periphery speed

circumferential speed

circumferential speeds

peripheral speed

peripheral speeds

peripheral velocities

peripheral velocity

periphery speed

periphery speeds

rim speed

rim speeds

1) General subject: peripheral speed

2) Aviation: tip speed

3) Naval: rotational speed

4) Military: annular velocity, circular velocity

5) Engineering: circumferential speed, circumferential velocity, peripheral velocity, periphery speed, rim speed, rotary velocity, rotational velocity, surface speed, velocity of rotation

6) Automobile industry: line speed

7) Forestry: rim speed (пилы)

8) Oil: peripheral speed (на периферии долота), peripheral velocity (на периферии долота), radial velocity

9) Mechanic engineering: circumference speed

10) Mechanics: surface velocity

11) Coolers: peripheral speed (рабочего колеса), tip speed (рабочего колеса)

12) Automation: surface foxtail

13) Plastics: speed of torque

14) Combustion gas turbines: tip speed (концов лопаток)

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1) General subject: circumferential, fringe

2) Geology: peripheric

3) Biology: extraneous, extraneous (существующий вблизи границы ареала или ближе к ней, чем к центру распространения), peripherical

4) Medicine: acentric, peripheral

5) Anatomy: distal

6) Mathematics: periphery

7) Mechanic engineering: rim speed

8) Makarov: rim

SUBJECT AREA: Aerospace, Ports and shipping

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He was educated at Gresham's School in Holt and at Peterhouse College, Cambridge, where he graduated in engineering in 1931; he was made an Honorary Fellow in 1974. Cockerell entered the engineering firm of W.H.Allen \& Sons of Bedford as a pupil in 1931, and two years later he returned to Cambridge to engage in radio research for a further two years. In 1935 he joined Marconi Wireless Telegraph Company, working on very high frequency (VHF) transmitters and direction finders. During the Second World War he worked on airborne navigation and communication equipment, and later he worked on radar. During this period he filed thirty six patents in the fields of radio and navigational systems.

In 1950 Cockerell left Marconi to set up his own boat-hire business on the Norfolk Broads. He began to consider how to increase the speed of boats by means of air lubrication. Since the 1870s engineers had at times sought to reduce the drag on a boat by means of a thin layer of air between hull and water. After his first experiments, Cockerell concluded that a significant reduction in drag could only be achieved with a thick cushion of air. After experimenting with several ways of applying the air-cushion principle, the first true hovercraft "took off" in 1955. It was a model in balsa wood, 2 ft 6 in. (762 mm) long and weighing 4½ oz. (27.6 g); it was powered by a model-aircraft petrol engine and could travel over land or water at 13 mph (20.8 km/h). Cockerell filed his first hovercraft patent on 12 December 1955. The following year he founded Hovercraft Ltd and began the search for a manufacturer. The government was impressed with the invention's military possibilities and placed it on the secret list. The secret leaked out, however, and the project was declassified. In 1958 the National Research and Development Corporation decided to give its backing, and the following year Saunders Roe Ltd with experience of making flying boats, produced the epoch-making SR N1, a hovercraft with an air cushion produced by air jets directed downwards and inwards arranged round the periphery of the craft. It made a successful crossing of the English Channel, with the inventor on board.

Meanwhile Cockerell had modified the hovercraft so that the air cushion was enclosed within flexible skirts. In this form it was taken up by manufacturers throughout the world and found wide application as a passenger-carrying vehicle, for military transport and in scientific exploration and survey work. The hover principle found other uses, such as for air-beds to relieve severely burned patients and for hover mowers.

The development of the hovercraft has occupied Cockerell since then and he has been actively involved in the several companies set up to exploit the invention, including Hovercraft Development Ltd and British Hovercraft Corporation. In the 1970s and 1980s he took up the idea of the generation of electricity by wavepower; he was Founder of Wavepower Ltd, of which he was Chairman from 1974 to 1982.

