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The modern combine harvester, or simply combine, is a machine that combines the tasks of harvesting, threshing, and cleaning grain crops. The objective is the harvest of the crop; corn (maize), soybeans, flax (linseed), oats, wheat, or rye, among others. The waste straw left behind on the field is the remaining dried stems and leaves of the crop with limited nutrients which is either chopped and spread on the field or baled for feed and bedding for livestock.
Combine harvesters are one of the most economically important labour saving inventions, significantly reducing the fraction of the population engaged in agriculture.
Old Style Harverster found in the Henty, Australia region.
History
A Lely open-cab- combine
In 1826 in Scotland, the inventor Reverend Patrick Bell designed (but did not patent) a reaper machine, which used the scissors principle of plant cutting – a principle that is still used today. The Bell machine was pushed by horses. A few Bell machines were available in the United States. In 1835, in the United States, Hiram Moore built and patented the first combine harvester, which was capable of reaping, threshing and winnowing cereal grain.
Early combines, some of them quite large, were drawn by horse or muleteams and used a bull wheel to provide power. Tractor-drawn, PTO-powered combines were used for a time. These combines used a shaker to separate the grain from the chaff and straw-walkers (grates with small teeth on an eccentric shaft) to eject the straw while retaining the grain. Tractor drawn combines evolved to have separate gas or diesel engines to power the grain separation. Today's combines are self-propelled and use diesel engines for power. A significant advance in the design of combines was the rotary design. Straw and grain were separated by use of a powerful fan. "Axial-Flow" rotary combines were introduced by International Harvester "IH" in 1977. About this time, on-board electronics were introduced to measure threshing efficiency. This new instrumentation allowed operators to get better grain yields by optimizing ground speed and other operating parameters.
In 1911, the Holt Manufacturing Company of California produced a self-propelled harvester.[7] In Australia in 1923, the patented Sunshine Auto Header was one of the first center-feeding self-propelled harvesters.[8] In 1923 in Kansas, the Baldwin brothers and their Gleaner Manufacturing Company patented a self-propelled harvester that included several other modern improvements in grain handling.[9] Both the Gleaner and the Sunshine used Fordson engines; early Gleaners used the entire Fordson chassis and driveline as a platform. In 1929, Alfredo Rotania of Argentina patented a self-propelled harvester.[10] International Harvester started making horse-pulled combines in 1915. At the time, horse powered binders and stand alone threshing machines were more common. In the 1920s, Case Corporation and John Deere made combines and these were starting to be tractor pulled with a second engine aboard the combine to power its workings. The world economic collapse in the 1930s stopped farm equipment purchases, and for this reason, people largely retained the older method of harvesting. A few farms did invest and used Caterpillar tractors to move the outfits.
Tractor-drawn combines (also called pull-type combines) became common after World War II as many farms began to use tractors. An example was the All-Crop Harvester series. These combines used a shaker to separate the grain from the chaff and straw-walkers (grates with small teeth on an eccentric shaft) to eject the straw while retaining the grain. Early tractor-drawn combines were usually powered by a separate gasoline engine, while later models were PTO-powered. These machines either put the harvested crop into bags that were then loaded onto a wagon or truck, or had a small bin that stored the grain until it was transferred to a truck or wagon with an auger.
In the U.S., Allis-Chalmers, Massey-Harris, International Harvester, Gleaner Manufacturing Company, John Deere, and Minneapolis Moline are past or present major combine producers. In 1937, the Australian-born Thomas Carroll, working for Massey-Harris in Canada, perfected a self-propelled model and in 1940, a lighter-weight model began to be marketed widely by the company.[11] Lyle Yost invented an auger that would lift grain out of a combine in 1947, making unloading grain much easier.[12] In 1952 Claeys launched the first self-propelled combine harvester in Europe;[13] in 1953, the European manufacturer Claas developed a self-propelled combine harvester named 'Hercules', it could harvest up to 5 tons of wheat a day.[14] This newer kind of combine is still in use and is powered by diesel or gasoline engines. Until the self-cleaning rotary screen was invented in the mid-1960s combine engines suffered from overheating as the chaff spewed out when harvesting small grains would clog radiators, blocking the airflow needed for cooling.
A significant advance in the design of combines was the rotary design. The grain is initially stripped from the stalk by passing along a helical rotor, instead of passing between rasp bars on the outside of a cylinder and a concave. Rotary combines were first introduced by Sperry-New Holland in 1975.[15]
In about the 1980s on-board electronics were introduced to measure threshing efficiency. This new instrumentation allowed operators to get better grain yields by optimizing ground speed and other operating parameters.
Combine heads
Combines are equipped with removable heads (called headers) that are designed for particular crops. The standard header, sometimes called a grain platform (or platform header), is equipped with a reciprocating knife cutter bar, and features a revolving reel with metal or plastic teeth to cause the cut crop to fall into the head. A cross auger then pulls the crop into the throat. The grain header is used for many crops, including grain, legumes, and many other crops.
