Editing Combine harvester (section)

==Hillside leveling==
[[File:Palouse hills northeast of Walla Walla.jpg|thumb|[[Palouse]] hills]]
[[File:Massey Ferguson 7260 AL-4 combine with hillside levelling - IMG 4759.jpg|thumb|A [[Massey Ferguson]] combine fitted with the hillside leveling option]]

Hillside leveling, in which a [[hydraulic]] system re-orients the combine, allows combines to harvest steep but fertile soil. Their primary advantage is increased threshing efficiency. Without leveling, grain and chaff slide to one side of the 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 thresh more efficiently. 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 steeper slopes; it is not uncommon for combines to roll over on extremely steep hills. Hillside leveling can be very important in regions with steep hills, such as the [[Palouse]] region of the Pacific Northwest of the United States, where hillsides can have slopes as steep as 50%.

The first leveling technology was developed by Holt Co., a US company in California, in 1891.<ref>{{Cite web |url=http://www.agpowermag.com/articles/articles.php?articleid=1384 |title=Ag Power Mag, Sept 2001 |access-date=2005-02-25 |archive-url=https://web.archive.org/web/20170107050723/http://www.agpowermag.com/articles/articles.php?articleid=1384 |archive-date=2017-01-07 |url-status=dead }}</ref> Modern leveling came into being with the invention and patent of a level sensitive [[mercury switch]] system invented by [[Raymond Alvah Hanson]] in 1946.<ref>{{Cite web|url=https://www.flsmidth.com:443/en-gb/company/about-us/product-brands|title=FLSmidth &#124; Product brands|website=FLSmidth}}</ref> A leveling system was also developed in Europe by the Italian combine manufacturer [[Laverda (harvesters)|Laverda]]. [[Gleaner Manufacturing Company|Gleaner]], [[Case IH|IH/Case IH]], [[Deere & Company|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. Newer leveling systems do not have as much tilt as the older ones, as modern combines use a rotary grain separator which makes leveling less critical. 

===Sidehill leveling===
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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.