Newcomen Steam Engine (Edited from Wikipedia)

SUMMARY

The atmospheric engine was invented by Thomas Newcomen in 1712, often referred to simply as a Newcomen engine. The engine operated by condensing steam drawn into the cylinder, thereby creating a partial vacuum, thereby allowing the atmospheric pressure to push the piston into the cylinder. It was the first practical device to harness steam to produce mechanical work. Newcomen engines were used throughout Britain and Europe, principally to pump water out of mines. Hundreds were constructed through the 18th century.

HOW IT WORKS

Although based on simple principles, Newcomen's engine was rather complex and showed signs of incremental development, problems being empirically addressed as they arose. It consisted of a boiler, usually a haystack boiler, situated directly below the cylinder. This produced large quantities of very low pressure steam, no more than 1 – 2 psi (0.07 – 0.14 bar) – the maximum allowable pressure for a boiler that in earlier versions was made of copper with a domed top of lead and later entirely assembled from small riveted iron plates.

The action of the engine was transmitted through a rocking "Great balanced Beam", the fulcrum of which rested on the very solid end-gable wall of the purpose-built engine house with the pump side projecting outside of the building, the engine being located in-house.

The pump rods were slung by a chain from the arch-head of the great beam. From the in-house arch-head was suspended a piston working in a cylinder, the top end of which was open to the atmosphere above the piston and the bottom end closed, apart from the short admission pipe connecting the cylinder to the boiler; early cylinders were made of cast brass, but cast iron was soon found more effective and much cheaper to produce.

The piston was surrounded by a seal in the form of a leather ring, but as the cylinder bore was finished by hand and not absolutely true, a layer of water had to be constantly maintained on top of the piston. Installed high up in the engine house was a water tank

1 (or header tank) fed by a small in-house pump slung from a smaller arch-head. The header tank supplied cold water under pressure via a stand-pipe for condensing the steam in the cylinder with a small branch supplying the cylinder-sealing water; at each top stroke of the piston excess warm sealing water overflowed down two pipes, one to the in-house well and the other to feed the boiler by gravity.

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, which was called "out of the house".

To start the engine, the regulator valve was opened and steam admitted into the cylinder from the boiler, filling the space beneath the piston. The regulator valve was then closed and the water injection valve 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. The pressure differential (difference) between the atmosphere above the piston and the partial vacuum below then drove the piston down making the power stroke, bringing the beam "into the house" and raising the pump gear.

Steam was then readmitted to the cylinder, destroying the vacuum and driving the condensate down the sinking or "eduction" pipe. As the low pressure steam from the boiler flowed into the cylinder, the weight of the pump and gear returned the beam to its initial position whilst at the same time driving the water up from the mine.

This cycle was repeated around 12 times per minute.

HISTORY

In 1698 Thomas Savery patented a steam-powered pump he called the "Miner's Friend", essentially identical to Somerset's design and almost certainly a direct copy. The process of cooling and creating the vacuum was fairly slow, so Savery later added an external cold water spray to quickly cool the steam.

Savery's invention cannot be strictly regarded as the first steam "engine" since it had no moving parts and 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 theoretical problem with Savery's device stemmed from the fact that a vacuum could only raise water to a maximum height of about 30 ft (9 m), to this could be added another 40 ft (12 m), or so, raised by steam pressure. This was insufficient to pump

2 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. The more practical problem concerned having a boiler operating under pressure, as demonstrated when the boiler of an engine at Wednesbury exploded, perhaps in 1705.

Denis Papin

While in Marburg in 1690, having observed the mechanical power of atmospheric pressure on his 'digester', Denis Papin built a model of a piston steam engine, the first of its kind.

Papin continued to work on steam engines for the next fifteen years. In 1695 he moved from Marburg to Kassel. In 1705 he developed a second steam engine with the help of Gottfried Leibniz, based on an invention by Thomas Savery, but this used steam pressure rather than atmospheric pressure. Details of the engine were published in 1707.

It seems that the idea came to Papin whilst working with Robert Boyle at the Royal Society in London. Papin describes first pouring a small quantity of water into the bottom of a vertical cylinder, inserting a piston on a rod and after first evacuating the air below the piston, placing a fire beneath the cylinder to boil the water away and create enough steam pressure to raise the piston to the top end of the cylinder.

The piston was then temporarily locked in the upper position by a spring catch engaging a notch in the rod. The fire was then removed, allowing the cylinder to cool, which condensed steam back into water, thus creating a vacuum beneath the piston. To the end of the piston rod was attached a cord passing over two pulleys and a weight hung down from the cord's end.

Upon releasing the catch, the piston was sharply drawn down to the bottom of the cylinder by the pressure differential between the atmosphere and the created vacuum; enough force was thus generated to raise a 60 lb (27 kg) weight.

Although the engine certainly worked as far as it went, it was devised merely to demonstrate the principle and having got thus far, Papin never developed it further, although in his paper he did write about the potential of boats driven by "firetubes". Instead he allowed himself to be distracted into developing a variant of the Savery engine.

3 Newcomen

Newcomen took forward Papin's experiment and made it workable, although little information exists as to exactly how this came about. The main problem to which Papin had given no solution was how to make the action repeatable at regular intervals.

The way forward was to provide, as Savery had, a boiler capable of ensuring the continuity of the supply of steam to the cylinder, providing the vacuum power stroke by condensing the steam, and disposing of the water once it had been condensed. The power piston was hung by chains from the end of a rocking beam.

Unlike Savery's device, pumping was entirely mechanical, the work of the steam engine being to lift a weighted rod slung from the opposite extremity of the rocking beam. The rod descended the mine shaft by gravity and drove a force pump, or pole pump (or most often a gang of two) inside the mineshaft.

The suction stroke of the pump was only for the length of the upward (priming) stroke, there consequently was no longer the 30-foot restriction of a vacuum pump and water could be forced up a column from far greater depths. The boiler supplied the steam at extremely low pressure and was at first located immediately beneath the power cylinder but could also be placed behind a separating wall with a connecting steam pipe.

Making all this work needed the skill of a practical engineer; Newcomen's trade as an "ironmonger" or metal merchant would have given him significant practical knowledge of what materials would be suitable for such an engine and brought him into contact with persons having even more detailed knowledge.

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

4 Dannemora, Sweden. Evidence of the use of a Newcomen Steam Engine associated with early coal mines was found in 2010 in Midlothian, VA (site of some of the first coal mines in the US).

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