. Handbook of railroad construction; for the use of American engineers. Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States .. . gth of A is TheeThe mean equated length of B isThe measured length of B is The difference Sum Mean Sum Mean rence 40 HANDBOOK OF RAILROAD CONSTRUCTION. The cost of construction being assumed as the actuallength, and that of working as the equated length, we havethe final approximate com
. Handbook of railroad construction; for the use of American engineers. Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States .. . gth of A is TheeThe mean equated length of B isThe measured length of B is The difference Sum Mean Sum Mean rence 40 HANDBOOK OF RAILROAD CONSTRUCTION. The cost of construction being assumed as the actuallength, and that of working as the equated length, we havethe final approximate comparison thus: — Assume the construction cost as $25,000 per mile, andthe cost of maintenance $4,000 per mile, and we have The line A to the line B as ^ , 100 X 25000 + X 4000 X H^ = 10^, is to 90 X 25000 + X 4000 X H^ = ; or A is to B as to nearly, although the line A is ten mileslonger than B. CHAPTER III LOCATION. ALIGNMENT. 57. The broken line furnished by the survey is of courseunfit for the centre line of a railroad. The angles requireto be rounded off to render the passage from one straightportion to the other easy. 58. Let A X B, fig. 26, represent the angle formed by Fig. 42 HANDBOOK OF RAILROAD CONSTRUCTION. any two tangents which it is required to connect by a circu-lar curve. It is plain that knowing the angle of deflectionof the lines A X, B X, we obtain also the angles A C X,X C B. The manner of laying these curves upon theground is by placing an angular instrument at any pointof the curve, as at A, and laying off the partial anglesE A fl, E A M, E A G, etc., which combined with the cor-responding distances A a, a M, M G, fix points in the curve. Thus small chords are generally assumed at one hundredfeet, except in curves of small radius (five hundred feet)when they are taken less. The only calculation necessary in laying out curves, is,knowing the partial deflection to find the correspondingchord, or knowing the chord,
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