The diameter of the steam-pipe is from 1/4 to 1/2 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, b, 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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