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Power Down

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.
(This enlargement, extending only in the direction of contraction,
and not in the line of the force.) The upper part of such a rail should
be hardened to resist the rolling of the wheels, while the webs must
possess the strength to act as a girder.
It is questionable whether, by dividing the rail, particularly when it is
done horizontally, we do not prevent the mutual extensile and
compressive actions which ought to have place in the top and
bottom; for we cannot make the bolts perfectly tight because of
expansion.
Some of the compound rails which have been laid in America have
given good results, others have not.
Mr. W. B. Adams observes, that a compressed rail to be as strong as a
sixty pound whole rail, must weigh ninety lbs. per yard.
Some engineers have proposed such a rail that when one side
becomes worn it may be turned over so that the lower may become
the upper table. This is quite wrong in principle; as when the lower
fibres have been subjected for some time to extension, they are
entirely unfitted to oppose compression.

OF THE LIFE OF RAILS.

288. The time which a rail will last, depends upon the form and
weight, and on the quality of the iron; and upon the number, weight,
and speed of engines and cars passing over it.
Note.—The effect of quality is altogether too little regarded in America. How
worthy of attention it is may be seen by the following.
Upon the same road were used two kinds of seventy-two pound rails, each five
inches deep, and having a bearing surface of 2.7 inches in width. The one was worn
out with a tonnage of 41,000,000 tons, the other of 22,000,000 tons; the
difference being entirely in the quality of the iron.
Upon the Philadelphia and Reading Railroad there have been used forty-five
pound rails of reheated and refined iron, which have lasted for eighteen years; and
that with a very heavy traffic upon them. While upon other American roads,
English sixty pound rails have required renewing in one, two, three, and four years.
The durability of rails is practically independent of time, and
depends entirely upon the amount of work done. The repairs of iron,
depending upon flaws and other physical defects, will be greater at
the commencement of operations than afterwards. After the first one
or two years the regular depreciation begins. The first Liverpool and
Manchester rail weighed thirty-five lbs. per yard, and the locomotive
seven and a half tons. As the traffic increased, so did the necessary
weight of engines, and a corresponding increase in the strength and
weight of rails was also rendered necessary. In 1831, the average
weight of engines with tenders was eighteen tons. In 1855, the
maximum engine with tender, fuel, and water weighed sixty tons;
and in like manner the rails increased from thirty-five to eighty-five
lbs. per yard.
Messrs. Stephenson and Locke, in a report to the London and North-
western Railroad Company, in 1849, recommend the adoption in
future of an eighty-five lb. rail.
Upon the roads of Belgium are used rails of fifty-five and sixty-four
lbs. per yard; but it is asserted that an eighty lb. rail would allow of
ten times more traffic.
For the average of American roads, when the iron is good, (in
quality,) fifty-five, sixty, and at most sixty-five lbs., will probably be
found ample for the heaviest traffic: the rail being of the form already
given, and supported on ties not more than two and a half feet from
centre to centre.
Mr. Belpaire, (of the Belgium engineers,) concludes, from many
experiments, that in sixty miles, each engine abrades 2.2 lbs.; each
empty car 4½ oz.; and each ton of load 1.4 oz.; the amounts being in
direct ratio to the several weights.
Captain Huish, of the London and North-western Railroad,
(England,) estimates (Report of April, 1849) that fifty trains per day,
or 18,250 trains per annum, for twenty years, would wear out a
seventy lb. rail.
The Belgian engineers have concluded that 3,000 trains per annum,
for one hundred and twenty years, would wear out a fifty-five lb. rail.
Now 120 × 3,000 = 360,000 Belgian, and 20 × 18,250 = 365,000
English, a very satisfactory coincidence, as the different observers
did not know of each other’s proceedings. The difference, 5,000
trains, being accounted for by the use of heavier engines upon the
roads of England.
From the above results the following table is formed, showing the life
of rails under from two to one hundred trains per day. American
roads being less nicely finished, as regards the road-bed, will of
course wear out rails faster than the roads of Europe. The table will
serve as a base for estimates.
Trains per Trains per No. of years’ life of
day. year. rails.
2 600 604
4 1,200 302
6 1,800 201
8 2,400 151
10 3,000 121
12 3,600 100
14 4,200 86
16 4,800 75
18 5,400 67
20 6,000 60
30 9,000 40
40 12,000 30
60 18,000 20
80 24,000 15
100 30,000 12
Probably one half of the above numbers of years would show the full
life of rails upon American roads.
As those rails which are most used wear out the soonest, they should
be made accordingly heavier. Such are those at depot grounds and at
sidings.
Note.—From the reports of the Reading (Penn.) Railroad it appears that in 1846
153
209
of the damaged rails were split; and that in 1845 285
295
were split.
As regards the quality of railroad iron, it is generally notoriously bad, and its
makers know it as well as those who buy it. Railroad companies are not willing to
pay for good iron. Comparisons between American and English iron amount to
little. First rate iron can be made in England or in America, and so can that which
will last about two years. Time will convince companies that the most expensive
iron is the cheapest.

TABLE OF THE WEIGHT PER MILE OF DIFFERENT RAILS.

Tons per mile. Tons per mile.

Weight in lbs. per yard.
(2,000 lbs.) (2,240 lbs.)
50 44.00 39.29
55 48.00 43.21
60 52.80 47.19
62 54.56 48.71
64 56.32 50.28
66 58.05 51.86
68 59.84 53.43
70 61.60 55.00
72 63.36 56.57
74 65.12 58.14
76 66.88 59.71
78 68.64 61.28
80 70.40 62.86

TRACK-LAYING.

289. As wrought iron expands 0.0000068 of its length per degree

(Fahrenheit) of heat, a change of 130° will cause the following
expansions:—
In a 15 feet rail .0135 ft.
In a 18 feet rail .0162 ft.
In a 20 feet rail .0176 ft.
and that the track may be kept in the right vertical and horizontal
line, rails laid in cold weather must not be placed in contact; but
separated by space enough to allow expansion to take place. In hot
weather they may be placed close together. Calling 100° the
maximum and -30° the minimum, we form the following table for
the average lengths of rail, (20 feet).
At 100° place the rails in contact.
90° at a distance of .00136 feet .016 inches.
80° at a distance of .00272 feet .032 inches.
70° at a distance of .00408 feet .049 inches.
60° at a distance of .00544 feet .065 inches.
50° at a distance of .00680 feet .082 inches.
40° at a distance of .00816 feet .092 inches.
30° at a distance of .00952 feet .114 inches.
20° at a distance of .01088 feet .131 inches.
10° at a distance of .01224 feet .147 inches.
0° at a distance of .01360 feet .163 inches.
-10° at a distance of .01496 feet .179 inches.
-20° at a distance of .01632 feet .196 inches.
-30° at a distance of .01768 feet .212 inches.

Fig. 140.
The proper distance of rails may be fixed by the use of the steel plates
shown in figs. 140 and 140 A, which are marked with the
temperature, according to their thickness, as in the above table.
To incline the rail base may be used, when the rail is not bevelled,
wedges one foot long and six inches wide, spiked with the rail to the
tie. When the chairs are of cast-iron, they may be cast to the required
slope.

