. 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 .. . m acquired is useful, but not be-yond. Any road being divided into locomotive sections, the sec-tion given to any one engine should be such as to require aconstant expenditure of power as nearly as possible; i. e.,one section, or the run of one engine, should not embracelong levels and steep grades. If an engine can carry a loadover a sixty feet grade, it will be too
. 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 .. . m acquired is useful, but not be-yond. Any road being divided into locomotive sections, the sec-tion given to any one engine should be such as to require aconstant expenditure of power as nearly as possible; i. e.,one section, or the run of one engine, should not embracelong levels and steep grades. If an engine can carry a loadover a sixty feet grade, it will be too heavy to work thesame load upon a level economically. It is best to groupall of the necessarily steep grades in one place, and also theeasy portions of the road; then by properly adapting thelocomotives the cost of power may be reduced to a min-imum. As to long levels and short inclines the same power is re-quired to overcome a given rise, but quite a difference maybe made in the means used to surmount that ascent. 52. Suppose we have the profiles A E D and A B D, The resist- y\t. vn. ance from A toD by the con-tinuous twentyfeet grade isthe same as the whole re-sistance from A to B and from B to D. The reason for. 34 HANDBOOK OF RAILROAD CONSTRUCTION. preferring A E D is, that an engine to take a given loadfrom B to D would be unnecessarily heavy for the sectionA B; while the same power must be exerted at each point,of A E D. Also the return by A E D is made by a smalland constant expenditure of power, being all of the wayaided by gravity ; while in descending by B, we have moreaid from gravity than we require from D to B, after whichwe have none. When the distances A B, B C, are sixty and twentymiles in place of six and two, we may consider the gradesgrouped at B D, and use a heavier engine at that point, aswe should hardly find eighty miles admitting of a continu-ous and uniform grade. EQUATING FOR GRADES. 53. In comparing the relative advantages of several linesha
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