. Field-book for railroad engineers. Containing formulas for laying out curves, determining frog angles, levelling, calculating earth-work, etc., etc., together with tables of radii, ordinates deflections, long chords, magnetic variation, logarithms, logarithmic and natural sines, tangents, etc., etc . 20 The first column contains the observed angles. The second containsthe bearings, which are found from tne angles of the first column, iv MISCELLANEOUS PROBLEMS. 55 the manner already explained. A Cis co
. Field-book for railroad engineers. Containing formulas for laying out curves, determining frog angles, levelling, calculating earth-work, etc., etc., together with tables of radii, ordinates deflections, long chords, magnetic variation, logarithms, logarithmic and natural sines, tangents, etc., etc . 20 The first column contains the observed angles. The second containsthe bearings, which are found from tne angles of the first column, iv MISCELLANEOUS PROBLEMS. 55 the manner already explained. A Cis considered as running northfrom A, and the bearings are, therefore, marked N. E. The other col-umns require no explanation. We find A G = , and B G = Then GC = — BG cot. I = — X cot. 100° = This value is positive, because it is the product of two nega-tive factors, cot. 100° being the same as —cot. 80°, a negative quanti-ty. Then AC= AG + GC= + = , and BC = -.—^bn = 1223 69. Having thus found the distances of Asin. 1UU- ° and B from the point of intersection, we can easily fix the tangentpoints for tangents of any given length. 76. Problem. To Uuj out a curve, when an obstruction of any kindprevents the use of the ordinarij ^ig. 27 Solution. First Method. Suppose the instrument to be placed atA (fig. 27), and that a house, for instance, covers the station at B, andalso obstructs the view from A to the stations at D and E. Lay offfrom A C, the tangent at yl, such a multiple of the deflection angle Z),iis will be sufficient to make the sight clear the obstruction. In thefigure it. is supposed that 4 Z) is the proper angle. The sight will thenpass through F, the fourth station from A, and this station will be de-termined by measuring from A the length of the chord A F, found by 56 CIRCULAR CURVES. § 69 or by Table II. From the station at i^ the stations at D and Emay afterwards be fixed, by laying off the pro
Size: 1517px × 1647px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectrailroadengineering
