Now if all the fittings are well made and oiled, the engine ought to work easily and smoothly without noise if the fly-wheel is spun round.
Fig. 26 at the end of this section represents the engine as finished.
We must now turn our attention to the boiler. For this you must obtain some sheet copper; get the size known as 12-lb. copper--that is, the sheet two feet by eight feet weighs 12 lb. You must also procure some copper tubing one-third of an inch in diameter. Get also the following articles; two brass gauge-taps, 1s. 3d. each; one steam-tap with union, 1s. 6d.; man-hole or water-filler, 1s. 6d.; spring safety-valve set to 30 lb. the inch, 1s. 4d. If these are not already fitted with screw-blocks get them so fitted when buying them. Fig. 12 represents the safety-valve with the screw-block.
Cut out of your copper a piece (Fig. 13) eighteen inches and three-quarters long and nine inches wide. Draw a line A B at right angles to the two long sides, and bisecting them. From A and B mark off the distances shown in the figure. Bore the holes, C, D, E, and F, the sizes marked, and in the places indicated. Bend the plate so that the middle eight inches form a semicircle with a radius of two and a half inches, and the five-inch parts are straight and five inches apart. Turn in the remaining half inch at each side to form a foot for the boiler to stand on. The copper will now be like Fig. 14, and will form the body of the boiler. Take two small sheets of copper eight inches long by six inches wide, and mark one as in Fig. 15 and the other as in Fig. 16. Cut them out carefully, and in Fig. 15 bore two holes one-eighth of an inch in diameter in the places marked. Turn up the edge all round the sides and circular portions of both plates, a quarter of an inch wide, till it is at right angles to the other part of the plate, as in Fig. 17. Fit one of these pieces on each end of the boiler body, so that the turned-up edges of the ends fit outside the boiler body. The Fig. 16 is to fit over the end of the boiler that has the two holes in the top. Solder or braze the ends to the boiler body.
I should strongly recommend all the joints of the boiler being brazed, as in the event of the vessel steaming far from shore, the water running short, and the lamp still burning, it would melt the solder, and the boiler would fall to pieces, but if brazed it would not be injured if made red-hot. If you solder the parts together you can do it yourself from directions given in the section on the magic-lantern, but in soldering copper or brass together both surfaces of the joint must be first tinned over.