Britain at Work
A Pictorial Description of Our National Industries

228 BRITAIN AT WORK. tube or barrel) is always made slightly less than the outside diameter of the cylinder which it has to cover. Expanded by the application of heat, the outside cylinder or “jacket” is easily slipped over the inner tube, and as it gradually cools the jacket grips with great power the inside cylinder. \\ hen the gun is thus being built up it stands in a pit, where the cylinder jacket next to be placed upon it is brought by a hydraulic lift from one of a series of furnaces heated by gas and dropped over it. With a shield over it, it then gradually cools, measures being taken to ensure that it cools in a uniform fashion. The grip of the cylinders upon each other grows in severity as the outside of the gun is reached, and the com- pression upon the original cylinder, of course, increases with each layer added. This fact discloses the application of an important principle in gun-making. In a natural way the great strain following upon the explosion of the charge of powder would fall heaviest upon the inner cylinder (or barrel), in which the explosion takes place, and the outer cylinders would only experi- ence it in a diminishing degree, in a degree which diminishes so rapidly, as it approaches the exterior part of the gun, that it might almost be said to have disappeared by the time it reaches the outside parts, for, as it will be clear, there is a point under such circumstances where thickness ceases to add strength. By subdividing the gun into cylinders, each cylinder—having been put into a high state of tension by being shrunk on—brings the full measure of its power to withstand strain to the support of the inner cylinder or bore, and the other parts of the gun, that is, each successive layer, reinforces the accumulated resisting power of the whole mass. A further consequence of the system of shrinking the cylinders one over the other is that the compression experienced by the original cylinder or barrel is so severe that the outer cylinders, owing to their being in a state of tension, first take the strain created by the explosion, and as the outer cylinders expand or extend (as the quality of metal guarantees that they will do), the strain is progressively imparted to the original tube, which ultimately receives its allotted proportion. It was to further distribute the strain over the whole gun that the wire or steel riband gun was adopted at Elswick with such success. Great additional strength and security are gained in a gun through con- struction by means of ribands. The gun is also lighter than one built in the ordinary way. The building-up of a gun in ribands minimises the danger from flaw, for even should a flaw escape observation when the riband is being bound on, it is confined to a small area, permits of the employment of steel of greater strength than is attainable in the ingot form, and secures more fully and efficiently than is possible in the usual form of manu- facture the measure of tension in the steel. If our gun is a wire gun, then, which it is nowadays pretty certain to be, the process of wiring must begin when the first steel cylinder barrel is so far finished as to be ready for its jacket. Before that is shrunk on, the wiring has to be done. The riband, which is apparently rather more than a quarter of an inch broad and not half that thickness, is wound on cold from a drum. The gun, revolving slowly, draws the riband from the drum, while the drum is controlled by a brake to ensure that the wire is brought into a full state of tension. The strain varies with each layer of riband, these strains being determined by the brake apparatus attached to the drum shaft, which regulates the amount of tension required for each successive layer. In the Io-inch gun there are fourteen layers of riband. The riband portion of the gun is covered by a casing of steel. The Io-inch riband gun has a thickness of walls of 11 inches, of which 3 inches is of steel riband. In some of the larger guns as much as 100 miles of riband are coiled up between its cylinders. Bored, wired, jacketed, a composite whole, the gun must now be “ rifled.” The rifling is one of the most interesting operations in the series. The cutter is directed in its twisted movements by a pinion and rack, which in their turn are acted upon by wheels rolling along a slightly curved track or framework of iron. The cutter appears to travel along the barrel at a quicker rate than does the boring bar when a gun is being bored ; but, although the rifling only extends up four- fifths of the length of the gun, the operation