CROSSARM BRACES Braces are used to give strength and rigidity to the crossarm. Metal crossarm braces are made of either flat bar or light angle iron. The size used varies with the size of the arm and the weight of the conductors. The usual flat-strap brace for ordinary distribution work (fig. 4-17) is 38 inches long and 1/ 4 by 1 1/ 4 inches. One end is attached to the crossarm by means of a carriage bolt and the other to the pole by means of a lag screw.

Figure 4-18.- A V-shaped angle-iron crossarm brace.

Figure 4-19.- Crossarm brace installation.

One brace extends to each side of the arm. Angle-iron braces are made in one piece and bent into the shape of a V, as shown in figure 4-18. These braces are fitted to the bottom of the crossarm instead of the side as is the flat type. Figure 4-19 gives an example of how these braces are used.

HARDWARE Line hardware consists of the miscellaneous bolts, nuts, braces, and clamps used to fasten crossarms, guys, and other equipment to the pole. Figure 4-20 shows some samples of common hardware used in power distribution.

INSULATORS An insulator is a material that prevents the flow of an electric current and can be used to support electrical conductors. The function of an insulator is to separate the line conductors from the pole. Insulators are fabricated from porcelain, glass, and fiber glass, treated with epoxy resins and rubberlike compounds. In

determining the size and type you need, you should consider the designed voltage of the circuit, conductor size, length of the pole-line spans, and cost of the various insulators. The most common types of insulators found in Navy use are the pin, post, suspension, and strain insulators.

Figure 4-20.- Line hardware.

Figure 4-21.- A single-layer porcelain pin insulator. Pin Insulator The pin insulator (fig. 4-21) gets its name from the fact that it is supported on a pin. The pin holds the insulator, and the insulator has the conductor tied to it. Pin insulators are made of either glass or porcelain. The glass insulator is always one solid piece. The porcelain insulator is also a one-piece insulator when used with low-voltage lines but will consist of two. three. or four layers cemented together to form a rigid unit when used on higher voltages (fig. 4-22).

Insulator Pins The function of an insulator pin is to hold the insulator mounted on it in a vertical position. Insulator pins are made of wood or metal. Wooden pins are usually made of locust. Locust is durable and retains its strength longer than other woods. Iron and steel pins are used whenever the pins must be extra long, because of high voltage, and whenever the tension on the conductor is great. One make is arranged to encircle the crossarm as a clamp pin- the clamp being held by bolts (fig. 4-23). In many cases. a steel rod is used as the base to permit the use of a 5/ 8 or a 3/ 4 hole to be drilled in the crossarm. Steel pins are in general use. Steel pins have a broad base which rests squarely on the crossarm, as shown in figure 4-24.

The spacing of the pins is generally suited to the voltage of the circuit. The spacing should provide sufficient working space for the lineman. For general distribution work, the spacing is 14 1/ 2 inches between centers.