Fig. 140 A.
 FROGS.
290. When one line of rail crosses another, a contrivance called a
frog is used; see figs. 141 and 142.

Fig. 141.

That the wheel may run smoothly from a to c, fig. 141, the rail b f
must be cut at D, and the rail a c must be cut at the same point.
Cutting the two gives the form shown in the figure, and further
developed in fig. 142.
In order that the flange of the wheel shall not leave the line a c, when
at the break D, the guard rail m m is used to confine the opposite
wheel. It should be placed at a distance of two inches from, and
parallel with, the main rail g g, from opposite six inches below the
frog point at s, to six inches above the shoulder at s′. From the ends
of the parallel line n n the guard rail should gently curve away at both
ends. Thus the wheel will be gradually brought into the right line,
kept so until the break in the rail is passed, and finally easily
released. To place and maintain the guard rail in the right position, it
is well to put both it and the main rail into a double chair, which is
spiked to the sleeper.
 Fig. 142.

The form and dimensions of the cast-iron frog depends upon the
angle at which the cutting rails cross, and upon the size of the wheel
tire.
To draw the frog, proceed as follows:—

Fig. 142 A.

Let a c b be the angle. Parallel with and two inches from b c draw d e,
e being in a c produced. In the same manner fix the point g. At the
width of the rail head (from 2¼ to 2½ inches) draw, parallel to a c, L
8. The point 8 is the limit to the solid steel. At double the rail width,
or 4½ inches, draw, also, parallel to a c, 16. 6; 5. 6 is the limit of the
flat steel, generally about half an inch in thickness. This is the least
amount of steel allowable; it is best to steel the whole tongue, and all
of that part of the wings acted upon by the wheels. The geometric
point is generally very thin, and is omitted to a distance far enough
back to make the point a third or half an inch wide, which is rounded
off; e L and d k are made two and a half inches; as also f m and g n; k
10 and m 11 are made six or seven inches, and joined to d and f by a
curve, abrupt at first, but afterwards more gentle. The distances, 5 a
and 6 b must be such that a 9 is three and one eighth inches,
(depending upon the breadth of rail base,) o m″ is from three to four
inches. At the other end of the frog e h must be enough to make s t at
least an inch, when e h and i g are from three to four inches; i m′
being, as at the other end, three or four inches. The steel plates N N
are one half inch in thickness. The surface, N, is two inches above the
bottom, M. The lower plate, M, is two inches thick. A B, C D, and E F
11
are six or seven inches wide, and one inch thick. The spike holes 16
square, the spike being one half inch. The sharp edges, i g, e h, a c, b
c, should be rounded off to fit the wheel at A, fig. 142 A. The surface
of the tongue N 9 should be formed to a double incline to fit the
wheel cone.
Note.—Fig. 142 A gives the shape and dimensions of the largest tires.
Another method of making a frog is to cut and weld the rails a and b
of the track, as in fig. 143. The continuations of these rails are bent as
shown in the figure.
 Fig. 143.

The whole angle is placed upon a firm wooden bearing.

There is no weaker part of the track than the frog. To make up the
strength at such places a heavy longitudinal timber twelve feet long
will answer a good end.
 SWITCHES.
291. The object of the switch is to adjust a single line of rails to two or
more pairs, so that any two lines may be made continuous. The form
in general use consists of two rails, as at a b, a b, fig. 144, moving
upon a and a as centres. Here the tangent point of the turnout curve
is at c. The data given for the switch are the length of switch rail and
the motion at the toe (c) (which determine the direction of the
starting tangent) and the radius of curvature of the turnout curve.
The required elements are, the angle of frog at b and the distance
from a to the point of the frog.

Fig. 144.

The following formula and table are by Josiah Hunt, Esq., (at present
chief engineer of the Hannibal and St. Joseph Railroad, Mo.). The
formula was first published in Appleton’s Mechanics’ Magazine, vol.
1, p. 575.

D = 2(g – s) × cot. S × cot. F

cot. S + cot. F
.

Where S = angle of switch.

F = angle of frog.
s = the movement.
g = the gauge.
Example.—How far from the toe of the switch is the point of the frog,
the gauge being 4′ 8½″, the rail twenty feet long, and moving five
inches; the frog being six feet long, six inches wide across the head,
and three inches at the mouth?
We have

D = 2(4.708 – .417) × 240/5 + 72/(6 + 3)

240/5 + 72/(6 + 3)

or, D = 8.582 × 48 ×8
48 + 8
= 58.85 feet.

In laying the rails, the distance from the point to the end of the frog
(towards the switch) is to be taken from the above.
Table showing the distance between the frog and switch, gauge 4′
8½″, movement of switch-rail five inches. Frog six inches across
head, and three inches at mouth. Main track being straight.
LENGTH OF SWITCH RAIL.
Length of frog.
12 14 16 18 20 22
3 29.1 29.7 30.1 30.4 30.7 30.9
3½ 33.3 34.0 34.5 35.0 35.3 35.6
4 37.3 38.2 38.8 39.4 39.8 40.2
4½ 41.1 42.2 43.0 43.7 44.3 44.7
5 44.8 46.1 47.1 47.9 48.5 49.1
5½ 48.3 49.8 51.0 51.9 52.7 53.2
6 51.7 53.4 54.8 55.9 56.8 57.6
6½ 55.0 56.9 58.5 59.8 60.8 61.7
7 58.1 60.3 62.1 63.4 64.7 65.7
7½ 61.2 63.6 65.6 67.2 68.5 69.6
292. When the switch rail is short, the angle between the main line
and the switch rail, when switched, is considerable; and causes quite
a shock to the passing engine. The switch shown in fig. 145 remedies
the evil, makes the machinery compact, and the calculation simple.
The tangent point of the turnout curve is at n n (the usual heel). In
place of adjusting the single to the double line of rails, the double is
adjusted to the single line. The data given are the gauge and radius of
curve; and as before, the elements required the frog angle and
distance from switch to frog point.

Fig. 145.

Now

Rad.2 – Rad. less gauge2 = distance2,

or R2 – R – g2 = D2,

and D = √R2 – (R – g)2.

The angle of frog is also

Sin angle of frog = Sin log

90 log D
R
.

The length of this switch rail depends upon the radius of curvature.
The distance between the two rails at S must be enough to admit the
wheel flange, that is, at least two inches.
Let A B, fig. 146, be the straight rail; E D the curved one. Draw G H
parallel with and two inches distant from the inner edge of A B. No
point of the curved rail must fall within G H; whence E is the
turning-point, and E D the length, found as follows.
Let R equal the radius of curve to outside of outer rail; d equal two
inches plus width of rail, or i e, and D equal D E.
Then

D = √R2 – (R – d)2.
 Fig. 146.

Example.—Let the radius of outer rail be five hundred feet, and the
gauge five feet. We have, then, the distance

(A.) D = √5002 – 4952 = 72 feet, very nearly.

Also, Sin E C D = Sin log

90 log D
R
,

(B.) or Sinlog
90 log 72
500
= 8° 17′,

and the length of switch

(C.) √5002 – 499.652 = 18¾ feet nearly.

