Average percentage of all of the above charged to locomotives 41⅔ of the whole locomotive expense; fuel absorbs 62½ percent.; and as a double amount of work requires ninety per cent. more fuel, we have, as the cost of working a grade causing a double resistance (say twenty-five feet per mile), 90
100 of 62
100 of 42
100, or very nearly 22 per cent. of the cost of working the train; to which add ⅒ more, interest on locomotive capital, and we have, as the bad effect of a twenty-five feet grade, when
C = locomotive capital,
D = annual cost of working,
⅒ of 6
100C + 22
100D.
Example.
| Locomotive capital | $1,000,000 | |
| Cost of working | 200,000 | |
| Annual expense of a level road (at six per cent.) | $60,000 | |
| + 200,000 | ||
| $260,000 | ||
| And upon a road with continuous 25 feet grades | $60,000 | |
| + 6,000 | ||
| + 200,000 | ||
| + 200,000 × 22 100, or | 44,000 | |
| Total | $310,000 | |
or 120 per cent. of the cost of working the level road, the increase being twenty per cent., or allowing five per cent. for other contingencies, twenty-five per cent.; also the increase due to a fifty feet grade, fifty per cent.; and so on as long as only one engine is required to draw the full train, (its power being increased by varying its dimensions). When the train has to be broken and two or more engines are needed, the percentage will of course increase. The point at which the train ought to be broken may be found easily, either as depending upon the load or the grade, by a comparison of working expenses.
G.
SPECIFICATION FOR A PASSENGER LOCOMOTIVE ENGINE FOR THE A. AND B. RAILROAD.
Requirement.
Speed 20 miles per hour, including stops; fuel, wood; weight of train 150 tons; maximum grade 60 feet per mile; sharpest curve 3° or 1,910 feet radius; rail 60 lbs. per yard on ties 2 feet from centre to centre.