. The elements of railroad engineering . sceles, and the angle G C E— angle C O E. Hence, ()50 SURVEYING. we have O C : C EwC E \ E G. Denoting the chord C Eby c and the chord deflection E G by c/, we have, from theabove proportion, R : ciw : d. Therefore, d: [92, To find the tangent deflection, draw C E to the middlepoint of E G. By Art. 1254, E E = D C = the tangentdeflection. Hence, tangent deflection = one-half the chorddeflection, from which tangent deflection = --73. (93.) 1256. Practical Method of Deterinining Tan-gent and Chord Deflections.—Let it be remembered fora basis of calculatio
. The elements of railroad engineering . sceles, and the angle G C E— angle C O E. Hence, ()50 SURVEYING. we have O C : C EwC E \ E G. Denoting the chord C Eby c and the chord deflection E G by c/, we have, from theabove proportion, R : ciw : d. Therefore, d: [92, To find the tangent deflection, draw C E to the middlepoint of E G. By Art. 1254, E E = D C = the tangentdeflection. Hence, tangent deflection = one-half the chorddeflection, from which tangent deflection = --73. (93.) 1256. Practical Method of Deterinining Tan-gent and Chord Deflections.—Let it be remembered fora basis of calculation that the chord deflection for a one-degree curve, the chord being 100 feet in length, is ; for a 2° curve, double the deflection for a 1° curve, feet, and so on. The tangent deflection being one-halfthe chord deflection, for a 1° curve it will be .873 foot, fora 2° curve it will be feet, etc. Distances measured either on chords or tangents areexpressed in decimal parts of a station, which is 100 feet, and. Fig. 284. is assumed as 1. Thus, the tangent deflection for 75 feetwill be expressed as the tangent deflection for .75 of astation. This expression is, however, confined entirely to SURVEYING. G51 the calculation, and is spoken ofdiS the tangent deflection for75 feet. Fig. 284 will be used to demonstrate the principleupon which tangent deflections are based. Let A B he Si tangent, and B the P. C. of a 2° curve tothe right. We determine the chord deflection for 100 feetchord of a 2° curve to be feet. The tangent deflectionis one-half the chord deflection, or feet. Let BC= 100 feet, a full station (which express as 1), then C L, the tangent deflection at C, will = feet, for, since this is a 2° curve, the chord deflection = X 2, and 1 745 X 2the tangent deflection = ~— = ft. To find the tangent deflection for any intermediate point6, 75 ft. from B^ express the distance as a decimal of thefull station, or, in this
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
