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.
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 by
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 by
The first part of the Story of the Cinematograph appears in part 32and part 33.
A Mobile Recording Unit
INTERIOR OF A MOBILE RECORDING UNIT as used for production of news reels or films “on location”. A complete sound-recording unit is installed in the van. On the right is the motor control panel and on the left is the recording main amplifier. Above the camera are the recording lamp and oscillograph control unit and the monitoring amplifier.
Machinery of the Sawmill
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, Edwin Judd explains the methods and machines used in a modern sawmill. 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. This is the second article in the series Industrial Machinery at Work.
Moulding Inner Tubes
MOULDING INNER TUBES. The moulds are hollow chambers through which steam is continually circulating. After the tube has been fitted in the mould, the closing of the mould causes a series of automatic controls to come into action, regulating temperature and pressure. At the end of (Page 1047)
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 story of the early days of John Rennie, the son of a farmer of Phantassie, East Lothian, resembles that of other pioneer engineers; for, even when he was a small boy, “making things” was more attractive to him than play. He was born on June 7, 1761. From the age of six his chief delight was to haunt the workshop of a millwright, Andrew Meikle, the inventor of the threshing machine. So keen was the boy on mechanical work that, at the age of twelve, he begged to be allowed to leave school and to enter the workshop.
Wisely, this concession was made; but, equally wisely, he was taken away after two years and sent to the High School at Dunbar. Here he so distinguished himself that, when not yet seventeen, he was recommended to succeed his mathematics master when the master received another appointment. This opened up prospects of a secure and respected future; but Rennie, though he filled the position for six months, felt the urge for building much too strongly to settle down as a schoolmaster. Back home he went, to frequent Meikle’s workshop once more and then to start as a millwright himself.
At the age of nineteen he had as much work as he could get through, but now the scientific side of his calling began to appeal to him, and he decided to enter the University of Edinburgh, and support himself by working in the long summer vacation. There was then nothing that corresponds to the present-day engineering curriculum, but Rennie entered the classes in what would now be called physics and mechanics under Dr. Robison, a friend of James Watt. So, alternately working as a millwright and studying hard, learning French and German, Rennie remained at Edinburgh until 1783. He then made a journey south to see what English engineers were doing. He visited the Bridgewater Canal, a much talked-of work of Brindley’s, some dock construction works at Liverpool, and Boulton and Watt’s famous factory at Birmingham.
The condensing steam engine was by this time fully established, and a notable pair were to be installed in a large new flour mill in London. After his visit to Birmingham, Rennie was appointed to take charge of the fitting up of the mill, which was on a scale hitherto unknown. The task of designing and erecting the plant occupied Rennie for nearly four years, the mill being finished in 1788. It was described, on good authority, as having “effected an entire revolution in millwork generally”. The Albion Mills, at one end of Blackfriars Bridge, London, were unfortunately entirely destroyed by fire early in 1791. About the end of 1791 Smeaton retired from practice and Rennie came to be regarded as his successor. Soon afterwards Rennie was occupied in a number of canal undertakings. His first work of this kind in England was a canal between Reading and Bath, followed by one at Rochdale, Lancashire. In both canals a large number of locks was necessary. Several other canals were surveyed and built by Rennie, this branch of his work becoming more or less a matter of routine. More important, because the subject had been for long shamefully neglected, was his drainage of the Lincolnshire and Cambridgeshire Fens. Few travellers nowadays, seeing these fertile districts from the train, can form an adequate idea of their submerged and desolate condition at the end of the eighteenth century. Attempts at drainage had been made previously, but they seemed abortive, whereas Rennie’s well-planned schemes, carried out between 1799 and 1821, permanently reclaimed immense swamps and wastes.
Perhaps the work with which Rennie is most commonly identified is Waterloo Bridge, across the River Thames. This bridge has been pulled down, sound as when it was built, though deformed at one point by settlement of one of its piers through erosion of the river bed. Rennie’s list of bridges is long. Two more of his -Southwark Bridge and London Bridge - span the River Thames. Below London Bridge, Rennie built the London Docks at Wapping and, with Ralph Walker, the East India Docks farther down the river. With regard to dock equipment, Rennie was ahead of his time. He proposed steam cranes and tramway roads, but both plans were rejected and goods continued to be expensively and laboriously man-handled for long afterwards.
Docks at Hull, Liverpool and many other places were built or designed by Rennie, and much harbour work was undertaken. The building of the breakwater across Plymouth Sound is perhaps the most spectacular of these works.
In the same way as his predecessor, Smeaton, Rennie was responsible for a well-known lighthouse, the Bell Rock, off the Scottish coast between the Firths of Forth and Tay. If his list of completed work is long, his list of reports and schemes is longer. Had some of these projects been carried out, Great Britain would have benefited greatly; but the official mind in those days seems to have been in general singularly timid and lethargic. Perhaps the matter of costs may have appalled it.
A characteristic of the earlier engineers is their intense application to work. Rennie, to his own detriment, was no exception, for it is stated that when he died on October 4, 1821, his unremitting toil had worn him out. A few days before he had been writing to the Navy Board on the subject of dock gates, but no leisured retirement was to round off his activities.
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.
A photograph of the works on the site of Turnpike Lane Station. The curved subway, with a lining of cast-iron segments, is one of the subways by which passengers gain access to the station underground. Escalators were installed in accordance with modern practice. The vertical shaft seen in the photograph was not intended for a lift but was sunk to give communication with the tube tunnel during construction.
A Cross-Cutting Circular Saw
CROSS-CUTTING CIRCULAR SAW at the wagon-building works of the London and North Eastern Railway at Darlington, Co. Durham. An 8-tons overhead travelling crane brings the logs into position. They are then cut into suitable lengths and carried to other types of saw for further cutting. The limit of thickness to which the circular saw will cut is rather less than half its diameter.
The Hudson River Spanned by the George Washington Bridge
THE HUDSON RIVER is spanned by the George Washington Bridge between Fort Washington Park, Manhattan, and Fort Lee, on the New Jersey shore. The bridge is carried on two towers whose centres are 3,500 feet apart. The anchor span on the Manhattan side is 650 feet long, and that on the other side is 610 feet long. Thus the total length is 4,760 feet. The complicated series of ramps and approach roads connecting the Riverside Drive and neighbouring streets with the bridge can be seen on the Manhattan bank.
A London Tube Extension - 2
ABOVE THE GROUND the extension involved the building of a viaduct to carry the line across the North Circular Road between Bounds Green and Southgate. The viaduct is built entirely of brick, with brick piers and rounded arches. The arches were built over timber falsework, as seen in the photograph.
RISING TO THE SURFACE, the railway emerges from the twin tube tunnels through the brickwork portals, as shown in this photograph. The gradient is continued through an excavated trench or cutting until surface level is reached. The line then proceeds as a normal double-track electric railway, running in cuttings or on embankments, bridges or viaducts.
Story of Tyre Production (Part 1)
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 by L H Thomas and is concluded in part 37. It is the twelfth article in the series on the Romance of Industry.