IMPROVEMENTS IN PRO- PELLING VESSELS, AND IN THE MACHINERY FOR WORKING THE SAME
Year: 1844

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
HODGSON, of Princes Street, Clapham Road, in the County of Surrey,
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent under the Great Seal of Great Britain, bearing date the Second
day of February, One thousand eight hundred and forty-four, and in the
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Robert Hodgson, Her especial licence, that
I, the said Robert Hodgson, my exors, adññors, and assigns, or such others as
I, the said Robert Hodgson, my exors, adiñors, and assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the terin of years therein expressed, should and lawfully might make,
use, exercise, and vend, within that part of Her said Majesty's United King-
dom of Great Britain and Ireland, called England, Her Dominion of Wales,
and Town of Berwick-upon-Tweed, my Invention for "IMPROVEMENTS IN PRO-
PELLING VESSELS, AND IN THE MACHINERY FOR WORKING THE SAME;" in which said
Letters Patent there is contained a proviso obliging me, the said Robert Hodgson,
by an instrument in writing under my hand and seal, particularly to describe
and ascertain the nature of my said Invention, and in what manner the same
is to be performed, and to cause the same to be inrolled in Her Majesty's
High Court of Chancery in England, within six calendar months next and

page_text: immediately after the date of the said recited Letters Patent, as in and by the
same, reference being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Robert Hodgson, do hereby declare that the nature of my said Invention, and
in what manner the same is to be performed, are particularly described and
ascertained in and the following Specification thereof, reference being had to
the Drawings hereunto annexed, that is to say :-
My improvements in propelling vessels consist, firstly, in propelling the same
by means of propellers, to be worked by steam or any other efficient power,
composed of two, three, or more blades attached to a common shaft or axis,
running fore and aft, and diverging rearwards from that axis in lines coincident
with the plane of a right cone placed longitudinally with the apex foremost,
whereby the said blades, instead of revolving like the floats of the common
paddle-wheel in directions at right angles with the line of the vessel's course,
revolve in directions coinciding more or less with that course, and in curves,
by which they exert a more uniformly propulsive effect, than I believe to be
obtainable from screw or any other propellers with fore and aft shafts or axes;
and, secondly, in making use of propelling blades which are themselves parabolic
sections, whether such blades are attached to a common shaft at the conical
tangents before described or in positions parallel to the shaft, whereby in
either case they act with better effect than blades of any other figure, because
of their driving backwards in lines parallel to their axes the bulk of the water
with which they come in contact. The machinery for working or carrying
into effect these improvements is represented in the Drawings hereunto
annexed and next herein-after described. Figure 1 is a geometrical figure
shewing how the positions proper to be given to the arms of a propeller con-
structed on the principle first before enunciated, are to be determined when the
blade is of any plain and uncurved surface. Supposing the propeller is intended
to be applied to the stern of a vessel, and fixed as usual in the dead wood,
the constructor has first to ascertain the diameter of the largest circle which
can be described within the largest space that can be cut out of the dead wood
without interfering with the rise of the floor abaft, or unduly weakening the
after-frame of the vessel (see Figure 8); with a radius A, B, of this circle let
him draw a semicircle B, C, D, and a perpendicular from the centre A to the
periphery at C; from C set off the chord of any angle between forty-five and
sixty degrees, as C, E, and from the point E draw a perpendicular to the line
A, C; then will E, F, be the sine and E, G, or F, A, which is equal to E, G, be
the co-sine of the said angle, and the arm to support the blade at its outer and
larger end; where it revolves through the largest space, should be of the angle

page_text: form corresponding with such sine and co-sine, the blade being attached to the
branch of the arm which represents the sine. The inner or fore-end of the
blade may be attached to the shaft either by means of an angle arm similar to
the preceding, but shorter in proportion, to the width of the blade at its interior
end and to the degree of obliquity desired to be given to it, or to a boss on the
shaft, as in the variety represented at N, in Figures 8 and 9, and herein-after
described. The width of the blade should at no part exceed the sine (E, F,)
of the angle. Figures 2 and 3 are side views of a propeller with two plain
blades constructed in the manner last herein-before described, and Figure 4 is
an end view of the same, shewing more clearly the relative position of the blades
to the shaft. Figure 5 is a side view, and Figure 6 is an end view, of a similar
propeller, having three blades fixed at the inner end to a boss instead of to
angle arms, but which may be also fixed to angle arms, if preferred. The
manner of constructing blades and the arms of blades when they are of the form
of parabolic sections as shewn in Figures 7, 8, and 9: A, B, in Figure 7, is the
axis of a parabola, and B, C, the half of the curve described by that parabola,.
supposing it to be turned round on its axis, and this curve B, C, represents the
form which must be given to the blades of the propeller. Each blade is sup-
ported by an angle arm, the length and position of the branches of which are to
be found in the same manner as before directed in the description of Figure 1,
only that the arm which carries the blade must be curved to correspond.
Figure 8 is a side elevation of a vessel fitted with a propeller having not only
parabolic section blades, but these blades affixed to the shaft in positions coin-
cident with the plane of the cone. Figure 9 is an end view of the propeller in
Figure 8, detached from its position in the vessel. In all the preceding cases
one propeller only is supposed to be employed, and that fixed at the stern, but
instead of one propeller at the stern there may be two, one under each quarter
in the run of the vessel, or there may be one propeller at the stern and another
at the bow, or such propellers may be fixed at the sides, in the places now usually
occupied by the common paddle-wheel, or they may be fixed in any other part
which may be found suitable; and in every case the propeller may either
embrace both of my said improvements or one of them only, that is to say, the
blades may either be fixed at conical tangents to their shaft, and to be
also themselves of the form of parabolic sections, or they may be of the form
of parabolic sections, but fixed in positions parallel to the shaft.
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that what I claim is,--
First, the attaching as before described of the blades of fore and aft pro-

page_text: pellers to their shafts at tangents coincident with the plane of a right cone,
placed longitudinally with the apex foremost.
And, second, the employment of blades of the form of parabolic sections or
of any other form possessing similar properties, whether attached to the shafts
at tangents coincident with a plane of a right cone placed longitudinally with
the apex foremost, or in positions parallel to the same.
In witness whereof, I have hereunto subscribed my name and affixed
my seal. this Second day of August, in the year of our Lord One
Enrolled the Second day of August, in the year of our Lord One
thousand eight hundred and forty-four.