Wheat headers are similar except that the reel is not equipped with teeth. Some wheat headers, called "draper" headers, use a fabric or rubber apron instead of a cross auger. Draper headers allow faster feeding than cross augers, leading to higher throughputs. In high yielding European crops, such headers have no advantage, as the limiting factor becomes grain separation. On many farms, platform headers are used to cut wheat, instead of separate wheat headers, so as to reduce overall costs.
Dummy heads, or pick-up headers, feature spring-tined pickups, usually attached to a heavy rubber belt. They are used for crops that have already been cut and placed in windrows or swaths. This is particularly useful in northern climates, such as western Canada, where swathing kills weeds, resulting in a faster dry down.
While a grain platform can be used for corn, a specialized corn head is ordinarily used instead. The corn head is equipped with snap rolls that strip the stalk and leaf away from the ear, so that only the ear (and husk) enter the throat. This improves efficiency dramatically since so much less material must go through the cylinder. The corn head can be recognized by the presence of points between each row.
Occasionally, row-crop heads are seen that function like a grain platform, but have points between rows like a corn head. These are used to reduce the amount of weed seed picked up when harvesting small grains.
Self propelled Gleaner combines could be fitted with special tracks instead of tires to assist in harvesting rice. Some combines, particularly pull type, have tires with a diamond tread, which prevents sinking in mud.
A John Deere 9410 Combine set to harvest Oats.
A combine harvesting corn
Conventional combine
The cut crop is carried up the feeder throat (commonly called the "feederhouse") by a chain and flight elevator, then fed into the threshing mechanism of the combine, consisting of a rotating threshing drum (commonly called the "cylinder"), to which grooved steel bars (rasp bars) are bolted. The rasp bars thresh or separate the grains and chaff from the straw through the action of the cylinder against the concave, a shaped "half drum", also fitted with steel bars and a meshed grill, through which grain, chaff and smaller debris may fall, whereas the straw, being too long, is carried through onto the straw walkers. This action is also allowed because grain is heavier than straw, which causes it to fall rather than "float" across from the cylinder/concave to the walkers. The drum speed is variably adjustable on most machines, whilst the distance between the drum and concave is finely adjustable fore, aft and together, to achieve optimum separation and output. Manually engaged disawning plates are usually fitted to the concave. These provide extra friction to remove the awns from barley crops. After the primary separation at the cylinder, the clean grain falls through the concave and to the shoe, which contains the chaffer and sieves. The shoe is common to both conventional combines and rotary combines.
Hillside leveling
In the Palouse region of the Pacific Northwest of the United States the combine is retrofitted with a hydraulic hillside leveling system. This allows the combine to harvest the steep but fertile soil in the region. Hillsides can be as steep as a 50% slope. Gleaner, IH and Case IH, John Deere, and others all have made combines with this hillside leveling system, and local machine shops have fabricated them as an aftermarket add-on.
The first leveling technology was developed by Holt Co., a California firm, in 1891. Modern leveling came into being with the invention and patent of a level sensitive mercury switch system invented by Raymond Alvah Hanson in 1946. Raymond's son, Raymond, Jr., produced leveling systems exclusively for John Deere combines until 1995 as R. A. Hanson Company, Inc. In 1995, his son, Richard, purchased the company from his father and renamed it RAHCO International, Inc. In March 2011, the company was renamed Hanson Worldwide, LLC. Production continues to this day.
Hillside leveling has several advantages. Primary among them is an increased threshing efficiency on hillsides. Without leveling, grain and chaff slide to one side of separator and come through the machine in a large ball rather than being separated, dumping large amounts of grain on the ground. By keeping the machinery level, the straw-walker is able to operate more efficiently, making for more efficient threshing. IH produced the 453 combine which leveled both side-to-side and front-to-back, enabling efficient threshing whether on a hillside or climbing a hill head on.
Secondarily, leveling changes a combine's center of gravity relative to the hill and allows the combine to harvest along the contour of a hill without tipping, a danger on the steeper slopes of the region; it is not uncommon for combines to roll over on extremely steep hills.
Newer leveling systems do not have as much tilt as the older ones. A John Deere 9600 combine equipped with a Rahco hillside conversion kit will level to 44%, while the newer STS combines will only go to 35%. These modern combines use the rotary grain separator which makes leveling less critical. Most combines on the Palouse have dual drive wheels on each side to stabilize them.
A leveling system was developed in Europe by the Italian combine manufacturer Laverda which still produces it today.
Palouse hills northeast of Walla Walla
John Deere Combine Leveling System
Sidehill leveling
Sidehill combines are very similar to hillside combines in that they level the combine to the ground so that the threshing can be efficiently conducted; however, they have some very distinct differences. Modern hillside combines level around 35% on average, while older machines were closer to 50%. Sidehill combines only level to 18%. They are sparsely used in the Palouse region. Rather, they are used on the gentle rolling slopes of the midwest. Sidehill combines are much more mass-produced than their hillside counterparts. The height of a sidehill machine is the same height as a level-land combine. Hillside combines have added steel that sets them up approximately 2–5 feet higher than a level-land combine and provide a smooth ride
Maintaining threshing speed
Combines are equipped with removable heads (called headers) that are designed for particular crops. The standard header, sometimes called a grain platform (or platform header), is equipped with a reciprocating knife cutter bar, and features a revolving reel with metal or plastic teeth to cause the cut crop to fall into the head. A cross auger then pulls the crop into the throat. The grain header is used for many crops, including grain, legumes, and many other crops.
