The Helena independent. [volume] (Helena, Mont.) 1875-1943, 1892-02-04
MAKING 4 MORTAR GUN.
Description Of the Process Of Put
ting Together an Engine
Of War. s5s
Tho Method and Intent Of the
Rodman Gold Core Casting
System.
In , Liquid StAts--Cost of =
Mortar.

VooIlA8 th0 inside WhtNo the OutSi0o is
In > Liquid StAts--Cost of =
Mortar.
From four O'Clock in the morning until
2:30 o'clock in the afternoon . workman
sat in 4 niche in tho roar Of the furnace III
the foundry Of this South Boston IRON
works, and from time to time he pulled oue
4 brick in the furnace wall and gazed at :
mass Of iron which was slowly being fused.
Just twenty-five tons Of iron were in tho
furnace. This iron in another form was to
b. ono OF the now twenty-five inch rifle
mortt.rs which are now being made for the
coast defense OF the United States. The
fortifoations, whom complete. will require
more than 800 Of these mortars. Of which
bat seventy-three are contracted for.
The South Boston iron works has . con-
tract for forty-three and the Buildsrs' iron
foundry of Providence . contract for thirty.
The Providence contractors have hnlshed
casting, and are now assembling the mortars.
The Hoston contractors cast the twsn:y-tfth
mortar yesterday. III the workshops are
liz big mortars in every stage OF compile
tior. from the rough casting down to the
nearly co mpletsd gun The cost is $500
each. bNf this the casting post $1.S5O, the
stoel $3. 100, and the assembling $3.50.
This is sxcA usivs of the csrriage.
The ~castin.y of the gun ia an interesting
onaration. Save the Boston Post. Capt. A.
II. Russell. Of Inc United States ordnance
Department. s~upsrNises the work. In the
center of the foundry is a big pat about six
taen feet deep, which is ijned with brick. a
day or two previous to the c2ntlng = big
task is lowered into thu pit. This flask is
in six sections of iron, and is divided
oncs loncitudinally and twice lateraslly. In
this flask, which ia perforated with htndreds
OF small holes for the escape OF tbs g.ss' Is a
lining min inches thick of molding sand,
baked hard. The inner surface 10 ccnted
with powdered plumbago or facing.
At the bottom of the pit under the CEN
ter Of the flask is an iron pot about six
teen inches in diameter, which contains q
laver Of sand. The curvature of the pot
10 followed in shape. Exactly in the confer
of the flask is placed an arbor of cast iron.
which is wound with rops covered with
fine clay and baked. This arbor is hollow.
The arbor is futed to allow the gases to
escape. The rops is gradually consumed in
the casting, and il il possible to withdraw
the arbor, leaving the coating OF clay IN
the interior to protect the bore OF the q
In the center OF the arbor is placed an
iron sipe, which extends nearly to tho bot
tom. Such il, briefly, tbs method Of cast
inc, Az $50 yesterday afternoon the
melton metal in the furnace was at the
proper consistency for casting. 6upt. Hun
around and ordered the men to 'let her
come" Two men rammsd bars OF iron
into the top of the furnace and worked
them back and forth, and the metal flowed
forth in I thin stream dow ths trouRhs
into the ladle and then to sither side OF the
flask and dropped to the bottom.
There was . sizzling. swapping, and sput-
terinR Of the iron, and ~ it disappeared in
the mold there was q regular Fourth of July
display of stars and fireworks. The work
men carefully scraped the Stag from the
metal and regulated the flow. In exactly
big ladls was placed upright to held tho
excess Of iron.
Over the end of the arbor was then placed
. big tripod, which has a cap with screw
connection for base attachments. Then q
workman approached with = hose and
arbor. Az the water reached the bottom
there WAS q report like . amor. and all of
the sand and refuse in the Arbor was blown
high in the air. The cap was placed on
the tripod and n hose attached to the pipe
on the arbor. Water at forty-threo degrees
Fahrenheit was turned on and soon filled
the arbor and flowed away in another pipe.
This is the Rodman cold core-casting sys-
tenn.
The object is to cool tho gunfrom the in
side and keep the outside as hot al possible
until the bore ia cold. This causes con-
traction as the layers of iron cool, each lay
or beng shrunk on to tho other, until the
casting finally is gradually compressed by
a constant pressure from the material COM
posing it. This wood and coal in the pit ia
then fred. and soon the flask il surrounded
by a roaring hot fire, which tenda to keep
the outside of the casting in a fluid state.
The first day the water flows into the arbor
at the rate OF twenty. one gallons a minute.
The water yesterday was GO degrees in tenn
pc ature whom it first came from the cast
ing:
70 degrees. Ths temperature is recorded
hourly after the first hour. At three o'clock
to-day the arbor will be removed and water
will be allowed to flow into the bore of the
gun. The temperature will then 60 up to
nearly if not quite, 2lo degrees. The fires
in tho pit Will burn until tomorrow
morning, and then the flask will be allowed
to cool. From sixty to eighty hours are
necessary for casting. The flask ig then
taken apart, the mold knocked to pieces,
and the rough gun taken out. During the
frst twenty-four hours the cast is watched
carefully. The %shrinkage OF metal il sup
piled in order that tho upper end may not
be defective. Draughts of air that would
chill the cast are also guarded against.
When the gun is taken from the pit it is
carefully examined and then taken to the
machine shop to be turned and finished.
These mortars are hoped with steel rings
and rihed and assembled. and sent where
the government may direct. The object of
casting them in the manner described is to
secure a CUR Of grsgt strength. In order
that the metal may thoroughly unite in the
mold and avoid laws and bubbles the fall
of the molten iron is frequently broken.
RIchlsE's Arnica Snive,