IMPROVEMENTS IN FLOATING GRIDIRONS! OR STAGES FOR REPAIRING SHIPS OR OTHER VESSELS
Year: 1859

page_text: LETTERS PATENT to William Collett Homersham, of Adelphi Terrace,
Strand, in the County of Middlesex, Civil Engineer, for the Invention
of." IMPROVEMENTS IN FLOATING GRIDIRONS! OR STAGES FOR REPAIRING SHIPS
OR OTHER VESSELS."
Sealed the 27th May. 1859, and-dated the 24th January 1859.
PROVISIONAL SPECIFICATION left by the said William Collett Homersham
at the Office of the Commissioners of Patents, with his Petition, on the
.24th January 1859..
I, WILLIAM COLLETT- HOMERSHAM, of Adelphi Terrace, Strand, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN FLOATING GRIDIRONS' OR STAGES FOR REPAIRING
SHIPS OR OTHER VESSELS," to be as follows:
My Invention has for its object the construction in the manner herein-after
described of floating "gridirons" or structures for supporting ships while under
repair. And I accomplish this.object by combining two series of hollow air-
tight caissons of cylindrical or other suitable form placed transversely to each
other, so as to form or constitute a rigid structure, on which the platforms for
carrying the ship or vessel is fixed. The caissons are arranged so that the
lower series lie in the direction of the length of the vessel, and the upper

page_text: series transversely to them. The upper or transverse series are curved so as
to give stability to the structure by counteracting its tendency to heel over in
a transverse direction, but they may be made straight, and the longitudinal
series are preferred to be straight, but they may be curved either in elevation
or in plan. I prefer that the upper or transverse series should be rectangular
in the cross section, and the lower or longitudinal series circular or oval.
The sinking of the structure and the required degree of buoyancy given to
the platform are caused by letting water into and out of the caissons. The
pumping or other apparatus for withdrawing or forcing the water therefrom,
may be fixed on a platform or platforms on one or each side of the structure,
and at such a height as to be above the surface of the water, when the
structure is sunk, in order to receive a vessel, but the apparatus for withdrawing
or forcing the water may be fixed on shore or on another floating vessel, and
be made to communicate with the caissons by means of a flexible pipe or
pipes.
Bulkheads or partitions are fixed in the longitudinal caissons at convenient
distances apart. They are of the full section of the caissons or not, as found
most convenient, and are furnished with valves which may be worked as
required by means of rods, chains, or other suitable gear from the said plat-
forms for the purpose of trimming the structure, and causing the keel of the
vessel resting thereon to lie in any required position. There are also bulk-
heads or partitions with valves in them fixed in the upper or transverse
caissons.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Collett Homersham in the Great Seal Patent Office:
on the 22nd July 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
COLLETT HOMERSHAM, of Adelphi Terrace, Strand, in the County of Middlesex,
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fourth day of January, in the year of our Lord
One thousand eight hundred and fifty-nine, in the twenty-second year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said William Collett Homersham, Her special license that I, the said
William Collett Homersham, my executors, administrators, and assigns, or a

page_text: such others as I, the said William Collett Homersham, my executors,
administrators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend, within
the United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN FLOATING GRIDIRONS' OR
STAGES FOR REPAIRING SHIPS OR OTHER VESSELS," upon the condition (amongst
others) that I, the said William Collett Homersham, by an instrument in
writing under my hand and seal, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date of
the said Letters Patent.
NOW KNOW YE, that I, the said William Collett Homersham, do hereby
declare the nature of my said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement, reference being had to the Drawing hereunto annexed,
and to the letters and figures marked thereon (that is to say):-
My Invention of Improvements in Floating Gridirons or Stages for
Repairing Ships or other Vessels" has for its object the construction in the
manner herein-after described of floating "gridirons" or structures for support-
ing ships while under repair; and I accomplish this object by combining
two series of hollow air-tight caissons of cylindrical or other suitable form
placed transversely to each other, so as to form or constitute a rigid structure,
on which the platform for carrying the ship or vessel is fixed. The caissons
are arranged so that the lower series lie in the direction of the length of the
vessel, and the upper series transversely to them. The upper or transverse
series are curved so as to give stability to the structure by counteracting the
tendency to heel over in a transverse direction, but they may be made straight,
and the longitudinal series are preferred to be straight, but they may be curved
either in elevation or in plan. I prefer that the upper or transverse series
should be rectangular in the cross section, and the lower or longitudinal series
circular or oval.
The sinking of the structure and the required degree of buoyancy given to the
platform are caused by letting water into or out of the caissons. The pumping
or other apparatus for withdrawing or forcing the water therefrom may be
fixed on a platform or platforms on one or on each side of the structure, and
at such a height as to be above the surface of the water when the structure is

