Improvements in and relating to the Manufacture of Helicoid Propellers.
Year: 1893

page_text: being date of first Foreign Application (in 3rd July, 1893
France),
Date of Application (in United Kingdom), 9th Nov., 1893
Complete Specification Left, 9th Nov., 1893-Accepted, 30th Dec., 1893
Date of Application (in United Kingdom), 9th Nov., 1893
Complete Specification Left, 9th Nov., 1893-Accepted, 30th Dec.,
1893
COMPLETE SPECIFICATION.
Improvements in and relating to the Manufacture of Helicoid
Propellers.
I, ALPHONSE LUCIEN FÉRAUD, of 33, Rue de Berlin, Paris, in the Republic
of France, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
This invention consists of improvements in and relating to the manufacture of
helicoid propellers.
The principle on which the present invention is based is adapted for application
in the production of helicoid propellers intended to operate either in water or in
the air.
In the present Specification, a helicoid propeller arranged for operation in the
water is described by way of example; but it will be understood that all that is
herein stated in reference to such propellers also applies to those which are intended
for use in the air.
It has hitherto been generally conceived that a helicoid propeller behaves in the
water like a screw in a nut; and hence propellers, as hitherto constructed, have
presented the same characteristics as ordinary screws. This idea, however, does not
appear to be in keeping with facts. In reality, as the object of the rotation of
helicoid propellers is to propel the ship as an effect of the inertia of the body of
water for the time being in contact with the helical surface of the revolving
propeller, the problem to be solved in determining the shape of the blades of the
propeller may be stated thus :-
At what angle of inclination should a given part of the surface of a helicoid
propeller be to the axis of rotation of the propeller and line of propulsion of the
ship to cause the inertia of the water to produce the maximum useful effect in the
direction of the said axis of rotation and line of propulsion; given a constant power
communicated to the propeller-shaft of the ship, and assuming that such shaft
coincides with the said axis of rotation and line of propulsion?
It is unnecessary in this Specification to go again through the process of
mathematical calculation which led to the solution of the problem just enunciated.
Let it suffice to give the solution itself, which is as follows:-
In the accompanying perspective diagram, wherein the arrow A B represents the
axis on which turns the helicoid propeller in order to impart motion to the ship in
the direction of that arrow, assuming the surface of the helicoid propeller to be cut
by the surface of a hollow cylinder CDE F, R being the radius of that cylinder,
then all the points G, H, I of the curve of intersection will be situated at the same
distance (that is, at the length. of R) from the arrow or axis A B. Supposing H to
be that one of these points through which passes the line J K, which may be
termed the generator of the cylinder C D E F: the tangent L M of the curve of
intersection G H I, touching that curve at H, must then be at an angle a, to the

page_text: generator J K, so that, if sine a = 2, then
=
(1-3)1-2 V
(2-3)
Rw
;
V being the
velocity of the movement of the ship in the direction of the arrow A B; R the
radius of the cylinder C D E F; and w the angular velocity of rotation of
the helicoid propeller about the axis A B. Now, in order to determine precisely
the angle a,
it should be understood that such angle is formed (1) by the
generator JK, the direction of which is assumed to be the same as that of the
arrow A B; and (2) by the tangent L M, the direction of which is supposed to be
the same as that of the movement of rotation of the helicoid propeller. Inasmuch
as R remains constant in relation to all points of the curve of intersection G H I,
is also constant, so is like-
wise the angle a in relation to all points aforesaid; this angle, then, represents the
inclination of a helix (shown in the diagram, for the sake of greater clearness, as
having more than one convolution). The degree of inclination of that helix, as
represented by the value of the angle a, thus enables the constant "pitch" of the
same helix to be determined. This being so, it will be understood that, in order to
determine the complete outline of a helical propeller surface, it is only necessary
to have a series of cylinders, such as C D E F, varying in size, but having a
common axis, the differences in the lengths of the radius R, and consequently in the
values of the angle a, being made as small as desired, and constructing upon such
series of concentric cylinders any suitable number of helices, such as G H I, which
need only then be connected by corresponding intermediate surfaces. The smaller
the variations of the radius R, the smaller will these intermediate surfaces be, and
consequently the more easily will they be given the true and serviceable shape.
and as, therefore, the second part of the equation (✓✓-)
Having
now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim :-
1. The improved manufacture of helicoid propeller substantially as herein
described with reference to the accompanying diagram and adapted to operate
either in water or in the air.
2. A helicoid propeller formed substantially as described with reference to the
accompanying diagram, the same having the helical surface determined by a series
of helical curves of different "pitches" borne on the surface of a series of hollow
cylinders varying in size and having one common axis, which helical curves are
inclined to the generating lines of the said cylinders at angles varying, as herein set
forth, according to the sizes of the said cylinders.
3. The improved manufacture of helicoid propeller substantially as described
with reference to the accompanying diagram, and wherein, as compared with an
ordinary propeller, there is a large increase in the numerical value of the relation
between the "pitch" of the helix on the largest intersecting hollow cylinder and
the diameter of that cylinder.
4. The improved method of determining the shape of a helicoid propeller
substantially as herein described.
Dated the 9th dow of Nazambo- 1902
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.