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Introduction to Lawn mowers
By C. singha
A typical modern gasoline-powered mower.
A lawn mower or lawnmower is a piece of equipment that has one or more revolving blades to cut grass or other plants of a lawn at an even length.
Lawn 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 are suitable for large lawns, and the largest, multi-gang 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 began in the 1860s. 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. 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 U.S. Patent 624,749 , 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 lawn mowers.
The rise in popularity of sports such as lawn tennis, croquet, cricket, football and rugby helped prompt the spread of the invention. Lawn 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 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.
An early Victa rotary mower - National Museum
Rotary lawn were not developed until engines were small enough and powerful enough to run the blades at a high speed. In the 1930s, Power Specialties Ltd. introduced a gasoline-powered rotary lawn mower. One company that produced rotary lawn 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 shaft, 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 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 lawn 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 by making it possible to mow closer to building and wall edges.
2 Criticism and safety problems
The two main issues with the popular gasoline lawn are air pollution and safety. Studies have shown that such a mower emits the same amount of pollution (emissions other than carbon dioxide) in one hour as driving a car for 650 miles. This is largely due to the lack of any real emissions equipment on most lawn mowers; cars have had the benefits of the catalytic converter, fuel injection, and other emissions equipment for decades, while most have little more than a simple muffler and carburetor. Their single-cylinder engines also need to run with a richer fuel-air mixture because of the irregular flow through the carburetor, leading to incomplete combustion.
In addition, rotary lawn 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.
Types of lawn
1. Reel (cylinder) lawn
Rear quarter view of push mower mechanism showing fixed cutting blade in front of roller and wheel-driven (through gears) rotary blades
There are four major types of reel mower: push, walk-behind power, ride-on power, and tow-behind gang mowers.
Push 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 20 inches.
The walk-behind, power reel lawn exist in many variations. The 'greens mower' is used for the precision cutting of golf greens. Unlike the push mower illustrated, these have the roller in front of the reel, the short putting green grass being little affected by this location for the roller. A motor spins the reel at great speed. For residential lawns, the front roller is replaced by small wheels at the sides, and either an electric or an internal combustion engine powers the reel. The operator pushes the mower along. The electric models can be corded or battery powered. Running times for the battery models range from 30 to 75 minutes, and 6 to 24 hours are required to fully recharge the batteries. Most batteries can be recharged several hundred times. Cordless electric reel weigh 30 – 35 pounds.
One type of walk-behind is now largely obsolete. These were powered versions of the push mower and were used for 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.
Riding power reel lawn 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. 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.
Gang reel lawn 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 are used to mow large areas of turf such as sports fields or parks.
The cutting action of a reel mower can provide a very clean cut to the blades of grass, avoiding tissue damage. 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 is made as the spinning blades push the grass past the horizontal cutting bar.
2. Rotary lawn mowers
Rotary lawn 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 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 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.
Rotary lawn powered by electric motors are increasingly popular. Usually, these 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 are also available for small lawns. Electric rotary weigh 45-50 pounds.
The deck of a rotary mower is typically made of steel. Lighter steel is used on less expensive models, heavier on more expensive, which lasts longer. Other deck materials include aluminum, which doesn't rust and is a staple of higher priced mowers, and hard composite plastic, which doesn't rust and is lighter and less expensive than aluminum. Electric lawn typically have a plastic deck.
Rotary lawn 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 lawn 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. Mower manufacturers market their 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 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 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 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 and lawn tractors and is considered more efficient. Bag are limited to smaller yards unless the operator wants to empty the bag several times during cutting. Mulching and bagging are not well suited to long grass or thick weeds. According to Consumer Reports, despite all of the new grass collecting/mulching technology, most Americans continue to use side-discharge when mowing.
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 (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 lawn come in three price ranges. Low priced use older technology, smaller motors, and lighter steel decks. These are targeted at the residential market and typically price is the most important selling point. These are sold through large discount and home improvement stores, range between $100-$400 and have a typical service life of 7-10 years. Higher priced are also primarily targeted at residential customers. These have more features and often have heavier steel, composite plastic or aluminum decks. Most of these are sold through independent dealers who also service the equipment and cost between $400 and $1000. These will last as much as twenty years given regular maintenance. Commercial grade 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 feature the latest technology and include features like disk drive, oil filters, and very heavy steel and, more often, aluminum decks. These 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 $1000.
3. Riding (ride-on) Lawn mowers
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 lawn 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.
A past alternative layout for a ride-on is a rear-mounted engine with one rear-wheel which did the steering, and a front-mounted deck. These were called zero-turning radius (or z-turns or ZT's). New generation ZT's now incorparate a skid steer design where each rear drive wheel is steered with levers rather than a steering wheel. Mower decks are generally behind the front caster wheels. This type of mower is more maneuverable around tight corners than the tractor type and are almost guaranteed to cut mowing time in half, but are generally more expensive than tractor type mowers.
The drives for these 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.
4. Hover Lawn mowers
Hover lawn are powered rotary push 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 are necessarily light in order to achieve the air cushion and typically have plastic bodies with an electric motor, although small petrol-engine versions are also available. A different style of movement is often employed with hover 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 lawn 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.
5. Robotic Lawn Mowers
These little battery operated machines take care of your yard? Yes, and they do an excellent job! When we first put in our robotic lawn everyone came from near and far to tell us why it would not work. Even our neighbors would come and throw sticks and leaves in front of our Robotic Lawn to see if it would chop them up. For two years now our Robotic Lawn have been out taking care of our yard. Making sure all the weeds are chopped down and our grass is perfect every day.
Now our neighbors no longer question whether this little battery operated machine can take care of our yard. Just a few weeks ago our next door neighbor installed one in his yard. Now he can go out and tend to his garden during the cool of the morning and retreat to the a/c during the heat of the afternoon and read instead of having to push that around.
Every morning or every other morning our Robotic Lawn comes out from the docking station and starts the search for tall grass. Once it finds that tall grass it makes a tight circle and slowly starts to make larger and larger circles, cutting down all the high grass in the area. After clearing the tall grass it starts the search and destroy mission again. Once its' battery life is drained, or it believes it has finished taking care of the yard, the mower returns to the charging station on its own to prepare for the next day's adventure.
6. Professional lawn 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 mowed surfaces demand the latter. Wide-area (WAMs) are commercial grade which have decks extended to either side, many to 12 feet. These extensions can be lowered for large area mowing or raised to decrease the mower's width and allow for easy transport on city roads or trailers
Ref: wikipedia, the free encyclopedia
C. singha, a freelance editor
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