The Locomotive Of Today

The Boiler : Firebox, Barret, S team-dorne, Stays. 9 cylindrical in form, but in all recent engines it has been made rectangular, roughly a box, with the sides and top or crown ni one sheet rolied to the requisite shape, the front or tube plate and back plate are flanged over on three edges to fit in- side this sheet and are rivetted to it. This internal firebox. is usually entirely surrounded with water, except at the bottom where the firegrate is placed. The majority of inner fireboxes are of copper, but a great number of Steel ones are now in use. When of copper the metal may be |-in. to thick through- out, except that portion of the tube plate which is drilled to receive the tubes, where, to secure a good joint, the plate is thickened up to about i-in. When Steel is used, the plate would probably be J-in. thick with |-in. at the tube plate. The outer firebox or shell is commonly built up of three plates—the wrapper which is rolied to form the sides and top, the throat or saddle plate which forms the front, and the back plate which has the firehole through it and acts as an end to the boiler. These latter are flanged to form the corners, either by hand on suitable blocks, or, as is now more customary, pressed to shape in a hydraulic press. The outer shell is rivetted to the inner firebox through the founclation ring, forming the bottom of the water space, and also round the firehole. The wrapper plate has a manhole on the top, which may be used as a seating for the safety valves; it is ot Steel, or best Yorkshire iron from ^-in. to j%-in. thick. The rivets are of best iron or mild steel. The barrel is the portion which contains the tubes, and is usually made up of two or three plates which are rivetted to- gether with either “butt” or “lap” joints; when “butt” jointed, the barrel is parallel throughout, but if “ lap” jointed, it is often telescopic with the smallest ring at the front end. Longitudinal joints are usually double plated “butt” joints. The front tube plate forms the end of the boiler, and in the majority of cases is attached to the barrel by an angle ring. It is frequently customary to rivet the smokebox to the tube plate. When a steam dorne is used it is placed on one of the barrel rings. It is the dry steam collector, and within it the regulator is usually placed; pipes also lead steam from it to several of the valves on the boiler front. The barrel plates are about T%-in. thick, the front tube plate f-in. or f-in. thick. The dorne is either built up of the same material as the barrel, or is cast in brass, iron, or steel, certain designers placing the safety valves upon it. All flat surfaces in the boilers are strengthened by means of stays to resist the pressures commonly employed, which vary from 120 to 200 pounds per sq. in., and all rivetting now,