The National tribune., 1894-07-05
NAVAL GUN FACTORY.
Interesting Process of Shrinking a Jacket on
a Heavy Machine.

u HeaVy Mdchne.
| Harper's Mdgazine.l
It is at the shrinking-pit that some of the
most striking of the details of manufacture
of gun are to be observed, and the shrink
ing on of 13-inch jacket is always the &C.
casion of a crowd of interested spectators.
In corner of the pit is the tube, cylinder of
| steel two feet in diameter and 40 feet long,
standing upright and clamped in position.
It's upper end, for distance of some 10 feet,
is bright and smooth, having been turned to
exact dimensions.
Inside of the tube cold water is circu-
lating, to prevent its expansion by the heat
radiated from the furnaces, and to keep it
cool while the jacket is going on. In the heat
ing furnace the jacket, another cylinder of
steel, II feet in length, and weighing some
% or "a tous, has been slowly heating since
the previous day, carefully watched both
day and night by the attendants, who so
regulate the supply of air that no excessive
temperature is obtained.
From time to time the cover of the fur
mace is lifted for moment, and the master
mechanic measures the inside diameter of
the jacket at its upper end. This must
agree with the calculated expansion of the
cylinder before the operation of assembling
is attempted. When all is ready the great
traveling-crane is brought over the furnace,
the cover is removed, and in moment the
enormous mass Of steel is suspended in the
air. Now its interior is carefully wiped out,
in order that the minutest particle of foreign
matter shall be removed, and the inside di-
ameter is measured throughout the length
of the jacket. -
Meantime, by means of bars of fusible
metal, the temperature is determined at
various points. The giant crane, directed
by a motion of the hand of the MASTER
mechanic, now swings the suspended mass
over the tube, where it is accurately aligned
and plumbed
When it is realized that the inside diane
ter of the expanded jacket is less than one
tenth of an inch greater than the exterior
diameter of the tube, and therefore that the
clearance between the two is only about
four One-hundredths of an inch, and that
the jacket must be lowered over IS feet of
the tube without coming in contact with it,
or if it does come in contact that the touch
must be light ard of the briefest duration,
ii is easy to see that this adjustment is of
supreme importance.
Finally the signal is given, and, slowly at
first and then more swiftly, the Jacket is
lowered TO its place. The anxious express
sion which has marked the countenance of
the officer in charge gives place TO one of
content the appreciation of the spectators is
manifested by smiles and applause, and the
operation is over. E
The jacketing of large gun is the single
process of the whole manufacture which
causes great concern TO the experimenting
ordnance officer. The lathe work, the boring
and turning of guns are questions of accurate
measurement and careful workmanship, to
which as much time may be devoted as is
necessary.
But from the moment that the heated
jacket is taken from the furnace it is losing
heat, and as consequence is contracting.
The loss of heat is, of course, very slow, but
any reduction in the diameter of the Jacket,
where the allowed clearance is already small,
is OF moment, and hence this work must be
done with celerity.
The time required to put on a 13-inch
jacket, when all goes we'll, is less than Is
minutes.