Page:Model Steam Locomotives by Greenly Henry.pdf/197

Model Steam Locomotives a motion plate of the vStyle shown in Fig. 223. It is also convenient in some instances to provide lugs or bosses on the upper edge to carry footplates. In the casting these are left square and, if necessary, are filed one way or the other to suit the inclination of the cylinders, as indicated at c (Fig. 223).

Slide Bars.—The general practice is to carry slide bars from the rear-cylinder cover and a lug or lugs are cast on the motion plate, as shown in Fig. 214. When slide bars only measure 1/8 in. or 3/16 in. wide the fixings require modification. In 1/2-in. scale practice the arrangement shown in Fig.131, Chapter VIII, is employed, the slide bars being turned down and screwed to bolt to a flange formed on the cylinder cover. When secured in this way the only function of the motion plate is to prevent the bars spreading. This is provided for in the two designs of motion plates illustrated in Figs. 221 and 222.

Coupling Rods.— For the same reasons as applied to connecting rods, coupling rods are made in nickel silver instead of the orthodox mild steel, and in all larger models rods should be bushed with brass or bronze bushes forced into holes in the rod ends. For small engines the scheme A, Fig. 224, is quite good and saves quite a lot of work in dealing with the rod. The arrangement at B is common, but more or less of an imitation. For six- or eight-coupled engines without springs rods may be made in one piece, otherwise it is necessary to joint the rods to cater for the vertical movement of the axle boxes when the engine is standing on a surface that is out of level. The usual method is shown in Fig. 224 (c), but Figs. 225 and 226 illustrate alternatives, the first being a modification of the orthodox arrangement to suit the smaller models. The “Atlantic,” “Pacific,” 4—-6—0 and other types of 188