Five hundred feet is, therefore, about the longest radius for which
such switches should be used.
 SIDINGS AND CROSSINGS.
Crossings occur where two tracks cross, and consist of four frogs,
with the corresponding guard rails, as in fig. 147.

Fig. 147.
 ELEVATION OF THE EXTERIOR RAIL.
293. The motion of a train of cars around a curve is accompanied by
a tangential force, depending in amount upon the velocity of the
train and the radius of curvature. This force tends to throw the cars
from the track; and is counteracted by elevating the exterior rail.
The centrifugal force of any body in motion in a curved line is shown
by the formula
WV2
32R
.

Where W is the weight in lbs.

V the velocity in feet per second.
R the radius of curvature,
and 32 the accelerating force of gravity.

The force tending to throw the car from the rail is not centrifugal but
tangential, but it matters not whether the body is kept in position by
tension upon the inside or by compression on the outside; the
amount of the force is the same.

Fig. 148.
The horizontal projection of the centre of gravity of the car, when at
rest, is at c, fig. 148, and when in motion the direction of the weight
should be a b; and the inclination, c′ a′ b′, must be such that a b will
be perpendicular to c′ a′; to effect which, c′ b′ should be to a′ b′ as
the weight to the tangential force; or E being the elevation of the rail,
g the gauge, W the weight, and c the tangential force; we have

E : g :: c : W,
2
or E = cg
W
, and c being = WV
32R
;

finally E = (WV
32R
2
)g/W or 32R
V g 2
= E.

Where W = weight of a car.

V = speed of train in feet per second.
g = gauge of road.
R = radius of curve.
E = elevation of outer rail in feet and decimals.

g and R are the only fixed quantities in the formula; and the average
weight and speed of a car must be assumed.
Examination of the formula shows how important it is that all trains
should run at such a velocity as to demand the same elevation of rail.
The absolute elevation must be arranged to meet the requirement of
the fastest trains; and other trains must conform, even at a
disadvantage.
Note.—The subject of the mechanics of traversing railroad curves, is yet quite in
the dark. The action of the train, as caused by its own momentum, is tangential;
while the action of the engine tends to pull the cars against the inner rail, being
opposed to the first motion. This might require a reduction of the elevation given
by the formula when the engine is exerting a strong tractive power, but when
running without steam the full elevation is needed, (see chapter III.)
 Fig. 149.

In laying and maintaining the rails to the proper elevation, a

clinometer attached to a rail gauge, as in fig. 149, answers a good
end: the small arc being graduated according to the different
elevations required by curves of different radii. Thus the index of the
level being placed at 2°, when the rails are fitted to A and B, the
elevation is correct for a 2° curve; or for a curve of 2,865 feet radius.
The difference in gauge of one foot makes a difference in the
elevation of but 0.009 feet, or about ⅒ of an inch.
The following table is calculated for the average of the different
gauges in use, thus,—
4.7
5.0
5.5
6.0

4)21.2

Average gauge, 5.3 feet.

TABLE OF ELEVATION OF OUTER RAIL.

ELEVATION OF OUTER RAIL IN FEET AND

Radius of DECIMALS, THE VELOCITY IN MILES PER
curve in HOUR BEING
feet, being
10. 15. 20. 25. 30. 40.
250 .130
500 .070
 1,000 .037 .079
2,000 .018 .040 .074 .111
3,000 .013 .026 .048 .074 .106
4,000 .009 .020 .037 .058 .079 .154
5,000 .007 .016 .031 .045 .065 .119
6,000 .006 .013 .024 .037 .053 .095
7,000 .005 .011 .021 .033 .046 .086
8,000 .004 .010 .018 .029 .039 .077
10,000 .003 .008 .010 .022 .032 .059
CHAPTER XIV.
EQUIPMENT.
 PART I.
LOCOMOTIVES.

As the locomotive engine is the power by which railroads are worked, and as its proportions and
dimensions are so intimately connected with the physical character of the road, it is thought proper to
take space enough at this point to examine the general principles of its construction, and of its
adaptation to the work required of it upon railroads.
Under the general principles, we recognize the production and consumption of steam, the disposition of
weight upon the several pairs of wheels which shall secure the necessary adhesion, the application of the
power generated in the boiler to the moving of the wheels, and that general arrangement of parts which
shall render the use of power economical.

BIRTH AND GROWTH OF THE LOCOMOTIVE.

294. The first idea of the application of steam to locomotion, is due to the unfortunate Solomon de Caus,
of Normandy (France), who was confined in a madhouse for insisting that steam could be made to move
wheeled carriages.
295. In the year 1784, William Murdoch, the friend and assistant of James Watt, built a non-condensing
steam locomotive engine, on a scale of about one inch per foot, having
Cylinders, ¾ × 2 inches,
Wheels, 9½ inches,
and Weight, 10 lbs.
This little engine, however, accomplished the speed of ten miles per hour.
296. In 1802, Richard Trevethick patented the application of the non-condensing steam-engine to the
propelling of carriages on railroads; his engine was fitted with one horizontal cylinder, which applied its
power to the wheels by means of spur gear.
297. In 1825, the truck was first applied, to relieve the driving wheels of a part of the weight, and to
enable the engine to pass freely around curves.
298. In 1827, Timothy Hackworth applied the blast pipe, for the purpose of draft. He applied, also,
spring balances to the safety-valves, and used the waste steam to heat the feed water. This engine drew
one hundred tons, at five miles per hour, and forty-five tons on a fifty feet grade.
299. In 1828, M. Seguin (France) introduced the multitubular boiler.
300. In 1829, the directors of the Liverpool and Manchester Railroad offered a premium for the best
locomotive, which should draw three times its own weight, at ten miles miles per hour. The “Rocket,” by
Robert Stephenson, of Newcastle on Tyne, was the successful competitor, and drew the load required,
seventy miles, at an average speed of 13.8 miles per hour; its maximum velocity was twenty-nine miles
per hour; it evaporated 5.4 lbs. of water per pound of coke, and 18.24 cubic feet per hour of water.
301. From 1830 to 1840, the changes that were made were rather those of dimension, proportion, and
arrangement, than of essential elements of steam producing.
302. In 1840, several truck frame engines were sent to England from the Norris Works of Philadelphia.
These locomotives would draw a load of one hundred and twenty tons over a sixteen feet grade, at the
rate of twenty miles per hour.
303. In 1845, the Great Western Railroad, of England, was supplied with an engine of twenty-two tons
weight, having cylinders 15¾ × 18, wheels 7 feet, heating surface 829 square feet. This locomotive
carried seventy-six and one half tons at a velocity of fifty-nine miles per hour. The consumption of coke
was 35.3 lbs. per mile, and of water, 201.5 cubic feet per hour.
 THE ENGLISH LOCOMOTIVE OF 1850.

