Railroad Engineering; An Authoritative Manual of Modern Practice in the Survey, Location, and Construction of Railroad Lines and Terminals, Their Oper
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 edition. Excerpt: ...it is desired to have one line cross another without having any switch connection, a crossing may be used. If the angle should be small (which is very undesirable) the method of movable frogs, shown by the crossing of the inner main rails of Fig. 137, may be used. But the lines should be required to cross each other as nearly at right angles as possible and then a bolted or riveted set of frogs, with fillers between the rails, such as is illustrated in Fig. 138, may be used. In general these crossings will need to be made to order according to the angle between the two lines. Since such crossings are sometimes operated at very high speeds the construction must be especially strong and rigid. When both tracks are straight the frog angles are identical, or more strictly, two of them are "complements" of the other two. When one or both tracks are curved, all four frogs will be different and the computation of their exact value becomes a somewhat complicated geometrical problem. The mechanical construction need not be essentially different from that shown in Fig. 138. 133. Crossing. One straight and one curved track. In Fig. 139, R is known and also the angle M, made by the center lines at their point of intersection. M = NCM and NC = R cos M To find the relative positions on the tracks of the frogs, we may write (100) F3F. = (K +-2 9/in F-(R--g"?)8"1 F. 11F, = (E-J 9) (8in F.-8i F.) (i01) F, F. = (R + )sin F2-(R-- 9) sin F, It should be noted that F8F4 will not be exactly equal to F, F, although the difference will be very small. 134. Crossing. Both tracks curved. The angle of the tangents (or radii) at their point of intersection is a known quantity (M) and also the two radii Rt and R2. But since we must deal...
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- 29 Jun 2012
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