In its construction, six pieces of hard wood, of the dimensions shown in the sketch, are required. White wood will do if there is no hard wood at hand. The coin slot is 1/8 in. wide by 1-1/4 in. long, and is cut in only one piece.
No difficulty will be experienced in putting the first five pieces together, but the sixth, or top, piece, shown in the sketch, will not go in, because the bottom edge of the raised side will strike the inside of the piece to the right. By beveling this edge with a chisel from top to bottom between the dadoes, or grooves, it can be forced down quite a distance and sprung in place by placing a block of wood on the high side and striking it a sharp blow with a heavy hammer.—Contributed by J. A. Shelly, Brooklyn, New York.
An Electric Anemometer
By Wm. H. Dettman
The construction of this instrument is so simple that any amateur can make one and if accurate calibrations are desired, these can be marked by comparison with a standard anemometer, while both are placed in the wind.
The Indicator
The case of the indicator is built of thin wood—the material of an old cigar box will do—9 in. long, 6 in. wide and 1-1/2 in. deep. If cigar-box material is used, it must first be soaked in warm water to remove the paper. If a cover is to be used on the box, a slot, on an arc of a circle, must be cut through it to show the scale beneath. The arc is determined by the length of the needle from a center over the axis on which the needle swings. When the box is completed, smooth up the outside surface with fine sandpaper and give it a coat of stain.
The core of the magnet is made by winding several layers of bond paper around a pencil of sufficient size to make an inside diameter of slightly over 1/4 in., and a tube 2 in. long. Each layer of the paper is glued to the preceding layer.
Two flanges or disks are attached to the tube to form a spool for the wire. The disks are cut from thin wood, 1-1/4 in. square, and a hole bored through their centers so that each will fit on the tube tightly. One of them is glued to one end of the tube and the other fastened at a point 1/2 in. from the opposite end. The space between the disks is filled with seven layers of No. 22 gauge insulated magnet wire, allowing sufficient ends of the wire to project for connections. The finished coil is located in the box, as shown at A, Fig. 1.
