Attention is now directed to the construction of the boiler and pumps. The boiler, which is rectangular in shape, is made of thin sheet copper, and measures 4 inches long by 3 inches wide by 2 inches deep. A hole is made in the top, and a brass or copper tube 6 inches long and about 3/4 inch in diameter is soldered in position, as depicted in [Fig. 123]. This tube acts as a chimney on the dry-dock, but it is really used for filling the boiler, and the top is supplied with a tightly fitting cork.
The ends of the boiler also act as supports, and they are made 4 inches long. The bottom edge is turned up for about 1/4 inch to enable the boiler to be screwed firmly to the lower deck. The boiler occupies a position at one end of the hull, and should fit easily in between decks. A small spirit-lamp is used to furnish heat, and no description need be given of this particular part of the equipment. Before the boiler is firmly fixed in place a small hole should be made near the top at one end. The feed steam-pipe is inserted in this, and soldered in place.
Two small oscillating cylinders, similar to those made for the engine on the Nancy Lee (Chapter 6), should be made. They should not be more than 3/4 inch in length, with a 3/8-inch bore. If the builder has any old model steam-engines in the shop, he may take the cylinders from them instead of constructing new ones for the dry-dock.
The engine is set up as shown in [Fig. 124]. The first job is to make the frame or standards, and this is in one piece. Two pieces of brass (A), measuring 51/2 inches long by 1/2 inch wide and 1/16 inch in thickness, are cut. Next the builder should mark off 11/2 inches from either end, and carefully bend at right angles, after which holes are drilled to accommodate the crank-axle B. Two holes must also be made for screws to enable the machine to be screwed to the deck.
The flywheel should be 11/2 inches in diameter, while the bent crank has a throw of 3/16 inch. The steam-cylinder is fixed on the outside of one of the uprights, and the steam-pipe must, of course, be fitted from the inside.
The pump-cylinder is composed of a small piece of brass tube 1 inch long and 3/8 inch in diameter. The plunger is 1/2 inch long, and the diameter is just sufficient to enable it to work freely up and down inside the brass tube. One end is shaped as shown in [Fig. 125] . This contains a saw cut that enables the pump-rod to be placed between and connected with a pin. The bottom end of the cylinder is now fitted with a brass disk in which a hole is made and a 3/32-inch tube soldered in place. The inside surface of this piece of brass should be countersunk, and the piece is then soldered into the end of the cylinder. Before the plunger is inserted a small lead shot is dropped in, which should be larger than the hole at the bottom of the cylinder, thereby covering it. A hole is drilled in at the side of the cylinder, and a small bent pipe fixed in it. At the top of this pipe a short piece of 3/8-inch brass tube is fixed in place, as indicated. This piece of tubing is closed at both ends. The bottom end is treated like that of the pump-barrel and supplied with a large shot. An outlet-pipe is soldered into the side of the delivery-valve chamber and leads to the side of the hull.