. Electric railway journal . -tical movement ofthe rails, while theU-shaped loop is welldesigned to with-stand stresses coming from other directions. Theseprecautions are necessary, however, as the extendedlength of the bonds is ordinarily only 7 in., too shortfor track which has not a fairly good foundation andwhich is not well maintained. Another type of expanded terminal bond which is ap-plied to the rail head is shown in the illustration onthis page. This has only one stud at each provide greater contact area than that in a holedrilled with the ordinary twist drill, a special m
. Electric railway journal . -tical movement ofthe rails, while theU-shaped loop is welldesigned to with-stand stresses coming from other directions. Theseprecautions are necessary, however, as the extendedlength of the bonds is ordinarily only 7 in., too shortfor track which has not a fairly good foundation andwhich is not well maintained. Another type of expanded terminal bond which is ap-plied to the rail head is shown in the illustration onthis page. This has only one stud at each provide greater contact area than that in a holedrilled with the ordinary twist drill, a special millingcutter is used. This cuts an annular hole in the rail fin. in diameter and I in. deep and leaves a i-in. pin inthe center of the hole. The stud of the bond is hollowto fit over this pin and into the groove surroundingit. The bond terminal is fitted into the hole and thenexpanded by blows from a hammer as is done in in-stalling the twin terminal bond. The contact area isprovided by the three sides of the annular FIG. 14—SINGLE-STUD, DOUBLE-CONDUCTOR RAIL BOND Survey of Pole Lines A letter has been sent to member companies of theNational Electric Light Association by William C. , chairman of the committee on safety rules andaccident prevention, calling to their attention the sur-vey of existing pole lines throughout the United Statesand Canada, which the committees engineers are con-ducting jointly with those of the Bureau of Standards. The survey is being made to determine for futureaerial line construction the effect of the loading require-ments proposed in the new issue of the National Elec-tric Safety Code. It will be conducted, so far as possiblethrough the geographic sections of the N. E. L. A., andit is expected that the work will be sufficiently well or-ganized so that each company to be visited will benotified in advance. Each company is requested to be prepared to desig-nate immediately the lines to be surveyed in order thatall possible speed wil
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