All About Engines
Forfatter: Edward Cressy
År: 1918
Forlag: Cassell and Company, LTD
Sted: London, New York, Toronto and Melbourne
Sider: 352
UDK: 621 1
With a coloured Frontispiece, and 182 halftone Illustrations and Diagrams.
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Fig. 34.—Girder stays on Loco firebox
the great difference in temperature
68 All About Engines
striking feature of locomotives of the “ Great Bear ”
type. The larger diameter lies behind the driving
wheels. It enables a bigger firebox to be used, and
increases the proportion of water at the hottest
end of the boiler. Another advantage is that the
surging backwards and forwards of the water
the engine varies its speed—which is liable to
the crown of the firebox uncovered—is to
extent prevented by the conical shape.
The firebox of a locomotive is fixed to the
shell by a ring
at the bottom,
by another ring
round the fire
door, and by
numerous stays,
about 4 inches
apart, to the
sides. Owing to
between the fire-
box and the outside shell, great stresses are thrown
on these stays, and failure is common. Some fire-
boxes have curved crowns, and others have flat crowns
like the Belpaire firebox—a type growing in popu-
larity. The curved crowns are merely suspended by
stays from the boiler shell; the flat crowns are stiffened
by small girders as shown in Fig. 34. The number
and dimensions of these stays or girders are largely a
matter of experience ; the tendency of the firebox to
change its shape renders it almost impossible to make
exact calculations of the stresses which have to be borne.