The Locomotive Of Today

The Boiler: Fire Doors, Air Deflecting Plates, Tubes. 19 this has been much adopted, as it is claimed to give greater flexibility to the firebox. D gives the third method we shall describe, in this both plates are flanged outwards and form a joint by being rivetted together. The great advantage in this is the removal of the rivets from the action of the fire, but it entails severe working of the plates in flanging. The position of the firehole is necessarily the same in all ordinary locomotives, being placed so as to be easily accessible from the foot-plate, but the fire-doors vary considerably on different lines. One type largely used is made with two half- doors which slide in grooves, and are worked by a system of levers, so that both are moved to open or shut together. The doors may be simply plain plates, which must be left partially open for the admittance of air to the fire, or they may be cast hollow, as at E, to allow air to pass up inside the shell then through suitable openings inclined downwards to direct the incoming current on to the fire. Other doors are hinged at the bottom and are opened by allowing them to fali back on to the foot plate, the latch. having a sector with notches, so that the fireman can regulate the quantity of air admitted above the fire by partially opening the door on the latch. This door—shown in elevation and section at F—necessitates the use of a flap plate to protect the men from the heat, as well as to keep the flame in the firebox from dazzling the eyes of the driver during darkness. Another popular pattern is made in halves, hinged top and bottom, the bottom portion opening downwards, and the top part upwards, sectors and catches being provided for the top door to admit a greater or less quantity of air as required. Others, again, hinge at the top and open inwards. These act as deflectors for the air admitted during firing, and the amount of opening is regulated as before by catches. In addition to the above methods some doors are made to hinge at the sides, and open similarly to those adopted on stationary boilers. Air-deflecting plates are provided with those styles ot doors which do not form deflectors in themselves, to direct the incoming atmospheric air downwards on to the fire, and so tend toward the complete combustion of the firebox gases, and also to prevent the cold air from passing direct to the tubes, and causing them to leak by the contraction of their ends in the holes of the tube plate. The diameter of the tubes or flues of the barrel in British practice is usually from if-in. to i-g-in. outside diameter. They are generally 13 S.W.G. thick throughout, but are sometimes made a little thicker for about 18-in. at the firebox end. The metals used are copper, brass, iron, or Steel. When