The morning news., 1898-08-07
THE DISEASES OF DIG GUNS.
''ErOsive Action of Infamed Cases."
Their Most Serious CompIaint.

Fiom the Chicago Times Herald.
The larger cannon the more extensive
are the injuries 81 receives with each sue
cessive discharge. All damage done to a
sun Is internal. The separate action of the
powder and the prOiectle damages ths
piece every time itais aimed and fired.
Obviously the amount OF the damage de-
peuds upon the material and workman
ship Of the gun. Men who make big guns
describe the harm done their pets with
many intricate and puzzling terms OF q
scientific turn. In one case a gun is dam
aged because the part Of the bore which
contains che powder Is enlarged. This hap
pens when the metal is compressed, and 1t
iS more dangerous and more plainly seen
II the gunners have been using wads be-
tween their explosive ana their prOjectle.
Then, again, cavities are produced by the
melting away OF part OF the metal by
the heat of combustion of the charge.
Cracks come from the tearing asunder OF
the particles OF the metal at the surface
of the bore. When it is first made a crack
of this particular kind Is barely percepu-
ble, but IL Increases each time the gun -
fred Gradually It extends completely
through the side of the piece. The crack
usually begins at the junction OF the cham
Der with the bore, simply because, as guns
now are. this part Is not 30 well supported
as the others.
Edward S. Farrow, U. s A., late assist
on damage to guns. although, like all 9TH
ers who have studied the question. he does
not agree with very many authorities on
all the points TO consider in the life OF a
cannon. He contends that furrowing or
scoring produced by the erosive action OF
inlamed gases Is the great disease which
attacks the very big guns first This par
ticular injury is most apparent where Tie
current 90 the gas Is most rapid or at the
interior orifice of U1e vent, and on the
surface of the bore, directly over the seat
Of the prOjectile. This scoring begins very
early in the life of very large gun, but
IL Is conceded that II does not become very
important until the piece has been dis
charged considerably. Lieut.. Farrow des-
CribSS this scoring as resembling the bark
of an aged elm tree, the metal being eaten
away into irregular burrows and ridges.
In extreme cases. however, scoring has not
killed the gun, although in some cases 1t
has acted like wedge and split the bore
at the place attacked.
Where the action Of the projecttle has
ruined the gun the damage has been done
around the projectlle and in front Of il.
The elasticity of the metal and the
crOwdiue up of portions of il in front OF
the shot cause a rehounding process. The
projectie, carried forward by the force
Of the charge, strikes against the upper
part of the bore. Then it Is sent against
the bottom and again rebounds to the
top and so on until II energies from the
piece. The effect of the bounding motion
is to raise and depress the gun In it's
trunnion holes. The accuracy OF fire Is
diminished, and of course the gun Is un-
NJ for service. Bronze guns are the worst
sufferers I'm this way. Mortars-short and
dumpy-are not affected. To stop the
bounding Of the projectile gunners wrap
the shell In cloth or paper or else shift
tho base of the mass to be hurled. This
last process is considered the best and Is
done by reducing the diameter of the
cartridge and adding to its length. Pro-
iectile injury Is also caused by burrows
OF scratches made by rough shells or case
shot. Small fragments, too, break away
very often from the shells and give the
bore a grinding and cutting process, pro-
ductive Of great damage.
Enlargement of the muzZle Is another
serious injury produced by the projectile.
This is caused by process which seems
unavoidable. As the shell leaves the piece
il strikes against one portion of the bore.
The resistance at the mouth being less
than at any other point the metal natu-
rally yields. and the muzzle Of the cannon
Is elongated In a vertical direction.
Some men who ought TO know say that
a hundred and fifty shots is the life of a
very big gun--a 12 or 13-inch weapon.
Others place the number Of shots at four
hundred or five hundred. As a matter of
fact IL Is all guess work. The great Krupp
gun shown at the Worlds Fair and con-
coded to be perfect-or supposed 10 be So
has been discharged less than ten times,
and 1t is now believed to have reached its
limit. On the other hand, the big guns
of the American battleships have passed
the life allotted them by wise men who
know guns, and apparently are as good
as when tested. How soor they may
yield, however Is not in the books. Lieut.
Farrow says that very large gun should
not be expected TO stand over four hum
dred or five hundred shots before IL will
be necessary to open new vent, closing
the old one at its interior orifice. When
the gun dies-burste-the lines Of fracture
are photographed. Specimens OF the metal
are saved Tests are made and conclu-
sions drawn. And Uncle Sam has figured
out so many things in this same connec-
ton that his guns nowadays are conceded
to be better than those Of any other
maker. They live longer than the wise
ones say they should.