The Locomotive Of Today

143 The Framing, Wheels, etc. : Bogies. ' ' o In some cases, especially in engines fitted with a four wheeled bogie, all the flexibility is provided at one end ; but when the other means are employed, they are often placed at each end of the engine with the rigid wheel base between them. The four-wheeled bogie is made in various ways, the simplest being in the form of a frame having four axle boxes to take bearing on the axles, and a top with a large hole in the centre, through which a pin fixed to the main framing of the engine passes, and about which the bogie works. This arrangement lias onty freedom to move as a pivottecl structure, for being' unprovidecl with lateral displacement, the flexibility of the engine is entirely obtained by the bogie partially turning. It follows, therefore, that this form of bogie is best when the centre pin is not placed exactly in the centre of the distance between the two axles, but when nearer the trailing axle, as then the movement is mostly with the leading axle, and the centre line of the engine is less affected. Fig. 29 illustrates the Adams type of bogie. Four wheels are placed with the axle boxes in guides in frames consisting of two flat plates held by a cross stay in the centre with a large transverse opening in it, exactly midway between the two axles. This has a faced horizontal surface on either upper side, with the ends closed in by cast iron boxes. Through holes in these, pins are passed having upon them the side controlling rubbers separated by thin metal plates. The transverse slide has projecting over upon each side of the part that fits the opening a ledge which engages upon the sliding faces on the cross stay, and the side rubbers are placed on each side between the slide and the distance pieces, an initial compression being given to the rubbers, the amount of which depends upon the average speed for which the engine is designed, being more for high speeds. The slide has an annular clish in its upper side and a hole through the centre for the centre pin. A large rubber pad is placed in the dish, and the bogie pin frame, which is fastened to the main engine frames, having a similar dish in its under surface, bears upon it. A long centre bolt passes through the whole, and a washer and nut is placed below. This pin, however, does not work, but is placed as a precaution against any parts leaving the engine in running. On the top of the axle boxes the ends of two cradles are carried one on either side; the springs are held down by long bolts having- eyes to take pins through the buckle. These pass through the distance pieces at each side, and have india- rubber washers upon them below to reduce the shocks to the