. Railroad construction : theory and practice : a textbook for the use of students in colleges and technical schools . ll for measurement. Example.—Given a main track on a 4° curve—a turnout to the outside, using a No. 9 frog;gauge 4 Sy; /=3^37; k=5r; DN=15 0 ando= 1° 50. Then for a straight track r would [d=S° 25^. For this curved track d willbe nearly (8° 25-4°) = 4° 25, or r will be for the straight track would be ; but sincethe lead is slightly increased (see § 267) when the turnout ison the outside of a curve, L may here be called H and I H6 /S Fig. 156- §2
. Railroad construction : theory and practice : a textbook for the use of students in colleges and technical schools . ll for measurement. Example.—Given a main track on a 4° curve—a turnout to the outside, using a No. 9 frog;gauge 4 Sy; /=3^37; k=5r; DN=15 0 ando= 1° 50. Then for a straight track r would [d=S° 25^. For this curved track d willbe nearly (8° 25-4°) = 4° 25, or r will be for the straight track would be ; but sincethe lead is slightly increased (see § 267) when the turnout ison the outside of a curve, L may here be called H and I H6 /S Fig. 156- §277. SWITCHES AND CROSSINGS. 319 M may be located as described above. MH may be measuredon the ground, or since it will be in this case about longerthan the computed value oi ST (=) given in Table III,and since it is slightly more for a turnout to the outside of a ()2 curve, it may be called Then x=dbfeet, and aa^^ and cc^^ = foot. = CROSSINGS. 277. Two straight tracks. When two straight tracks crosseach other, four frogs are necessary, the angles of two of them. being supplementary to the angles of the other. Since suchcrossings are sometimes operated at high speeds, they should be 320 RAILROAD CONSTRUCTION. §278. Structurally the very strongly constructed., and the angles should preferably be90° or as near that as possible. The frogs will not in generalbe stock frogs of an even number, especially if the angles arelarge, but must be made to order with the required angles asmeasured. In Fig. 157 are shown the details of such a the fillers, bolts, and guard-rails. 278. One straight and one curved track,crossing is about the same as above,but the frog angles are all Fig. 158, R is known, and theangle M, made by the center linesof the tracks at their point of inter-section, is also known. M = NCM. XC = R cos M.(R-^g) cos F,=XC + ig; cos F^ = R cos M 4- ig Similarly cos F2 = cos Fg = cos -P4 = R R-hj cos
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