LOCOMOTIVE ENGINE.
423
an hour and three quarters on an average, and requires the consumption of about one
and a half or two cwt. of coke; in some places the boiler and tender are supplied
with hot water by means of a stationary boiler, in order to expedite the getting up of
the steam, and also as a means of economy.
The area of the fire-grate is 9| square feet; it is 18 inches below the bottom of
the lowest tubes, and the space for the fire when quite filled up to the tubes is 14
cubic feet, and holds about 2-J cwt. of coke; but the fire-box is not always filled so
full as this, and usually contains about one and a half or two cwt.
The surface of water exposed to the heat directly radiated from the fire is the
whole surface of the internal fire-box, deducting the fire-door and the tubes, and is
equal to 50 square feet; and that exposed to the current of hot air, or conducted heat,
is the interior surface of the tubes, and is equal to 432 square feet. The surface
exposed to radiated heat is considerably more efficacious in generating steam than
that exposed to conducted heat only, as the supply of heat is more copious, and the
proportion was found to be about three times in an experiment tried by Mr. Stephen
son, which is the only one that has been made upon the subject; the experiment was
made with an old engine and the proportion may be somewhat different in the mo
dern engines.
The area of passage for the heated air from the fire-box to the chimney is the
sectional area of all the tubes inside the ferrules ; the ferrules are three eighths of an
inch less than the outside of the tubes, and are therefore an inch and a quarter in diame
ter inside; and the sectional area of them all, (124 in number,) is T06 square feet.
The area of the passage through the chimney is rather more, or 1*23 feet.
In the Rocket engine the area of passage through the tubes was ’90 square feet or
nearly the same as in this engine, though the fire-grate was but half the size ; but
the heating surface of the tubes was only one third, from the large size and small
number of the tubes ; the heating surface of the fire-box was also only three quarters
of that of the present engine.
In the old engines before the Rocket, the area of passage through the flue was
two and a half times the size, but the heating surface was only one thirteenth of
that in the present engine; the fire-box had also only one fifth of the heating surface;
the fire-grate was three quarters of the size.
THE CYLINDERS AND THE MANNER OF USING THE STEAM.
Steam Pipe.—S S, (Plates XC. and XCII.,) is the steam pijie for conveying the
steam from the boiler to the cylinder where it is to be used; it is made of copper
three sixteenths of an inch thick, and the part within the boiler is 5 inches’ diameter in
side ; it passes through the tube plate of the smoke-box and is bolted to it by a flanch.
The pipe then divides into two smaller ones, 3j inches in diameter, which pass down