gigatos | January 2, 2022
Thomas Newcomen was an English mechanic, born on February 24, 1663 in Dartmouth (Devon, England), died on August 5, 1729 in London.
The Devon region was rich in tin and many mines were exploited there. The evacuation of seepage water was a major problem, and the flooding of shafts prevented the extraction of ore from a certain depth. Newcomen”s contribution was to develop a steam engine that could be used for drainage and that would later replace all machines traditionally dependent on the force of a river.
Newcomen developed his steam engine with his associate Thomas Savery in 1712. Savery had proposed a “hearth engine” that functioned as a kind of thermosiphon. The device consisted of an empty tank connected by a pipe to a sump at the bottom of the mine. Low-pressure steam was admitted into the tank, then condensed by cold water spray, to produce a relative vacuum that sucked in the piston of the machine under the effect of the atmospheric pressure, which was about 1 kgcm2 and acted on the other side of the piston (outer side). The pendulum actuates the piston of a pump that extracts water from a sump. The water retained in the tank was evacuated, and the process was repeated. This “hearth machine” was not very efficient, and could only work below a shallow depth.
The cylinder on the first machines was a prism with a square section. The steam engine was used to pump water in coal mines.
Newcomen designed a pendulum machine, consisting of a large wooden beam swinging around a central pivot. On one side of this beam was a chain connected to a pump at the bottom of the mine, and on the other side was a chain connected to the rod of a piston that could move inside a vertical cylinder open at the top. The sealing was ensured by a primitive seal made of a hemp rope wrapped around the piston, the circumference of which was bevelled. This rope, inflated by humidity, was pressed by means of metal weights.
Steam at low pressure, produced in the drum of a boiler, was admitted into the cylinder. A vacuum was then created by a spray of water condensing the steam, and the atmospheric pressure exerted on the upper face of the piston caused it to descend. This movement activated the moving parts of the pump, which then returned to their initial position by their own weight. The steam was then admitted again under the piston, expelling the condensates through a drain pipe, and renewing the process.
The steam is produced in A and passes into the cylinder B through the pipe C. In this cylinder the steam pushes the piston D upwards, as in Papin”s machine, helped by the counterweight K. The connection between the piston D and the beam F (whose ends are terminated by arcs of circle) is ensured by the fixed rod E and a chain.the counterweight K is attached via the chain H to the other end of the beam. The pump rod is attached to the base of the counterweight. This rod is pushed up and down by the corresponding movement of the counterweight. When the admission of steam through pipe C is stopped by the shut-off valve the contents of the cylinder are confined. Water from the tank L is injected into the cylinder via the pipe P. This water injected into the cylinder accelerates the condensation of the steam in the cylinder, which creates a (relative) vacuum. The piston is then pushed down by the pressure of the external (ambient) air, the piston also drives the beam F. This movement lifts the counterweight K and also the rod I of the pump upwards (this is when the pumping of water from the bottom of the well occurs, the rod works in traction).The pipe R evacuates the condensed water, the immersed part of this pipe, (which has the shape of a U) is represented by the letter S. and closing the circuit of the cylinder firmly M is the connection of a small auxiliary pump that fills the tank L through the pipe N. In the original version the shut-off valves were operated manually.
Sniffing” valve: Newcomen noticed that after several cycles, the machine stopped. This is due to air dissolved in the water (from the boiler and the condensate jet) that accumulates in the cylinder over time. A valve is added to the bottom of the cylinder to vent this air. This valve is loaded with lead so that it only opens when the pressure is at its maximum. When the piston is down and the cylinder is connected to the boiler, the “sniffer” valve opens and lets out air and some steam. It closes when the piston, while going up, discovers the cold cylinder, which makes slightly lower the pressure in the cylinder. Its name comes from the noise it produces.
In the beginning, the steam and sprinkler valves were operated manually. It is reported that in 1713 a boy named Humphrey Potter, in charge of opening and closing the valves of the engine, operated it without assistance by properly placing ropes and stops to open and close the valves. This device was simplified in 1718 by Henry Beighton, who suspended from the pendulum a bar acting on rods that operated the valves.
Newcomen built a marketable machine in 1711, with a power equivalent to six horsepower, or about 4,500 watts. In 1712, Newcomen and John Calley built their first engine near a flooded mine shaft, and pumped it for hours to demonstrate its power. It was later used the same year by Conygree Coalworks near Dudley in the West Midlands, and a working replica of this machine can be seen in a nearby museum, the Black Country Living Museum. Soon orders poured in from wetland mines all over England. Newcomen shared his patent with Savery, because of the use of his sprinkler system. Newcomen”s machine was widely used in the mines of southwest England, particularly in the tin mines of Cornwall.
By the time he died, Newcomen had installed more than a hundred of his machines in the southwest of England, in the Midlands, in North Wales and in Cumbria. Newcomen”s machines and their engine houses, more than 10 meters high and topped by a chimney, multiplied and literally dominated the landscape of the industrial basins to become a characteristic element.
The first machine on the continent was installed in 1721 by the Irishman John O”Kelly in a coal mine at Jemeppe-sur-Meuse in Belgium.
By 1725, these machines were in common use in coal mines, where they were operated without much change for three-quarters of a century. John Smeaton, who built many of these machines around 1770, improved them with many technical details.
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