. The elements of railroad engineering . point C, and it is required to swing the tangentB X into the position B X\ so that it shall pass throughthe point C. With the instrument at B measure the angleC B C. Divide this angle by the degree of the curve A quotient will be the distance, in stations, which must beadded to the curve A B to bring the P. T. at B\ and thetangent will pass through the required point C. Example.—Let ^ i? be a 6° curve, and the angle C B C — \^ 30. Swing the tangent B C so as to pass through the point C . Solution.—Reducing 4 30 to decimal form and dividing by 6, t
. The elements of railroad engineering . point C, and it is required to swing the tangentB X into the position B X\ so that it shall pass throughthe point C. With the instrument at B measure the angleC B C. Divide this angle by the degree of the curve A quotient will be the distance, in stations, which must beadded to the curve A B to bring the P. T. at B\ and thetangent will pass through the required point C. Example.—Let ^ i? be a 6° curve, and the angle C B C — \^ 30. Swing the tangent B C so as to pass through the point C . Solution.—Reducing 4 30 to decimal form and dividing by 6, the of the curve A B, we have -—- = .75 of a full station = 75 ft., which we must add to the curve A B, bringing the P. T. at B, and thetangent B A will pass through the point C. Ans. It will be evident that, had B X been the given tangentand C the required point, it would have been necessary to RAILROAD LOCATION. 841 move the point of tangent B backwards to />, i. e., tosubtract 75 ft. from the given curve. 3130 \. 1429. Problem VII.—To find the distance across ariver in a preliminary survey: Let the line A B, Fig. 368,cross a river, too wide fordirect measurement. With the instrument at A, sight A llllll Illll B to a flag held at B, and turnan angle ^y^ C= 1°. Setaplug at C, opposite B in A C, and measure thedistance B C. The required distance^ C X 100 AB =
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
