Combine harvester

Combine harvesters are one of the most economically important labour-saving inventions, significantly reducing the fraction of the population engaged in agriculture.

[1] Among the crops harvested with a combine are wheat, rice, oats, rye, barley, corn (maize), sorghum, millet, soybeans, flax (linseed), sunflowers and rapeseed (canola).

The separated straw (consisting of stems and any remaining leaves with limited nutrients left in it) is then either chopped onto the field and ploughed back in, or laid out in rows, ready to be baled and used for bedding and cattle feed.

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.

[6] The stripper and later headers had the advantage of fewer moving parts and only collecting heads, requiring less power to operate.

Refinements by Hugh Victor McKay produced a commercially successful combine harvester in 1885, the Sunshine Header-Harvester.

[8] At the turn of the twentieth century, horse-drawn combines were starting to be used on the American plains and Idaho (often pulled by teams of twenty or more horses).

[10] 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.

The world economic collapse in the 1930s stopped farm equipment purchases, and for this reason, people largely retained the older method of harvesting.

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 via a chute.

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.

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.

The largest "class 10-plus" combines, which emerged in the early 2020's, have nearly 800 engine horsepower (600 kW)[17] and are fitted with headers up to 60 feet (18 m) wide.

Draper headers allow faster feeding than cross augers, leading to higher throughputs due to lower power requirements.

Dummy heads or pick-up headers feature spring-tined pickups, usually attached to a heavy rubber belt.

Some combines, particularly the pull type, have tires with a deep diamond tread which prevents sinking in mud.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.

Gleaner, IH/Case IH, John Deere, and others all have made combines with a hillside leveling system, and local machine shops have fabricated them as an aftermarket add-on.

Self-propelled combines started with standard manual transmissions that provided one speed based on input rpm.

Deficiencies were noted and in the early 1950s combines were equipped with what John Deere called the "Variable Speed Drive".

Despite great advances in mechanics and computer control, the basic operation of the combine harvester has remained unchanged almost since it was invented.

A frequent problem is the presence of airborne chaff and straw, which can accumulate causing a fire hazard and to radiators which can become plugged.

Most machines have addressed these problems with enclosed engine compartments and rotary centrifugal inlet screens which prevent chaff buildup.

A rotor is a long, longitudinally mounted rotating cylinder with plates similar to rub bars (except for in the above-mentioned Gleaner rotaries).

In 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.

While the principles of basic threshing have changed little over the years, modern advancements in electronics and monitoring technology has continued to develop.

Early on, simple magnetic pickups were used to monitor shaft rotation, and issue a warning when they deviated beyond preset limits.

Temperature sensors can also give warning when bearings overheat due to lack of lubrication, sometimes leading to combine fires.

The job of monitoring how much grain is wasted by the thresher by being discharged with the chaff and straw used to require going behind the machine to check.

The application of appropriate synthetic greases will reduce the friction experienced at crucial points (i.e., chains, sprockets and gear boxes) compared to petroleum based lubricants.