Study with care the accompanying plans. The materials are one-half by one-quarter-inch pine, free from knots, ten common brass rings three-quarters of an inch in diameter, two round-headed brass screws one inch in length, two flat-headed ones of the same dimensions, two small screw-hooks, and eight assorted brass screw-eyes, there being two of each size. Now that we have the material for the frames, we will begin with Fig. 7, which shows the sail and sheer plan. The frame is made of six pieces of wood. The top piece is exactly two feet in length. The two uprights which hold the wheels are each one foot and one inch long. The two angle pieces are one foot nine inches each. The lower horizontal strip measures two feet three and one-half inches, and is joined to the two angle strips by means of a screw-eye and screw at each extremity. Now cut a strip of pine, making it exactly three feet in length. Set it on the frame in an upright position, allowing a half-inch clearance from the upper horizontal piece. It should be eleven inches from one of the angle pieces at the lower end. Round the upper part above the horizontal strip; it should be brought to a taper at the upper end. This forms the mast. The lower part is uniform, and allows the weight to be moved up and down to insure a correct balance, which is regulated according to the force of the wind. The weight is made of one-and-a-half-inch lead pipe, and is two inches in length. A round plug of pine is driven in the centre of the lead pipe, and a hole is bored in the centre of the plug to fit the balancing-bar.
One of the screw-eyes is inserted through the piece of lead pipe, and by this means the weight can be elevated or brought down the shaft and held firmly in the required place, which will depend on the force of the wind. In regard to the wheels, Fig. 8 shows the simplest constructed. They are made in three parts. Take two of the largest-sized wooden button moulds and a piece of thin board (cut in a circle) smaller than the button moulds. We will say, for instance, the button moulds are one and one-half inches in diameter, and the centre piece of pine is one inch in diameter and one-eighth of an inch thick. The way to get a true circle on this soft pine is to take the one-eighth-inch wood and measure on a separate piece of pine one-half inch, drive in a small wire nail in one extreme of the previously measured strip, and on the other extremity insert the point of a sharp knife. Place on the board used for centre of wheel, and turn in a circle from right to left several times. If the distance between the knife-blade and nail is one-half inch, the wheel cut out will be exactly one inch in diameter.