304. The “ne plus ultra” for the seven feet gauge (Great Western Railway) by Gooch, has inside cylinders
18 × 24 inches, one pair of eight feet driving wheels, grate area twenty-one square feet. Fire-box surface,
one hundred and fifty-three feet. Three hundred and five two inch tubes, giving 1,799 feet of surface.
Total heating surface, 1,952 square feet. Weight of engine, empty, thirty-one tons; of tender, eight and
one half tons; whole weight with wood and water, fifty tons. Evaporating power, three hundred cubic
feet of water per hour. This engine can draw two hundred and thirty-six tons, at forty miles per hour.
The maximum for the London and North-western Railroad, four feet, eight and one half inches gauge
(Crampton’s patent), has cylinders 18 × 24 inches; wheels, eight feet; two hundred two and three
sixteenths inch (outside diameter) tubes; grate, twenty-one and one half square feet; fire surface, one
hundred and fifty-four feet; tube surface, 2,136 feet; whole heating surface, 2,290 square feet; weight,
loaded, thirty-five tons; twelve tons upon driving wheels; tender, twenty-one tons, loaded; whole weight,
fifty-six tons.

THE AMERICAN LOCOMOTIVE OF 1855.

305. The engine “Charles Ellet, Jr.,” drew on the 9th of August, 1854, forty tons, over a grade of two
hundred and seventy-five feet per mile, and over grades of two hundred and thirty-eight feet, upon
curves of three hundred feet radius. This engine has wheels four and one half feet in diameter coupled
seven feet apart; cylinders 14 × 26 inches; and weighs, including wood and water, 53,058 lbs. This is a
tank locomotive, the tender is dispensed with, and in its room a tank containing one hundred cubic feet
of water, and one cord of wood is used. This engine was built by Richard Norris and Son.
An engine built by the Cuyahoga Steam Furnace Co. of Cleveland, Ohio, performed the following feat.
An ordinary passenger train was carried one hundred and one miles, over a total ascent of 1,255 feet of
grades, making twenty stops, at an average speed of twenty-five miles per hour, with a consumption of
only ninety cubic feet of wood.
The same engine drew an average load of three and one third cars four hundred and thirty miles, making
seventy-five stops, surmounting a total ascent of 5,439 feet, averaging twenty-five miles per hour, with
one tender full of wood only.
In the months of July and August, 1856, two engines upon the Pacific Railroad (Missouri), one by R. K.
and G., and one by Palm & Robertson, ran each one hundred and twenty-five miles, with three passenger
and one baggage cars, using only one cord of wood.
Note.—For an interesting example of what can be done by the American locomotive, and an illustration of engineering
peculiarly American, the reader is referred to a description of the “Mountain top track” at the Rock-fish Gap crossing of the
Blue Ridge (Va.), by the Virginia Central Railroad, given by the engineer under whose direction the work was proposed and
executed (Charles Ellet, Esq.), from which is extracted the following:—
4 68
“The eastern slope is 12,500 feet long, and rises 610 feet; the average grade being 25710 feet, and the maximum 295100 feet
6
per mile. The least radius of curvature 234 feet; upon which curve the grade is 23710 feet per mile. The western slope is
84
10,650 feet long, and falls 450 feet; the average grade being 223⅒, and the range 279100 feet per mile.
“The engines, which have taken loads ranging from twenty-five to fifty tons up one slope at seven and one half miles per hour,
and down the opposite one at six miles per hour, making four trips of eight miles per day for three years, were designed and
built by M. W. Baldwin & Co., Philadelphia, and have three pair of forty-two inch wheels all coupled, the flange base being 9′
4″, cylinders 16½ × 20 inches, weigh, with wood and water, 55,000 lbs., or twenty-seven and one half tons. They run without
a tender, the engine carrying its own feed; thus gaining the double advantage of increasing the adhesion of the engine, and
avoiding the resistance of a tender.”

GENERAL DESCRIPTION.

306. The locomotive is a non-condensing, high pressure engine, working at a greater or less degree of
expansion, according to the labor to be performed, and placed upon wheels which are so connected with
the piston, that any motion of the latter is communicated to the former, by which the whole is moved.
The power exerted in the cylinder and referred to the circumference of the driving wheel, is called
traction; its amount depends upon the cylinder diameter and steam pressure, upon the diameter of
wheel and stroke, this latter being the distance between the wheel centre and point of application of
power.
The means by which the “traction” is rendered available for moving the engine and its load, is the
resistance which the wheel offers to slipping on the rail, or its bite, and is called adhesion; it is directly as
the weight applied to the wheels, but depends also upon the state of the rails. It varies from nothing,
when there is ice on the rail, to one fifth of the weight upon the driving wheels when the rail is clean and
dry, and in some cases has reached as high as nearly one third. It should be enough to resist the
maximum force of traction, that is, the wheel should not slip when the engine is doing its greatest work.
Steam producing, Traction, and Adhesion, are the three elements which determine the ability of an
engine to perform work. The proportions and dimensions of the machine depend upon the duty required
of it; sufficient adhesion for a required effect should be obtained rather by a proper distribution, than by
increase of weight.
Fig. 150 shows the relative position of parts in the locomotive engine as at present constructed in
America.
1 2, Grate upon which the fuel is placed.
1 2 3 4, Interior fire-box.
5 6, Exterior fire-box.
7 7 8 8, Shell of the boiler.
9 9, Boiler flues.
10 11 12 13, Exhaust chamber, or smoke box.
14, Steam dome, entrance to steam pipe.
15, Steam pipe.
16, Piston.
18, Piston rod.
19, Connecting rod.
20, Crank.
21, Driving wheel.
22, Blast pipe.
23, Chimney.
27 28, Leading wheels, supporting the front end of the engine, turning on a swivel, 29.
30, “Blow off” safety-valve.

Fig. 150.

307. The operation of generating and applying steam for the production of motion is as follows:—
The boiler and the space between the two fire-boxes being filled with water, (high enough at least to
cover the flues and the top of the inner box,) fire is applied to the fuel placed upon the grate; the heat
which fills the fire-box and tubes, is communicated to the water and converts the same to steam; which
entering the mouth of the pipe, 15, flows to the cylinder, where it forces the piston to the end of the
stroke. This motion is transferred through the connecting rods and cranks to the wheels, which
revolving, move the engine upon the rails. At the same time the eccentrics, placed upon the driving axle,
give a motion to the valve gear, and thence to the valves, by which the admission of steam is stopped at
the first end of the cylinder, and commenced at the other. The volume of steam which entered during the
first half stroke is forced out of the cylinder by the returning piston, up the blast pipe, and out at the
chimney, where a vacuum is produced, which can be supplied with air only from the chamber 10 11 12
13; after a few strokes the air is exhausted from the chamber, which can be refilled only by the external
air drawn through the fuel, furnace, and tubes. The more complete this vacuum, the stronger the
current of air drawn through the fire, which (current) is the draft. The admission of fresh air is regulated
by a damper placed at 2. The fuel is placed upon the grate by means of a door in the rear of the fire-box.
The necessary height of water is maintained in the boiler by pumps worked by the engine, in such a
manner as to secure at all times the proper supply. The proportions and dimensions of the boiler, the
engine, and the carriage, with the rules for obtaining the same will be considered shortly.

DUTIES EXPECTED OF LOCOMOTIVE ENGINES.

