The atmospheric engine invented by Thomas Newcomen in 1712, today referred to as a Newcomen steam engine (or simply Newcomen engine), was the first practical device to harness the power of steam to produce mechanical work. Newcomen engines were used throughout Britain and Europe, principally to pump water out of mines, starting in the early 18th century. James Watt's later engine was an improved version. Although Watt is far more famous today, Newcomen rightly deserves the first credit for the widespread introduction of steam power.
In 1662 Edward Somerset, second Marquess of Worcester, published a book containing several ideas he had been working on. One was for a steam-powered pump to supply water to fountains; the device alternately used a vacuum and steam pressure. Two containers were alternately filled with steam, then sprayed with cold water making the steam condense; this produced a vacuum that would draw water through a pipe up from a well to the container. A fresh charge of steam under pressure then drove the water from the container up another pipe to a higher-level header before being condensed and repeating the cycle. By working the two containers alternately, delivery rate to the header tank could be increased.
Savery's invention had no moving parts. Consequently it cannot be strictly regarded as the first steam "engine", since it could not transmit its power to any external device. There were evidently high hopes for the Miner's Friend, which led Parliament to extend the life of the patent by 21 years, so that the 1699 patent would not expire until 1733. Unfortunately, Savery's device proved much less successful than had been hoped.
A problem with Savery's device stemmed from the fact that a vacuum could only raise water to a maximum height of about , to this could be added another , or so, raised by steam pressure. This was insufficient to pump water out of a mine. In Savery's pamphlet, he suggests setting the boiler and containers on a ledge in the mineshaft and even a series of two or more pumps for deeper levels. Obviously these were inconvenient solutions and some sort of mechanical pump working at surface level – one that lifted the water directly instead of "sucking" it up – was desirable. Such pumps were common already, powered by horses, but required a vertical reciprocating drive that Savery's system did not provide.
It is probable that the first Newcomen engine was in Cornwall, but its location is uncertain, the first two reliable traces being in the Black Country, of which the more famous was that erected at the Conygree Coalworks near Dudley, but this was probably preceded by one built a mile and a half east of Wolverhampton. Both these were used by Newcomen and his partner John Calley to pump out water-filled coal mines. A working replica can today be seen at the nearby Black Country Living Museum, which stands on another part of what was Lord Dudley's Conygree Park.
Soon orders from wet mines all over England were coming in, and some have suggested that word of his achievement was spread through his Baptist connections. Since Savery's patent had not yet run out, Newcomen was forced to come to an arrangement with Savery and operate under the latter's patent,as its term was much longer than any Newcomen could have easily obtained. During the latter years of its currency, the patent belonged to an unincorporated company, The Proprietors of the Invention for raising water by fire.
Although its first use was in coal-mining areas, Newcomen's engine was also used for pumping water out of the metal mines in his native West Country, such as the tin mines of Cornwall. By the time of his death, Newcomen and others had installed over a hundred of his engines, not only in the West Country and the Midlands but also in north Wales, near Newcastle and in Cumbria. Small numbers were built in other European countries, including in France, Belgium, Spain, and Hungary, also at Dannemora, Sweden. Few (if any) were built in America, perhaps because abundant water power was available.
Operation. The pump equipment was heavier than the steam piston, so that the position of the beam at rest was pump-side down/engine-side up. When the regulator valve V was opened, steam was let out of the boiler filling the space in the cylinder beneath the piston. The regulator valve was then closed and the water injection valve V' briefly snapped open and shut sending a spray of cold water into the cylinder. This condensed the steam and created a partial vacuum under the piston. Pressure differential with the atmosphere then drove the piston down making the power stroke whilst raising the pump gear. Steam was then readmitted, driving the condensate down the sinking pipe and destroying the vacuum by pushing on a release valve snifter valve that opened to atmosphere. Meanwhile, the weight of the pump returned the beam to its initial position whilst driving the water up from the mine. This cycle was repeated around 12 times per minute.
Automation. In early versions the valves or plugs as they were then called, were operated manually by the plug man but the repetitive action demanded precise timing, making automatic action desirable. This was obtained by means of a plug tree which was a beam suspended vertically alongside the cylinder from a small arch head by crossed chains (an early case of double action?) its function being to open and close the valves automatically by means of tappets and escapement mechanisms using weights as and when the beam reached certain positions. On the 1712 engine, the water feed pump was attached to the bottom of the plug tree, but later engines had the pump outside suspended from a separate small arch-head. There is a common legend is that in 1713 a boy named Humphrey Potter, whose duty it was to open and shut the valves of an engine he attended, made the engine self-acting by causing the beam itself to open and close the valves by suitable cords and catches (known as the "potter cord"). ), however the plug tree device (the first form of valve gear) was very likely established practice before 1715 and is clearly depicted in the earliest known images of Newcomen engines by Henry Beighton 1717 (believed by Hulse to depict the 1714 Griff colliery engine) and by Thomas Barney (1719) (depicting the 1712 Dudley Castle engine). Because of the very heavy steam demands, the engine had to be periodically stopped and restarted, but even this process was automated by means of a buoy rising and falling in a vertical stand pipe fixed to the boiler (the first pressure gauge?). The buoy was attached to the scoggen, a weighted lever that worked a stop blocking the water injection valve shut until more steam had been raised.
Pumps Most images show only the engine side, giving no information on the pumps. Current opinion is that at least on the early engines, dead-weight force pumps were used, the work of the engine being solely to lift the pump side ready for the next downwards pump stroke. This is the arrangement used for the Dudley Castle replica which effectively works at the original stated rate of 12 strokes per minute/10 gallons (54.6litres) lifted per stroke. The later Watt engines worked lift pumps powered by the engine stroke and it may be that later versions of the Newcomen engine did so too.
By 1725 the Newcomen engine was in common use in collieries, and it held its place without material change for about three-quarters of a century. Towards the close of its career, the atmospheric engine was much improved in its mechanical details and its proportions by John Smeaton, who built many large engines of this type during the 1770s. Use of the Newcomen engine was extended in some places to pump municipal water supply, circulate water for water wheels driving machinery (for example by Richard Arkwright); one was used to refill the upper pool at Coalbrookdale so that there was more water available to drive the blast furnaces; this was also done at Madeley Wood or Bedlam Furnaces and others of the same period (the 1750s). But the urgent need for an engine to give rotary motion was making itself felt and this was done with limited success by Wasborough and Pickard using a Newcomen engine to drive a flywheel through a crank. Although the principle of the crank had long been known, Pickard managed to obtain a 12-year patent in 1780 for the specific application of the crank to steam engines; this was a setback to Boulton and Watt who got round the patent by applying the sun and planet motion to their advanced double-acting rotative engine of 1782.
Newcomen's engine was only replaced when James Watt improved it to avoid this problem (Watt had been asked to repair a model of a Newcomen engine by Glasgow University. A model exaggerated the scale problem of the Newcomen engine). In the Watt steam engine, condensation took place in a separate container, attached to the steam cylinder via a pipe. When a valve on the pipe was opened, the vacuum in the condensor would, in turn, evacuate that part of the cylinder below the piston. This eliminated the cooling of the main cylinder, and dramatically reduced fuel use. It also enabled the development of a reciprocating engine, with upwards and downwards power strokes more suited to transmitting power to a wheel.
The expiry of the patents led to a rush to install Watt engines in the 1790s, and Newcomen engines were eclipsed - even in collieries. Probably the last Newcomen-style engine to be used commercially – and the last still remaining on its original site – is at Elsecar, near Barnsley in South Yorkshire (at Elsecar Heritage Centre).