Fig. 73. Details of Switch Parts.
Some may prefer to make the complete switch, and in that case the dimensions given in Fig. 73 may be of aid. The knife blades are 6 inches long, 5/8 inch wide and 1/8 inch thick. Three are required. A 1/8-inch hole is bored 3/8 inch from one end, and the other end is cut out in the shape shown in the illustration. An insulating bar 5 x 3/4 x 5/8 inches is made of hard rubber and three notches are cut in the back face, one directly in the center and one 2 inches on either side.
Fig. 74. Method of Fastening Knife.
Three 1/8-inch holes are bored one in the center of each groove and at right angles to it. An 8-32 machine screw 3/4 inch long is placed in the notch in the end of the knife blade and the screw passed through the hole in the insulating bar. The blade may then be clamped tightly in place by putting a nut on the end of the screw. The screw which holds the middle knife blade in place is longer than the other two so that a handle may be fitted on.
The bearings are made the same size and shape as the contacts illustrated in Fig. 72, with the exception that a 1/8-inch hole is bored through near the top so that a small bolt may be slipped in to hold the knife blades in place.
The base of the switch measures 8 x 9 x 3/4 inches. The parts are assembled as in Fig. 71.
Another type of aerial switch called a "T" switch is illustrated in the same figure. A piece of 3/4-inch hard rubber is sawed in the shape of a T, 3 1/2 inches high and 6 1/2 inches wide at the top. The upper contacts are mounted on arms of the "T" and connected to binding posts placed immediately above them, A slot, 1/2 inch wide and 3 inches long, sawed in the center of the leg of the T, permits the middle knife blade to move without obstruction.
