IMPROVED APPARATUS FOR PROPELLING VESSELS
Year: 1853

page_text: LETTERS PATENT to James Mackay, of Aigburth, near Liverpool,
in the County of Lancaster, Merchant, for the Invention of
"IMPROVED APPARATUS FOR PROPELLING VESSELS."
PROVISIONAL SPECIFICATION left by the said James Mackay at
the Office of the Commissioners of Patents, with his Petition,
on the 29th July 1858.
I, JAMES MACKAY, do hereby declare the nature of the said
Invention for "IMPROVED APPARATUS FOR PROPELLING VESSELS" to be as
follows:-
This Invention relates to a novel construction of propelling apparatus,
which is intended to prevent the loss of power occasioned by the slip of
the common screw propeller, and also to avoid the loss of power
occasioned by the dead resistance which the boss and arms of submerged
propellers present to the water during the onward progress of the
vessel.
In carrying out my Invention I form a kind of double threaded
screw by affixing to the opposite sides of a boss, which is carried by the
propeller shaft, a semicircular disc. These discs form broil propelling

page_text: blades, and they are set at an angle to each other, their lines of
divergence crossing in the axis of the shaft which carries them. The
vessel is provided at its sides with a horizontal tubular projection
through which the propeller shaft runs, and against which the boss of
the propeller abuts, the object being to displace the water in front of
the boss of the propeller, and thus avoid the loss of power which the
direct resistance of the forward end of the boss would otherwise
occasion.
The semicircular blades, which lie close against the boss which carries
them, may be made of malleable cast iron or otherwise, provision being
made by an increased thickness at their middle to ensure the requisite
degree of strength.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said James Mackay in the Great Seal Patent Office,
on the 28th January 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
JAMES MACKAY, of Aigburth, near Liverpool, in the County of Lan-
caster, Merchant, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-ninth day of July, in the year
of our Lord One thousand eight hundred and fifty-three, in the seven-
teenth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said James Mackay, Her special license
that I, the said James Mackay, my exccutors, administrators, and
assigns, or such others as I, the said James Mackay, 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 "IMPROVED
APPARATUS FOR PROPELLING VESSELS," upon the condition (amongst
others) that, the said James Mackay, by an instrument in writing
under my hand and seal, should particularly describe and ascertain the

page_text: 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 James Mackay, 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 here-
unto annexed, and to the letters and figures marked thereon (that is to
say):
This Invention relates to a novel construction of propelling apparatus,
which is intended to prevent the loss of power occasioned by the slip of
the common screw propeller, and also to avoid the loss of power
occasioned by the dead resistance which the boss and arms of sub-
merged propellers present to the water during the onward progress of
the vessel.
-
In carrying out my Invention I form a kind of double-threaded
screw by lapping round a boss, which is carried by a propeller shaft.
two segment blades formed out of a circnlar lise cut into two equal
parts, which blades are set at an angle to each other, their lines of
divergence crossing in the axis of the shaft that carries them. The
vessel to the stern of which the improved propeller is to be fitted I
provide with a horizontal tubular projection, through which the pro-
peller shaft runs, and against which the boss of the propeller abuts, the
object being to displace the water in front of the boss of the propeller,
and thus avoid the loss of power which the direct resistance of the
forward end of the boss would otherwise occasion.
In the accompanying Drawing Fig. 1, is a partial side elevation of
a ship fitted with my improvements, and Fig. 2, represents the stern
end of the vessel. a, is the boss, and b, b, are the blades of the pro-
peller. c, is the propeller shaft, connected in the usual manner to the
motive power machinery, and running through a tubular projection d, ils
This
having a diameter corresponding to the diameter of the boss a.
projection d, it will be seen is parallel or nearly so to the keel, and
falls away, and is lost in the swell of the hull of the vessel. It is thus

page_text: virtually a forward prolongation of the boss of the propeller, and pre-
vents the water which is displaced by the hull of the vessel from closing
in and pressing upon the forward end of the boss a. In forming the
blades of my improved propeller I have said that I employ two semi-
circular plates. These blades I prefer to place excentrically upon their
boss, as I thereby cause the forward end of the propeller to describe a
circle of a larger diameter than the hinder end, the effect of which
arrangement is that the propelling power of each blade will be great
immediately it enters the water, and that the lift of back water will be
inconsiderable. The diagram, Fig. 3, shews the pattern of the kind of
blade which I prefer to employ, as laid out flat, with its outer edge
concentric with the boss which is to carry it. The inner edge of the
blade is formed by making in the semicircular plate (from which the
blade is supposed to be formed) an excentric circular or curved cnt.
When, therefore, a blade formed after this pattern is applied to the
boss so that its inner edge lies in contact with the cylindrical surface
of the boss, the blade will take the configuration shewn at Fig. 2.
Having now described my Invention, and the manner of carrying the
same into effect, I wish it to be understood that under the above in part
recited Letters Patent I claim the means herein-before described for
propelling or facilitating the propulsion of vessels through the water.
In witness whereof, J, the said James Mackay, have hereunto
set my hand and seal, the Eighteenth day of January, in the
year of our Lord One thousand eight hundred and fifty-four.
Witness,
WILLIAM RUTHERFORD,
of 88, Windsor Street,
Liverpool, in the County
of Lancaster.
JAMES MACKAY. (L.S.)