IMPROVED MEANS FOR STRENGTHENING MASTS, SPARS, POLES, AND SHAFTING, CAST-IRON PILLARS, COLUMNS, PIERS, Box GIRDERS, AND THE LIKE, TO ENABLE THEM THE BETTER TO WITHSTAND LATERAL STRAINS AND EVEN TO KEEP THEIR POSITION AND ACT AS A SUPPORT WHEN CRACKED OR BROKEN."
Year: 1881

page_text: LETTERS PATENT to Henry James Harrison, of Liverpool, in the County of
Lancaster, for an Invention of "IMPROVED MEANS FOR STRENGTHENING
MASTS, SPARS, POLES, AND SHAFTING, CAST-IRON PILLARS, COLUMNS, PIERS,
Box GIRDERS, AND THE LIKE, TO ENABLE THEM THE BETTER TO WITHSTAND
LATERAL STRAINS AND EVEN TO KEEP THEIR POSITION AND ACT AS A
SUPPORT WHEN CRACKED OR BROKEN."
PROVISIONAL SPECIFICATION left by the said Henry James Harrison at
the Office of the Commissioners of Patents on the 4th March 1881.
HENRY JAMES HARRISON, of Liverpool, in the County of Lancaster. " IMPROVED
MEANS FOR STRENGTHENING MASTS, SPARS, AND POLES, AND SHAFTING, CAST-
IRON PILLARS, COLUMNS, PIERS, Box GIRDERS, AND THE LIKE, TO ENABLE THEM
THE BETTER TO WITHSTAND LATERAL STRAINS AND
EVEN TO KEEP THEIR
POSITION AND ACT AS A SUPPORT WHEN CRACKED OR BROKEN."
This Invention consists essentially in giving to each column or girder a strong
wooden or other tough core. This core not merely fills the interior of the column
but projects downwards into a recess in the pier, and upwards if desirable into the
superstructure, so as not merely to hold the column together if cracked by a strong
transverse strain, but to prevent it breaking from the pier or the superstructure
from a failure of the bolts under a strong horizontal strain.
This core can be placed in position in a variety of ways. It can be rather
smaller than the interior of the column, and placed loose in it, and the surplus
space filled with bitumen or otherwise. If the interior of the column be bored the
wood can be turned too to accurately fit and be driven in; care must however be
taken in such case to prevent the possibility of damp getting to the wood and
swelling it out till it bursts the pillar. This can be done by enclosing the wood
with a layer of waterproof material, or by filling the pores of the wood with such
material as would prevent the damp getting in and swelling out the wood, or by
previously saturating the wood with moisture, and turning it and introducing it wet.
The latter plan should only be adopted when the columns are to be placed in or
under water as in piers.
Although I have only spoken of wood, I of course include composite structures
of wrought iron and wood, or compositions having qualities of the same nature as
wood. I prefer to use for this purpose oȧk, rock elm, greenheart, teak, or other
kinds of wood that are at the same time very tough and not liable to speedy
decav

