Evening star. [volume] (Washington, D.C.) 1854-1972, 1882-03-22
HOW BIG PROPELLERs ARE CAST.


AN INTERESTING PROCESS At THE NAVY YARD
THE WAY THE BRASS Is MELTED AND POURED
INTO THE MOULD.
The important work of manufacturing the
huge brass propellers that are used on the large
steamers of our navy, is carried on exclusively
In the navy yard in this city, where the propel-
iers of all the principal steamers in the navy
are made. The method Of constructing these
mammoth pieces of machinery is interesting.
Only the most skilled and reliable workmen are
entrusted with their construction, for the
slightest mistake or carelessness on the part Of
a single workman during any stage of the
work would spoil the whole job and cause the
government heavy loss.
A PROPELLER,
such as is used on naval vessels, consists O (
four large oval blades. the smaller ends of
which are connected with heavy hub. which
forms the center, and which is made to fit on the
screw of the steamer in the manner of wheel
on an axle. Propellers are of course, of different
sizes. the larger ones measuring twenty feet in
diameter and weighing several tons. They are
made in the large building known as the
foundry. which comes under the bureau of steam
engineering. of which Chief Engineer William
H. Shock, OF the navy. is chief, and Mr.. George
Wilson boss. To give the propeller the
great strength it requires, it is not cast in sec
tions, but in one piece. and its large size is
what makes the job so difficult.
THE PIT.
There is in the center of the shop large cir
cular pit, which, when propeller is to be
cast, is filled with preparation of fine sand
loan and other porous substances, in which the
pattern or model of the propeller is placed
and covered with the loam gang of
B.. L..
pattern for hours until it becomes solid. Then
the pattern is removed and perfect impression
Of it is found left in the loan. Several tons of
brass are then place In an immense cupola in
layers. there Being between each layer Of brass
layer of hard coal and some wood on the bot
tom to ignite the coal. The wood is ignited.
and by means of a revolving fan the coal is made
to burn vigorously and in an hours time the
brass commences to melt. Being heavier than
the coal. it sinks to tiA bottom of the cupoia
and is drawn off through an opening in the bot
tom. being thus separated from the coal and
cinders which accumulate on the top.
THE LADI.E.
The metal is drawn off into large ladIe
which is kept heated by burning charcoal. When
the metal is all drawn off the large lad!e con-
tains several tons of mouten brass, and the
workmen are ready to pour" The pouring.
which is generally done in the afternoon. is the
ration. When this part of the work is bein.
performed there are often large number of
visitors present The large lad1e, which con-
ta!ns the molten brass. is hosted by means Of q
crane and hangs suspended in mid air. directly
over the pit which contains the mould. Every
man is at his post. and has to work with the uil-
erring regularity of machine. for the slightest
variation would spoil the job. and most likely
cause serious accident. The metal is slowly
poured through an opening (Which is left for
that purpose) in the mould until it is filled.
THE GASES.
Several pieces of gas-pipe are stuck in differ
ent parts of the mould to give vent to the gases.
and after all the metal is poured large jet of
fame. fed by the gas from the mould, burns fer
ten or fifteen minutes. Then nothing more is
done until the following day. when the sand is
shoveled off tlie propeller, and it is hOsted out
OF the mould by means Of the crane. The rough
surface is somewhat smoothcd. and if it is to Ice
used for a ship that is being built Or repaired at
another yard. it is hauled down to the dock. put
aboard Of the Tallapoosa. and taken to its ,esti-
nation.