[Illustration: Fig. 15. [Full Page] ELECTRICAL CONDUITS: METHODS OF LAYING, RODDING, ETC. A. FORK ENDED STEEL BONDS FOR CONDUITS. B. SEQUENCE OF METHODS OF BUILDING BENCH-WALL PROPOSED WHEN USING EXPANDED METAL BONDS. C. ISOMETRIC DRAWING OF EXPANDING MANDREL. D. DETAILS OF “WEASEL” Used for gripping disconnected pipe rods in conduit E. CUTTER FOR REMOVING OBSTRUCTIONS IN CONDUITS. F. ISOMETRIC SKETCH SHOWING METHOD OF BREAKING JOINTS AND POSITION FORKED BONDS. G. PLAN AND SECTIONS OF EXPANDING MANDREL.
INDEX +-----+------------+-------------+ | | Multi-Duct | Single-Duct | | | Mandrel | Mandrel | +-----+------------+-------------+ | _A_ | 3¼” | 3⅜” | | _B_ | ¾” | ⅞” | | _C_ | 2½” | 2⅝” | +-----+------------+-------------+
End pipe connections may be changed to suit connections of rodding outfit, care being taken to use a connection which will not split and expand the mandrel if it should be driven back into it, in attempting to ram the mandrel back when stuck in a duct.
Connection at Head End may be dispensed with, if the mandrel is threaded through ducts by rods attached to the trailing end.]
Wooden rods were used at first, but proved entirely too light, as the mandrels used were a close fit, and it required considerable effort to push them through 400 ft. of conduit. Iron pipe with ordinary couplings was next tried, but the couplings broke quite often, as the threads became worn in uncoupling the sections to move the rods from one line to another, and the break was generally inside a duct line. The long couplings were finally adopted, and a set of rods was put in each line, that is, six sets in all, so that when coupled up they remained in the line until it was finished. The expense of the extra quantity of pipe thus required was more than offset by the decreased labor cost.
It was thought necessary at first to run a cutter, Fig. 15, _E_, through the conduits ahead of the final rodding mandrel, but this was soon found to be unnecessary except in a very few instances, and, after a short experience, the cutter was only used at places where an obstruction was encountered by the mandrel.
At such times as the pipe became uncoupled inside the duct line, the part remaining inside was recovered by the use of the tool shown at _D_, Fig. 15, called a “weasel.” In two instances, the mandrel became stuck in such a manner that the duct line had to be cut into in order to take it out.