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Henry John Harrison in the Great Seal Patent Office on the
3rd September 1881.
HENRY JAMES HARRISON, of Liverpool, in the County of Lancaster. "IMPROVED
MEANS FOR STRENGTHENING MASTS, SPARS, POLES, AND SHAFTING, CAST IRON
PILLARS, COLUMNS, PIERS, Box GIRDERS, AND THE LIKE, TO ENABLE THEM THE
BETTER TO WITHSTAND LATERAL STRAINS AND EVEN TO KEEP THEIR POSITION
AND ACT AS A SUPPORT WHEN CRACKED OR BROKEN."
This Invention consists essentially in giving to the column or girder a core of
wood. This core is firmly secured to the iron girder at each end, so that it can
form a tension member of the girder, while at the same time it fills up the hollow
centre, and thus prevents in great measure a collapse of the structure. Furthermore
the wood is made to project beyond the ironwork into the pier and the superstructure,
into each of which it is firmly fixed, and in the case of girders it is preferably firmly
secured into the next girder or abutment, so as to make a continuous girder to some
extent. The object of this core is not merely to strengthen the column, which it
does to a remarkable and altogether unexpected extent, but should the ironwork of
the girder be cracked with a sudden strain or side blow the wooden core remains
to keep the broken pieces in position. In the case of columns for piers, I prefer
to place the core loosely in the iron column projecting at each end, and fill the
entire interstices with melted pitch of a hard tough nature when set. This pitch.
cements the iron and wood together, so that the column can be actually broken
with a transverse strain without the wood being drawn from either end. If the
wood draws out of the ends it is of little or no value in strengthening the column,
the wood when fast acting mainly as a tension member. I have not yet calculated
or found from experiment the comparative thicknesses of iron and wood that give
the best results, but would state that the best results will probably be obtained
(provided the pitch is sufficiently adhesive) when the tensile strength of the wood.
taken as a whole equals at least half the compressive strength of the iron column.
In this way the thickness of iron for any given diameter of column can be
calculated from the ordinary tables of strength of materials.
In employing my Invention for shafts I prefer to drill holes right through the
wood and iron, at intervals of, say, half the diameter, and in various directions
perpendicular to the axis of the shaft, and place therein closely fitting bolts
securely screwed up. This assists the pitch in preventing the iron moving on the
wood. If there be any fear of damp getting into the wood, especially where the
structure is to be placed in water, it is best either to entirely fill the pores of
the wood with hydrocarbonaceous or siliceous matter under pressure, or saturate
them with moisture before inserting the core in the pillar, and prevent the water
from evaporating out by incrusting the outer surface well with pitch and placing it
in its position as soon as possible. The object of this is that if the wood be inserted
perfectly dry and is then allowed to imbibe moisture, it is apt to strain or fracture
the ironwork enclosing it. The kinds of wood I prefer are rock-elm, oak, green-
heart, and teak, but other woods will do nearly as well.
This Invention is applicable for iron masts, for girders, for columns, piers, and for
nearly all structures in which a hollow iron structure is used to counteract strains,
and is specially applicable for the piers of bridges like the Tay and Solway bridges,
which are liable to receive strong transverse strains; it can even be used in ship
building by inserting a layer of timber between the outer exterior iron structure
and an inner floor, the whole bolted together.
Although the Invention can be well understood from the foregoing description"

page_text: without Drawings, I have added the accompanying diagrams to illustrate it more
effectually.
Fig. 1 is a line of piers with columns and superstructure.
Fig. 2, transverse view of piers with the bolts.
Fig. 3, section of marine screw shaft.
Fig. 4, section of a hull of a ship.
In Figs. 1 and 2 the wooden core is seen built into the pier, ascending upward
through the iron column into the superstructure, and again cased in an iron column.
The upper part forms the main pillar for the tension or suspension bars, the cap
from which those bars proceed being placed round the wood core and bolted into
the iron pillar. Pitch run into the interstices unites all together.
In Fig. 3 a hollow iron shaft with wooden core is shewn, fitted with bolts run
through at intervals of half a diameter. The dimensions of this shaft are supposed
to be, diameter of shaft, twenty four inches; diameter of core, twenty inches;
bolts, one and a quarter inches.
.
In Fig. 4 is shown my Invention as applied to hulls of ships. In this A is a
sheathing of beams of wood between the outer iron skin of the ship and an inner
casing. These beams are dowelled together as shown, and the two metallic casings
or skins of iron or steel, and the beams are all bolted together, the interstices being
filled with pitch as in the other cases. The beams are placed inside the ribs or
frames, the intervening space between the ribs being filled up with wood, lagging,
or cement as now practised.
Having now described my Invention sufficiently for an ordinary engineer to
work it with success, I wish it to be understood that I do not claim the principle
of composite girders or piers of wood and iron broadly, as I am well aware that
wooden girders and struts have been strengthened with iron, but that what
I believe to be new and claim as the Invention secured to me by Letters Patent
is,
First. The manufacture of columns, masts, pillars, girders, shafts, and other
similar structures of a metal exterior structure and a wooden core, the two being
made to cohere, and being so thoroughly fastened together as to not move on each
other under a heavy strain, thus making full use of the tensile strength of the
wood.
Second. The manufacture of structures such as those mentioned in the title of
this Patent, with a wooden core projecting beyond the metal part at each end and
firmly fixed in structures beyond, substantially as described.
Third. The mode of strengthening iron columns, struts, piers, girders, masts,
spars, poles, shafts, and the like, by giving them a wooden core, and filling the
interstice with pitch, so as to bind metal envelope and core securely together,
substantially as described.
In witness whereof, I, the said Henry James Harrison, have hereunto set
my hand and seal, this Second day of September, in the year of our Lord
One thousand eight hundred and eighty one.
HENRY JAMES HARRISON. (L.S.)