. The elements of railroad engineering . Solution.—90°-50° = 40°. 40 x-0000066 (the rate of expansionper degree) = .000264, the amount of expansion for eacli unit of lengthof line. The line measures feet. The total expansion will,therefore, be .000264 X - .019 ft. ft. ft. r= , thenormal length of the line. For measurements of 100 feet or less a tension of 16 poundsis sufficient. This process of measuring is illustrated inFig. 42G. The head tapeman holds the zero end of the tape with thespring balance attached at B. The hind tapeman, standing at A^ holds the t
. The elements of railroad engineering . Solution.—90°-50° = 40°. 40 x-0000066 (the rate of expansionper degree) = .000264, the amount of expansion for eacli unit of lengthof line. The line measures feet. The total expansion will,therefore, be .000264 X - .019 ft. ft. ft. r= , thenormal length of the line. For measurements of 100 feet or less a tension of 16 poundsis sufficient. This process of measuring is illustrated inFig. 42G. The head tapeman holds the zero end of the tape with thespring balance attached at B. The hind tapeman, standing at A^ holds the tape abovethe stake until it is in a horizontal position. The tapecarries a rider containing a spirit level and a small eyethrough which the plumb-bob cord is passed. There aretwo rear tapemen. One holds the tape and gives it the RAILROAD CONSTRUCTION. 939 requisite tension, which is reported by the head tapeman atB; the other directs the raising or lowering of the tape whilebringing it into a horizontal position, adjusts the plumb-. bob, and reads the tape. The reading is then rear tapemen then change places and repeat the workand record the measurements. Each man must read and 2E ||iiii a|iiiiliiii]iiiiliin|& w^ J E mfL„i.„?l„„i„:?l^^ Fig. 437 record his measurements independently of the other, in orderthat they may the better check each others work. Accord-ingly they do not call out the measurements, but after each 940 RAILROAD CONSTRUCTION. has read and recorded his measurements, they compareresults, and if there is any considerable discrepancy, the workmust be repeated. Fig. 437 shows form of tape rider for plumbing tape. Itconsists of a piece of sheet brass A />, (! inches in length, anend view being shown at C. It is bent so as to fit closelyto the sides and top of the tape when stretched, and slidesalong the tape. An open slot a /;, 3 inches in length, in theside of the rider shows the graduations on the tape. A spiritlevel D E is attached
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
