This week’s cover shows a circular saw which has no teeth at all and which, moreover, cuts its way through steel much more rapidly than a toothed saw. This saw, in the Swansea works of Sir William Arrol & Co Ltd, is what is known as a friction saw. The steel disk spins round with a peripheral speed of 20,000 feet a minute. The resulting friction of the disk against the work is so great that the metal is burnt away, the saw being fed in as the cut is made. Friction saws are suitable only for work which is not thick, as, for instance, the joist shown in the illustration. For thicker work a toothed saw revolving comparatively slowly is used. The disk of a friction saw is sometimes made of abrasive material.
Separating New York from New Jersey, the great Hudson River has long been an obstacle to transport. The opening of the great George Washington Suspension Bridge in 1932 completed an important new link in the highway systems of the two States. This chapter is the twelfth article in the series Linking the World’s Highways.
LINKING NEW YORK AND NEW JERSEY, the George Washington Bridge across the Hudson River was opened for traffic in 1932. Each of the two towers is 559 ft 6 in high from the top of its pier to the summit of the steelwork. The two great piers have their centres 3,500 feet apart. The anchor span on the Manhattan side is 650 feet long, that on the New Jersey side is 610 feet long. The total length of the bridge, with its approach ramps, is 8,716 feet. The headway in the middle is 213 feet above the river. The two towers contain 41,000 tons of steel.
The network of tube railways under the busy streets of London is the largest in the world. The development of this system of underground transport is a triumph of subterranean engineering. Londoners are justly proud of their transport facilities in general and of their underground railways in particular. The operation of London’s underground railway system is one of the many functions of the London Passenger Transport Board, or London Transport, as the Board is generally called. Such is the prestige of London’s underground that traffic chiefs from the world’s great cities frequently visit London to study the working of the system. There are two main groups of underground lines, the shallow-level tracks of the former Metropolitan and Metropolitan District Railways and the deep-level tubes such as the Central, Bakerloo, Northern and Piccadilly lines. The shallow-level lines were long ago extended above ground into the outer suburbs: the same thing is happening now to many of the deep-level tubes. This chapter not only describes the familiar aspect of this famous underground railway system, but also explains the methods of building the railways and of running them. The chapter is the ninth article in the series Below the Surface.
A pictorial article describing the extension of the Piccadilly Line of London Transport. Until 1932 the northern terminus was Finsbury Park. In that year the tube was extended to Manor House, Turnpike Lane, Wood Green, Bounds Green and Arnos Grove. In the following year the line was extended to Southgate, Enfield West and Cockfosters, in Middlesex.
The name of John Rennie is familiar in connexion with Waterloo Bridge, London Bridge and other bridges. His work as a builder of canals, docks and harbours was probably more important, although his ideas were sometimes wasted by official lack of enterprise.
The shriek of the circular saw is the most familiar sound associated with the sawmill, but many other types of saw are used to cut up the timber in preparation for the ingenious planing and finishing machines used by the woodworker. In this chapter, the methods and machines used in a modern sawmill are explained. The huge circular and band saws operating at high speeds are particularly fascinating objects to the layman, and this chapter will be, in addition, of outstanding interest to the engineer.
The manufacture of pneumatic tyres is a huge industry in which every stage of the conversion from raw rubber to finished tyre is carried out by complex and ingenious machinery. This chapter is concluded in part 37.