,« STEEL CASTINGS AS USED IK MARINE MACHINERY. ■|"fa —ni «.n I. i . ' ' '*", ' '
;fo"Xiin thet ships of the nftvy, encouraged its use.
teppt« showed that, while patterns of simple fori t_io |W» sefction could be made quite successfully, ^rfjjn J"ie#"B required much care and skill to avoid tearing oi&jrdness, which might develop partly from the grea [e^in cooling in the hard unyielding mould, and partly from to- evolution of gases after the metal had been poured, so v.j$bat, at first, it was difficult to get these castings quite solid w-jjjpKl the surfaces were always rough.
i-läk;' Dr. Kirk»$f Napier?s/looking to the reduction of the weight "of moving parts in high-speed engines and the resulting decrease of the inertia strains, found in the piston a suitable v&ubject for cast steel, and designed his large pistons of one fe conical sheet of. steel. In conjunction with the West ;fof"'ßootlaijid Steel Co., he succeeded, aft|r much patient experi-' Stent and many failures, in getting reliable, light, and strong ms. About 1880, the first of these was tnade for H. M. 8. ander, " and they have been adopted for nearly all war Ships and in most first-class merchant ships built since that .#lime.
■ In 1882, turning gear-wheels were added to the list, and . though strong were very rough. Beversing-levers, being of «imple forms, were also cast quite successfully, no machining |ferag required beyond boring and facing.
In 1883, with the introduction of radial valve-gears, came complicated quadrants, with right-angle arms and trun-ms. These quadrants and level's would have been heavy oast-iron, and expensive in bronze or forged steel; where* fore cast-steel did much to render these gears commercial possibilities. The only machining required was that of the slide, faces and trunnions, and these proved quite sound, and free from blow-holes and flaws. Cylinder-frames and rams for hydraulic flanging-presses and riveters were found light and sound'. Thrust-block shoes and eccentric-straps formed simple and reliable castings. In ships, particularly men-of-war, the stern-posts, rudder framing, ram bows, and the A-frames ,or struts of twin screws, huge steel castings of simple sections, were madje with entire success.
About 1886, engine-framing was attempted. After many failures and mishaps comparative success was obtained. Accidents such as that to the engine-framing of one of H. M.