A is the chimney, B steam-blast used to increase the intensity of the fire, and is worked by rod C running through the hollow handrail D, and ending in handle F. G the steam-dome and safety-valve is the same pattern as previously used, H extra safety-valve, worked from foot-plate; I steam-whistle, K wind-guard, L starting-lever, M smoke-box (with door), N O spring-buffers; P is the line-clearer, or wheel-guard; Q leading wheels, and R R driving ditto; S one of the cylinders, with piston-rod and guides bolted to frame, and showing double connecting rod at T T; U U are the springs which support the weight of the boiler, etc., on the axle-bearings; the spring on rear wheel does not show, being inside the safety-guard and handrail V. W is the back-pressure valve, through which the water is thrown by the force-pump into the boiler; and X is the blow-off tap to clear the model from all water after having used it; and Y shows the side of ash-pan.
Fig. 21.
Now to commence making the framework. This should be made of one-eighth of an inch sheet-iron, squared up perfectly true and flat, and cut out as shown in [Fig. 21], commencing four inches and a half from A, and leaving six inches at B, and cutting it six inches wide there by eight inches long, and continuing it four inches wide for the rest of the distance. Be careful to keep it quite central on the line A B, and leave two connecting strips one inch wide, as at C C.
Fig. 22.
The side-frames come next. These must be much stronger, and quite different from those used in our previous model, and should be cut from the same eighth of an inch plate-iron to the shape shown in [Fig. 22].
The centre of slot B is seventeen inches from one end, the centre of A ten inches from B, and centre of C thirteen inches from B.
In marking out work always measure from a fixed centre, for if you add one measurement to another any slight inaccuracy gets increased with each fresh measurement, and you might finally get the different portions out of place.
The slots are each an inch and a quarter wide by two inches deep, leaving one inch of iron at top as shown. The ornamental spaces can then be cut out, which lightens it considerably without weakening it much.