Page:The American Cyclopædia (1879) Volume III.djvu/722

712 CANNON ship, and then uniting them successively, either by welding, forcing, or shrinking one part over another, and in some instances by screwing them together. The various plans of making built-up guns will be best illus- trated by describing some of the most noted. Armstrong guns are of two kinds, breech - FIG. 10. Breech-loading Armstrong Gun. loaders and muzzle-loaders. The former are made by welding together several wrought- iron tubes at their ends; each tube is from two to three feet long, and is formed by wrap- ping a square bar of iron around a mandrel and welding the edges together. The part in rear of the trunnions is strengthened by envel- oping it with two additional thicknesses or tubes, the outer one of which is like the inner one, but the intermediate one is formed by bending an iron slab into the proper shape and welding its edges. The details of the breech and other parts are shown in fig. 10. The muzzle-loading Armstrong gun (fig. FIG. 11. Muzzle-loading Armstrong Gun. 11) is constructed as follows: The barrel is made of solid steel tempered in oil, by which its brittleness is decreased and tenacity in- creased ; that part of the barrel at and in rear of the trunnions is enveloped by three layers of wronght-iron tubes, not welded together at the ends, but hooked to each other by shoulders and recesses. This operation is accomplished by expanding the end of a tube by heat and slipping it over the shoulder of another, upon which it contracts by cooling. The Armstrong gun is not liable to burst with- out previously showing considerable enlarge- ment. It is stated that of 3,000 guns built on this system, not one has failed by explosion. They have been made as large as 13-inch cali- bre, weighing over 50,000 Ibs. The Whitworth guns are made of a substance called homo- geneous iron, or a species of low steel said to FIG. 12 Whitworth Gun. be made by melting short bars of Swedish iron and adding a small quantity of carbona- ceous matter, after which it is cast into ingots. The smaller Whitworth guns are forged solid ; the larger ones are built up with shells or hoops, forced into each other by hydraulic pressure. For this purpose they are made with a slight taper. The ends of the hoops are joined by screw threads. The hoops are first cast hol- low and then hammered out over a steel man- drel or rolled out in a machine like that used for forming wheel tires. These guns have been made of various sizes up to 7-inch calibre. The Blakely gun is made as follows : The in- FlG. 13. Blakely Gnn. ner tube or barrel is formed of low steel ; the next tube consists of high steel, and is shrunk on the barrel with just sufficient tension to compensate for the difference of elasticity be- tween the two. The outer jacket to which the trunnions are attached is of cast iron, and is put on with only the shrinkage attained by warming it over the fire. The steel tubes are cast hollow and hammered over steel mandrels by steam hammers, by which process they are elongated about 130 per cent., and the tenacity of the metal at the same time increased. They are made to throw 700-lb. projectiles, with a calibre of 12 inches, and weigh as much as 40, 000 Ibs. (See fig. 13.) Palliser and Parsons guns are made by boring out cast-iron guns FIG. 14. Palliser Gun. of old patterns and inserting a new barrel of coiled wrought iron. (See fig. 14.) Krupp guns are made at Krupp's works at Essen, Prus- sia, of solid low cast steel, and have achieved a great celebrity, partly through their enor- mous size and partly through their great dura- bility. The steel is formed in crucibles in the usual way, and is then cast into a large ingot constituting the mass of the gun. This ingot is wrought under powerful steam hammers, to give the requisite texture to the metal and proper form to the gun. In this way it is said that 20-inch muzzle-loading rifle cannon have been made, weighing over 120,000 Ibs. The details of this manufacture are kept secret, but its success is probably due to the very heavy machinery employed, the skilful heating of the large masses to the centre without burning the outside, the presence of manganese in the