308. The work required of any engine depends upon the nature and amount of traffic, and upon the
physical character of the road.
The nature of the traffic, whether bulky or compact, and whether requiring quick or slow transport,
determines somewhat the number and size of the trains, and consequently the number and power of the
engines.
A road with steep grades and sharp curves, with the same amount of traffic, will need stronger engines
than a road with easy grades and large curves.
The amount of motive power and cost of working it, depends in a great degree upon the disposition of
grades as regards the direction of the traffic movement. The most economically worked road will be
either a level one, or one where the bulk of the traffic is moved down hill.
The mineral, commercial, or agricultural nature of the country, determines the direction of the traffic,
and the physical nature, the arrangement of the grades.
The different kinds of labor required of locomotives, necessitate the employment of engines of different
proportions; and the different classes of railways, require engines possessing different amounts of
power.
309. The classification of locomotives should be determined according to the following relations.
Department depends upon commercial duty.
Division depends upon character of road.
Order depends upon weight of trains.
Class depends upon speed of trains.

Note.—The general classification is given at the end of this chapter.

High rates of speed are generally combined with light loads, and heavy trains are required to move at the
lower velocities.
Great speeds require the rapid production and consumption of a large bulk of steam of but little density;
large wheels and short stroke, that the ratio of velocities of piston and wheel may be as great as possible.
Heavy trains consume less steam by bulk, per mile, but of a much greater density, and combine a long
stroke with a small wheel, by which great leverage is obtained.
In general, engines for winter use should be heavier than those for summer, upon the same ground, as
natural causes are more liable to resist adhesion in the winter.
The locomotive engine may be so proportioned as to run at any speed from ten to sixty miles per hour,
over grades from ten to two hundred feet per mile, and to carry loads from two hundred to two thousand
tons.
The rules by which the necessary dimensions to perform any required duty are fixed, depend upon the
very simplest mechanical laws.
Note.—The formulæ expressing the most proper relations to exist between the several steam-producing and steam-
consuming parts are more reliable than the assertions of any machinist in America, and though taken from books, are the
result of the experience of the most able and practical men for twenty years. Operatives are too apt to despise book
knowledge, forgetting that the very knowledge so despised is the result of more practice than a lifetime can afford them.
Railroad managers are too apt to receive as indisputable, the opinions of men who are practical, simply because they
understand nothing of principle.
Since the work of D. K. Clark (England) has appeared, any dimension from the beginning to the end of a locomotive may be
fixed, to the eighth of an inch, with absolute correctness, and there is no excuse for departing from the proper proportions. It
does not follow that because a locomotive does actually start off and draw the train, that it is properly made. A race-horse can
draw a plough, and a yoke of oxen a “trotting buggy,” but this is by no means the correct adaptation of power.
310. The elements which govern the requirements of power are
The maximum grades.
The weight of the train.
The required speed.

And the elements which govern our ability to produce the power needed,
The grate area.
The heating surface.
The cylinder diameter.
The steam pressure.
The stroke.
The diameter of wheels.
The weight upon driving wheels.

MECHANICAL AND PHYSICAL PRINCIPLES GOVERNING THE CONSTRUCTION OF THE

LOCOMOTIVE ENGINE.

RESISTANCE TO THE MOTION OF RAILROAD TRAINS.

311. The exact resistance to the motion of a railroad train cannot be determined, as some of the elements
are so variable; for example, the state of the weather. An approximate estimate, near enough for
practice, is easily obtained. To arrive at correct data the observations must be made upon trains working
under the same conditions that they are subject to in practice.
The whole resistance is made up of several partial resistances, some of which are constant at all speeds,
and some of which increase with the velocity.
The engine and tender resistance is composed of the friction of pistons, cross heads, slide valves, cranks,
eccentrics, pumps, the back pressure of the blast, and various erratic movements, rolling, twisting, and
pitching together with both wheel and axle friction, which is common to the engine and tender.
The atmospheric resistance is not due to the direct action of the air upon the front and sides of the train
entirely, but chiefly to the exhausting action in the rear. The train has, as it were, to pull along a large
column of air like the water in the wake of a ship; form or amount of frontage has little or no effect. The
resistance depends upon the bulk of the train and its velocity. A train with the same frontage offers more
resistance as its bulk increases.
Oscillatory resistance is caused by irregularities in the surface of the rails, and increases with the
velocity, and also with increase of height of the centre of gravity of the car or engine.
Frictional resistance may be divided into wheel and axle friction. That of the axle is composed of two
parts, the direct vertical friction on the journal, and the side friction on the collar, consequent upon
lateral motion. The vertical friction is independent of the surface pressed or of velocity, but is directly
proportional to the pressure, and the same remark applies to that of the collars. As the diameter of wheel
increases, the oscillation is increased, the centre of gravity being raised. The direct cause of the vertical
friction is the weight of the car or engine, and of the lateral irregularities in the surface of the rails, which
cause the car to sway from side to side. Wheel friction which acts between the periphery of the wheel and
the surface of the rail increases with the load, and decreases as the wheel diameter augments.
For the total resistance to the motion of a railroad train, D. K. Clark gives the following formula:—
V2
171
+ 8 = R,

Where R is the resistance in lbs. per ton,

and V the velocity in miles per hour.

From this expression we form the following table:—

Velocity in miles per hour. Resistance in lbs. per ton.
10 8.585
12 8.842
15 9.315
20 10.339
25 11.655
30 13.263
40 17.356
50 22.620
60 29.052
100 66.480
From a great number of experiments made by Mr. Clark, the relative resistance to the motion of inside
and outside connected engines is as follows:—
Inside connections 17
Outside connections 14
The effect of curves, bad state of the road, and adverse winds, amounts (according to the same author) to
the following percentages:—
Bad state of the road 40
Curves 20
Strong head and side winds 20

In all 80

The resistance due to grades depends entirely upon the rate of incline, and is quite independent of all
other considerations. The relative effect of grades decreases with the absolute increase of resistance on a
level. Thus common roads admit of steeper grades than do railroads, because the level resistance is
much more upon the former than on the latter.
The exact determination of the resistance due to any grade depends upon the very simple mechanical
principle, regulating motion upon the inclined plane. For each foot rise of grade per mile, the resistance
per ton is
1
2240 × 5280.

Thus the resistance to one ton upon a forty feet grade is

 40
2240 × 5280 or 17 lbs.

And if we are moving at thirty miles per hour the sum of all other resistances is, by the formula, or the
table at the end of Chapter XIV., part I., 13.3 lbs. per ton; whence the whole resistance to the motion of
one ton, at thirty miles per hour, upon a forty feet grade, is
17 + 13.3 or 30.3 lbs.

and one hundred tons would be one hundred times as much. Table 1, at the end of Chapter XIV., part I.,
gives the whole resistance to the motion of trains of from fifty to one thousand tons, moving at speeds
varying from ten to one hundred miles per hour, and table 2 gives the resistance upon grades from ten to
one hundred feet per mile.

TRACTION AND ADHESION.

