chance+led+him+to+london

SUBJECT AREA: Electricity, Electronics and information technology, Public utilities

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After attending Owens College, Manchester, Hopkinson was admitted to Trinity College, Cambridge, in 1867 to read for the Mathematical Tripos. An appointment in 1872 with the lighthouse department of the Chance Optical Works in Birmingham directed his attention to electrical engineering. His most noteworthy contribution to lighthouse engineering was an optical system to produce flashing lights that distinguished between individual beacons. His extensive researches on the dielectric properties of glass were recognized when he was elected to a Fellowship of the Royal Society at the age of 29. Moving to London in 1877 he became established as a consulting engineer at a time when electricity supply was about to begin on a commercial scale. During the remainder of his life, Hopkinson's researches resulted in fundamental contributions to electrical engineering practice, dynamo design and alternating current machine theory. In making a critical study of the Edison dynamo he developed the principle of the magnetic circuit, a concept also arrived at by Gisbert Kapp around the same time. Hopkinson's improvement of the Edison dynamo by reducing the length of the field magnets almost doubled its output. In 1890, in addition to-his consulting practice, Hopkinson accepted a post as the first Professor of Electrical Engineering and Head of the Siemens laboratory recently established at King's College, London. Although he was not involved in lecturing, the position gave him the necessary facilities and staff and student assistance to continue his researches. Hopkinson was consulted on many proposals for electric traction and electricity supply, including schemes in London, Manchester, Liverpool and Leeds. He also advised Mather and Platt when they were acting as contractors for the locomotives and generating plant for the City and South London tube railway. As early as 1882 he considered that an ideal method of charging for the supply of electricity should be based on a two-part tariff, with a charge related to maximum demand together with a charge for energy supplied. Hopkinson was one the foremost expert witnesses of his day in patent actions and was himself the patentee of over forty inventions, of which the three-wire system of distribution and the series-parallel connection of traction motors were his most successful. Jointly with his brother Edward, John Hopkinson communicated the outcome of his investigations to the Royal Society in a paper entitled "Dynamo Electric Machinery" in 1886. In this he also described the later widely used "back to back" test for determining the characteristics of two identical machines. His interest in electrical machines led him to more fundamental research on magnetic materials, including the phenomenon of recalescence and the disappearance of magnetism at a well-defined temperature. For his work on the magnetic properties of iron, in 1890 he was awarded the Royal Society Royal Medal. He was a member of the Alpine Club and a pioneer of rock climbing in Britain; he died, together with three of his children, in a climbing accident.

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SUBJECT AREA: Metallurgy

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The most valuable part of Bessemer's education took place in the workshop of his inventor father. At the age of only 17 he went to London to seek his fortune and set himself up in the trade of casting art works in white metal. He went on to the embossing of metals and other materials and this led to his first major invention, whereby a date was incorporated in the die for embossing seals, thus preventing the wholesale forgeries that had previously been committed. For this, a grateful Government promised Bessemer a paid position, a promise that was never kept; recognition came only in 1879 with a belated knighthood. Bessemer turned to other inventions, mainly in metalworking, including a process for making bronze powder and gold paint. After he had overcome technical problems, the process became highly profitable, earning him a considerable income during the forty years it was in use.

The Crimean War presented inventors such as Bessemer with a challenge when weaknesses in the iron used to make the cannon became apparent. In 1856, at his Baxter House premises in St Paneras, London, he tried fusing cast iron with steel. Noticing the effect of an air current on the molten mixture, he constructed a reaction vessel or converter in which air was blown through molten cast iron. There was a vigorous reaction which nearly burned the house down, and Bessemer found the iron to be almost completely decarburized, without the slag threads always present in wrought iron. Bessemer had in fact invented not only a new process but a new material, mild steel. His paper "On the manufacture of malleable iron and steel without fuel" at the British Association meeting in Cheltenham later that year created a stir. Bessemer was courted by ironmasters to license the process. However, success was short-lived, for they found that phosphorus in the original iron ore passed into the metal and rendered it useless. By chance, Bessemer had used in his trials pig-iron, derived from haematite, a phosphorus-free ore. Bessemer tried hard to overcome the problem, but lacking chemical knowledge he resigned himself to limiting his process to this kind of pig-iron. This limitation was removed in 1879 by Sidney Gilchrist Thomas, who substituted a chemically basic lining in the converter in place of the acid lining used by Bessemer. This reacted with the phosphorus to form a substance that could be tapped off with the slag, leaving the steel free from this harmful element. Even so, the new material had begun to be applied in engineering, especially for railways. The open-hearth process developed by Siemens and the Martin brothers complemented rather than competed with Bessemer steel. The widespread use of the two processes had a revolutionary effect on mechanical and structural engineering and earned Bessemer around £1 million in royalties before the patents expired.

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SUBJECT AREA: Electricity, Land transport, Public utilities, Railways and locomotives

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George Westinghouse's father was an ingenious manufacturer of agricultural implements; the son, after a spell in the Union Army during the Civil War, and subsequently in the Navy as an engineer, went to work for his father. He invented a rotary steam engine, which proved impracticable; a rerailing device for railway rolling stock in 1865; and a cast-steel frog for railway points, with longer life than the cast-iron frogs then used, in 1868–9. During the same period Westinghouse, like many other inventors, was considering how best to meet the evident need for a continuous brake for trains, i.e. one by which the driver could apply the brakes on all vehicles in a train simultaneously instead of relying on brakesmen on individual vehicles. By chance he encountered a magazine article about the construction of the Mont Cenis Tunnel, with a description of the pneumatic tools invented for it, and from this it occurred to him that compressed air might be used to operate the brakes along a train.

The first prototype was ready in 1869 and the Westinghouse Air Brake Company was set up to manufacture it. However, despite impressive demonstration of the brake's powers when it saved the test train from otherwise certain collision with a horse-drawn dray on a level crossing, railways were at first slow to adopt it. Then in 1872 Westinghouse added to it the triple valve, which enabled the train pipe to charge reservoirs beneath each vehicle, from which the compressed air would apply the brakes when pressure in the train pipe was reduced. This meant that the brake was now automatic: if a train became divided, the brakes on both parts would be applied. From then on, more and more American railways adopted the Westinghouse brake and the Railroad Safety Appliance Act of 1893 made air brakes compulsory in the USA. Air brakes were also adopted in most other parts of the world, although only a minority of British railway companies took them up, the remainder, with insular reluctance, preferring the less effective vacuum brake.

From 1880 Westinghouse was purchasing patents relating to means of interlocking railway signals and points; he combined them with his own inventions to produce a complete signalling system. The first really practical power signalling scheme, installed in the USA by Westinghouse in 1884, was operated pneumatically, but the development of railway signalling required an awareness of the powers of electricity, and it was probably this that first led Westinghouse to become interested in electrical processes and inventions. The Westinghouse Electric Company was formed in 1886: it pioneered the use of electricity distribution systems using high-voltage single-phase alternating current, which it developed from European practice. Initially this was violently opposed by established operators of direct-current distribution systems, but eventually the use of alternating current became widespread.

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