. Railroad construction. Theory and practice . ^ unusual practice, but is successfullyoperated on that road. The curve is concave upward for two-thirds of its length and then reverses so that it is convex upward. TABLE FOR RUN-OFF OF ELEVATION OF OUTER RAIL OF in inches for each 30-foot rail commencing at theoretical point of curve. £.2 V Y ¥ ¥ r r ¥ \ \¥ W IF \ ¥ ¥ ¥ ¥ ¥ ¥ 1 Iti ,t ^e o w H V 30 30 30 30 120 2 30 30 30 30 30 150 r 30 30 30 30 30 30 180 r 30 30 30 30 30 30 30 30 . . ^40 b 30 30 30 30 30 30 30 30 30 270 & 30 30 30 30 . . 30 30 30 30 30 30 300 T 30 30 30 30 30 30 30
. Railroad construction. Theory and practice . ^ unusual practice, but is successfullyoperated on that road. The curve is concave upward for two-thirds of its length and then reverses so that it is convex upward. TABLE FOR RUN-OFF OF ELEVATION OF OUTER RAIL OF in inches for each 30-foot rail commencing at theoretical point of curve. £.2 V Y ¥ ¥ r r ¥ \ \¥ W IF \ ¥ ¥ ¥ ¥ ¥ ¥ 1 Iti ,t ^e o w H V 30 30 30 30 120 2 30 30 30 30 30 150 r 30 30 30 30 30 30 180 r 30 30 30 30 30 30 30 30 . . ^40 b 30 30 30 30 30 30 30 30 30 270 & 30 30 30 30 . . 30 30 30 30 30 30 300 T 30 30 30 30 30 30 30 30 30 30 30 330 ^ 30 30 30 30 30 30 30 30 30 30 30 30 360 ^ 30 30 30 30 30 30 30 30 30 30 30 30 30 30 420 10 30 30 30 ■ • 30 30 30 30 30 30 30 30 30 30 30 30 450. The figure (and also the lower line of the tabulated form)shows the drop for each thirty-foot rail length. For shorterlengths of run-ofi, the drop for each 30 feet is shown by the cor-responding hues in the tabular form. Note in each horizontalhne that the sum of the drops, under which 30 is found, equalsthe total superelevation as found in the first column. Forexample, for 4 inches superelevation, length of curve 240 feet,the successive drops are \, ¥\ i\ |, f, §, i, and iwhose sum is 4 inches. Possibly the more convenient formwould be to indicate for each 30-foot point the actual super-elevation of the outer rail, which would be for the above case(running from the tangent to the curve) J, |, |, U, 2|,3r, 3r, 4-. 44. Fundamental principle of transition curves. If a curve 48 RAILROAD CONSTRUCTION. § 45. has variable curvature, beginning at the tangent with a curveof infinite radius, and the curvature gradually sharpens until itequals the curvature of the required simple curve and t
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