IMPROVED SYSTEM OF ARMOUR PLATES FOR FORTS AND IRONCLAD SHIPS
Year: 1878

page_text: LETTERS PATENT to Thorsten Nordenfelt, of 1, St. Swithin's Lane, in the City
of London, Civil Engineer, for the Invention of "IMPROVED SYSTEM OF ARMOUR
PLATES FOR FORTS AND IRONCLAD SHIPS."
Sealed the 23rd July 1878, and dated the 5th February 1878.
PROVISIONAL SPECIFICATION left by the said Thorsten Nordenfelt at the
Office of the Commissioners of Patents on the 5th February 1878.
THORSTEN NORDEN FELT, of 1, St. Swithin's Lane, in the City of London, Civil
Engineer. "IMPROVED SYSTEM OF ARMOUR PLATES FOR FORTS AND IRONCLAD.
SHIPS."
The object of this Invention is to secure increased protection to forts and ironclad
vessels so as to prevent the penetration of projectiles more efficiently than is done
by the armour plates before used, and so as to reduce to a minimum the damaging
effects of a projectile if or when it does penetrate or crack the armour. In order to
effect this I use a double armour, the outer of which consists of iron plates, and the
inner of plates of steel, or steely or other hard iron.
The outer and the inner plates are not welded together, but are placed either the
one immediately outside the other, or with a thin plate of soft iron, or a boarding
of wood between the two; and both are bolted together and to the backing.
The outer plates, made of rolled iron and as large as they can conveniently be
made, will of course be penetrated by large projectiles, but they will not crack or
break up, and the inner ones, which are inade either of steel, or of steely or other
hard iron, and being hardened or tempered on the outside, if required, will break
up the projectile or otherwise prevent its penetrating the side of the fort or vessel.
The inner plates are made much smaller than the outer ones, so that if an inner.
plate should crack or break the fractures will only go as far as the edges of such
small inner plate. Each of the inner plates is to be held by at least two bolts, so
[Price 6d1

page_text: that wherever a projectile may hit one of them there will always be at least one
bolt left to hold fast the remaining part of it, and if an inner plate becomes cracked
or broken the larger outer plate will-prevent any considerable pieces of such inner
plates from falling out of their places.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thorsten Nordenfelt in the Great Seal Patent Office on the 3rd
August 1878.
«
THORSTEN NORDENFELT, of 1, St. Swithin's Lane, in the City of London, Civil
Engineer. IMPROVED SYSTEM OF ARMOUR PLATES FOR FORTS AND IRONCLAD
SHIPS."
The object of this Invention is to secure increased protection to forts and ironclad
vessels so as to prevent the penetration of projectiles more efficiently than is done
by the armour plates before used, and so as to reduce to a minimum the damaging
effects of a projectile if or when it does penetrate or crack the armour. In order to
effect this I use a double armour, the outer of which consists of iron plates, and the
inner of plates of steel or steely or other hard iron.
The outer and the inner plates are not welded together, but are placed either
the one immediately outside the other, or with a thin plate of soft iron, or a
boarding of wood between the two, and both are bolted together and to the
backing.
The outer plates, made of rolled iron and as large as they can conveniently be
made, will of course be penetrated by large projectiles, but they will not crack or
break up, and the inner ones, which are made either of steel, or of steely or other
hard iron, and being hardened or tempered on the outside, if required, will break
up the projectile or otherwise prevent its penetrating the side of the fort or vessel.
The inner plates are made much smaller than the outer ones, so that if an inner
plate should crack or break the fractures will only go as far as the edges of such
such small inner plate. Each of the inner plates is to be held by at least two bolts,
so that wherever a projectile may hit one of them there will always be at least one
bolt left to hold fast the remaining part of it; and if an inner plate becomes cracked
or broken the larger outer plate will prevent any considerable pieces of such inner
plates from falling out of their places."
In order that my said Invention may be most fully understood, and readily
carried into effect, I will proceed to describe the Drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is an elevation and Figure 2 is a transverse section of armour. con-

page_text: layer of soft material (I employ wood), which I prefer to insert between the outer
soft plates and the inner hard plates; C are the inner hard plates, of hardened or
tempered steel, or steely or hard iron; D is the backing, such as is usually employed
behind armour plates; E is an iron plate forming part of the ship's side or of other
supporting structure; F are the bolts by which the armour is attached to the ship's
side, or to other supporting structure.
The main objects of the Invention are,―
1. To break up the projectiles by means of a hardened plate of steel, or steely or
otherwise hard iron. But as such plates are apt to crack and break in several
directions, although they do not allow the projectiles to pass through unless any
considerable pieces are allowed to fall out, I therefore cover these hard plates on
the outside by soft iron plates in order.
2. To prevent any pieces of the hard plate to fall out if or when they crack, but
to hold such broken pieces still in their places. The outside plate should be made
of such soft iron that it does not crack, but simply allows the projectile to pass
through it; the wooden or other soft substance which can, if desired, be put, and
which I prefer to put between the outer and inner plates, would be there in order
still further to secure the outer plate against cracking or breaking by acting as a
cushion to it.
The sizes of the different classes of plates can be varied in proportion to the
ordnance against which it is proposed to defend a fort or a ship. As to thickness
the inner hard plate should always be thick enough effectually to prevent the
projectile to pierce it, and the outer soft plate should be of a thickness sufficient to
prevent any considerable pieces of the inner plate from breaking through it in case
the projectile after passing through the outer plate should crack though not pierce
the inner hard plate.
If the thinner plates be made one-quarter the thickness of the inner hard plates
it will be found suitable.
As to length and width the inner hard plates should be small, in order that if a
projectile cracks them the cracks should not be able to go farther than to the next
plate, while the next plates ou each side would remain undamaged. Being small
each plate is also more easily and cheaply replaced. I should recommend, for instance,
2 feet by 4 feet as a convenient size for the inner hard plates of an armour intended
to resist projectiles of 6 inch to 9 inch diameter, and so on.
The size of the outer plates is to a certain extent governed by the size of the
inner ones.
As the outer plate should under any circumstances be able to prevent
any large pieces of the inner plate from breaking, and I would, for instance,
recommend that each outer plate in length as well as in width should cover at least
three of the inner ones; being large the outer plates are also less likely to crack
when penetrated.
The plates can be bolted to the ship's side or to other parts of the structure in
any way that is usual or may be considered advantageous. It is not necessary that
every bolt should pass through both plates, but I prefer to have it so.
Thus my armour consists of hard inner plates of sufficient thickness to stop a
given projectile, and which is so small that it can be easily replaced, and that if it is
broken by this projectile the cracks cannot extend far, while these hard innér plates
are covered (with or without a softer substance between) by soft iron plates, which
are only just thick enough, and so much larger than the inner plates, as to prevent
any pieces of the inner plates from falling out in case such inner plates aro cracked
by the projectile.
This armour is very much cheaper to make than large steel plates, which when
they have nothing to prevent their broken pieces from falling off must be made
with extreme care and great expenditure if they are to be at all reliable.
What I claim is, my system of armour plates for forts and ironclad ships con-
sisting in the combination of thick plates or slabs of small area, made of hard inetal,
suitable to resist penetration, with a surface covering of thin plates of comparatively

page_text: large area, made of soft metal; such as is not liable to crack; substantially as
described.
In witness whereof, I, the said Thorsten Nordenfelt, have hereunto set my.
hand and seal, this First day of August, in the year of our Lord One
thousand eight hundred and seventy-eight.
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