Improvements in Duplex Rudders.
Year: 1890

page_text: Date of Application, 21st Jan., 1890-Accepted, 1st Mar., 1890
COMPLEIE DIEUITIVATION
Improvements in Duplex Rudders.
I, VALDEMAR FREDERIK LÄSSOE of No. 83 Decatur Street, Brooklyn, in the County
of the Kings and State of New York, United States of America, Engineer and
Surveyor, 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 improvement is more especially designed for screw steamers, and particularly
for such as have a single screw, though it may be applied to vessels with twin
screws. Its object is to produce, by changing the relative angular position of two
rudders, such divergence of the column of water thrown back by the propeller, that
this will flow at such an angle to the line of the keel, as, by its reaction, to turn the
vessel very sharply, even to the extent, if desired, of making it turn on its centre
of displacement, with a force proportionate to the propelling power of the engine.
Fig. 1 in the accompanying drawings represents a side view of the stern of a screw
vessel having my invention applied thereto.
Fig. 2 is a horizontal sectional view corresponding with Fig. 1, but showing the
working parts of my invention in plan.
Figs. 3 and 4 are views corresponding with Fig. 2, but showing the rudders in
different positions.
Fig. 5 is a plan view of a modification of my invention.
Similar letters of reference designate corresponding parts in all the Figures.
C designates the stern of the vessel. A, a a¹, bb₁, designate a frame consisting of
the shaft A, substantially similar to the rudder stock of a common rudder, having
forged to it, or otherwise secured upon it, two arms, a a¹, at the bottom, and two other
arms, bb, at or near the load line, each pair of arms being set at an angle resembling
a V. The said arms are provided with suitable holes or bearings for the reception
of the pivots c, provided at the top and bottom of the duplex rudders B B', near their
forward edges. One, B, of the said rudders is pivoted in the arms a b, and the
other, B', is pivotted in the arms a b'. The distance of the two rudders from each
other is preferably such, that the angle formed by centre lines from the centre of the
The rudder frame or
stock to the centre of the trunnions (c, is nearly 60°.
stock A, a a, b 61, may be hinged to the rudder post in any suitable manner, either
by pintles and gudgeons or bands. In the vessels without a rudder post, the stock or
frame can be stepped in a shoe projecting from the foot of the stern below the
propeller.
At a suitable distance above or below the arms b 61, there is fastened to the
said frame or stock, the tiller yoke e (see Fig. 1). Below this yoke, but above
the arms bb, there is represented, as secured to the said stock or frame, a con-
centric toothed sector d. The rudders B B¹ are connected at their upper parts, near
their rear edges by links or swinging arms 9 9', one for each rudder with a
pivot i, the connection of each link or swinging arm of each rudder being made
by a pivot fat the top of the rudder.. In the example of my invention represented in
Figs. 1, 2, 3, 4, this pivot i is attached to a slide k, which works on a fixed
horizontal guide arranged longitudinally and centrally to the vessel. This guide
is represented as formed on a hanging bracket m, bolted to the overhanging stern
of the vessel, the configuration of the said bracket depending on the shape of the
stern. There are also provided, forward of this guide 1, two stationary pillow
blocks n, for the reception of the journals of a short upright shaft h, which has
at its lower end a crank p. These pillow blocks are in the centre line of the vessel,
The
and are represented as formed upon, or attached to the hanging bracket m.
crank p has its crank pin p¹ connected by a rod q with the slide k. The crank
l