312. The whole steam pressure upon both pistons, referred by means of the crank, connecting, and
piston rods, and wheel, to the rail, is called “traction.” It is the drawing power of the engine. Its amount
depends upon the diameter of cylinder, steam pressure, stroke, and diameter of wheel.
By increasing the steam pressure, we increase the power. By increasing the cylinder diameter, we
increase the power. By increasing the stroke, we increase the power. By decreasing the wheel diameter,
we increase the power. And by adjusting the dimensions of the above parts, we may give any desired
amount of power to the engine.
The formula expressing the tractive power of an engine, of any dimensions, is
(2A) P × 2S
C
.

Where A = the area of one piston.

P = the steam pressure in cylinder per square inch,
S = the stroke in inches.
C = the circumference of the wheel in inches.

The formula is expressed verbally as follows: Double the stroke and multiply it by the total steam
pressure on both pistons; divide the product by the circumference of the driving-wheel in inches.

ADHESION.

313. As observed on page 307, the adhesion or the bite of the wheels upon the rail is, as an average, from
one fifth to one sixth of the weight; one fifth when the rail is in a good state, and less when wet or greasy;
we cannot depend upon more than one sixth in practice. Therefore, if the tractive power of an engine is
3,000 lbs. we must, to make it available, place 3,000 × 6 or 18,000 lbs. upon those wheels which are
connected with the machinery, (driving wheels).

FUEL.

314. The fuels employed in the locomotive engine for the evaporation of water are wood, coal, and coke.
In England the latter is used exclusively. In America the first has, on account of its cheapness, been quite
generally adopted; but of late railroad companies have been turning their attention to coal and coke.
The immense beds of coal distributed throughout the United States will furnish fuel to railroad
companies almost without limit. Its position as well as its amount will render its adoption practicable in
nearly all of the States. Ohio alone contains more coal than all of Great Britain. The following table is
from the iron manufacture of Frederick Overman.
 Name of State. Area of Coal-fields.
Georgia 150 square miles.
Maryland 550 square miles.
Alabama 3,400 square miles.
Tennessee 4,300 square miles.
Michigan 5,000 square miles.
Missouri 6,000 square miles.
Indiana 7,700 square miles.
Ohio 11,900 square miles.
Kentucky 13,500 square miles.
Pennsylvania 15,437 square miles.
Virginia 21,195 square miles.
Illinois 44,000 square miles.

In all 133,132 square miles.

315. The following table (also from the works of Overman) gives the nature and evaporative power of the
different American coals.
State Steam of 212° Quantity of Percentage of
Name of Percentage
where evaporated per heat by coke by
Coal. of carbon.
found. lb. volume. weight.

Anthracite.
Beaver
Pa. 88.9 10.4 94
Meadow,
Forest
Pa. 90.7 10.8 94
Improvement,
Lehigh, Pa. 89.1 9.6 94
Lackawanna, Pa. 87.7 10.7 94

Coke.
Midlothian, Va. 10.3 92 .66
Cumberland, Md. 10.3 92 .75

Bituminous.
Maryland, Md. 73.5 11.2 85
Cumberland, Md. 74.3 11.0 85
Blossburg, Pa. 73.4 10.9 85 .83
Karthans, Pa. 73.8 9.8 85 .88
Cambria
Pa. 69.4 10.2 85
County,
Clover Hill, Va. 56.8 8.5 85 .68
Tippecanoe, Va. 64.6 8.5 85
Pittsburgh, Pa. 55.0 8.9 85 .68
Missouri, Mo. .57
316. The employment of the several varieties of wood depends more upon the commercial than the
chemical character. The following table shows the specific gravity, the nature and the evaporative value
of the different species.
Species. Specific Specific Specific Degrees of Percentage Quantity Weight Rel
gravity gravity gravity heat of of heat of one valu
green. air kiln which Charcoal. as to cord in fu
dried. dried. volume. lbs.
 may be
generated.
Hickory, 3000 44.69 25 4469 1.
White
1.07 0.71 0.66 3000 21.62 25 3821 0
Oak,
Black
3000 23.80 25 3254 0
Oak,
Red Oak, 1.05 0.68 0.66 3000 22.43 25 3254 0
Beech, 0.98 0.59 0.58 3000 32.36 25 3236 0
Birch, 0.90 0.63 0.57 3000 25
Maple, 0.90 0.64 0.61 3000 27.00 25 2700 0
Yellow
2800 24.63 23 2463 0
Pine,
Chestnut, 3000 25.25 25 2333 0
Pitch
2800 19.04 23 1904 0
Pine,
White
0.87 0.47 0.38 2800 18.68 23 1868 0
Pine,
Degrees of
Specific Specific Quantity Weight
Specific heat Percentage Rel
gravity gravity of heat of one
Species. gravity which of valu
air kiln as to cord in
green. may be Charcoal. fu
dried. dried. volume. lbs.
generated.
Of the relative value of wood and coal, we have the following results of experience.
In the engines of the Baltimore and Ohio Railway 2.55 lbs. of pine wood were found equal to one pound
of Cumberland coal.
On the Reading Railroad (Pennsylvania), three pounds of pine wood equal to one pound of Anthracite
coal.
Mr. Haswell estimates the best varieties of wood fuel to contain twenty per cent. of carbon.
Walter R. Johnson found that one pound of wood, upon an average, evaporated two and one half pounds
of water.
The average percentage of coke from American bituminous coal from the above table is seventy-three
per cent., and the average percentage of carbon, sixty-seven and one half per cent.
317. The following table shows the relative properties of good coke, coal, and wood.
Equivalen
Economic Economic,
Weight Cubic feet economic
bulk, or or
Name per Degrees of Percentage of air to bulk, to
cubic feet stowage
of cubic heat of carbon, evaporate evaporate
required weight
fuel. foot, in generated. in the fuel. one lb. of the same
to stow per cubic
lbs. water. weight of
one ton. foot.
water.
Coke. 63 4300 95 80 28 22.4 13
Coal. 80 4000 88 44 51 32.0 10
Wood. 30 2800 20 107 21 16.0 60
The power of fuel depends upon the amount of carbon in it.
Pure coke is solid carbon.
Hence its superior value as a heat generator.

OF THE PROCESS OF COKING.

