A lawn mower or lawnmower is a machine that has one or more revolving blades to cut a lawn at an even length.
Lawn mowers employing a blade that rotates about a vertical axis are known as rotary mowers, while those employing a blade assembly that rotates about a horizontal axis are known as cylinder or reel mowers.
Many different designs have been made, each suited to a particular purpose. The smallest types, pushed by a human, are suitable for small residential lawns and gardens, while larger, self-contained, ride-on mowers are suitable for large lawns, and the largest, multi-gang mowers pulled behind a tractor, are designed for large expanses of grass such as golf courses and municipal parks.
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 expensive 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." It took ten more years and further innovations to create a machine that could be worked by donkey or horse power, and sixty years before a steam-powered lawn mower was built. 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 lawn mowers. (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.
Manufacture of lawn mowers began in the 1860s. By 1862, Farrabee's company was making eight models in various roller sizes up to 36 inches (900 mm). 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. In 1870, Elwood McGuire of Richmond, Indiana designed a human-pushed lawn mower, which was very lightweight and a commercial success. On May 9, 1899, an improved cylinder mower was patented in , with the wheel placement altered for better performance. Amariah M. Hills went on to found the Archimedean Lawn Mower Co. in 1871. 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 lawn mower 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 lawn mower 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 enough and powerful enough to run the blades at a high speed. Many people experimented with rotary blades in the late 1920s and early 1930s, and Power Specialties Ltd. introduced a gasoline-powered rotary mower. One company that produced rotary mowers commercially was the Australian Victa company, starting in 1947. The story of one experiment in the design of rotary mowing equipment is that of C C Stacy, a farmer in the Midwest region of the United States. His concept was the use of a toothed circular saw blade mounted horizontally on a vertical shaft, which would be suspended at a height of approximately 2 inches (50 mm) 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 two factors: the relatively small diameter of the saw blades he used for his experiments, which were about 8 inches (200 mm); and the fact that toothed circular saw blades are not an ideal tool for cutting 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.
In addition to air pollution, the EPA states that 17 million gallons of fuel, mostly gasoline, are spilled each year while refueling lawn equipment. That is more than all the oil spilled by the Exxon Valdez, in the Gulf of Alaska. Oil spills contaminate groundwater as well as evaporate into the air making smog-forming ozone when heated by sunlight.
Regarding safety issues, rotary mowers can also throw out debris with tremendous force. In the US, there are over 80,000 people per year who are hospitalized due to mower accidents. The vast majority of these injuries could be avoided by wearing footwear while mowing. The American Academy of Pediatrics recommends that children be 12 before they mow.
A further problem that people have with petrol powered lawn mowers, especially those with a 'zip' start pulling cord mechanism is that it is often very difficult and cumbersome to start, especially as the mower starts to age. Proper care of the engine can delay this problem.
Proper storage of a gasoline lawn mower begins with adding a gas preservative such as Sta-Bil brand or similar preservative to the added gasoline and then running the engine for at least 3 minutes to assure the treated gasoline makes its way through all the engine parts. This additive prevents gasoline from 'gumming' and keeps the gasoline fresh for the next season. Keeping equipment indoors is the best option, if you cannot do this, storage in a shed or garage is your next best option. Also, some people prefer to empty a machine's gas tank and run it until all fuel is gone and the engine stops from lack of fuel. This is not an ideal method as this leaves fuel residue on carburetor parts which often becomes sticky and prevents proper operation when the engine attempts a start the following season.
Another risk of lawn mowing is Pneumonic Tularemia.
The reel mower was the original form of mechanical mower for lawns, and the mechanism has changed little over the years. A horizontal cutting blade is carried close to the grass, at the desired height of cut. Over this is a fast spinning reel of blades. Each blade in the reel forms a helix around the reel axis, and the set of spinning blades describes a cylinder. The spinning blades force the grass past the cutting bar.
Of all the mowers, a properly adjusted reel mower makes the cleanest cut of the grass, and this allows the grass to heal quicker. The cutting action is often likened to that of scissors; however, it is not necessary for the blades of the spinning reel to contact the horizontal cutting bar. If the gap between the blades is less than the thickness of the grass, a clean cut can still be made.
There are many variants of the reel mower. Push mowers (illustrated) have no motor and are used on small lawns. As the mower is pushed along, the wheels drive gears which rapidly spin the reel. Typical cutting widths are 12 to .
The basic push mower mechanism is also used in gangs towed behind a tractor. The individual mowers are arranged in a vee behind the tractor with each mower's track slightly overlapping that of the mower in front of it. Gang mowers are used over large areas of turf such as sports fields or parks.
An engine can be added to a walk-behind mower to power the reel, the wheels, or both. A typical arrangement for residential lawns has either an electric or an internal combustion engine spinning the reel while the operator pushes the mower along. The electric models can be corded or battery powered. Some variants have only 3 blades in a reel spinning at great speed, and these models can cut grass which has grown too long for ordinary push mowers. One type of walk-behind is now largely obsolete. These were powered versions of the traditional, side wheel push mower and were used on residential lawns. An internal combustion engine sat atop the reel housing and drove the wheels, usually though a belt. The wheels in turn drove the reel, as in the push mower.
Greens (roller) mowers are used for the precision cutting of golf greens. The reel is followed by a large roller which smooths the freshly cut lawn and minimizes wheel marks. Due to their weight, the engine also propels the mower. Much smaller and lighter variants of the roller mower are sometimes used for small patches of ornamental lawns around flower beds, and these have no engine.
