Combine harvester

A combine harvester, often called a combine, is a vital piece of agricultural machinery. It is designed to harvest a wide variety of cultivated seeds. These crops include wheat, rice, oats, rye, barley, corn (also known as maize), sorghum, millet, soybeans, flax, sunflowers, and rapeseed. This machine is one of the most important labor-saving inventions in history. It has significantly reduced the percentage of the population that must work in agriculture.

The name "combine" describes how the machine works. Around the start of the 20th century, it combined three separate operations into one single process. These processes are reaping, threshing, and winnowing. A combine can be divided into four main functional parts. First is the intake mechanism that gathers the crop. Second is the threshing and separation system. Third is the cleaning system. Finally, the grain handling and storage system holds the harvested product.

In a conventional combine, the mechanism follows a specific sequence. The cut crop enters the feeder throat, which is also called a feederhouse. A chain and flight elevator carry the crop into the threshing mechanism. This mechanism uses a rotating threshing drum called a cylinder. Grooved steel bars, known as rasp bars, are bolted to this cylinder. As the cylinder rotates, the rasp bars rub the plants against a shaped half-drum called a concave. The concave has a meshed grill that allows grain and chaff to fall through. Because grain is heavier than straw, it falls through the grill rather than floating across. The long straw is carried onto straw walkers to be ejected.

Different crops require different specialized attachments called headers. A standard grain platform uses a reciprocating knife cutter bar and a revolving reel. Some farmers use a "flex" platform for soybeans because the cutter bar can bend over ground contours. For wheat, some use "draper" headers which use a fabric or rubber apron instead of a cross auger. Corn requires a specialized corn head. This head uses snap rolls to strip the leaves and stalks away from the ear. This ensures only the ear and husk enter the machine throat.

The history of the combine shows a long path of mechanical evolution. In 1826, Reverend Patrick Bell designed a reaper in Scotland using the scissors principle. In 1835, Hiram Moore built the first patent for a combine in the United States. His 1835 model was 5.2 meters long and had a cut width of 4.57 meters. By 1839, a version of this machine required 20 horses to pull it. In 1885, Hugh Victor McKay produced the commercially successful Sunshine Header-Harvester in Australia. By 1911, the Holt Manufacturing Company produced a self-propelled harvester.

Technological shifts changed how these machines were powered. Early combines were pulled by teams of horses, mules, or oxen. Some used a bullwheel to provide power. Later, steam power was introduced, and George Stockton Berry integrated combines with steam engines. In the 1920s, companies like Case and John Deere introduced tractor-pulled combines. These used a second engine on the combine to power its internal workings. In 1975, Sperry-New Holland introduced the rotary design. This design uses a helical rotor to strip grain from the stalk instead of rasp bars.

Modern combines are highly advanced and efficient. In 1953, Claas developed the 'Hercules' self-propelled combine, which could harvest 5 tons of wheat per day. Today, the largest "class 10-plus" combines have nearly 800 engine horsepower. They use electronic monitoring to provide operators with data on machine operation and field yield. Some machines even feature hillside leveling systems. This hydraulic system re-orients the machine on steep slopes, such as those in the Palouse region. This prevents grain from sliding to one side and being lost during threshing.