“TUNNELS ON THE NEW LINE up the Serra do Mar inclines have a total length of 1,476 yards. There are no tunnels on the earlier line. The triple rail shown in this illustration is used at all points except the “passing loops”. Thus, for the greater part of the line, the centre rail is common to the two tracks, and is subject to twice as much wear as the outer rails.”
Electricity has been made available in every part of Great Britain by a national network of transmission lines which link the powerful generating stations with local undertakings all over the country. This chapter was written by L H Thomas.
“IN THE HUGE POWER STATION AT DUNSTON-ON-TYNE, one of the more recent stations operating in the Grid scheme. This station, which has a capacity of 150,000 kilowatts -equivalent to some 200,000 horse-power - is housed in a magnificent building of steel and glass. It was opened in February 1933.”
The giant cantilever bridge which spans the Firth of Forth was opened in 1890 and remains one of the wonders of engineering. Built to link the railway systems of the east coast of Scotland, the Forth Bridge has a total length of more than one and a half miles. From the engineer’s point of view the Forth Bridge opened a new era in cantilever construction. This chapter is by Cecil J Allen and is illustrated with pictures provided with the helpful co-operation of Sir William Arrol & Co. Ltd, the builders of the bridge. This is the second article in the series Linking the World’s Highways.
Click on the small image to see a short British Pathe newsreel clip Painting the Forth Bridge and of the men "working on a job that never ends, keeping in good order the great spans of the mighty Forth Bridge" (1930).
The Fife Cantilever of the Forth Bridge
“THE FIFE CANTILEVER of the Forth Bridge with work in progress. Each cantilever arm extends for nearly 700 feet. The gaps between the ends of the cantilevers are spanned by lattice girder bridges 346 ft 6 in long. The main spans of the Forth Bridge are each 1,710 feet in length.”
The Forth Bridge: Photogravure Supplement
“THE TAPERING "UPRIGHTS" of the central towers, from which the Forth Bridge cantilevers extend, consist of steel tubes, 12 feet in diameter. They taper inwards, from 120 feet apart at the base to only 33 feet apart at the top. The whole structure is held together by a complex arrangement of cross-bracings of lattice steelwork.”
Modern methods of treating gold-bearing quartz and the scientific separation of gold from impurities have not destroyed the romance always associated with the discovery of gold. This chapter on gold mining is written by DrMalcolm Burr.
At a Gold Mine in Johannesburg, South Africa
“CYANIDE TANKS at a gold mine in Johannesburg, South Africa. Finely ground ore is admitted to these tanks and treated with a weak solution of cyanide, which dissolves the gold. The solution is then passed over zinc shavings, and the gold precipitates.”
Electric Travelling Crane
An electric crane capable of lifting a load of 200 tons, and made by the Dominion Bridge Company Limited, near Montreal, for the Canadian National Railway. A full description appears above.
Thousands of miles of canals, bringing water from scores of massive dams and barrages to the arid regions of India, have done much to stamp out famine, the scourge that has caused innumerable deaths. This chapter is by Harold Shepstone and is the second article in the series on Triumphs of Irrigation. It is concluded in part 4.
Electric Travelling Crane
ALTHOUGH the jib cranes of the docks or those perched aloft during the building of a steel skyscraper are familiar to many, the more impressive overhead travelling crane seems to be less familiar. Yet without the overhead crane it would be almost impossible to handle the great weights of modern machine parts. It could certainly not be done with the degree of speed necessary nowadays. A visit to a steelworks will show immense ladles of molten steel or brightly glowing forgings transported, without giving them time to cool, by a mighty crane high up in the shadows of the roof. An early invention, the overhead travelling crane was originally worked by hand winches. Later, steam engines and boilers were used, to be superseded by the electric drive. An excellent example of modern overhead crane practice is seen in the photograph below, which shows an electric crane capable of lifting a load of 200 tons, and made by the Dominion Bridge Company Limited, near Montreal, for the Canadian National Railway. Here, a 4-8-2 locomotive, without its tender, is being lifted from its bogie; but that is only one of the operations of which an overhead travelling crane is capable. With its deep girders of great span and furnished with heavy carriages, the crane can be run from one end of a long shop to the other on the rails of the side gantries. The load can be taken across the shop, the bogie or crab, which carries the winch and crane hook, traversing rails on top of the girders. As both motions can be used together, the load can be taken down the shop in any path desired ; thus it can move in a curve if an obstacle is to be avoided, or, should the obstacle extend right across the path, it can be surmounted by lifting the load as the crane travels, just as a steeplechaser clears a fence. Lowering the load is generally done by gravity, powerful brakes being used to stop or check the descent. All these movements are controlled by an operator sitting in a cabin suspended from one of the girders, and having a clear view of the hook and its load. The current for the motors controlling the several motions is picked up from conductors by shoes sliding along them, just as an electric train collects its current from a rail by the side of a line. An overhead crane does not always have two large bogies such as are fitted to the one in the photograph. Often only one is needed, but in large cranes there is generally a small bogie also, so that lighter loads can be handled without using more power than is necessary. The crane illustrated has such an auxiliary bogie, but this is not taking any part in the lifting of the locomotive. The small overhead electric travelling crane is sometimes controlled by suspended pushbuttons, the operator walking on the floor as the crane moves. A useful form of hand-operated overhead crane for light loads is operated by hanging chains passing over sprocket wheels and handled from the door. In electric cranes a large electro-magnet sometimes replaces the hook.
“AT THE BASE OF EACH CANTILEVER the “skewbacks” or connexions of the 12-feet tubs, are extremely complicated in arrangement. From the skewback steel tubes, splayed fanwise, extend to the top member of the cantilever, as may be seen in the photograph of the Fife cantilever. The skewbacks of the Forth bridge are more than 40 feet long.”
Lattice Girders on the Forth Bridge
“A NETWORK OF LATTICE GIRDERS strengthens the cantilevers of the Forth Bridge so that it will withstand a wind pressure of 56 lb. to the square foot. This photograph shows the lattice steelwork in a cantilever at rail level.”
The Mettur Dam
“THE FLOOD WATERS, which greatly impeded work on the Mettur Dam, on the Cauvery River, in Madras, are now released through the sluices of this enormous structure. The effect of building the Mettur Dam has been to bring 1,000,000 acres under cultivation in the Cauvery delta and to protect the chief granaries of madras from drought and famine.”
Work on the Krishnaraja Sagara Dam
“WORK ON THE KRISHNARAJA SAGARA DAM, across the Cauvery River, which runs through Mysore and Madras. The great retaining wall has created a reservoir of 50 square miles, having a capacity of 44,000 million cubic feet. The water irrigates 130,000 acres of parched land and gives power for generating electricity for the cities of Mysore, Bangalore and other centres.”