Riding reel mowers are also produced. Typically, the cutting reels are ahead of the vehicle's main wheels, so that the grass can be cut before the wheels push the grass over onto the ground. The reels are often hydraulically powered.
Most rotary push mowers are 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. In the past rotary mowers had a manually controlled throttle to increase or decrease engine speed. Newer models usually have a pre-set throttle speed that prevents over-revving and improves engine life.
Gasoline mowers unfortunately have the disadvantages of having to travel to procure the fuel, store and dispose of the fuel on premise, and providing the proper fuel/oil mixture for two-stroke gasoline mowers. Rotary mowers powered by electric motors have none of these disadvantages, and are available to the consumer in increasing numbers. Usually, these mowers are moved by manual motive power—the on-board engine or motor only spins the blades.
Electric rotary mowers may be further subdivided into the corded and cordless subcategories. Corded electric mowers are naturally limited in range by their trailing power cord, which may limit their use with lawns extending outward more than 100-150 feet from the nearest available power outlet. There is the additional hazard with these machines of accidentally mowing over the power cable, which stops the mower and may put users at risk of receiving a dangerous electric shock. Installing a residual-current device (GFCI) on the outlet may reduce the shock risk when using a corded electric mower. On the United States market as of summer 2008, a corded electric mower from a respectable manufacturer costs about the same as an entry-level internal-combustion mower ($150-200), with significantly higher reliability, significantly lower cost of ownership, and a significantly reduced carbon footprint.
Hover mowers are powered rotary push lawn 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.
A popular alternative for larger lawns is the riding (or ride-on) mower. The operator is provided with a seat and controls on the mower and literally 'rides' on the machine. Most use the horizontal rotating blade system, though usually with multiple blades.
A common form of ride-on mower is the lawn tractor. These are usually designed to resemble a small agricultural tractor, with the cutting deck mounted amidships between the front and rear axles.
The drives for these mowers are in several categories. The most common transmission for tractors is a manual transmission. The second most common transmission type is a form of continuously variable transmission called the hydrostatic transmission. These transmissions take several forms, from pumps driving separate motors, which may incorporate a gear reduction, to fully integrated units containing a pump, motor and gear reduction. Hydrostatic transmissions are more expensive than mechanical transmissions but they are easier to use and can transmit greater torque to the wheels as compared to a typical mechanical transmission. The least common drive type, and the most expensive, is electric.
There have been a number of attempts to replace hydrostatic transmissions with a lower cost alternative, but these attempts, which include variable belt types (e.g., MTD's Auto Drive) and toroidal, have various performance or perception problems that has caused their market life to be short or their market penetration to be limited.
Riding lawnmowers can often mount other devices such as rototillers, snowplows, snowblowers, yard vacuums, occasionally even front buckets or fork-lift tines.
The deck of a rotary mower is typically made of steel. Lighter steel is used on less expensive models, and heavier steel on more expensive models for durability. Other deck materials include aluminum, which does not rust and is a staple of higher priced mowers, and hard composite plastic, which does not rust and is lighter and less expensive than aluminum. Electric mowers typically have a plastic deck.
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 the clippings are chopped quite small. Other designs have twin blades to mulch the clippings to small pieces. Mower manufacturers market their mowers as side discharge, 2-in-1, meaning bagging and mulching or side discharging and mulching, and 3-in-1, meaning bagging, mulching, and side discharge. Most 2 in 1 bagging and mulching mowers require a separate attachment to discharge grass onto the lawn. Some side discharge mower manufacturers also sell separate "mulching plates" that will cover the opening on the side discharge mower and, in combination with the proper blades, will convert the mower to a mulching mower. These conversions are impractical when compared with 2 or 3-in-1 mowers which can be converted in the field in seconds. There are two types of bagging mowers. A rear bag mower features an opening on the back of the mower through which the grass is expelled into the bag. Hi-vac mowers have a tunnel that extends from the side discharge to the bag. Hi-vac is also the type of grass collection used on riding lawn mowers and lawn tractors and is considered more efficient. Mulching and bagging mowers are not well suited to long grass or thick weeds.
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. Most higher priced mowers (and many at lower prices) have a manually activated blade clutch that allows the operator to stop the blade rotating without turning off the motor.
Rotary mowers with internal combustion engines come in three price ranges. Low priced mowers use older technology, smaller motors, and lighter steel decks. These mowers are targeted at the residential market and typically price is the most important selling point. These mowers are sold through large discount and home improvement stores, range between $100–400 on the US market, and have a typical service life of 7–10 years. Higher priced mowers are also primarily targeted at residential customers. These mowers have more features and often have heavier steel, composite plastic or aluminum decks. Most of these mowers are sold through independent dealers who also service the equipment and cost between $400 and $1,000. These mowers will last as much as twenty years given regular maintenance. Commercial grade mowers are the most expensive rotary mowers. They are "targeted" at grounds maintenance companies and other professionals, but are commonly sold to home owners as well. These mowers feature the latest technology and include features like disk drive, oil filters, and very heavy steel and, more often, aluminum decks. These mowers are sold through independent dealers who service the product and have a service life far beyond twenty years given regular maintenance. A commercial grade mower typically costs well over $1,000.
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 locate the boundary of the area to be trimmed and in some cases to locate a recharging dock. Robotic mowers are capable of maintaining up to of grass.
Robotic lawn mowers are increasingly sophisticated, are self-docking and contain rain sensors, nearly eliminating human interaction for mowing grass.