The modern express engines are of two types. The first is a single engine
with 6 ft. 6 in. driving wheels, and leading and trailing wheels 4 ft. 6
in. in diameter and a wheel base of 15 ft. 9 in. The frames are single,
with inside bearings to all the wheels; the cylinders are inside, 17 in.
diameter and 24 in. stroke. The boiler is 10 ft. 2 in. long and 4 ft. 3
in. diameter; the fire-box is of copper with a fire-grate area of 17.8
square feet, and the heating surface is in the tubes 1,080 square feet,
fire-box 102 square feet; total, 1182 square feet. The weight in working
order is about 35 tons. These engines have a tractive power of 89 lb. per
pound of mean steam pressure in the cylinders, and their consumption of
coal with trains averaging nine coaches is about 20 lb. per mile. The next
type of engine designed has coupled wheels under the barrel of the boiler
6 ft. 6 in. diameter, with cylinders 171/4 in. diameter and 26 in. stroke,
and were found so successful that Mr. Stroudley designed a more powerful
engine of the same class, especially to take the heaviest fast trains in
all weathers.
The 8:45 A.M. train from Brighton has grown to be one of the heaviest fast
trains in the kingdom, although the distance it runs is but very short,
while it is also exceptional in consisting entirely of first class
coaches, and the passengers mainly season ticket holders; it often weighs
in the gross 350 tons, and to take this weight at a mean speed of
forty-five to fifty miles an hour over gradients of 1 in 264 is no light
work.
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