[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
The secondary railways in rural districts in Austria having no gates or
bars at the level crossings, or guards at such points, but being open like
tramways, special precautions are required to avoid accidents, and the
public has to be warned of the approach of the train from a sufficient
distance. This is done by ringing bells preferably to sounding whistles,
as these are more likely to startle horses. The steam bell shown by our
illustrations has been adopted for this purpose on the Austrian lines, and
is a simple contrivance. It consists of a cylindrical chamber, a, ending
in a narrower tube, c, which forms the seating for a flap valve, d, to
which the hammer or clapper, e, is fixed. Steam is admitted through a
small pipe, b, at the bottom, and after a certain interval attains
sufficient pressure to lift the valve. The opening being large compared
with the pipe, b, steam escapes more rapidly than it arrives through the
small orifice; the pressure falls, and the valve drops down and causes the
hammer to strike a bell surrounding the cylinder. The valve is provided
with an internal collar as shown, so that it has to rise for the width of
this before the steam is let out, and thus determines the swing of the
clapper and the force of the blow. To intensify the latter and multiply
the number of blows, the clapper spring is prolonged over the fulcrum and
bent back so as to form a spring, which is tightened by the lifting of the
flap, and sends the clapper down on the bell with increased force. The
hinge of the flap does not require any lubrication besides what it gets
through the steam. The bell is fixed upon the roof of the driver's cab, so
that the steam does not interfere with his lookout, and fastened by three
bolts or screws. The diameter of the steam-pipe is from ¼ to ½ inch
according to the size of the bell, and the distance of the clapper from
the bell is a little less than the diameter of the corresponding cock. The
steam cock is perforated as shown by the illustration to drain the pipe
when shut, and a small hole, b¹, in the bell cylinder drains the latter.
The steam-pipe is made with a bend as usual, to allow for contraction and
expansion. The number of blows given varies according to the steam
pressure, and the opening of the steam cock; it is
With 90 lb. pressure, and cock 1/2 open, 170 blows per min.
" " " " 1/3 " 136 "
105 " " " 1/2 " 240 "
" " " " 1/3 " 156 "
" " " " 1/5 " 136 "
120 " " " 1/3 " 228 "
135 " " " 1/5 " 200 "
To start the bell, the cock is opened full, and afterward partly closed.
The blows follow in such rapid succession that a kind of uniform sound
with louder intervals is produced, but not of the same shrill character as
by a steam whistle. The same kind of bell is used on the shunting engines
in goods yards, where roadways have to be crossed on which lurries and
handtrucks circulate, and the results as far as prevention of accidents is
concerned are stated to be very satisfactory.
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