What is a Lawnmower ?
What is a Lawnmower? A lawn mower is a machine that makes use of 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 a cylinder mower (sometimes called a hand or reel mower).
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 Machines
The first lawn mower was invented by Edwin Budding in 1827 in Thrupp, just outside Stroud, in Gloucestershire. Budding's mower was designed primarily to cut the lawn on sports grounds and expensive gardens, as a superior alternative to the scythe, and was patented in 1830. It took ten more years and further innovations to create a machine that could be worked by animals, 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.
Thomas Green produced the first chain-driven mower in 1859. Manufacture of lawn mowers began in the 1860s. By 1862, Farrabee's company was making eight models in various roller sizes. He manufactured over 5000 machines until production ceased in 1863. In 1870, Elwood McGuire of Richmond, Indiana designed a human-pushed lawn mower, which was very lightweight and a commercial success. John Burr patented an improved rotary-blade lawn mower in 1899, with the wheel placement altered for better performance. Amariah 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 lawn sports helped prompt the spread of the invention. Lawn mowers became a more efficient alternative to the scythe and domesticated grazing animals. James Sumner of Lancashire patented the first steam-powered lawn mower in 1893. His machine burned petrol and/or kerosene as 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 Victa company, starting in 1952: these mowers were lighter and easier to use than the mowers that came before.
The cylinder mower carries a fixed, horizontal cutting blade at the desired height of cut. Over this is a fast-spinning cylinder of blades which force the grass past the cutting bar. Each blade in the cylinder forms a helix around the reel axis, and the set of spinning blades describes a cylinder.
Of all the mowers, a properly adjusted cylinder mower makes the cleanest cut of the grass, and this allows the grass to heal more quickly. 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 cylinder mower. Push mowers have no motor and are used on small lawns. As the mower is pushed along, the wheels drive gears which rapidly spin the cylinder. Typical cutting widths are 12 to 20 inches (510 mm).
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.
A petrol engine or electric motor can be added to a cylinder mower to power the cylinder, the wheels, or both. A typical arrangement for residential lawns has the motor spinning the cylinder while the operator pushes the mower along. The electric models can be corded or cordless. 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.
A popular choice for rotary mowers are machines powered by internal combustion engines. Such engines can be either two-stroke (now obselete) or four-stroke cycle engines, running on petrol.
Internal combustion engines used with lawn mowers normally have only one cylinder. Power generally ranges from two to seven horsepower (1.5 to 6.75 kW). The engines are usually carbureted and require a manual pull crank to start them, although electric starting is offered on some models. Some mowers have a throttle control on the handlebar with which the operator can adjust the engine speed.
Other mowers have a fixed, pre-set engine speed. Petrol mowers have the advantages over electric mowers of greater power and distance range. However, they create substantial pollution and their engines require periodic maintenance such as cleaning or replacement of the spark plug and air filter.
Corded Electric Mowers
Corded electric mowers are 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 (RCD) on the outlet may reduce the shock risk.
Cordless Electric Battery Mowers
Cordless electric mowers are powered by a variable number (typically 1-4) of 12 volt rechargeable batteries. Typically more batteries mean more run time and/or power. Batteries can be in the interior of the lawn mower or on the outside. If on the outside the drained batteries can be replaced with recharged batteries. Cordless mowers have the maneuverability of a petrol powered mower and the environmental friendliness of a corded electric but are more expensive and come in fewer models (particularly self-propelling) than either.
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 above the ground. 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. The most significant downside, however, is the cumbersome usability in rough terrain or on the edges of lawns, as the lifting air-cushion is destroyed by wide gaps between the chassis and the ground.