The Sun.
London, England, 1859-01-12 00:00:00

THE .N.ETV HYDRAULIC LIET AT TILE
VICTORIA DOCKS.

The delay, expense, and inconvenience attendant
upon placing a vessel in dry dock, either for, the
purpOses of:examination or repair, have long been
a practical evil, productive of the worst results to
the shipping interest, and yet the difficulty seemed
to admit of no solution ; for, as the dry docks could
only be entered or left at: high-water, the delay,
which was of course productive of the greatest
amount of inconvenience, appeared unavoidable.
The sUbjeCt at first sight does not appear to have
the influence on :the safety of shipping which it
has. But when it is considered how frequently
shipowners send their-vessels to sea in a defective
state of repair, rather than incur the expense and
delay of having them. -docked, it may be easily
understood how large a proportion of the vessels
reported as foundering at sea may trace their de-
struction Solely to this-cause. A short time ago,
.howtver, - an expedient ,was discovered, which
afforded a speedy and efficacious means of docking
and undocking a ship for the Purpose of examina-
tion. during all phases of the tide in about two hours.
The plan consists of sinking a shallow buoy or
pontoon under the ship to be docked, and afterwards
raising the buoy, ship and: all, bodily out of water
by hydraulic power. :The pontoon, having become
clear of water, the valves are closed—one watertight,.
and the apparatus towed away to some suitable
position with the ship dn. it high and dry. The
Victoria Dock Company, seeing the advantages and
the feasibility of the plan, .'soon after its invention
entered into contracts for .the construction of an
extensive _ series .of graving docks, in 'connection.
with their property. The works, which have re-
,cently been completed, occupy about 10 acres of
water, and consist of one deep dock, in which the
hydraulic apparatus for lifting the ships is placed,
and eight shallow (leeks Or the reception of the
pontoons containing the Vessels when raised; -The
lifting dock is about 320 feet long, 64 feet broad,
and about 30 feet deep. -Along each side of it, but
below the level of the water, are fixed 32 10-inch
hydraulic rams, which are probably the longest
apparatus of the kind in the world, being nearly
30 feet long, and having a stroke of 25 feet. These
are of course properly set and secured in solid
masses of masonry to resist the tremendous pres-
sure whiCh is brought to bear on their foundations,
when the apparatus is in action. To the head of
each of the pistons of these rams is attached a strong
wrought-iron cross-head. • Fastened to each pair of
hydraulic rams, and extending across the docks
are massive trussed iron girders, weighing upward;
of 60 tons each, and capable of sustaining a weight
of nearly 300 tons. There are thus 16 of these
iron,girders, traversing the-dock from side to side,
at distances of 20ft. apart, forming a gigantic frame-
work, capable of sustaining a weight of nearly
4,000 tons, or far greater than that of the ordinary
run of large first-class ships, To avoid the.risk of
the rams breaking
.(which would be a very consi-
derable one, owing to their Unusual length, and the
great weight they have to support when in use)
the cross heads to which the iron girders are at-
tached run in massive -cast iron. guides, which rise
some 28 feet above the water. - The iron pontoons
which are used for floating the ships after they are
lifted, and during their repair, are to be eight in
number; all 60 feet broad, and varying in length
from 240 to Over, 300 feet. At present,, however,
there is only one in use and another approaching
completion, both .of which are of the minimum
length of 240-feet. They are constructed of boiler
plate iron, strengthened,. of course, with stout
wrought iron"girders, secured transversely across
the pontoon, at intervals of three or four feet.. They
are extremely light, weighing altogether little more
than 300 tons, though the .great surface which they
present to the water (14,400 superficial feet) enables
them to support a weight •of '2,000' tons., with an
immersion of little over 4 feet' 'At one end of each
of these pontoons is placed. a. large ,valve which,
opening 'and shutting with a.kind of screw break,
can be sunk or. rendered water tight in a very few
minutes. The modus operandi of lifting a vessel is
as follows :—Th.l iron pontoon is first moored over
the lifting dock, the valves are opened, and it is
allowed to sink until.it rests upon the iron girders
attached to the ram. The ship to be docked is then
moored immediately over the pontoon, and the force '
pumps worked until the keel rests upon the pontoon.
