Grain-harvesting Combine

Grain-harvesting Combine


a machine that mows and threshes grain, drops it into a bin, and collects straw and chafT in a receptacle or throws them onto the field. Grain-harvesting combines harvest grain, leguminous, and oil crops, grass seeds, lupine, and grain corn by direct combining (simultaneous cutting and threshing of the grain) or two-phase complete harvesting (the stalks are mowed by a harvester and set in a windrow, and the windrows are picked up and threshed). A distinction is made between self-propelled and trailer combines. The working elements of a trailer combine towed by a tractor are driven by an engine mounted on the combine or by a power takeoff shaft of the tractor. The engines of self-propelled grain-harvesting combines also drive all the working elements.

The first grain-harvesting combines were manufactured in the USA in the late 19th century. Those cumbersome machines, built almost entirely of wood, required a team of 20–30 horses to move them. In the first quarter of the 20th century grain-harvesting combines were substantially improved. Wooden parts were replaced by metal parts, and the internal-combustion engine was introduced to drive the working elements; horses gave way first to locomobiles and then to tractors. As the design improved, the production of grain-harvesting combines increased, from 30 combines in 1914 to more than 3,500 in 1920, more than 11,000 in 1925, and almost 37,000 in 1929. At first, trailer harvesting combines were manufactured, but during the last decades their output abroad has decreased sharply. At present, mainly self-propelled combines are produced. A grain-harvesting combine mounted on a self-propelled chassis has been developed.

The first Russian grain-harvesting combine, called the Horse-drawn Root Grain Harvester, was built by the agronomist A. R. Vlasenko in 1868. Grain-harvesting combines were not produced in tsarist Russia. In the USSR, mass production of Kommunar trailer combines with an operating width of 4.6 m was begun in 1930. The Rostsel’mash plant soon mastered production of the S-1 combine with an operating width of 6.1 m. The production of grain-harvesting combines with an operating width of 2.4 m began in 1936, and production of the S-6 trailer combine, as well as the first self-propelled combine, the S-4, began in 1947. Production of the RSM-8 trailer combine, with an operating width of 6 m, and the SK-3 self-propelled combine began in 1956. Since 1962 industry has been producing SK-4 self-propelled combines with capacities of up to 4 kg/sec of the crops being harvested, where the ratio of the weight of the grain to the weight of the straw is 1:1.5. Production of the SKD-5 Sibiriak combine, with a capacity of 5 kg/sec, began in 1969, and production of the SK-5 Niva combine, with a capacity of 5 kg/sec, and the SK-6–8 Kolos, with a capacity of 6 and 8 kg/sec (with the same ratio between the weight of the grain and the weight of the straw), began in 1972. By the end of 1970 there were 884,000 grain-harvesting combines in USSR agriculture.

A combine consists of a harvester, a thresher, a straw collector, a bin, an engine, a cabin or area with control instruments, and the undercarriage. For two-phase harvesting, a pickup attachment is mounted on the harvester.

Production process of the grain-harvesting combine. The cutting apparatus of the harvester cuts the stalks, and the reel places them on the harvester’s platform. A two-way auger conveyor rakes the stalks to the middle of the platform, to the tine mechanism, which feeds the stalks to the inclined transporter. The inclined transporter moves them to the receiving chamber of the thresher. A feed beater feeds the stalks evenly to the thresher. A revolving cylinder interacting with a concave threshes the grain. Most of the threshed grain and small impurities fall through the holes in the concave to a conveyor board. The cylinder ejects the straw and remaining grain onto a bar grate. The tines of the stripper beater throw the straw to a grated straw shaker, which separates the remaining grain and small impurities. The straw enters the collector chamber; when the chamber is filled, the combine operator releases the bottom, using a special mechanism, and the collected straw falls onto the ground. The conveyor board feeds a mixture to the upper cleaning grate. A ventilator blows a stream of air under the cleaning grate. The upper cleaning grate separates the large and light impurities, which are directed by the stream of air into a collector chamber. The grain falls through to the lower cleaning grate, which separates the remaining impurities. The cleaned grain falls down the grain board into the auger trough, which feeds the grain to the bin. When two-phase harvesting is used, the reel is removed and a pickup attachment is secured to the harvester of the combine to thresh grain that has partially dried in windrows. This attachment throws the windrow onto the inclined conveyor, which moves the pickedup stalks to the receiving chamber of the combine thresher. The straw collector on the combine may be replaced by a straw pulverizer, which feeds the crushed stalks and the chaff into a trailer dump wagon. To control the grain-harvesting combine while in motion and to adjust its working elements there is a hydraulic system that raises and lowers the harvester, shifts the reel, and changes its speed of rotation and the speed of movement of the combine. The control mechanisms and monitoring instruments are placed in the operator’s area. The grain-harvesting combine has a diesel engine connected by a V-belt drive to a receiving pulley on the axle of the drive wheels and to the main counterdrive shaft of the thresher.

On the basis of the self-propelled combine described above, modifications have been built for operation in various soil and climatic zones and on soils of various composition and moisture content. In addition, attachments for grain-harvesting combines are manufactured to harvest grass seeds, grain corn, buckwheat, millet, oil crops, and legumes. The self-propelled combine for harvesting rice and grain crops on very moist soils has two caterpillar propulsion devices instead of drive wheels. Some combines for harvesting rice have a second, pintype threshing apparatus. The bulk grain that has been threshed by a pintype thresher is fed to the blade thresher device for final processing.

Combines with highly mobile caterpillar undercarriages are used to harvest grain crops and rice on irrigated fields. When harvesting grain crops that are difficult to thresh and crops whose grain is easily damaged, combines with two threshing devices are used; this increases the capacity by 30 percent and reduces grain losses.


Portnov, M. N. Zernovye kombainy, 5th ed. Moscow, 1966.
Izakson, Kh. I. Samokhodnye kombainy SK-3 i SK4, 3rd ed. Moscow, 1963.
Karpenko, A. N., and A. A. Zelenev. Sel’skokhoziaistvennye mashiny, 2nd ed. Moscow, 1968.