XLVIII. CROSSINGS ON STRAIGHT LINES. 1. Having located frogs B and C by the preceding methods, stretch the cord any convenient distance, CD, in the range of G B E the outer gauge side of the frog C. Set off EF parallel to CD, and distant the gauge-width from it. The intersection of said parallel at F with the near rail of the side track marks the spot for point of side-track frog; the curve F G, thence to toe of switch, corresponds to AC on the main track, and may be staked out in like manner. XLIX. CROSSINGS ON CURVES. 1. Having located frogs B and C by the preceding methods, set off the width of gauge, CD, from point of frog C, and square to its outer gauge side. Stick a pin at D. 2. Next calculate the distance D E to the point of side-track tance, HI, between the gauge sides of the nearest rails of the main and side tracks; multiply the remainder by the number 3. Suppose, for example, the gauge sides of the nearest rails of the main and side tracks are 6 feet 6 inches asunder; gauge of track, 4 feet 8 inches; frog, a No. 9. Reducing inches to decimals, we have then the distance between tracks 6.5 feet, less the gauge, 4.7 feet, = 1.8 feet; and 1.8 multiplied by 9, the number of the frog, gives 16.2 feet for the distance DE. The proper spring will be given to rail DE on the ground; and curve EG, from frog to toe of side-track switch, will be staked off as directed in the section on turnouts. L. ELEVATION OF THE OUTER RAIL ON CURVES. 1. Great precision in this adjustment is unattainable, owing to differences in the speed of trains and to the cost of trackmaintenance, if it were attempted. 2. Molesworth gives the following formula for determining the elevation of the outer rail with any gauge: V = greatest velocity of trains in feet per second. G = gauge of railway in feet. C = length of chord whose middle ordinate will give the required elevation. of the outer rail on the standard gauge of 4 feet 8 inches, multiply the speed of trains in miles per hour by 5, and divide the product by 3. This will give the length of tape, C, to stretch on the gauge side of the outer rail; and the distance, e, from the middle of the tape to the gauge side of the rail, will be the proper elevation. For guage of one metre, = 3.28 feet, make C equal to one and one-third times the speed of trains in miles per hour. For 3-feet gauge, make C equal to one and one-fourth time TABLE OF ELEVATIONS OF OUTER RAIL ON CURVES. This table was formulated by the writer from Pennsylvania Rail Road practice as follows: (speed in miles per hour + 1) × (by the degree of curve) = elevation of outer rail expressed in 8ths of an inch. NOTE.-The limit of elevation of outer rail is 6 inches. |