page_text: shaft has fast upon it a pinion o, gearing with the toothed sector d hereinbefore
mentioned as attached to the rudder frame or stock. The proportion between the
pinion and sector might be varied, but it is preferable, for reasons to be hereinafter
explained, that the said proportions should be such, that by turning the tiller-yoke
with which the sector moves 60°, the pinion o makes one full revolution.
At the bottom of the rudder frame or stock, there is represented, as fastened to the
lower arms a a¹, a horizontal sector shape plate r, the object of which is to prevent
the water thrown back from the propeller, from passing under the rudders, and
thereby reducing their efficiency. This plate, however, would hardly be necessary,
except in cases where the propeller shaft has considerable inclination downwards
toward the stern, as in torpedo boats.
In the example represented in Fig. 5, the parts are all the same as in the examples
represented in Figs. 1, 2, 3 and 4, except that the crank p and its shaft, the pinion o,
and sector d, the rod q and the slide k, are all dispensed with, and the pivot i is
supposed to be secured in a fixed position to the stern of the vessel.
I will now describe the operation with reference to Figs. 1, 2, 3 and 4.
The normal position of the two rudders is parallel with each other, and with the
centre line of the vessel, as shown in Fig. 2. When the rudder stock or frame is
turned by the tiller in one direction or the other, the rudder on that side towards
which the said frame or stock is turned, remains nearly parallel with the side of the
vessel, as shown in Fig. 2, but the rudder on the other side is given an inclination at
a very considerable angle to the vessel, as shown in Figs. 3 and 4. For example, if it
be desired to turn the vessel's head to starboard, the tiller is turned in a direction to
throw the rudder frame or stock slightly to port, thereby giving the starboard rudder
an inclination with its front to port, while the port rudder retains a position almost
parallel to the vessel's centre line. The vessel will now commence to turn to star-
board, and as the rudder frame or stock is moved more to port, the starboard rudder
will increase its angle, while the port one still merely retains a parallel position.
Having turned the tiller through 30°, the position of the rudder is as shown in plan
in Fig. 3. In this position, the action of the rudders is similar to that of a common
or single rudder, the vessel moving to starboard in a circle of considerable diameter,
and its headway being but slightly checked. By moving the tiller further to port, the
starboard rudder keeps on increasing its. angle until, as shown in Fig. 4, it has
passed 90°, the port rudder still occupying approximately a fore and aft position.
The speed of the vessel under this last described part of the operation is gradually
checked, and after a while, entirely lost, the column or body of water thrown back by
the propeller being so deflected by the angle of the rudders, as to produce, in a
direction lateral to the vessel, as illustrated by the broken lines in Fig. 4, a stream,
the reaction of which tends to turn the vessel, but not to drive it ahead. The vessel
will then pivot around a point at or near its centre of displacement, with the rudders
in this position. By turning the tiller to starboard, the action of the rudders will be
reversed. The vessel will finally pivot to port, if the tiller is brought fully over to
starboard.
In backing, the most advantageous position of the rudders for turning the vessel
short, is an intermediate position between that shown in plan in Fig. 3 and plan
Fig. 4, produced by 45° motion of the tiller to either side. The vessel will, with the
ridders in this position, back around in a sharp curve better than a vessel with a single
rudder, but will not pivot, as to attain this, would necessitate the rudders being swung
around on the forward side of the propeller.
In the above described operation, the movement of the active rudder, which, in the
illustration given by the drawings, is the starboard rudder B', is produced mainly by
the movement of the forward end or side of the said rudder in a direction transverse
to the centre line of the vessel, produced by the turning of the rudder frame or stock,
bat this movement is also produced in part, and is always controlled, by the links or
swinging arms gg. The nature of the movement of these arms depends in part on
the fixity or mobility of the pivot i. In the operations of the rudders hereinbefore
described with reference to Figs. 2, 3 and 4, the slide k, and with it the pivot i, are

page_text: moved towards and from the centre of the rudder frame or stock by the rotation of the
crank, produced through the sector d and pinion o, and by this means the arms or
links 9 g¹ are caused to exert an effective leverage on the after parts of the rudders,
and thereby to assist in turning them, and it is for the purpose of this effective
leverage, that I give the said pivot the movement fore and aft. The comparative
effect of making the pivot thus movable, and making it fixed, may be understood by
comparing Figs. 3 and 5, which both represent the rudder frame or stock in the same
position. The advantage of the movable pivot will be then apparent, for it will be
seen that the movement of the rudder B¹, in Fig. 5, is much less than in Fig. 3, and
the leverage exerted by the link or swinging arm g' in the position represented in
Fig. 5, is of very little effect. For very small vessels, on account of the greater
simplicity, the fixed pivot i might be adopted, but for vessels of any considerable size,
I prefer to make the said pivot movable, as described with reference to Figs. 1, 2, 3, 4.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. The combination substantially as herein set forth, with a vessel, of two
rudders, a stock or frame which is pivoted to the vessel, and in which said rudders
are separately pivoted at a distance apart near their forward ends, and links or
swinging arms each connected with one of the rudders, and pivoted substantially as
herein described, to the stern of the vessel.
2. The combination with a vessel and two rudders, of a rudder stock or frame
which is pivoted to the vessel, and in which said rudders are separately pivoted
at a distance apart, links or swinging arms each connected with one of the rudders,
and a sliding pivotal connection between the said links or arms and the stern of
the vessel, substantially as and for the purpose herein set forth.
3. The combination with a vessel and two rudders, of a rudder stock or frame
in which rudders are separately pivoted, links or swinging arms each connected with
one of the said rudders, a pivot common to both of said links or arms, a slide
carrying said pivot, a fixed slideway on the vessel arranged lengthwise thereof and
centrally thereto, for the said slide to run on, and a crank geared with the rudder
stock and connected with said slide, all substantially as herein set forth.
4. The combination of the rudder stock or frame consisting of a shaft A and
V-shaped arms a a¹ and b₁, the two rudders bb pivoted in said arms, the fixed
slideway attached to the stern of the vessel, the slide k and pivot i attached thereto,
movable on said slideway, the links or swinging arms 9 g¹ connecting the rudders
with the pivot i, the crank p and crank shaft h, and the fixed bearings n n therefor,
attached to the stern of the vessel, the rod y connecting said crank with the slide k,
the pinion o on the crank shaft h, and the sector d on the rudder stock gearing with
said pinion, all substantially as and for the purpose herein set forth.
Dated this 20th day of January 1890.
NEWTON & SON,
Agents for the Applicant.