318. Anthracite coal is used for locomotive fuel in its natural state. It is employed chiefly upon those
roads on the eastern slope of the Alleghanies. The bituminous coal lies in the Mississippi valley, and may
be found anywhere between the summits of the Alleghanies and the Rocky Mountains. This, in its
natural state, contains so much pitchy matter as to render it unfit for locomotive purposes. Upon being
heated, it melts, runs into a mass, and clogs the grate; requiring frequent poking and a strong draft. But
when the bitumen is burnt off by slow and careful baking, (as described below,) no fuel equals it.
Just as carbonized wood is charcoal, so carbonized coal is coke. Coke is bituminous coal deprived of its
bitumen, the raw coal being baked in ovens having vents so regulated as to admit air enough to char,
without consuming the coal. The ovens being closed at the proper time, the fire is gradually
extinguished, and the coke, compacted into large masses, requiring to be broken up before taken out.
Coal may be coked by piling loosely in heaps, covering with earth, and firing through openings, which,
after forty or fifty hours, are closed. In preparing coke, however, in the large quantities required for
railroads, and that it may be of the very best quality, a good deal of care must be taken.
Probably in no place more or better coke is made, or the operation more skilfully carried on, than at the
Camden-town station of the London and North-western Railroad, (England).
The company have built eighteen ovens, in two rows, all discharging their volatile gases into a horizontal
flue terminating in a chimney one hundred and fifteen feet high; having an internal diameter of eleven
feet, and being three feet thick, (making the external diameter seventeen feet). The ovens are elliptical,
11 × 12 feet inside, with walls three feet thick. The height is ten feet, the first three feet from the ground
being solid, and furnished with a fire brick floor, on which the coal is placed. Each oven communicates
with the flue by an opening in the top two and one half feet by twenty-one inches; which opening is
closed by an iron damper, to regulate the draft. The openings for the doors are three and one half feet
square outside, and two and three fourths inside, being closed with iron doors four and one half by five
feet, lined with fire brick, and balanced in opening by counterweights. (The object of the chimney and
horizontal flue is to carry the smoke and unburned gases so far up that they shall not be a nuisance. In
America we might allow the smoke of each oven to escape through a low chimney of its own, (ten or
twelve feet high,) and save the cost of a large stack; like the coking ovens in our foundries).
The operation of coking is carried on as follows:—Each alternate oven is charged between eight and ten
A. M. every day, with three and one half tons of good coals. A whisp of straw is then thrown in, which
takes fire from radiation from the top, and inflames the smoke then arising from the surface, by the
reaction of the hot sides and bottom upon the body of the fuel. In this way the smoke is consumed at the
very point of the process, where it would otherwise be the most abundant. The coking process is a
complete combustion of the volatile principles of the coal. The mass of coal being first kindled at the
surface, where it is supplied with an abundance of oxygen, because the doors in front and vents in the
rear are open, no more smoke goes from the chimney than from that of a common kitchen fire. The gas
generated from the slightly heated coal cannot escape destruction in passing up to the bright flame of
the oven. Any deficiency in oxygen for consuming the smoke is supplied by the air entering the grooves
of the dampers.
As the coking process advances most slowly from the top to the bottom, only one layer is consumed at a
time; while the surface is covered with red-hot cinders, ready to consume any particles of carburetted or
sulphuretted hydrogen gases which may escape from below. The greatest mass cannot emit more gases
than the smallest heap.
The coke being perfectly freed from all smoky and volatile matters, by a calcination of forty hours, is
cooled down to a moderate ignition by sliding in the dampers and opening the doors, which had been
partly closed during the latter part of the operation.
The coal is now converted into a clean, crystalline, porous, columnar mass, of a steel-gray color, and so
hard as to cut glass. This is broken up and taken out—coke. It is sometimes extinguished by a watering-
pot. This is wrong, it ought not to be wet, and even more, ought to be immediately shut up in fire-proof
boxes and bins. Even left to itself in the air, it absorbs moisture rapidly, which must be burned off in the
boiler; it should by all means be kept in a dry place. Mr. Woods (England) observes, that coke may
absorb as much as eight per cent. of water in going from the oven to the storehouse. The amount of
absorption depends upon the nature of the coke. D. K. Clark records the following, the coke being
immersed in water.
No. 1. Close-grained and good, absorbed 14.5 per cent. of water.
No. 2. Porous and ordinary, absorbed 21 per cent.
No. 3. Very close-grained and good, 9 per cent.
The time of coking may be stated generally as fifty hours, though it is somewhat improved by being
allowed forty hours more; this gives time for a better consolidation, and gives a firmer, brighter, and
more crystalline mass.
Mr. Gooch, of the Great Western (England) Railroad, experimented upon the time of coking with the
following results.
In oven. Yield per ton of coal. Water evaporated per lb. of coke. Result.
48 hours 12.71 cwt. 7.1 lbs. 902.
72 hours 12.00 cwt. 7.7 lbs. 924.
Thus, though the yield per ton is decreased by a greater time, the value of the coke per pound is
augmented, and the increase overbalances the decrease.
Firstrate coal gives from seventy-five to eighty per cent. by weight, of compact glistening coke, weighing
about 14 cwt. per chaldron, (thirty-six bushels). The bulk is increased from ten to fifty per cent.
In breaking out the coke from the ovens, a great deal is unavoidably reduced too fine for use in the
locomotive furnace under a strong draft; such may, however, be used in firing up, in standing still, and
at the stations.
In taking the coke from the ovens it should be separated into the three following classes.
Large coke. Cubes of 9 inches to the side.
Medium coke. Cubes of 6 inches to the side.
Small coke. Cubes of 3 inches to the side.
Pittsburgh coal carefully coked for forty-eight hours, gives seventy-five per cent., by weight, and one
hundred twenty-five per cent. by bulk, of firstrate, firm, bright, clean coke.
The best test for coke is to place it in water. Water, weighing sixty-two and one half pounds per cubic
foot, should not float good coke, which ought to weigh sixty-three pounds per cubic foot, therefore if the
coke floats it is too light.
Much of the bituminous coal in the Mississippi valley does not coke, but burns up. A large part cokes
moderately well, but not so well as the Pittsburgh coal. In estimating for a comparison of fuels, the
particular coal of any location must be tested.

OF THE COMPARATIVE VALUE OF WOOD, COAL, AND COKE.

This question divides itself into two parts,

The relative cost of the different fuels,
and The relative power to produce heat.

319. It does not follow that because coke in England, anthracite in Pennsylvania, or wood in New
England, is the most economical fuel, that either of the above will be so in Ohio, Indiana, or Illinois, or
because wood is the cheapest in some parts of a State, that it is so throughout, or even that one fuel
should be applied to the whole length of a single road.
The heat used to evaporate water in the locomotive boiler is developed by combustion; combustion is
produced by chemically combining the oxygen of the air with the carbon of the fuel; whence, that
material containing in a given cost the largest amount of carbon will produce heat the most
economically.
From the table on page 320, we see that, by bulk, thirteen of coke are equal to sixty of wood; that one
pound of coke evaporates eight and one half pounds of water; that one pound of wood will evaporate two
and one half pounds of water. Tables of specific gravity give as an average weight per cubic foot of hard
wood, thirty pounds. A cord of wood, by very careful measurement, contains one hundred cubic feet
solid, or one hundred twenty-eight feet as piled, taking the average size of wood; whence a cord will
weigh three thousand pounds. And we have as the relative evaporative efficiency of a cord of wood and a
ton of coke,
2240 × 8½ = 19040,
3000 × 2½ = 7500.
Now if the cost of a cord of wood is to the price of a ton of coke as 7,500 to 19,040, it is immaterial which
we use.
As an example of the use of the above proportion, when the absolute cost of wood, coal, coke, and labor
are known, take the following.
If wood, cut and ready for burning, costs $3.00 per cord, how much may be given for a ton of coke?

As 7,500 is to 19,040, so is 300 to 762, or $7.62.

From the same proportion we form the following table.

