OF VIRGINIA 57 



INSULATOR PINS, BRACKETS, AND CROSS ARMS 



Under Table 8 was discussed the kinds of wood used in under- 

 ground construction for the distribution of telephone, telegraph, and 

 electric power, but in Table 17 the statistics represent woods used for 

 the construction and manufacture of over head lines. The commodi- 

 ties which make up the table are cross-arms, insulator pins, and 

 brackets, pole steps, and tree blocks. . Telephone and telegraph poles are 

 not included because they do not come within the range of this study. 

 ^Statistics concerning these products are given in Circular 9 issued by 

 the Bureau of the Census. 



The raw material for making insulator pins and brackets was 

 purchased in the form of bolts and reported in terms of cords. For 

 convenience in tabulation the number of cords were reduced to board 

 feet. Locust, white oak, and hickory were the woods used, the first 

 named greatly exceeding in quantity the other two. The most ex- 

 acting demand for locust is for these commodities. Its durability in 

 exposed positions recommends it probably above all other woods for 

 this use, though white oak, owing to the scarcity of locust, is meeting 

 a growing demand for pin wood. In North Carolina the quantity 

 consumed exceeded the quantity of locust. White oak is not con- 

 sidered as durable an outdoor wood as locust, and for that reason 

 white oak pins are usually dipped in paint or in other preservative 

 solutions like zinc chloride or creosote oil. White oak alone was re- 

 ported for pole steps and tree block. Hickory pins on account of their 

 superior strength were used for holding the heavy porcelain insulators 

 used on high-tension lines. 



Longleaf pine and shortleaf pine were the only woods reported for 

 cross-arms. Excepting a small per cent of Virginia-grown shortleaf 

 pine all of the cross-arm wood came from the sawmills operating in 

 States further South. It was purchased in the form of squares and the 

 operations of shaping the arms by machinery and boring holes for the 

 insulator pins and for the bolts holding them to the poles was simple 

 and rapid. All the cross-arms produced in Virginia in 1911 were im- 

 pregnated with the oil of creosote before they were marketed. In other 

 States, important woods for cross-arms are Douglas fir, cypress, spruce, 

 and loblolly pine. 



