The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1894-07-26
SHRINKING ON A GUN JACKET.
[Harper's Magazine.I


1t is at the shrinking pit that some
| of the most striking of the details of
manufacture of a gun are to be OBJ
served, and the shrinking of a 13-inch
jacket is always the occasion of
crowd of interested spectators. In the
corner of the pit is a tube, a cylinder
| of steel two feet in diameter and forty
feet long, standing upright and clamped
in position. It's upper end, for a. dis
tance of some fifteen feet, is bright and
smooth, having been turned to exact
dimensions. Inside of the tube cold
water is circulating, to prevent its ex-
pansion by the heat radiated from the
furnaces and to keep it cool while the
jacket is going on.
| In the heating furnace the jacket,
another cylinder of steel, seventeen
feet in length and weighing some
twenty-three or twenty-four tons, has
l'been slowly heating since the previous
day, carefully watched both day and
night by the attendants, who so regu-
late the supply of air that no excessive
Temperature is obtained. From time to
time the cover of the furnace is lifted
measures the inside diameter of the
jacket at it's 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 travelling crane is
brought over the furnace, the cover is
removed and in a moment the enor-
nous mass of steI is suspended in the
air. Now its interior is carefully wiped
out in order that the minutest particle
4 of foreign matter shall be removed,
and the inside diameter is measured
throughout the length of the jacket.
Meantime, by means of bars Of fusi-
BILE metal, the temperature is deter
mined at various points. The giant
crane, directed by 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 diameter Of the expanded
Jacket is less than one-tenth of an inch
greater than the exterior diameter of
the tube, and therefore that the clear
ance between the two is only about
i4-100ths of an inch, ard that the jacket
must be lowered over fifteen feet of
the tube without coming in contact
with it, or if it does come in contact
that the touch must be light and of the
briefest duration, it is easy to see that
this adjustment is of supreme import
ance. Finally the signal is given, and,
slowly at first, and then more swiftly,
the jacket is lowered to it's place. The
anxious expression 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,
land the operation is over.
The jacketing Of a large gun is the
single process of the whole manufac-
ture which causes great concern to the
experimenting ordnance officer. The
lathe work, the boring and turning of
guns are questions of accurate measure
ment' 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 a
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 celebrity
The time required to put on 13-inct
jacket, when all goes well, is less thar
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