Engineering Wonders of the World
Volume I

ENGINEERING WONDERS OF THE WORLD. 292 Elevation Wheels gearing Drums together Plan Fig. 14.—DIAGRAMS TO SHOW THE PRINCIPLES OF BRIGHT’S PAYING-OUT GEAR. (For explanation see text. Some of the details shown in the elevation are omitted from the plan.) the indicator shows the strain to be increasing, the mechanic in charge, by turning the winch, can at once, wholly or par- tially, release the weights that tighten the friction straps, so letting the cable run more or less freely through the pay ing- out machine. “ The cable in coming from the tanks passes under a lightly - weighted 1 jockey ’ pulley, which arrangement, whilst leading the line on to the drum, also checks it slightly. “ From here it is guided by a grooved pulley or V-sheave, L, along the tops of both drums A and B, then three (or four) times round them, and hence over another V-sheave, The working of the entire gear (Fig. 14) was as follows :— * “ Between the two brake drums and the stern of the vessel the cable was led under the grooved wheel 0 of the dynamometer. This wheel had a weight attached to it, and could be moved up or down in an iron frame. If the strain upon the cable was small, the weighted wheel would, by its own weight, bend the cable downwards, and its index would show a low degree of pressure ; but whenever the strain increased, the cable, in straightening itself, would at once lift the dynamometer sheave with the indicator at- tached to it, the latter thereby showing the tension in hundredweights and tons. The amount of strain with a given weight upon the wheel is determined by experiment, and a hand-wheel, or winch, controls the levers of the paying-out machine placed immediately opposite the dynamometer. So that directly * Submarine Tdegraphs: their History, Construction, and Working. By Charles Bright, F.R.S.E., A.M.Inst.C.E., M.I.E.E. (London: Crosby Lockwood and Son.) F, and under the dynamometer sheave 0. From here the cable passes over a second pulley, from whence it is led into the sea by the sheave at the stern of the vessel.” The entire apparatus—simplified as regards the brake—has since been universally adopted for submarine cable work, with the exception that a single flanged drum fitted with a sort of plough, skid, or knife-edge—to guide or “ fleet ” the incoming turn of cable correctly on to the drum—is now applied in place of the grooved sheave, or sheaves, forward of the paying-out machine. As soon as the new gear was installed, all the engineering staff were gathered together for the purpose of thoroughly acquainting themselves with its working. Since the manufacture of the cable in 1857 Professor Thomson had become convinced that the electric conductivity of copper varied greatly with its degree of purity. As a result of the professor’s further investigations, tho