. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . 921 frames in forming a hafkhoiic or founda-tion from which to brace machinery parts,the boiler shell is subjected to additionalstresses which result in cracks in thesheets. The most frequent causes of thesecracks are guide-yoke braces, valve-motion braces and the ordinary bellybraces to frames. Guide-yoke and valve-motion braces are often very stiff and arebolted securely to the frames and studdedto the boiler. When the boiler expandsthe braces and connections are held rigidlyby the frame an
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . 921 frames in forming a hafkhoiic or founda-tion from which to brace machinery parts,the boiler shell is subjected to additionalstresses which result in cracks in thesheets. The most frequent causes of thesecracks are guide-yoke braces, valve-motion braces and the ordinary bellybraces to frames. Guide-yoke and valve-motion braces are often very stiff and arebolted securely to the frames and studdedto the boiler. When the boiler expandsthe braces and connections are held rigidlyby the frame and there is a tendency forthe boiler to tear itself loose from these lisr punishment to which flue-sheetknuckles are subjected, it is important tospecify this material carefully. The fol-lowing limits have been demonstrated byexperience as practical:Tensile strength: 52,000 to 60,000 pounds per square : Not less than 25 per : to per : Not over per cent. The Ashp.^n Various details at the rear of a locomo-tive should be arranged to permit a large. FIG. 4. FRAMES AND FRAME BRACING OF A LARGE LOCOMOTIVE fastenings. This .sets up strains in themetal which are aggravated l)y the vibra-tion and pounding to which braces aresubjected. In an effort to overcome these cracks,outside welt plates have been riveted tot!ie boiler to reinforce it where the bracepads are studded Experiments havebeen made with flexible, or partially flex-ible, braces, some of which have so farbeen successful. On engines where breakage of braceshas occurred, some of them are beingreplaced by braces with a pin connectionat the lower as well as upper end. Wherethe use of pins is not favored, however,a thin plate in connection with a cast-steelbrace should provide sufficient flexibilityfor expansion of the boiler and properstiffness for bracing machinery parts. The Back Flue Sheet Boiler back flue sheets of large locomo-tives are renewed and patched more fre-
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