. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . The , is moved jonvardalong the easier curve an angulardistance of J/ —ii = J2~^2- Fia. 33. In case the tangent is moved inward, transpose as before andwe have cos J/=cos Ji X .R2—R1 (27) The is moved backward d. Assume that the radius of one curve is to be altered with-out changing either tangent. Assume conditions as in Fig. 34. For the diagrammatic solutionassume that i?2 is to be increasedby O2S. Then
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . The , is moved jonvardalong the easier curve an angulardistance of J/ —ii = J2~^2- Fia. 33. In case the tangent is moved inward, transpose as before andwe have cos J/=cos Ji X .R2—R1 (27) The is moved backward d. Assume that the radius of one curve is to be altered with-out changing either tangent. Assume conditions as in Fig. 34. For the diagrammatic solutionassume that i?2 is to be increasedby O2S. Then, since R2 mustpass through Oj and extend be-yond Oi a distance 0,*S, the,locus of the new center must lieon the arc drawn about 0, ascenter and with OiS as locus of O2 is a] so givenby a line Oa/) parallel to BVand at a distance of 7?/ (equalto S .. ) from it. Thenew center is therefore at O2. An arc with ra-dius R2 will therefore be tangentat B and tangent to the olrfcurve produced at new Draw Otti perpendicular to O2B. |. Fig. 34. § 70. ALINEMENT. 81 With O2 as center draw the arc 0{m., and with O2 as center drawthe arc mB = mB =R^. .*. mn^mn = {R2 —R^ vers J/ = (i?2—i^i) vers ^2- .. versJ/ = ^^^persJ2 (28) 0{n, = (7?2—-^1) sin A2,Oin = (i?2--Ri) sin =^0{a-0{ii = (R2-Ri) sin J/-(^2-^1) sin J2- (291 This problem may be further modified by assuming that theradius of the curve is decreased rather than increased, or thatthe smaller radius follows the larger. The solution is similarand is suggested as a profitable exercise. It might also be assumed that, instead of making a givenchange in the radius Ro, a given change BB^ is to be made. J2and 7^2 ^^^ required. Eliminate R2 from Eqs. 28 and 29and solve the resulting equation for J2. Then determine R2by a suitable inversion of either Eq. 28 or 29. As in §§ 62 and 63, the above problems are but a few, althoughperhaps the most common, of the problems the engineer maym
Size: 1450px × 1723px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorwebbwalt, bookcentury1900, bookdecade1920, bookyear1922
