. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools . Fig. 154.—Single and Double Slips. § 316, SWITCHES AND CROSSINGS. 361. CROSSINGS. 315. Two straight tracks. When twostraight tracks cross each other, four frogsare necessary, the angles of two of thembeing supplementary to the angles of theother. Since such crossings are sometimesoperated at high speeds, they should be 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, esp
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools . Fig. 154.—Single and Double Slips. § 316, SWITCHES AND CROSSINGS. 361. CROSSINGS. 315. Two straight tracks. When twostraight tracks cross each other, four frogsare necessary, the angles of two of thembeing supplementary to the angles of theother. Since such crossings are sometimesoperated at high speeds, they should be 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. 155 are shown the details of such a the fillers, bolts, and guard-rails. 316. One straight and one curved track. Structurally thecrossing is about the same as above, but the frog angles are allunequal. In Fig. 156, R is known, and the angle M, made by 362 RAILROAD CONSTRUCTION. §317. the center lines of the tracks at their point of intersection, isalso known. m = NCM, NC = R cos M. R cos M+ig {R-hg) cos Fi = NC-\-ig] :. cos Fi =Similarly cos r2 = 7r7~x ^ cos 13 ^g
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