Thomas Newcomen

Thomas Newcomen (baptised February 24, 1664; died August 5, 1729) was a blacksmith, plumber, and tinsmith by trade, and a baptist lay preacher by calling. He was born in Dartmouth, Devon, England, near a part of the country noted for a number of tin mines. Flooding was a major problem, restricting the depth at which the mineral could be mined. Newcomen's contribution was to perfect a practicable steam engine for pumping water. In consequence, he is often referred to as a father of the Industrial Revolution, as the inventor of the Newcomen steam engine.

Newcomen developed his steam engine with his business partner Thomas Savery in 1712. Savery had proposed a 'fire engine' that would act as a kind of thermic syphon. In this process, an empty container was attached to a tube that terminated in a sump at the bottom of the mine. Low pressure steam was admitted and then condensed (with the assistance of a cold water spray) to produce a vacuum. This resulted in water being sucked up the pipe into the container, where it was trapped and then released, prior to the cycle repeating itself. The 'fire engine' was not very effective, and could not work beyond a limited depth.

Newcomen thought that this process might have a mechanical application. He conceived the idea of a beam engine, in which a large wooden beam rocked up and down upon a central fulcrum. One side of the beam was attached by a chain to the pump at the base of the mine, and the chain at the other side suspended a piston within a cylinder. The cylinder was open at the top end, above the piston, to the atmosphere. The piston had a bevelled edge, around which hemp rope, kept in place by metal weights, acted as a primitive seal. (The rope was kept wet, so that it would expand against the sides.)

Low pressure steam was admitted into the cylinder below the piston. (This was produced in a haystack boiler, and was all that the then level of technology could tolerate). This was condensed by means of the spray, and the external air (or atmospheric) pressure above the piston acted upon the vacuum created beneath it, pushing the piston down in the power stroke. This raised the working parts of the pump, but their weight immediately returned the beam to its original position. Steam was then readmitted, driving the remains of the condensate out through a one way snifter valve as the process started all over again.

Early versions used manual operation of the valves to work, but the action was slow enough that this was not a serious concern. Later versions used controls attached to the rocking beam to open and close the valves automatically when the beam reached certain positions. The common story 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"). This device was simplified in 1718 by Henry Beighton, who suspended from the beam a rod called the plugtree, which worked the valves by means of tappets.

By 1711 his first commercial engine was completed, replacing a team of 500 horses. In 1712, Newcomen and John Calley built their first engine on top of a water-filled mine shaft to demonstrate its power, pumping it out in hours. It was used later that year at the Conygree Coalworks near Dudley in the West Midlands and a working replica can today be seen at the Black Country Living Museum nearby. 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 shared the patent due to his use of the water spray. Although its first use was in a coal-mining area, Newcomen's engine would find its greatest use pumping water out of the mineral mines in his native West Country, such as the tin mines of Cornwall.

By the time of his death, Newcomen had installed over a hundred of his engines, not only in the West Country and the Midlands but also in north Wales and Cumbria.

By 1725, the engine was in common use in collieries, and it held its place without material change for about three-quarters of a century. Near the close of its career the atmospheric engine was much improved in its mechanical details by John Smeaton, who built many large engines of this type about the year 1770.

The main problem with the Newcomen design was that it was very expensive to operate. After the cylinder was cooled to create the vacuum, the cylinder walls were cold enough to condense some of the steam as it was sprayed in. 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. However, this did not matter very much within the context of a colliery, where coal was freely available. Attempts were made to drive machinery by Newcomen engines, but these were unsuccessful, as the single power stroke produced a very jerky motion.

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 ) 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 cylider 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.

Watt's design, introduced in 1769, did not eliminate Newcomen engines immediately. Watt's vigorous defence of his patents resulted in the desire to avoid royalty payments as far as possible. Richard Arkwright, for example, even attempted to use a Newcomen engine to pump water to power a waterwheel!

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.