On a straight line without excessive strains, crossarms are used singly-mounted face-to-face or back-to-back, as previously mentioned. At line terminals, corners, angles, or other points of excessive strain, crossarms are doubled. When a power line crosses a railroad or a telephone line, crossarms should also be doubled.
When double arms are used, they are fastened together at the ends with double-arm bolts. One of these is threaded all the way and has two square washers and two nuts on each bolt between the arms. The lineman can adjust the spacing between a pair of crossarms by setting these nuts the desired distance apart on the threaded bolts.
Secondary conductors may be strung on crossarms but are usually put on secondary "racks." These racks are made in sizes to accommodate two, three, or four conductors. A secondary rack is mounted on the side of a pole (for a straight run) or on the inside of a pole (for a dead end). A rack is fastened to the pole with lag bolts on a straight line with a through bolt at the top and a lag screw at the bottom, or with through bolts with nuts for a dead end or when a branch line takes off from the main line. A dead-end secondary rack is shown in figure 4-61.
Insulators are held to a rack by a rod passing through the insulators and brackets on the rack, as shown in figure 4-61. On a straight line or inside angle, the conductor is run on the inside of the insulator. On an outside angle, it is run on the outside. The conductor is always placed here with strain against the insulator. Figure 4-62 shows rack arrangements at comers and angles.
There are various ways of stringing conductors. You may place the wire reels on a truck or on a wire trailer and drive along the right-of-way unreeling the
Figure 4-62. - Rack arrangements at corners and angles.Continue Reading