Editing Newcomen atmospheric engine (section)

==Successor==
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[[File:Elsecar Newcomen engine.jpg|thumb|upright|Newcomen-style engine at the [[Elsecar Heritage Centre]], in 2006]]
The main problem with the Newcomen design was that it used energy inefficiently, and was therefore expensive to operate. After the water vapor within was cooled enough to create the vacuum, the cylinder walls were cold enough to condense some of the steam as it was admitted during the next intake stroke. This meant that a considerable amount of fuel was being used just to heat the cylinder back to the point where the steam would start to fill it again. As the heat losses were related to the surfaces, while useful work related to the volume, increases in the size of the engine increased efficiency, and Newcomen engines became larger in time. However, efficiency did not matter very much within the context of a colliery, where coal was freely available.

Newcomen's engine was only replaced when [[James Watt]] improved it in 1769 to avoid this problem (Watt had been asked to repair a model of a Newcomen engine by [[Glasgow University]]; a small model that exaggerated the problem). In the [[Watt steam engine]], condensation took place in an exterior condenser unit, attached to the steam cylinder via a pipe. When a valve on the pipe was opened, the vacuum in the condenser would, in turn, evacuate that part of the cylinder below the piston. This eliminated the cooling of the main cylinder walls and such, and dramatically reduced fuel use. It also enabled the development of a [[double-acting cylinder]], with both upwards and downwards power strokes, increasing amount of power from the engine without a great increase in the size of the engine.<ref>{{Cite web |last=Cartwright |first=Mark |title=Watt Steam Engine |url=https://www.worldhistory.org/Watt_Steam_Engine/ |access-date=2024-06-12 |website=World History Encyclopedia |language=en}}</ref>

Watt's design, introduced in 1769, did not eliminate Newcomen engines immediately. Watt's vigorous defence of his [[patents]] resulted in the continued use of the Newcomen engine in an effort to avoid [[royalty payments]]. When his patents expired in 1800, there was a rush to install Watt engines, and Newcomen engines were eclipsed, even in collieries.