The story of railway development in the north-west of the American continent. This chapter is by Harold Shepstone and is concluded from part 11. It is the third article in the series on Railway Engineers at Work.
For more than four years thousands of engineers and labourers were engaged on the building of an enormous power scheme by which the waters of the River Shannon, in the Irish Free State, have been harnessed to drive massive turbines. The River Shannon, with a length of 240 miles, is the longest river in the British Isles. Above the well-known city of Limerick, water from the Shannon has been diverted by a huge weir into a headrace or large canal which is seven and a half miles long. At Ardnacrusha the headrace is dammed by the intake building, in which is incorporated a navigational lock. Through enormous pipes known as penstocks the water flows, with a head of 100 feet, to the turbines. Having passed through the power-house, the water is returned to the Shannon through a tailrace which is more than a mile long.
Situated 1,292 feet below the level of the Mediterranean, the Dead Sea has a concentration of salts about eight times greater than that found normally in other seas. The extraction of these salts, which have great commercial value, called for many years of pioneering and experimental work. The Dead Sea itself is more than 1,000 feet deep and forms part of a great natural rift that extends from Syria right into the heart of Africa. The waters of the Dead Sea are impregnated with salts such as potash, which are of great importance to various industries, and, indeed, to our everyday life. Plant has been installed on the shores of this natural chemical store to extract the wealth from the waters. This chapter is by Harold Shepstone, who describes how a great pipe lines was sunk to the bottom of the Dead Sea so that its waters could be pumped into huge evaporating pans to extract the salts.
Although Trevithick is now known as the "father of the steam locomotive", his work on the
development of steam engines, stationary as well as locomotive, was unrecognized until long after his death in 1833.
A FEW years ago - and a hundred years after his death - tardy recognition was made of the genius of a great engineering pioneer, Richard Trevithick, by the unveiling of a statue of him at Camborne, Cornwall. In one hand of the figurer is a model of what was really the first locomotive to be built, that is, the first steam engine which could haul a load along a built track. Before Trevithick such tentative machines as had been made were only steam-driven carriages for travel on roads.
Trevithick was born on April 13,1771, at Carn Brea, not far from Camborne, his father being manager of the Dolcoath Mine and other mines. He was the only boy of a family of five, and when he reached his schooldays he seems to have been anything but a model scholar. The letters of his manhood show that he had not mastered spelling, but he was good at arithmetic and so quick and observant in practical matters that he rapidly picked up mining methods. At the age of twenty-one his reputation for practical engineering was such that mineowners trusted him to report on the comparative merits of the different kinds of pumping engines in Cornwall.
At that time the efficient Boulton and Watt engine had a number of imitators, but the patent protecting it could not be upset. In 1795 the activities of Trevithick and of another engineer named Bull were checked by an injunction for infringement. This, however, merely turned Trevithick's inventiveness into another channel and the next year or two saw his invention
of a water-pressure pumping engine and the building of his first steam carriage. The steam carriage appeared in 1801.
The Boulton and Watt patent had now expired and Trevithick was free to develop his ideas. In 1802 he patented steam engines for stationary and for locomotive use, which had pressures as high as 145 lb, as against the normal Watt pressure of about 5 lb per square inch. This increase was a marked advance in steam engineering. It was, indeed, before its time, as later engineers reverted to lower pressures, primarily for the reason that boiler making was for long carried on in a primitive way. One of the difficulties in the way of making sound boilers was that of obtaining suitable plates. Another was that the correct principles of design were barely understood. Trevithick used cast iron at first but later developed a simple and safe type made of plates. This, under the name of the Cornish boiler, is still manufactured.
The most decisive step was taken in 1804, when the first real locomotive was built. This was made for a colliery tramroad at Penydarran, near Merthyr Tydfil, South Wales. On one of its first trials it went at a speed of five miles an hour, hauling 10 tons of iron and seventy men in five wagons, a feat, far in excess of what could be done with the horse haulage it displaced. This engine was ultimately discarded, as the cast-iron rails on which the train ran had not been built for such a heavy load and kept breaking. Trevithick made a second locomotive for a New-
castle Colliery, and it was a poor copy of this that started the famous George Stephenson on his successful career of locomotive building. Trevithick's final locomotive was exhibited on a circular track in London, but it attracted little attention. The inventor then devoted his time to improving the stationary steam engine.
The date of the London locomotive was 1808, and from then till 1810 Trevithick remained in that city, full of energy and ready to turn his hand to anything in the way of engineering. He
fitted his engines to dredgers on the River Thames and was concerned with an attempt to drive a tunnel under the river between Rotherhithe and Limehouse (see The First Thames Tunnel). In this again he was before his day. The list of patents he took out while in London is striking. They covered machinery for towing ships and discharging cargo, iron tanks for cargo storage - a sound scheme, as the leaky wooden hulls of the time often ruined a cargo - iron floating docks, iron masts, iron ships and iron buoys.
