An unusual subject has been chosen for this week’s cover. The photograph shows a set of immense gearwheels, whose size gives a good indication of the scale of modern engineering. These wheels, of cast steel, were designed for a large crane and were made in a German steelworks. The largest wheel in the photograph has a diameter of more than 16 feet. The double helical, or herringbone teeth were cut after the wheels had been cast. This process is described in the chapter Gears and Gear Cutting in this week’s Part.
The use of concrete in engineering is exemplified by dams, bridges, tunnels, roads and buildings all over the world. The manufacture of Portland cement, which is used in making the concrete, has become a vast industry in which many spectacular processes are involved.
Cement and concrete are perhaps the most common of the materials used by engineers in the construction of the world’s great dams, docks, tunnels, roads, buildings and the like. The colour plate accompanying this chapter reproduces the cover of Part 26, which is based on a remarkable photograph of one of the huge concrete mixing plants used in connexion with the building of the Boulder Dam.
CONCRETE MIXING PLANT used during the building of the Boulder Dam (see pages 47-58), one of the largest concrete structures ever built. Altogether, including subsidiary works, about 4,000,000 cubic yards of concrete were required. This amount involved the consumption of 755,360 tons of cement and the use of many mixing plants. Compressed air was used to force cement from the silos through pipes to the containers of each mixing plant. In one instance the pipe was 5,600 feet long (over a mile), and the cement was delivered to the container at the rate of 76 tons an hour.
Marine engineering practice, similarly to many other branches of engineering, no longer follows precedent. Not long ago the recognized propelling machinery for the coasting vessel was a steam engine with boiler. To-day the heavy-oil engine is often fitted. An excellent example is the motor vessel Castle Combe, a cargo vessel of 454 tons gross, 155 feet long. A view of her engine-room is shown below. There are no boiler-room or coal bunkers and the space thus set free gives more room for cargo and provides much better accommodation for officers and crew than is found in a steamer. This is the twentieth article in the series Modern Engineering Practice.
There are many uses of gearwheels in every form of engineering and the methods of cutting the various kinds of gears are remarkable for their ingenuity and precision. This chapter describes different types of gears used in engineering and the various ways in which gearwheels are cut. It is appropriate that artists should choose the gearwheel, or cogwheel, as it is sometimes called, as a general symbol of the engineer’s work. It represents the transmission of power and is used in almost every form of machine. The gearwheels of a watch or of a motor car are familiar to everyone nowadays, but few people who are not themselves engineers understand how these vital parts are made. The operation of the various cutting machines are described and illustrated in this chapter.
The highest engineering skill is required for the design and construction of the huge locomotives which haul heavy trains at high speeds across the North American continent. Rail transport in America has many distinguishing characteristics, entailed by the vastness of the continent. From the Atlantic to the Pacific is a distance of more than 3,000 miles, and every day huge freight trains, sometimes of 4,000 tons or more, speed across the plains and hills, over the Rockies and the Sierras. The heavy loads, the long distances and the desire for speed have produced the largest and most powerful locomotives in the world. This chapter describes in detail how these mammoths of the American railroads are built. This is the fourth article in the series Marvels of Modern Transport.
Disaster befell the first great viaduct across the Firth of Tay, but the engineers, undaunted, succeeded in building a new bridge, more than two miles long, across the windswept waterway. The bridging of the Firth of Tay is a story of ultimate success after a disastrous failure in a battle against the forces of Nature. The disaster which overtook the first Tay Bridge was caused by the underestimation of the force of the wind which suddenly sweeps up the Firth in a winter gale. The engineers who built the new structure, more than two miles long, succeeded in overcoming the great stresses which are imposed by the strongest gales. This chapter is concluded in part 39.