. Railroad construction. Theory and practice . ^used. The remarkable agreement of the computed values of L iI § 268, SWITCHES AND CROSSINGS. 279 Frog Z) = 4°. L for num-ber. d d-D Error. L straighttrack. 6 9 12 12° 54 203 30 270 13 33 12° 57 523 31 040 13 36 0° 03 320 0 370 0 03 Frog Z) = 10°. L forstraighttrack. num-ber. d d-D Error. L 6 9 12 6° 53 242 27 545 44 26 6° 57 522 28 565 46 24 0° 04 280 01 020 01 58 84. 75 with the corresponding values for a straight main track (the leadrails circular throughout) shows that the er
. Railroad construction. Theory and practice . ^used. The remarkable agreement of the computed values of L iI § 268, SWITCHES AND CROSSINGS. 279 Frog Z) = 4°. L for num-ber. d d-D Error. L straighttrack. 6 9 12 12° 54 203 30 270 13 33 12° 57 523 31 040 13 36 0° 03 320 0 370 0 03 Frog Z) = 10°. L forstraighttrack. num-ber. d d-D Error. L 6 9 12 6° 53 242 27 545 44 26 6° 57 522 28 565 46 24 0° 04 280 01 020 01 58 84. 75 with the corresponding values for a straight main track (the leadrails circular throughout) shows that the error is insignificant inusing the more easily computed values. 268. Dimensions for a turnout from the INNER side of a curvedtrack. (Lead rails circular throughout.) From Fig. 142 wehave, from the triangle DFC,. DF+FC: DF-FC :: tan i(DFC+FDC): tan i(DFC-FDC);but i(DFC + FDO =90°-§^ and iiiDFC-FDC)=iF; /. 2R : g ::cot id : tan JF:-cotiFtani^; tanj^ = ^. (95) 280 Fiom OFCj RAILROAD ::smd:(F + d). sin (F + dyL=BF=2(R--ig)sm §<9. 269. (96)(97) As in § 267, it may be readily shown that the degree of theturnout (d) is nearly the sum of the degree of the main track (D)and the degree (cV) of a turnout from a straight track when thefrog angle is the same. The discrepancy in this case is some-what greater than in the other, especially when the curvatureof the main track is sharp. If the frog angle is also large, thecurvature of the turnout is excessively sharp. If the frog angleis ver}^ small, the liability to derailment is great. Turnouts tothe inside of a curved track should therefore be avoided, unlessthe curvature of the main track is small. ^H 269. Double turnout from a straight track. In Fig. 143 thefrogs Fi and Fr are generally made equal. Then, if there are
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