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.

By table 4, with a wheel five feet in diameter, and a stroke of twenty inches, we have the decimal .2122.

By table 5, the mean cylinder pressure being sixty pounds per inch, and piston twelve inches in diameter, we have as the total pressure

By table 6, we see that five feet wheels at twenty-five miles per hour, use 33,600 cylinders of steam per hour.

By table 7, the capacity of a cylinder 12 × 20 is 1.31 cubic feet; also 33600 × 1.31 = 44016 cubic feet of steam per hour.

Assuming the mean cylinder pressure at sixty pounds, and the entering pressure at eighty pounds, also the loss in passing from the boiler at twenty pounds, we must generate the steam at one hundred pounds per square inch.

By table 8, we see that when steam is produced under one hundred pounds pressure per inch, each cubic foot of water makes 293 cubic feet of steam; whence

is the number of cubic feet of water to be evaporated per hour. At sixteen cubic feet of water per hour per square foot of grate, we thus require

and by table 9, we find the heating surface necessary to evaporate 150 cubic feet of water per hour, with nine square feet of grate surface, to be 779 square feet; and by the formula, with 9.4 square feet, we have,

the fuel being coke; for wood, multiply the grate area (as mentioned before) by 1.4 and the grate area will be 1.4 × 9.4 = 13.16. The tube surface of course remains the same, as, when the necessary amount of heat is developed, the same surface only is enough to apply it to the water.

To obtain 779 square feet of heating surface, we see, by table 10, that it is given by

or by consulting the table, and having given the number and length, the number and diameter, or the length and diameter, we may easily find the third factor of the surface. Thus the length being eleven feet, and diameter two inches, 779 feet is obtained by

To obtain the diameter of barrel to contain 135 two inch tubes, we use the formula

We have already found d = 2 inches, n = 135, whence c will be by formula,

and

also,

and

and allowing three fourths of the boiler cross section to be filled with tubes, we have,

also,

the square root of which is 38.5 nearly, to which add 38.5
8 or 4.8 inches, (see page 359), and we have

as the inside diameter of boiler, whence the following locomotive to meet the requirement as stated.

and under the most favorable circumstances, the chimney may be 40 inches high, 12.7 inches in diameter; the blast orifice 5.8 inches in diameter; and the capacity of smoke box 39½ cubic feet.

363. We may vary the tractive power of an engine by using the steam at a greater or less degree of expansion, but the adhesion remains the same. If an engine was built able to work a road partly level, and partly on steep grades, varying the power simply by varying the expansion, it would be unnecessarily heavy for the easy parts of the road. The expansive principle may be advantageously employed in adjusting the power to the difference of resistance on any one division of a road, and also to the varying load which each day’s traffic will present.

Suppose we would move a load of two hundred tons over the road below; and suppose, also, that we require the cylinder pressures set opposite the several divisions.

The boiler pressure being 150 lbs., and the pressure at entering the cylinder 145 lbs.,

We should work the engine as follows:—

GENERAL CLASSIFICATION.

The speed is assumed from twelve to fifteen miles per hour. The mean cylinder pressure is assumed at sixty lbs. per square inch; the initial pressure at ninety pounds, and the boiler pressure at 120 lbs. per square inch. The grate areas are designed for coke; for wood multiply the same by 1.4.

365. Department 2. Passenger.

The engines in the Northern States require more power in winter than in summer.

To the above classification might be added, an engine for “making up trains,” and similar station work; such an engine should be able to start easily the extreme weights of trains, from fifty to one thousand tons, and should be fitted with a power of varying its adhesion.

The speed being thirty miles per hour, and load 250 tons.

366. Table 1. Showing the required traction on a level for loads from fifty to one thousand tons, and for velocities from ten to one hundred miles per hour.

The tractive power to overcome the resistance of 750 tons upon a sixty feet grade is

367. Table 2. Showing the tractive power necessary to overcome grades from ten to one hundred feet per mile with loads from one to one thousand tons.

Required traction 5,000 lbs.; upon driving axles the weight is 5000 × 6 = 30,000 lbs.

368. Table 3. Giving the weight which should be placed upon the driving axles to secure any amount of adhesion; the latter being one sixth of the weight.

Let stroke be twenty inches, and diameter of wheel five feet, the ratio will be

369. Table of decimals, which, multiplied by the total piston pressures (table 5) will give the traction in pounds, or ratio between double stroke and wheel circumference. Table 4.

The whole pressure at one hundred pounds per inch on two sixteen inch pistons will be

370. Table 5. Total pressures upon pistons from ten to twenty-four inches in diameter, and for steam pressures from fifty to one hundred and fifty pounds per square inch.

Speed twenty-five miles per hour, wheels four and a half feet, the number of cylinders per hour is

371. Table 6. Showing the hourly consumption of steam in terms of the capacity of one cylinder, with wheels from three and a half to eight feet, and speeds from ten to sixty miles per hour.