The side frames come next. These must be much stronger and quite different from those used in the previous model. They may be cut from the same eighth inch iron to the shape shown in Fig. 22.
The center of slot B is 17 inches from one end, the center of A 10 inches from B, and the center of C 13 inches from B.
In measuring, always start from a given center if you want to be accurate. That is, from B to A and from B to C; not from B to A and from C to B.
The slots are each 1-1/4 inches wide by 2 inches deep, leaving 1 inch of iron at the top, as shown. The four large boles shown in Fig. 23 are only ornamental, and can be now cut out. They also serve to lighten the frame.
The frames, after being smoothed up can be fastened to the bed plate in the manner described before, by angle-irons, or knees, riveted on.
Two end pieces must also be prepared. Let them be 1 inch deep, with the ends hammered square, at right angles, and then riveted to the bed plate and side frames, as shown in Fig. 20. Then drill three holes in them, about an inch and a half from either end, and one in the center, by which to bolt on the buffer beams by means of a couple of screws put in at the back. The buffer beams should be mahogany, 1 inch wide by 2 deep by 10 long, squared nicely and sandpapered. A hook can then be made—Fig. 23—and a hole being drilled in the center of the beam, you can pass the hook stem through and into the central hole of framework, and screw up tight with nut at back, which will hold all firmly in place. The buffers for this model must be properly made, with springs to take the pressure in case you should run into anything.
Fig. 24 shows this buffer. You will have to get it cast. Turn out in your lathe a wooden mold and get four castings in brass made from it. A Fig. 24 is cast with a square base plate 2 inches square, as in front view B, and is secured to the buffer beam by four flat-headed screws. The piece C must be turned true and just the size to slide in and out of A easily. Each part must be finished up in the lathe. A should be an inch and a half long. Drill a hole in the buffer beam to allow the head of the pin to work freely, and another hole in base plate of buffer the size of the pin, whose head prevents the spring from forcing C entirely away from A.
The spring should be made of thick steel wire; the buffers can then be screwed in as just mentioned. The wheel-guard or line-clearer P (Fig. 20) can next be cut out to shape and bolted on to frame, and should just clear the line by a quarter of an inch.
We will now proceed to the axle bearings and springs, U, Fig. 20.
Make a wooden model like Fig. 25, and get 6 castings in brass made from it. They must then be filed up square and smooth and fitted into the slots cut at A, B, C, Fig 22, and either screwed or riveted on by the side holes. Before finally fixing them prepare 6 brass bearings, B, Fig 25, which must fit exactly and slide easily in the inner surface of A, then drilling a hole through each five-eighths of an inch in diameter. These take the axles, which in this model are all straight, and three-quarters of an inch in diameter, shouldered off to five-eighths for the bearings.