To a more worldly-minded man than Trevithick fortune would have now come, but he seems to have been habitually indifferent in monetary affairs, and imprisonment for debt and a serious illness followed. Having returned to Cornwall, Trevithick remained there until 1816, still actively inventive and energetic. Notable inventions of this period were steam-driven agricultural machines and a screw propeller. Then, having superintended the building of high-pressure winding engines and pumping engines for a Peruvian mine, he set out with them - and with high
Hopes - for Lima. Eleven years of frustration and wandering followed, civil war having brought mining to an end.
Back in London, Trevithick became a consulting engineer, drawing up schemes for reclaiming part of the Zuider Zee, and. investigating mechanical refrigeration, superheating and surface condensers - all to become the subjects of attention by others in later days. Plans for a tower 1,000 feet in height, in commemoration of the passing of the Reform Bill, anticipated Eiffel in
intention though not in performance. Trevithick's last days were again clouded by poverty. He died at Dartford (Kent) in the year 1833 and lies there in some lonely unknown grave.
“A SPILLWAY CHANNEL alongside the navigational locks at Ardnacrusha is designed to take an emergency flow of water from the headrace. Thus when a turbine is shut down a valve opens the spillway sluice and the release of water compensates for the sudden stoppage of the flow through the penstocks. On the left is the special sluice which empties the water from the lock into the tailrace.”
By having made it possible to control the temperature and humidity of air supplied to factories, houses and transport vehicles, the engineer has added materially to the efficiency of many industries, and also to personal comfort. The science of air conditioning is receiving a great deal of attention nowadays. It has considerable influence not only on health and comfort, but also on industrial conditions. The various systems which engineers can now install in buildings, ships, factories and so on are described in this chapter by Sidney Howard.
Continual experiment and research are being carried out by engineers to find new methods of mining for coal and to minimize the many dangers which miners incur in their work underground. Coal mining is one of the most important of engineering subjects, one in which the human element is a big factor. This chapter describes the marvellous improvements which are now used to aid the miner in his work and to minimize the danger in which he toils. This chapter by David Masters describes also machines such as the automatic cutters which are replacing where possible the more laborious method of hand cutting from the coal face. The author describes, too, how the coal is graded and brought to the surface from these underground works of man. The article is concluded in part 13.
The Shannon Power Scheme:
“GENERATORS at Ardnacrusha Power Station are rated at 30,000 kVA. The generator in the foreground is partly dismantled. To the generators are coupled turbines, each having a maximum output of 38,600 horse-power.”
The Shannon Power Scheme:
“THE FISH LADDER at Parteen Villa is one of the largest in the world, having a length of more than 600 feet. It consists of a series of steps and pools designed to allow salmon to pass the weir on their way to and from their breeding places upstream.”
The Shannon Power Scheme:
“THE ENORMOUS PENSTOCKS at Ardnacrusha have a diameter of 19 ft 8 in. They are 131 feet long and are laid on a slope of 31 degrees. They connect the headrace with the spiral casings of the turbines.”
No. 4482, Golden Eagle, illustrated below, is one of a class of seventeen A4 Pacifics built in 1936-7 to haul the fastest expresses on the LNER. Four earlier engines, of the Silver Link class, were built in 1935. Their duties include the haulage of the Silver Jubilee express between Newcastle-on-Tyne and King's Cross, London. This train, whose standard make-up is seven coaches, weighing 220 tons tare, is booked to cover the 268.3 miles between the two cities in four hours, with an intermediate stop at Darlington. Engines of the Golden Eagle class differ from the four of the Silver Link class, in that they are painted in the standard LNER colours, whereas the earlier engines were finished in grey to tone with the colour of the Silver Jubilee train. Locomotives of the A4 class have three cylinders 18½ in diameter by 26 in stroke. The boiler has a total heating surface of 3325.2 sq feet, to which the tubes contribute 2345.1, the firebox 231.2 and the superheater 748.9 sq feet. The working pressure is 250 lb per sq in. The cylinder diameter is half an inch less and the working pressure 30 lb more than in the A3 Pacifics. The grate area is 41¼ sq feet. Tractive effort, at 85 per cent working pressure, is
35,455 lb. The driving wheels are 6 ft 8 in, the bogie wheels 3 ft. 2 in, and the trailing wheels
3 ft 8 in diameter. The engine weighs, in working order, 102 tons 19 cwt, of which 66 tons are available for adhesion. The eight-wheeled tender has a coal capacity of 8 tons and a water
capacity of 5,000 gallons. The weight of the tender, in working order, is 64 tons 3 cwt. Particular attention has been given to the streamlining. From the buffer beam a casing, extending across the width of the locomotive, rises in a curve to the top of the boiler and merges at the rear into the wedge-shaped front of the cab. A lower casing on either side of the engine covers the cylinders and sweeps back in a curve to the base of the cab. Thus the streamlining forms a horizontal wedge, which tends to lift the exhaust, steam clear above the cab. This is the fifth article in the series on Modern Engineering Practice.