all along the bed knife. If the machine is too tight to be easily pushed, the left and right sides should be loosened slightly, by the same amount on each side, until it is loose enough to push. It is sometimes helpful to spray the reel with oil or silicone lubricant to allow it to turn freely. During use, the blades are lubricated with juice from the freshly cut grass.

The scissor-like action of a reel mower provides a much cleaner cut on the blades of grass than a rotary mower, avoiding brown ends that result from tearing or bruising of the remaining portion of the blade of grass.

Rotary mowers

File:Electric mower-250px.jpg
Electric rotary lawn mower with rear grass catcher.

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.

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. Special mulching blades are available for rotary mowers. The blade is designed to keep the clippings circulating underneath the mower until t he 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. [2]

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 2005. A typical robotic lawn mower requires the user to set up a border wire around the lawn that defines the area to be mowed. The robot uses this wire to trim and in some cases to locate a recharging dock. Robotic mowers are capable of maintaining up to 5 acres of grass. Electricity usage varies from about 100 watts (compare to light bulb) for 1/2 acre to 500 watts (compare to refrigerator) to maintain 5 acres.

Robotic lawnmowers are increasingly sophisticated, are self-docking and contain rain sensors nearly eliminating human interaction for mowing grass. Some models will adapt it's programming by detecting the speed in which grass grows as needed to maintain a perfect cut lawn.

The Friendly Robotics mower uses sophisticated tiling algorithms to calculate the most effective pattern for cutting the entire lawn. Lawnbott mowers rely on a combination of random and smart spiraling patterns combined with quick charging and longer mowing times to ensure an evenly cut lawn. Smart spiraling starts randomly or when the robot senses high grass patches.

Pull mowers

A bull drawn pull mower on the lawns of Taj Mahal.

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.


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 (though they may be attached to a long handle to give you the opportunity to work in an up-right position, saving your knees and back). The simplest forms of these are shears, which are like scissors with long blades.


See also

External links


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