International Library of Technology · Scranton, International Textbook Co. · leaf 127
now most commonly usedis shown in Fig. 14, this being usually made in 18-inch lengths, having an inter-nal diameter of from 3to 3^ inches and being4f inches square outside.This duct has a greatadvantage over the mul-tiple-duct sections in thegreater ease of handlingand also in the fact thatit is… … FIG. 14. 12 ELECTRIC TRANSMISSION. 15 together with mortar, and enclosed on all sides and on topby concrete. In laying, a wooden mandrel, such as isshown in Fig. 15, 3 inches in diameter and about 30 inchesin length, is used. At one end is provided an eye a, whichmay be engaged by a hook, in order…
Electrical engineering
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