Evening star., 1902-02-22
Expert Opinion on the Recent
Test at Sandy Hook.
THIN SHELL WALLS
RESULT OF THE SHOTS ON SIDE
OF battle SHIP.
Comparison With the Regular Army
Gun-The Claim for Alb
solute Safety.
From the Engineer.

From the Engineer.
On November Is last a competitive triai
Of the Gathmann torpedo gun and the l.
inch American army gun was made al
Sandy Hook The two targets attacked,
Identical In every particular. typefed struc-
turally the water-line section OF the pattle
ship Iowa, but were really somewhat
stronger They were feet high and 10
feet long and rested upon heavy timbers
They were backed by stout struts OF wood,
is inches square, and upon these supports
were piled several hundred tons OF sand;
the effort in every way was to make the
targets as stable and as strong as the ship
itself. The face plate, of uniform thick
ness from top to bottom-where the Iowa 8
belt is tapered-was 111a inches thick of
Harveyized steel. The protective deck was
represented by two layers of nickel steel,
the lower of 1 inch and the upper of liz
inches, and on the ground in front of the
Gathmann target was laid 3-lnch plate
Of steel, the purpose of which, on the plea
Of the inventors, was to show to some ex-
tent the possible damage or extension or
injury to the underwater hull Immediately
in wake of an exploding Gathmann shell
The army target was distant 1iS feet, the
Gathmann target 500 feet. After the hrlngS
the army target had not been moved an
inch, while the Gathmann target-a mass
of % tons-had been driven bodily back
into the supporting sand butt feet, and
moved to the left s feet. SO badly crum-
pling the structural support of steel that
ship similarly circumstanced must nave
been very seriously injured. while the con-
cussion of those explosions would have
been frightfully demoraliZing to the person
mel, IL not correspondingly destructive.
The first shot from the Gathmann gun,
even though II dished the target face about
@ inches, was admittedly a failure, and
that because of the imperfect detonation of
the great mass of wet gun-cotton, the
safety pin delaying action until the shell
had been crushed and a large part of the
cotton scattered Several hundred pounds,
In q powdered form, were found subse
quently scattered all about the ground in
front Of the target.
The second shot struck the target to the
left of the center and crushed into the
backing, while the heavier upper layer of
the protective deck was torn away and
hurled thirty feet to the rear. The third
shot, striking fairly to the right of the
center. split the face plate from top
to bottom, completed the destruction of the
backing and effected substantially the final
dislocation of the heavy armor plate from
Its structural setting. The three-inch plate
In front of the target was doubled into a
big and driven six feet into the ground;
while the whole target a mass, as has
already been said. was driven back rine
feet into the sand and moved to the left
matter of eight feet. Such was the condi-
tion of the Gathmann target after two at
tackS.
Thin Walls.
The walls of the Gathmann shell appear
ridiculously thin as compared with the
service shell, whether of the explosive or
the armor-plercing type. The purpose of
this is, incidentally. to reduce the weight
OF metal, to increase the mass Of explosive
charge and to insure wide contact with :he
opposing structure as the shell is crushed
and spread against the surface just before
detonatiOn. The whole shell loaded weighs
1,So0 pounds, against the 1Hkepound
projectile of the army 12-inch rifle. The
prime safety element of the Gathna ann
shell consists in the rear housing of the
detonator and it's retention in that posi-
tion-separated from the explosive charge
by steel walls-Until Well clear Of the gun
and long way on itG road to the target.
The moment the impelling charge Is explod-
ed In the gun the powder gases work their
way into the opening leading to the first
brittle safety pin. This pin is promptly
broken and the large retaining pin driven
into the head Of the two big safety bolts.
Now. but for the pressure still exerted by
the powder gases, the bolts would be eject
ed by the centrifugal action of the rotating
shell. Instead, however, the bolts are held
in place till the shell is out of the gun In
flight the detOnatOr creepS up into the inner
end of the fuse well. where the walls are
greatly thinned: but the illuminate caps are
still held away from the striking anvil by
another safety pin. This is not broken
down until the moment OF impact In all
three of the shells fired at Sandy Hook the
anvil, with the three perfect indcntations
of the illuminate caps was found In each
case, telling the whole story Of successful
working. To insure the complete satura-
H., Of the gun-cotton charge perforated
LIN son leads through the center Of the
~ cnaILisi he cap.
1t will be se, UPON eNlLiln'rs inc di-
mensionS of the col. t"ha: '!idI
It has decided taper. A. o si'eii rs III the