page_text: sunk in order to receive a vessel; but the apparatus for withdrawing or
forcing the water may be fixed on shore or on another floating vessel, and be
made to communicate with the caissons by means of a flexible pipe or pipes.
Bulkheads or partitions are fixed in the longitudinal caissons at convenient
distances apart. They are of the full section of the caissons or not, as found
most convenient, and are furnished with valves which may be worked as
required by means of rods, chains, or other suitable gear from the said plat-
forms for the purpose of trimming the structure, and causing the keel of the
vessel resting thereon to lie in any required position. There are also bulkheads
or partitions with valves in them fixed in the upper or transverse caissons.
Having thus stated the nature of my Invention, I proceed to describe
more particularly in what manner the same is to be performed, by reference
to the accompanying Drawings, in which is represented the floating "gridiron "
Figs. 1 and 2 are end and side elevations OI
Structure
In
a plan or horizontal view of the same, shewing the longitudinal and transverse
series of caissons with a portion of the flooring or platform removed.
these several Figures the same letters of reference indicate corresponding
parts.
A, A, are the longitudinal or lower series of caissons, which are preferred to
be circular in their cross section for economy of construction, but may be
oval or of any other convenient form, if the difference in the draught of
water is material. These caissons have bulkheads fixed in them at convenient
intervals, as indicated by dotted lines in the side elevation Fig. 2. These
bulkheads have the effect of dividing the caissons into portions, into some of
which water may be admitted, or from some of which it may be withdrawn as
required for the purpose of trimming the structure. B, B, are the transverse
or upper series of caissons, which are shewn as rectangular in their cross
section and partly curved under the vessel's bottom, but they may be formed
in such manner as is best adapted for giving lateral stiffness and steadiness to
the structure when afloat. These transverse caissons are united firmly to each
of the longitudinal caissons, but need not have any internal communication
therewith, excepting as to the centre one or other which may be preferred, and
which likewise communicate with the engine and pump rooms C, C, by means
of the hollow columns D, D. The engine and pump rooms, consisting of a
hollow pontoon on each side of the structure, may be supported by means of