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SUBJECT AREA: Electricity, Land transport, Railways and locomotives

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Davidson, son of an Aberdeen merchant, attended Marischal College, Aberdeen, between 1819 and 1822: his studies included mathematics, mechanics and chemistry. He subsequently joined his father's grocery business, which from time to time received enquiries for yeast: to meet these, Davidson began to manufacture yeast for sale and from that start built up a successful chemical manufacturing business with the emphasis on yeast and dyes. About 1837 he started to experiment first with electric batteries and then with motors. He invented a form of electromagnetic engine in which soft iron bars arranged on the periphery of a wooden cylinder, parallel to its axis, around which the cylinder could rotate, were attracted by fixed electromagnets. These were energized in turn by current controlled by a simple commutaring device. Electric current was produced by his batteries. His activities were brought to the attention of Michael Faraday and to the scientific world in general by a letter from Professor Forbes of King's College, Aberdeen. Davidson declined to patent his inventions, believing that all should be able freely to draw advantage from them, and in order to afford an opportunity for all interested parties to inspect them an exhibition was held at 36 Union Street, Aberdeen, in October 1840 to demonstrate his "apparatus actuated by electro-magnetic power". It included: a model locomotive carriage, large enough to carry two people, that ran on a railway; a turning lathe with tools for visitors to use; and a small printing machine. In the spring of 1842 he put on a similar exhibition in Edinburgh, this time including a sawmill. Davidson sought support from railway companies for further experiments and the construction of an electromagnetic locomotive; the Edinburgh exhibition successfully attracted the attention of the proprietors of the Edinburgh 585\& Glasgow Railway (E \& GR), whose line had been opened in February 1842. Davidson built a full-size locomotive incorporating his principle, apparently at the expense of the railway company. The locomotive weighed 7 tons: each of its two axles carried a cylinder upon which were fastened three iron bars, and four electromagnets were arranged in pairs on each side of the cylinders. The motors he used were reluctance motors, the power source being zinc-iron batteries. It was named Galvani and was demonstrated on the E \& GR that autumn, when it achieved a speed of 4 mph (6.4 km/h) while hauling a load of 6 tons over a distance of 1 1/2 miles (2.4 km); it was the first electric locomotive. Nevertheless, further support from the railway company was not forthcoming, although to some railway workers the locomotive seems to have appeared promising enough: they destroyed it in Luddite reaction. Davidson staged a further exhibition in London in 1843 without result and then, the cost of battery chemicals being high, ceased further experiments of this type. He survived long enough to see the electric railway become truly practicable in the 1880s.

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PJGR / GW

SUBJECT AREA: Agricultural and food technology, Electricity, Mechanical, pneumatic and hydraulic engineering, Steam and internal combustion engines

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Gustaf de Laval was educated at the Stockholm Technical Institute and Uppsala University. He proved to have an unfailing vigour and variety in his inventive talent, for his interests ranged from electric lighting and electrometallurgy to aerodynamics. In the 1890s he employed over one hundred engineers to develop his inventions, but he was best known for two: the cream separator and a steam turbine. In 1877 he invented the high-speed centrifugal cream separator, which was probably the greatest advance in butter-making up to that time. By 1880 the separators were being successfully marketed all over the world, for they were quickly adopted in larger dairies where they effected enormous savings in labour and space. He followed this with various devices for the dairy industry, including a vacuum milking machine perfected in 1913. In c. 1882, de Laval invented a turbine on the principle of Hero's engine, but he quickly turned his attention to the impulse type, which was like Branca's, with a jet of steam impinging on a set of blades around the periphery of a wheel. He applied for a British patent in 1889. The steam was expanded in a single stage from the initial to the final pressure: to secure economy with the steam issuing at high velocity, the blades also had to rotate at high velocity. An early 5 hp (3.7 kW) turbine rotated at 30,000 rpm, so reduction gearing had to be introduced. Production started in Sweden in 1893 and in other countries at about the same time. In 1892 de Laval proposed employing one of his turbines of 15 hp (11 kW) in an experimental launch, but there is no evidence that it was ever actually installed in a vessel. However, his turbines were popular for powering electric generating sets for lighting textile mills and ships, and by 1900 were available in sizes up to 300 bhp (224 kW).

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