Wheat headers are similar except that the reel is not equipped with teeth. Some wheat headers, called "draper" headers, use a fabric or rubber apron instead of a cross auger. Draper headers allow faster feeding than cross augers, leading to higher throughputs. In high yielding European crops, such headers have no advantage, as the limiting factor becomes grain separation. On many farms, platform headers are used to cut wheat, instead of separate wheat headers, so as to reduce overall costs.
Dummy heads, or pick-up headers, feature spring-tined pickups, usually attached to a heavy rubber belt. They are used for crops that have already been cut and placed in windrows or swaths. This is particularly useful in northern climates, such as western Canada, where swathing kills weeds, resulting in a faster dry down.
While a grain platform can be used for corn, a specialized corn head is ordinarily used instead. The corn head is equipped with snap rolls that strip the stalk and leaf away from the ear, so that only the ear (and husk) enter the throat. This improves efficiency dramatically since so much less material must go through the cylinder. The corn head can be recognized by the presence of points between each row.
Occasionally, row-crop heads are seen that function like a grain platform, but have points between rows like a corn head. These are used to reduce the amount of weed seed picked up when harvesting small grains.
Self propelled Gleaner combines could be fitted with special tracks instead of tires to assist in harvesting rice. Some combines, particularly pull type, have tires with a diamond tread, which prevents sinking in mud.
Allis-Chalmers GLEANER L
CLAAS LEXION 570
The threshing process
Despite great advances mechanically and in computer control, the basic operation of the combine harvester has remained unchanged almost since it was invented.
First of all the header, described above, cuts the crop and feeds it into the threshing cylinder. This consists of a series of horizontal rasp bars fixed across the path of the crop and in the shape of a quarter cylinder, guiding the crop upwards through a 90 degree turn. Moving rasp bars or rub bars pull the crop through concaved grates that separate the grain and chaff from the straw. The grain heads fall through the fixed concaves onto the sieves. The straw exits the top of the concave onto the straw walkers.
Since the IH 1440 and 1460 Axial-Flow Combines came out in 1977, combines have rotors in place of conventional cylinders. A rotor is a long, longitudinally mounted rotating cylinder with plates similar to rub bars.
There are usually two sieves, one above the other. Each is a flat metal plate with holes set according to the size of the grain mounted at an angle which shakes. The holes in the top sieve are set larger than the holes in the bottom sieve. While straw is carried to the rear, crop and weed seeds, as well as chaff, fall onto the second sieves, where chaff and crop fall though and are blown out by a fan. The crop is carried to the elevator which carries it into the hopper. Setting the concave clearance, fan speed, and sieve size is critical to ensure that the crop is threshed properly, the grain is clean of debris, and that all of the grain entering the machine reaches the grain tank. (For example, when traveling uphill, the fan speed must be reduced to account for the shallower gradient of the sieves.)
Heavy material, such as unthreshed heads, fall off the front of the sieves and are returned to the concave for re-threshing.
The straw walkers are located above the sieves, and also have holes in them. Any grain remaining attached to the straw is shaken off and falls onto the top sieve.
When the straw reaches the end of the walkers it falls out the rear of the combine. It can then be baled for cattle bedding or spread by two rotating straw spreaders with rubber arms. Most modern combines are equipped with a straw spreader.
Rotary vs. conventional design
For a considerable time, combine harvesters used the conventional design, which used a rotating cylinder at the front-end which knocked the seeds out of the heads, and then used the rest of the machine to separate the straw from the chaff, and the chaff from the grain.
Case IH Combine set to harvest soybeans.
n the decades before the widespread adoption of the rotary combine in the late seventies, several inventors had pioneered designs which relied more on centrifugal force for grain separation and less on gravity alone. By the early eighties, most major manufacturers had settled on a "walkerless" design with much larger threshing cylinders to do most of the work. Advantages were faster grain harvesting and gentler treatment of fragile seeds, which were often cracked by the faster rotational speeds of conventional combine threshing cylinders.
The disadvantages of the rotary combine (which were increased power requirements and pulverization of the straw by-product) prompted a resurgence of conventional combines in the late nineties. Perhaps overlooked, but nonetheless true, when the large engines utilized to power the rotary machines were employed in conventional machines, the two types of machines delivered similar production capacities. Also, research was beginning to show that incorporating above-ground crop residue (straw) into the soil is less useful for rebuilding soil fertility than previously believed. This meant that working pulverized straw into the soil became more of a hindrance than a benefit. An increase in feedlot beef production also created a higher demand for straw as fodder. Conventional combines, which use straw walkers, preserve the quality of straw and allow it to be baled and removed from the field.