The wooden dogs which are fixed sous to slide back-
wards and forwards on the floor of the float are
then, by means of ropes, drawn under the sides of
the'yessel so as to support her in an upright posi-
tion, and prevent her from " canting over" when
she is raised out of the water. When all these pre-
liminaries (which in their performance do not
occupy much more time than that taken to describe
them) have been properly adjusted, the hydraulic
pumps are again set to work, and the whole appa-
ratus, pontoon, ship, and all, is fairly raised out of
the water. When all the water,has discharged itself
through the valves in the bottom of the pontoon,
they are firmly closed water-tight by means of the
vulcanised India rubber seams, and the water being
allowed to escape from the hydraulic cylinders, the
rams, with their attached girders, sink down, leaving
the pontoon floating with the vessel in it high and
dry. The whole operation, from the very commence-
ment, does not occupy more than one hour or so. If
the object of docking the ship be merely to examine
the bottom or to execute some slight repair, which
will occupy but a few. hours, the pontoon is not
moved from the lifting dock ; but should the neces-
sary repairs be of such a nature as to occupy any
length of time, it is towed away into one of the eight
shallow docks built for the purpose, the depth of
water in which varies, according to the tide, from
six to eight feet. When the scheme is fully carried
out, it is intended to have regilarly fitted work-
shops placed on the banks of each of these pontoon
basins for the repair of both steam and sailing ships
constructed of either iron or timber. When it is
wished to float a ship again, the pontoon is moored
in the lifting dock, and the girders are raised up
sufficiently high just to take the weight of the ship
off the pontoon. The valves of the latter are then
opened, and'at the same time water is allowed to
escape from the hydraulic cylinders, so that the
whole apparatus quickly sinks, effectually launch-
ing the ship again in about ten minutes. The great
advantages attendant upon. having a simple and
efficacious apparatus of this kind in connexion with
a large dock company, are too manifest to require
comment. By it the expense of docking a ship is
Much reduced, and at the same time infinitely
greater facilities are afforded for the performance
of the operation, and the time occupied by it re 7
diked in a most important degree. Should it become
necessary to dock a ship just as she is preparing to
sail (as is very frequently the case), the operation
can now be immediately performed in less than two
hours, in any state of the tide, and without there
being any necessity to discharge the cargo. If the
necessary repairs were of a trifling nature, the ship
might again be launched and pursuing her course
down th Thames within four or five hours. The
hydraulic pumps and rams connected with the.
"lift" are of course the most important and inte-
resting parts of this gigantic apparatus. They are
worked by a 50-horse power, combined high and'
low-pressure, engine. The water is pumped from
the engine-house through the common pipe to a.
reservoir in the valve-room (where all the tubes
through which the hydraulic cylinders are supplied
concentrate) at a pressure of about a ton to the cir-
cular metre. The valves in this room are so arranged
that the rams may be made to act together in sets
of six, or each may be put into action :p2rfectly
independent of the other. These complicated series
of valves are of course, during the operation of lift-
ing, under the charge of a competent engineer,
who, by increasing or diminishing the action of
each pair or series of rams, can cause the ship to be
raised either perpendicular or in any other desired
position. It has been said that the water is pumped
into the hydraulic cylinder at a pressure of one ton
to the circular. inch, which gives,n. lifting force
with the whole 32 10-inch rams of 3,200 tons.
This is the Ordinary working pressure when ordinary
ships of less than 2,800 tons weight .have to be
raised. But with heavy laden vessels a much
greater force would 'be required. The moveable
portions or the pistons of the rams, together with
the cross heads, iron girders, &c., weigh about
1,100 tons, and the iron portion about 300 tons
more ; but as about 1,000 tons of this iron work is
never raised above the water, 100 tons must be de-
ducted from this for displacement. Thus about
1,300 tons of the ordinary working force of 3,200
tons is consumed in raising the apparatus itself,
leaving only 2,900 tons for the weight of the ship.
As none of the pontoons yet constructed will carry
more than about 2,000 tons, the ordinary force is
sufficient. But should it at any future time be
deemed necessary to raise a ship and cargo of
greater weight, the rams would easily bear a pres-
sure of two tons to the circular inch, which (sup-
posing the rest of the apparatus would resist such a
strain) would give an available lifting power of
about 5,000 tons. This invention is doubtless only
the precursor of great and sweeping changes in the
method of both launching and docking ships to be
effected through the agency of the hydraulic ram,
which supplies us with such a ready and efficacious
means of concentrating mechanical power.