page_text: "
caissons E, E, tapering towards the bottom as shewn, or by columns, or in other
convenient manner. F, F, are caissons which are intended to be placed on the
top and along the outer ends of the transverse caissons B, when a "gridiron
of considerable magnitude is constructed, such caissons having each a power
of displacement equal to about one-twentieth of the entire weight to be lifted.
G, G, are gangways one on each side of the structure, which will be found
convenient in working; these are supported on columns of timber or metal
H, H, having racks formed on their sides; I, I, are water-tight caissons
built with holes or passages through them corresponding with the columns H,
in such a manner as to allow of the latter passing through them, and working
up and down therein with the raising and lowering of the structure. The
caissons I, I,. are capable of sliding freely on the colums H, H, or of being
retained as required by pawls taking in to the racks, and the parallelism of
their up and down motion may be regulated by a shaft with bearings and
pinions taking into racks or otherwise. The object of these caissons is to
increase the stability of the structure when the water has been admitted into
the lower caissons A, A, and in combination with the engine and pump rooms
or hollow.pontoons C, C, prevent the structure from sinking. It may be here
remarked that I prefer to have the transverse caissons B, B, of such cubical
contents as to render the whole structure slightly above the specific gravity of
water at the time when the lower caissons A, A, only are filled with water, as
K is a
I prefer never to admit water into the transverse caissons B, B.
flooring on the top of the caissons B, B, forming an extended platform on
which workmen may carry on their operations; I is the bed for the keel
of the vessel to rest on, extending as usual along the centre of the dock
or "gridiron." M, M, are the ordinary sliding blocks for shoring up or
supporting the vessel.
The mode of using the "gridiron." is as follows:-Water is let into the
longitudinal caissons A, so as to lower the structure to the required depth, as
represented by dotted lines in Figs. 1 and 2, and by regulating the quantity
of water admitted between the different bulkheads, the structure is brought
into the position adapted to receive the keel of a vessel which may be drawing
more water abaft than forward, or vice versa.. It will also be seen that by taking
a greater portion of water from between the bulkheads situated immediately
beneath that part of the vessel containing the greatest weight, (say, the engine
room of a steamer,) all undue tendency to strain the vessel or the "gridiron
is avoided. When the vessel has been placed in position over the "gridiron
thus sunk to receive it, the moveable caissons I, I, are floating freely on the
"
""

page_text: top of the water, (their pawls having been thrown out of gear before the
sinking commenced,) and in order to raise the vessel the. water is pumped or
forced out of the caissons A, A, at an equal rate on both sides of the keelson.
I prefer emptying first the two nearest the centre of the structure, and working
outwards on each side. As the caissons A, A, are lightened of the water, the
whole structure gradually rises on a level, while the water is pumped out
equally on both sides, but should there be an inequality in the puniping, or
should the centre of gravity of the vessel get displaced, the "gridiron " would
have a tendency to sink on the heavier side. This tendency, however, will be
counteracted by the caissons I, I, the pawls of which being now in gear
establish a connection between them and the structure, so that the latter
cannot go down without taking the said caissons with it, and these are made
of sufficient capacity to resist such tendency. Hence by merely pumping
faster from the heavier side, the whole structure is readily made to assume its
required horizontal position. As the vessel is raised out of the water, the
weight on the structure becomes materially increased, and therefore I prefer
in lifting large vessels to have fixed caissons as shewn at F, F, to come into
'operation when the vessel is drawing five to six feet of water; these caissons
may be in any number of pieces and of very light material, as they are not
intended to add strength to the structure.
In cases wherein it may be required to move the structure frequently, the
pumping engines may be furnished with gearing adapted for working a screw
or other propeller, and it is probable that sufficient propelling power might be
obtained by forcing water through a pipe or pipes. When the water is
admitted to the lower caissons A, A, alone, the buoyant power of the empty
* transverse ones being above, and the centre of gravity of the water being
unable to shift materially, the whole structure has but little tendency to
be thrown out of a horizontal position, and this slight tendency is amply over-
come by the floating caissons I, I. Manholes will be formed in each of
the transverse caissons. B, B, in order to admit of their being examined
internally when floating on the surface of the water. The structure is appli-
cable to the lifting of saucers, such as are employed in conjunction with the
hydraulic lift in the Victoria Docks. The structure may be moored in a
similar manner to ships, or caused to act between piles. or walls.
Having thus described the nature of the said Invention, and in what manner
the same is to be performed, I hereby declare that what I claim as of my
Invention is, the construction of floating "gridirons" by combining two series
of hollow air-tight caissons (one series being longitudinal and the other

page_text: transverse) in such a manner as to form a rigid structure, and connecting
therewith apparatus, by means of which the structure may be sunk, raised, and
trimmed as required by the regulated admission and discharge of water into
and from the caissons as described.
In witness whereof, I, the said William Collett Homersham, have here-
unto set my hand and seal, the Twenty-second day of July; in the
year of our Lord One thousand eight hundred and fifty-nine.
Witness,
WILLIAM SPENCE,
50, Chancery Lane,
Patent Agent.
W. COLLETT HOMERSHAM. (L.S.)