TREE-LINE CONSTRUCTION 



69 



In the second system (Fig. 31) the line is built in the form of a series of long 

 reversed curves. On curves, while all insulators are on the same side of adjacent 

 trees the wire nevertheless pulls away from all trees on the curve. By laying out the 



Fig. 3>0 Zigzag system of alignment 



9 



Fig. 31 Reverse curve system of alignment 



entire line in a series of reverse curves, each of six or eight spans in length, the desired 

 pull away from the tie trees is secured without the frequent crooks in the line 

 encountered in the first method. 



Section 60 Line Construction 



1 THE " Six EULES " FOR TREE-LINE WORK 



For successful tree-line construction, the following six rules should be kept con- 

 stantly in mind: 



1 Slack wire. 



2 Equalized spans. 



3 Weak ties. 



4 Standard installations. 



5 No sharp turns in line. 



6 Avoid attaching wire too high on trees. 



2 LINE MATERIALS 



For tree-line work, only No. 9 B.W.G., B.B., galvanized-iron wire, or heavier, can 

 be successfully employed. This is true, regardless of the length of line. The strains 

 to which tree lines are exposed are much greater than with pole lines and no wire of 

 lighter weight than No. 9 will resist them successfully. Copper wire cannot be 

 employed at all with this method of construction. Although tree-line methods involve 

 the building of a very crooked line with a great deal of slack, the actual length of 

 wire is not thereby seriously increased. Only about 100 feet per mile of line wire need 

 be allowed for the normal crooks and slack of a standard tree line. 



For tie wire No. 12 B.W.G.. galvanized-iron wire is employed. A mile of No. 12 

 wire will s make about 2,700 tie wires or enough for approximately 60 miles of line, 

 allowing 45 ties to the mile. 



Split tree insulators and 4-in. staples, sufficient for 45 to 50 ties per mile of line r 

 are the only other line materials required. The latest form of split tree insulator (See 



