Memphis daily appeal. [volume] (Memphis, Tenn.) 1847-1886, 1862-08-07
Aron-CIsd misunderstanding their Ar
NOR Plates,

! keeping.
Iron-CIsd misunderstanding their Ar
NOR Plates.
From the Scientific American
The steam fIigate Roanoke, which is now il
the navy yard at Brooklyn, has been raced
anu is being converted into an iron-clad turre
war-ship. She is to be clothed amidships witt
thick iron plates, which are to extend shout five
feet below the water line; and she will have
three great revolving gun-turrets on deck, aud
a powerful iron beak or ram on her bow. This
beak resembles huge axe, and is formed o
plates twenty feet lOng, four and half inchs
| thick-thus making nine inches thick-thus
making nine inches of iron on the front edge
Each of the rev living gun turrets will be twenty
feet inside diameter, and the sides viii be formed
Of eleven courses of inch iron plates
These plates are laid over and riveted to one
another in such manner as to "break Joints, -
and her vertical plates are also bolted 10 several
courses so as 20 secure the whole IN the most
rigid and perfect manner These gun-towers
/ Tor the Roanoke are now being constructed at
the novelty works, in this city, where the plates
for them, likewise those for the srmor, are bent
to the proper curves. Each plate for the turrst
is about nine feet in length by forty inches in
width, and al inch in thickness. Two courses
OF rivet holes are punched out in each, and they
are all bent cold in powerful hydraulic press
The bed plate Of the press is of a concave from,
and the top block is Of convex fora
plate to be bent IS placed upon the concaye
bed-piate Of the press, and when properly adjust
ed, the pump forces up three rams under it, and
the plate is reduced to The proper curve against
the top block. The pressure to which each plate
is submitted, to give it the proper curve, is three
and hslt million pounds. BY this method of
bending the tUrret plates cold, there is perfect
uniformity and accuracy secured to the whole.
The tuTrets for the Roanoke will be of superior
character, but only six courses of plates have
as yet been laid on two of them
The bending Of the thick plates for the ram,
and also for the sides of the iTigate is quite a
different and difficult operation to perform com
pared with those Of the guu-towers. Esch of
these plates has to be bent to the proper curve
to suit its own particular place on the vessel.
and not only the broad side bit the edges also
must be bent to suit the particular curves. The
bending operations are under the charge Of Mr.
George BoEniwel, an intelligent young ship
wright All these plates are hammered iron,
and are furnished by several companies in
Pennsylvania, New York, and Massachusetts
When they arrive they resemble huge straight
iron slabs, varying in length from eleven to
twenty-five feet, Gnd IN breadth from twenty
two to twepty-four inches, and their average
thickness is four aud 4 half inches OGe Of
eleven and half feet in length weighs about
4,24O pounds; one Of twenty-five feet, for the
ram weighs over four tuus. Such masses Of
iron sre difficult 70 move about, aud the opera
tons cou2ected with bending them are necassa-
rily tedious and Troublesome and they REQUIRE
great care and skill to conduct properly oil
course 1t is impossible to bend such masses Of
iron cod, hence each plate IS first heated to
nearly white heat in a long furnace, shaped |
like bakers oven, with movable !
arched cover
The press for bending is quite different from |
the one used for the turret plates. Outwardy |
it resembles long, strong iron screw press, used
for pressing woollen cloth. It's top block, Or |
platen, is moved up and down. The bed upon |
which the heated plate is laid, is formed of g |
3. ries of adjustable bolster blocks, each of |
which is capable Of being set by G screw to any |
desired hight on either side, and at any desired /
angle to suit the bend to be given to plate |
which is compressed between the descending |
top block and the adjustable bed. A plate is /
hrst placed in the furnace, and it is then raised
to nearly s white heat. The cover of the furnace |
is now raised by block and tackle, and the 1
plate is then seized by powerful crane, secured
on carriage. The heated plate is now lifted, |
.he crane carriage moved back, and the plate |
swung around and placed in the press, where It |
Is perfectly adjusted to obtain the proper curves.
The huge top block is then forced down, suueez-
ing the great mass of iron into the desired 1
shape.
In about half an hpur the plate has acquired
a permanent set, and it is taken out. ready to
have its edges plated, when it is ft for boiling
10 the frigate. The bolt holes il these plates
are all drilled. 1t requires a large number Of men
70 move such great heavy masses Of iron, and
from the time glowing plate is lifted out Of the
furnace until it is secured in the press, the scene
s one of extraordinary activity and excitement,
As the plate requires to be placed in the press as
sxpeditiously as possible before it becomes cool
The metal of these plates appears to be first
class, but until within q few days past, they
were furnished very slowly by the different coz
ractors. The plating of the Roanoke will now
proceed with greater rapidty; still, she viii 20.
pc finished for several months to come. We are
old that this fdgate is expected to obtain a
ipeed Of about ten knots per hour. If she makes
line knots, we shall be sgreesbly disappointed.
As the Roanoke viii sit very low in the water,
We hope that proper arrangements will be made
or ventilation on the main deck. The defects
# the Galena and Monitor, SO clearly pointed
,ut in the Scientific American of last week, by
N intelligent correspondent, will be reproduced
n ths Roanoke, rendering her very deficient as
"sea-bost,' unless this advice is needed.