ox AMKRICAN PERMANENT WAT. 



597 



i\ve Intended to be run. If one I'idcs at a rapid rate over a road adapted 

 ill tliis respect for hImw speed, he will soon discover the want of elevation 

 JO the curves. Jtiliu 15. Heiick, an American civil engineer of great 

 reputation for his ' Field-book for Railroad. Engineers,' ])ublished many 

 vears ago, gives the following table for elevation of the outer rail on 

 curves, based on the question of centrifugal force tending to throw the 

 oar against the outer rail, and the elevation of the same above the inner 

 diio to counteract it. Practical use of this table has demonstrated its 

 correctness. M in the table represents the speed of train in miles per 

 luiuv, and the elevaii(m is given in decimals of u, foot for the degree of 

 curvature r>nd the speed of train M. 



olvc a 



laid to 

 lie two 

 outer 

 coni- 

 tc also 

 curve 

 liiiount 

 Is and 

 1 traiu.s 



i:r.i;v,\TiON or orri;u i;.\n. ox cirves. 



John ]}. Uciick, .\..M., C.K. 



■02-2 

 •014 

 'Ofii; 



■OSS 



■no 

 ■i:{| 

 • I :,•:, 



■17.-) 

 •1!t7 

 ■2111 



Of course some of these figures arc merely theoretical, and out of the 

 (|uestion practically. \o one would expect to go around a teu-degreo 

 curve at 5'» miles per hour, but would reduce speed. 



The Atlantic? ami Pacific Railroad Company elevate the curve one 

 half-inch per degrci' up to a ten-degree curve which has an elevation of 

 .') inches, and all sliarper curves are ke])t at tliis same elevation. This 

 corresponds very nearly with ileuck's table for thirty miles per hour. 

 The elevation of outer rail is I'un otF, on to straight track, a distance of 

 li» feet ])er degree of curvature. Thus for a two-degree curve the 

 distance on the tangent is liD feet, and for a ten-degree curve it is lOu 

 lect. There may be cases where i^everse curves come close together, and 

 this rule cannot be stricjtly carried out ; but an endeavour is always made 

 in such cases, if possible, to secure at least r>(.) feet of level track on a 

 tangent. Where two curves in the same direction are connected by a 

 tangent less than lu<* feet long, the elevation is carried through from 

 curve to curve without reduction ; and if the tangent exceeds 100 feet the 

 regular inclinations are made from each curve until they meet, or until 

 level track is reached. The.se illustrations will serve to show the varia- 

 tions in practice with different roads. The rules lor elevation of course do 

 not apply in yard tracks. All rails for curves should be bent to tho 

 l)roper curvature belbre being laid on the ties. 



Several different standards of gauge of track have been used on 

 American roads : f. feet, 5 feet, 4 feet 8^ inches or 4 feet 9 inches (a 

 modification adopted for compromise cars), also the various narrow gauges, 

 from 2 feet inches to :> feet ('» inches. There is a considerable tendeucy 



ii 



