Page:Model Steam Locomotives by Greenly Henry.pdf/234

Boiler Mountings and Fittings be double cased, the outer ornamental covering being made from a stamping or spinning or turned up from a casting. In modern engines the dome is usually much more squat than those on older locomotives, due to the restrictions of the loading gauge and the use of high pitched boilers. The diagram (Fig. 276) illustrates typical shapes, their relative dimensions being obtainable from the appended scale. Chimneys.—The scientific importance of the locomo

tive funnel has already been discussed in Chapter IV, In this country the engineer generally attempts to give the funnel an ornate character, and some of the distinctive shapes are illustrated in the diagram. Where a free- lance design of model is being built, a proportion in which the smallest diameter of the stalk is in a ratio of 1 to 3 3/4 to that of the smokebox on which the chimney rests will be found to give a good appearance. Builtup chimneys are usually distinguished by the joint lines across them, cast-iron ones usually being quite plain; and

Bronse Ball

adjusting screiw

Pad piece with cup shaped under surface

Boiler surface

Goi/er she ft American type of casing

Fig. 274.-“ Ball Safety Valve with Internal Springs.

Fig. 275.—Ball Safety Valve with External Spring. 225