. Railroad construction. Theory and practice. A textbook for the use of students in colleges and technical schools. By Walter Loring Webb . 8° ° ° 25 This shows that the effect of using straight frog-rails andstraight switch-rails is to sharpen the curve and shorten the leadin each case separately, and that the combined effect is stillgreater. The effect of the straight switch-rails is especiallymarked in reducing the length of lead, and therefore Eq. 78 to80, although having the advantage of extreme simplicity, can-not be used for point-switches without mat
. Railroad construction. Theory and practice. A textbook for the use of students in colleges and technical schools. By Walter Loring Webb . 8° ° ° 25 This shows that the effect of using straight frog-rails andstraight switch-rails is to sharpen the curve and shorten the leadin each case separately, and that the combined effect is stillgreater. The effect of the straight switch-rails is especiallymarked in reducing the length of lead, and therefore Eq. 78 to80, although having the advantage of extreme simplicity, can-not be used for point-switches without material error. Theeffect of the straio-ht froo^-rail is less, and since it can be mate-rially reduced by bending the free end of the frog-rails, the in-fluence of this feature is frequently ignored, the frog-rails areassumed to be curved and Eq. 85 and 86 are used. (Soe § 276for a further discussion of this point.) 284 RAILROAD CONSTRUCTION. 267. 267. Dimensions for a turnout from the outer side of a curvedtrack. In this demonstration the switch-rails will be consideredas uniformly circular from the switch-points to the Fig. the triangle FCD (Fig. 141) we have {FC+ CD): (FC- CD):: tan i{FDC+DFC): tan i(FDC-DFC);but i{_FDC+ DFC) = 90° - \d and \{FDC - DFC) = iF. Also FG+ CD = 2E and FC - CD = g; .-. 2B:g: : cot |^: tan iF: : cot ^F: tan ^(^; tan ^6 = ^. (91) Also OF : FC: : sin 6 : sin 0; but cp = {F — 6)\ then r -X- -ka = (M -X- ^a^-.—r-^^-—:^. . (92) (93) ^7^ = L = 2{R + ^g) sin i^. If the curvature of the main track is very sharp or the frogangle unusually small, i^may be less than 6-^ in which case thecenter 0 will be on the same side of the main track as C, will become (by calling r =. — r and changing the signs) (r - \g) = (^ + \g) sin B sin {6-F)- (94) §267. SWITCHES AND CROSSINGS. 285 If we call d the degree of curve corresponding to the radiusr, and D the degree of curve corresponding to the radius i?, alsod the degree of curve of a
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