Cost per cord of wood ready for burning. Price that may be paid per ton for coke.
(Cents.) (Cents.)
200 508
225 571
250 635
275 698
300 762
325 825
350 877
375 952
400 1016
425 1079
450 1143
475 1206
500 1270
In the comparison above, the maximum evaporative power of wood has been used, 2½ lbs., and the
ordinary power of coke, 8½ lbs. of water per pound of fuel.
320. In making coke in large quantities, the ovens should be at the mines, as we thus save transporting
the extra weight of coal over coke.
The cost of making coke, exclusive of the cost of the coal, is approximately as follows:—
10 ovens capable of making annually 5,000 tons of coke, $5,000
Sheds, and apparatus to correspond, 3,000

In all, 8,000
Annual interest at 6 per cent., 480
Annual cost of attendance, 2 men, 1,000

The sum of which is, $1,480

And the cost per ton, 6
0.2910

or in round numbers, thirty cents per ton; and if coal is $1.50 per ton, adding twenty-five per cent. we
have $1.87 as the cost of coal that will make one ton of coke, to which add the cost of making per ton,
thirty cents, and we have as the whole cost of one ton of coke $2.17; and from the rule on page 327 we
see that wood must not cost over $0.85 per cord to be as economical as coke at $2.17; of course inferior
qualities of coal will give less good coke and change the comparison.
 COMBUSTION.

321. The combustible element in all fuels is carbon; the heat necessary for steam producing, is obtained
by combining the carbon of the fuel with the oxygen of the air, forming carbonic acid gas.
Carbonic acid gas consists of
Oxygen 16
Parts by weight.
Carbon 6
Atmospheric air consists of
Oxygen 8
Parts by weight.
Nitrogen 28
Whence, for the combustion of one pound of carbon, we require
Carbon 1.00
Oxygen 2.66
But to obtain 2.66 of oxygen from the atmospheric air, we also use nitrogen in the proportion of 28
nitrogen to 8 oxygen; whence, for converting one pound of carbon to carbonic acid, we require
Oxygen 2.66
Nitrogen 9.31

Or 11.97 lbs. of atmospheric air.

From careful observations on the gases passing through the chimneys of well-constructed boilers,
oxygen is found free, varying in amount from one quarter to one half of the quantity necessary for
combustion; this is owing to the mechanical obstructions to the perfect conversion of the air arising from
leakage through the fuel.
More than the above 11.97 lbs. of air should, therefore, be applied to the fire for each pound of carbon
consumed. Twenty-five per cent. is found by experience to be a sufficient surplus allowance to convert
the carbon.
Whence, to 11.97
add 3.03

and we have 15.00 lbs. of atmospheric air per lb. of carbon.

15
Air weighs .075 lbs. per cubic foot, whence .075
or 200 cubic feet of air are necessary for the proper
combustion of one lb. of pure carbon.
Knowing the necessary amount of air for one lb. of carbon, and also the percentage of carbon in the
different kinds of fuel, it becomes a simple arithmetical operation to fix the bulk of air required for any
species of coal, coke, or wood. The result of such a calculation is shown in the seventh column of the
table on page 320.
“There are two causes why all the heat which fuel may furnish is not obtained. First, that the
inflammable gases evolved by the heat are not all consumed from want of a sufficient supply of oxygen,
the air drawn through the fire being only sufficient to decompose more fuel than when decomposed it
could burn, or supply with oxygen. The thick smoke that escapes from a chimney when fresh fuel is
thrown on a hot fire, is unconsumed gas; decomposed from the fuel, but without oxygen enough to burn
—although there may have been a sufficient supply of heat. From this cause it is, perhaps, that flame is
seen coming from the top of a steamboat chimney which appears to be continuous from the furnace; but
which, in fact, is ignited by contact with the air, having retained sufficient heat for that purpose.
“All smoke-consuming furnaces are simply means of admitting fresh air to the unconsumed gases above
the fire, which, in a common chimney, will effect the object, as so large a mass of smoke retains the
necessary amount of heat. This only prevents the nuisance of smoke. To render the gases thus reheated
useful in evaporating water, this supply of oxygen must be added while the gases are yet in the flues.”
This might seem difficult. Mr. McConnell (England) divides the flues of his locomotives into two parts,
connecting the front ends of the first part and the back ends of the second part by a space of twelve or
fifteen inches, (called by him a ‘combustion chamber,’) into which he admits any required amount of
fresh air. (See appendix E.)
“A second cause why the full value of the fuel produced is not obtained is, that so much is abstracted
from the gases in passing through long tubes, that there is not enough left to continue combustion,
although the inflammable gas is still there. That a tube or any substance in the way of the hot gases does
absorb the heat enough to prevent the burning of the gas, is proved by the action of Davy’s Safety Lamp;
this is a common light surrounded by a wire gauze, which so absorbs the heat from the flame as to
extinguish the latter at the wire; by applying fire above the gauze, the gas is again kindled, showing
plainly that want of heat above had quenched the flame.” See Stöckhardt’s Chemistry; translation by C.
H. Peirce, M. D., Cambridge, Mass., 1852, page 105.
We require, then, in every boiler, first, to have a sufficient supply of oxygen to decompose the fuel; next,
a quantity above the fire to consume the produced gases; third, such an arrangement of communicating
surface that so much heat shall not be abstracted from the gases as to deaden their combustion, until
just as they are discharged, at which period they ought to be consumed. (See appendix E.)

GENERATION OF STEAM.

322. The means of producing the power is of course of the first importance.
The heat generated in the fire-box is conducted through the tubes to the exhaust chamber; during which
passage it is imparted to the metal, and from thence absorbed by the adjacent water, which being
thereby made lighter, rises to the surface and gives place to a new supply. The duty of the furnace is to
generate, and of the tubes to communicate, heat.
The power of a plain surface to generate steam, depends upon its position and on the ability of the
material to transmit heat An experiment recorded in Clark’s Railway Machinery, gave the following
results: A cubic metallic box submerged in water and heated from within, generated steam from its
upper surface more than twice as fast as from the sides when vertical, while the bottom yielded none at
all. By slightly inclining the box the elevated side produced steam much faster, while the depressed one
parted so badly with it as to cause overheating of the metal.
Acting upon this result, most builders of engines of the present day give an inclination of from one inch
to one quarter of an inch per foot to the sides of the inner fire-box. That the heat should be applied in the
most effectual manner to the water, the latter should circulate freely around the hot metal, carrying off
the heat as soon as it reaches the surface. As the heat is applied to the inside of the furnace and tubes, it
must, therefore, be the inside dimensions which determine the amount of heating surface.
Note.—If we multiply the interior surface of a tube by the intensity of heat applied, and divide the product by the exterior
surface, we shall have the intensity at the outside. We also apply more heat to the outside of a tube, which, passing to the
inner surface, augments in intensity per unit of area.
The area of the inner fire-box is not all available for heating, but requires to be reduced as follows:—
For the fire-door.
For the ferrule area.
For the top stays.
For the side stay bolts.

The area is, therefore,

Sides, twice length by height, less stay bolts.
Back, height by width, less fire-door.
Front, height by width, less ferrule area.
Top, length by width, less top stays.

TUBES.