LOCOMOTIVE ENGINE.
465
have not the inner ones; and instead of them a strong iron frame is placed imme
diately within the wheels, bearing upon the axles, and having the whole engine
resting upon it; this gives the engine a lighter appearance, as the wheels are quite
on the outside. But the outside frame adds considerably to the stiffness of the engine,
and is of great utility in that respect, particularly when the engine gets thrown off
the line, as happens occasionally; when the outside frame serves materially to
protect the machinery. It has also an advantage in enabling the engine man to
have access to any part of the engine whilst it is working, as the wheels and the
space between them are covered over by the splashers, and can be readily passed over;
this is very useful, as the working parts frequently require examining and replenish
ing with oil whilst running. The friction is less when there is no outside frame, as
there are but two bearings on the cranked axle instead of five; but they have to
be the full size of the axle, as they are inside the wheels, which much increases the
friction of each, and renders the whole but little less than in the other plan; the axle
is also not held so steadily as with the middle inside bearings.
Whistle.—Z' (Plates LXXXIX., XC., and XCII.,) is a steam whistle used for the
purpose of giving warning of the approach of the engine when running; the con
struction of it is shewn to one quarter size, or four times the scale of the engravings,
in figs. 45 and 46. It is all of
brass, and the foot, A, is cast
hollow, with a fianch, />, at the
bottom to bolt it upon the fire
box; it has a cock, G, placed in
it, with the handle D, and screw
E, to keep it tight, the handle
projecting out to allow firm hold
to be taken of it. The cup F, is
fixed upon the foot A, by screw
ing the piece G, upon it, and both
are turned truly at their outer edges,
leaving a very narrow passage, II,
four inches diameter, between them all round. The piece G is hollow, having
holes, IF, in its sides ; and a pillar, K, stands upon its centre, on which is screwed
the bell L L, the thin edge of which is brought just over the opening I, and half an
inch above it. When the cock is opened, the steam enters the cup E, through
the holes H, and rushes out at the narrow slit I, striking the thin edge of the bell E,
in a similar manner to the action in organ pipes, and producing an exceedingly shrill
sound ; some holes, M, are made in the top of the bell, to allow the steam to pass
3 N
Fig. 45. Fig. 46.