being lightly riveted over and “caulked” with a light tool which has a circular head. The principal trouble, however, is with broken stays. This
_Steam_Locomotive_Construction_and_Maintenance_Fig49.png) |
Fig. 49.—Cracked and Broken Stays, with Heads Wasted Away Inside Firebox |
defect is shown in Fig. 49. The copper or inside firebox expands in a vertical direction as the steam is being raised, and rises so that the stay is bent or inclined as shown at A, since the outer steel firebox shell to which the stays connect it does not rise so rapidly or to the same extent. The constant bending and re-straightening of the stays causes them to crack as at B and finally fracture as at C. When putting in new stays the holes are slightly enlarged, tapped for new screw threads, and fitted with correspondingly larger stays.
Tubes. The chief defects of steel tubes are (1) pitting of the outsides due to the same cause as pitting of the boiler plates, and more particularly (2) leakage at the firebox tube-plate. In former years leakages were stopped temporarily by driving a conical tool, known as a “drift,” into the open firebox-end of the tube. This forced the metal of the tube against the walls of the tube-holes, but was very injurious to the tubeplate, and its use is now forbidden. Instead,
