Wood County reporter. [volume] (Grand Rapids [i.e. Wisconsin Rapids], Wis.) 1857-1923, 1891-04-23
A MONSTER MORTAR.
1t Weighs Fourteen Tons and VIII Send a
Shell Six Miles.

Providence Telegram.
One of the big mortars being built by
the Builders iron foundry for the United
States government is finished and ON ex-
hibition at the foundry.
The gun is a 12-inch breech-loading
rifed mortar, 10 feet 9 inches long and
about 5 feet in diameter at the largest
part. Although called mortar. It is as
long the old-fashioned guns.
The mortar was cast in the following
manner: A pit Is feet deep and 10 feet in
diameter was dug in the floor of the found
ry. Into this hole an iron flask was low
cred containing the dry sand mould IN
which The mortar was cast. Tie Roman
principle was used In the casting The
core was bored its entire length, and into
the tunnel thus made stream OF pawtuXet
water was constantly kept running
through an iron pipe extending to the
bottom of the core. The water rose up In
the core on the outside of the water pipe
and escaped through the cap of the core.
About fifteen gallons minute are used.
This water aids greatly in the cooling of
the iron, and also gives the extra heat OF
the metal at the various stages of cooling.
The water does not become as got as the
iron, but its temperature is IN certain pro-
portion to the temperature of the iron.
The iron, which is the best charcoal pig,
is placed In a large furnace, about twenty
two tons of each gun, and when melted
was run out through long trough into
the mould. 1t took about eight hours to
melt the iron. The metal was held in the
furnace until of a proper degree of heat
and hardness.
! After the mortar was cast it took five or
six days for it to cool. 1t was then taken
| to the machine shop and turned on the
outside and bored out. The gun as ii
then stood without the steel rings, which
were afterward put on, was obliged &c
stand a pressuse of 80, 900 pounds to the
square inch.
The mortar was then hoped with the
steel rings. Two layers of these were Put
on. The first layer consisted of sever
rings 238 inches thick and 10 inches wide
The second layer consisted of six rings pa
inches thick. These rings make the NOR
tar much stronger than would be the case
had it been made Of same size of solid
steel without the rings. By the means Of
the rings the pressure is made ever
throughout.
The rings were put on in the following
manner: The mortar is placed on car
riage and run over an oven in which a fierce
fire of gas is burning. The rings are
brought hot to the gun and forced
on by pressure The metal is ther
cooled by water, thus shrinking tie rings
| on
The rings themselves are low steel, anc
are made at the Midvale Steel Works il
Philadelphia. They are forged in great
round discs. The center is then cut ou
and the rings rolled between large rollers
until they are Of the proper thickness anC
diameter, then turned very carefully to the
required size. The second layer is laid OF
| the first so as to break joints. The amour
of shrinkage is calculated so as not to over
compress the bore, but still give exterior
support to the interior.
After the first boring the bore wa
measured by a star gauge, which measured
as fine as .OO5 of an inch. After the rings
were shrunk the final boring Was dom
and the bore rihAd; latitude of of .Q03 o
an inch is allowed The breach is thread
ed. each alternate sixth of the thread
being cut away The breach block is mad
to fit into the breach, and has alter1at
sixths of threads The threads of tn
breach block slide into the smooth sixth
of the block, when it is to be used, ant
then turned sixth of the way around an,
is so fastened.
The projectile is an oblong iron shell
charged with bursting charge of thirt
pounds of powder. The projectile is pro
PEELED by charge of eighty pounds o
powder. The whole charge weighs 60
pounds and costs Uncle Sam about S6
every time it is discharged. The morta
has range of six miles and cost abou
$4,000,
The remainder of the morta1s are all i
process of construction, and will b
made exectly like the one just finished
The guns will be used for coast defens
! purposes.