Weather Vane, Compass
Weather VaneA simple model is shown in Fig. 37. The spindle, A, is the same as the one used for the anemometer, but three cotton reels are used. The arm, B, is formed from 1/2 in. diameter dowelling, which is 1 ft. 6 in. in length. Drill a hole through the centre, of such a diameter that the arm will turn freely on the spindle. Make fine saw cuts, which are 3 in. in length at each end of the arm. Next, cut the two shapes, C and D, from thin tin and make them 6 in. in length and 3 in. at the widest points. Insert these in the saw cuts, and secure them by means of glue and fine nails driven through the arm. Now prepare the stand. For the base piece, E, use 1/4 in. plywood or hardboard which is 2 ft. square and battened underneath to prevent it warping. Cut the cardinal points from thin tin or plastic. Each letter is cut from a 3 in. square of the material and is pegged to a small piece of dowelling as at F. Drill holes at the corners of the base piece and insert the pegs. Glue them securely in place. The base piece is mounted on a centre column, as for the anemometer, but in this case it is round in shape.
Assemble the vane by slipping the arm on the spindle. Place a brass washer above and below the arm. Make a cap from a small block of wood, as shown at G, and wedge this on top of the spindle by means of a centre hole, drilled halfway through. Make this hole a little less in diameter than that of the spindle, so that the cap needs tapping home with a mallet. Secure with glue. The arms should balance evenly on the spindle and should revolve freely. Paint the vane in black enamel, first applying a coat of size to the wooden parts. Lubricate the hole in the arm with a little fine machine oil. The vane may be fixed at some convenient place which is open to the wind: for example, to the top of a shed, or a post. It must be secured so that the base is truly horizontal and the spindle truly vertical. The cardinal points are found in the first place by means of a compass, and the vane is set up to correspond to compass reading.
CompassThough a good compass can be bought quite reasonably, some readers may find it interesting to make this simple type for themselves (Fig. 38).
The first stage is to make a compass card, A, which is 2 in. in diameter. Draw two concentric circles on thin card; the outer one is 2 in. in diameter; the inner one is 1 in. in diameter. Mark on it the cardinal points, as shown. Cut out the centre portion. Next, make the pieces B and C from thin card. B has a raised part in the centre, and from the underside of this a small depression is made by means of a round point. C is a flat strip with a small hole punched in the centre. Magnetize a steel safety razor blade by drawing a magnet across it, one way only. Before this is done, for safety's sake, place the blade in a vice and blunt the edges with a fine file. Glue the blade to the underside of the flat strip. Now, make a small cardboard box to house the compass, with sufficient clearance for the compass card to turn freely in it. Assemble the parts upon a needle which is stuck into a piece of cork. Glue the strips B and C to the underside of the compass card; B so that the raised part fits through the centre hole; and C so that the blade is underneath. Glue two small beads above and below the hole in the strip C. The top of the needle rests in the small depression in the raised part of B.