About 4 inches from one end of the bottom sheet cut a ½-inch hole for the water inlet and outlet, that is the hole where the water flows into and out of the tank. In this hole solder a piece of ½-inch brass pipe ½ an inch long and flush with the surface of the tin, as shown at A in Fig 14; and also at B in [Fig. 11].
Now, with a pair of dividers 1¾ inches in diameter, scribe a circle which has its center 3¼ inches from the other end of the bottom and in the middle of it. Cut out three strips of tin ¼ inch wide and 2 inches long—or wire will do—and bend over one end of each one ¼ inch.
Solder these strips to the bottom at equal distances around the circle as shown by the dotted line at B in [Fig. 14], and in the cross-sectional drawing [Fig. 15]. The upright strips serve as guides to keep the cork float in place and yet let it move freely up and down in the tank.
Cut a hole ½ inch in diameter, 2 inches from one end of the cover, or top, of the tank as shown at A in [Fig. 14]. This is for the pipe of the valve mechanism.
Next cut out a hole exactly ¾ inch in diameter, and have its center 3¼ inches from the end. Take a piece of tin and make a valve seat so that its small end is 9/16 inch in diameter and solder it to the top over the hole. This valve seat must be made with particular care, so that it will be perfectly smooth and the valve plug will fit it airtight.
The valve plug is a piece of cork cut in the shape of a cone and must fit the valve seat exactly; soak it in machine oil, then run a piece of aluminum wire 1¾ inches long through it and bend it over on the bottom as shown at C in [Fig. 14] and in [Fig. 15].
FIG. 15. THE AIR CONTROL MECHANISM AND POWER PLANT.
Next solder the bottom to the sides of the tank. Drop the cork float between the upright guides as shown at B in [Fig. 14]. Set the cork valve plug on the cork float. Put on the cover with the aluminum wire sticking up through the hole in the valve seat; and finally solder on the cover.