IM- PROVEMENTS IN SCREW STEAMERS
Year: 1872

page_text: LETTERS PATENT to Thomas Henderson, of Glasgow, in the County of
Lanark, North Britain, Merchant, for the Invention of "IM-
PROVEMENTS IN SCREW STEAMERS.”
Sealed the 13th August 1872, and dated the 17th February 1872.
PROVISIONAL SPECIFICATION left by the said Thomas Henderson at
the Office of the Commissioners of Patents, with his Petition, on
the 17th February 1872.
I, THOMAS HENDERSON, of Glasgow, in the County of Lanark, North
Britain, Merchant, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN SCREW STEAMERS," to be as follows, that is to say :-
This Invention has for its objects the providing of additional security
to life and property in screw steamers; the obtaining of an increased
speed from a given steam power; and the enabling of screw steamers to
safely dispense with masts and sails for propelling purposes.
The Invention consists in constructing a screw steamer with two
screw apertures, one before the other in a line with the keel, the after

page_text: one being of the ordinary dimensions, and the forward one about half
the dimensions of the other, and each being fitted with a separate propeller
shaft and screw. The forward screw is of a size suitable to work in the
space available between the keel and the shaft of the after screw.
The two propeller shafts may be connected to one set of engines or to
separate sets of engines, or the smaller shaft may be fitted with coupling
appliances admitting of its being connected either with the main engines
or with a set of smaller engines. In ordinary circumstances it is
proposed to use both propellers and all the available engine power to
ensure the maximum speed.
In the event of accident to either set of engines, shaft, or propeller,
the disabled propeller may be instantly disconnected, and the propelling
of the steamer be continued with the other propeller; this enabling the
voyage to be prosecuted independently of any assistance from masts and
sails or from other vessels.
The Invention is especially applicable to war ships and floating
batteries from the additional security afforded against complete dis-
ablement of the propelling apparatus, and to the larger class of ocean
steamers of the merchant service engaged in carrying passengers from
the greatly increased speed, security, and comfort which its adoption will
necessarily ensure.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Henderson in the Great Seal Patent Office
on the 16th August 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS 2
HENDERSON, of Glasgow, in the County of Lanark, North Britain,
Merchant, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventeenth day of February, in the
year of our Lord One thousand eight hundred and seventy-two, in the 3
thirty-fifth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Thomas Henderson, Her special licence
that I, the said Thomas Henderson, my executors, administrators, and

page_text: assigns, or such others as I, the said Thomas Henderson, 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 "IMPROVEMENTS IN SCREW
STEAMERS," upon the condition (amongst others) that I, the said Thomas
Henderson, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the 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 Thomas Henderson, 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 in writing, reference being had to the
accompanying Drawings, that is to say :—
My said Invention has for its objects the providing of additional
security to life and property in screw steamers; the obtaining of an
increased speed from a given steam power; and the enabling of screw
steamers to safely dispense with masts and sails for propelling purposes.
My Invention consists in providing a screw steamer with two
propellers, one of which propellers is of the ordinary relative dimensions,
and is placed in the position usual with screw steamers having single
propellers, whilst the other one is smaller and is placed immediately
in front of the ordinary one, and below its shaft.
And in order that my said Invention and the manner of performing
the same may be properly understood, I hereunto append a Sheet of
explanatory Drawings, to be herein-after referred to, and representing
the stern of a screw steamer as fitted with my improved combination of
propellers.
Figure 1 is a side elevation, and Figure 2 is a transverse vertical
section as taken through the aperture of the ordinary or larger propeller.
The steamer is represented as built of iron. The forging A, B, C,
(partly indicated by a dotted line in Figure 1) ordinarily comprising the

page_text: rudder post A and the frame A, B, of the aperture for the ordinary
propeller D, is constructed with an extension B, C, which forms the
frame of an additional smaller aperture in front of the lower part of the
ordinary aperture A, B. The shaft E of the ordinary propeller D passes
through a bearing in the intermediate vertical post B of the frame,
across the top of the smaller aperture B, C, and thence enters through a
stern pipe into the interior of the steamer in the ordinary way. The
added propeller G is considerably smaller than the ordinary one D, but
still as large as can be arranged to work conveniently beneath the main
propeller shaft E and between it and the keel H; and the shaft J of
this smaller propeller G is carried in bearings in the frame B, C, of its
aperture, just as the larger propeller is in its frame, and enters the
steamer by a stern pipe below the other one.
The two propeller shafts E, J, may be connected to one set of engines
or to separate engines of any suitable known arrangement or design.
When one set only of engines is used, the main shaft (E) may be
connected to the smaller shaft (J) by spur gearing provided with
coupling appliances admitting of their being connected or disconnected
at pleasure.
When provision is made for driving the two shafts by separate engines,
these engines may be entirely disconnected or they may be connected by
spur gearing provided with coupling appliances admitting of the smaller
shaft (J) being driven either from the larger or smaller engines.
Provision may also be made for coupling the two propeller shafts with
gearing arranged so that when the smaller engines only are working,
the after or larger propeller may be turned at a comparatively slow rate
corresponding to the reduced speed of ship obtainable with the smaller
engines, and thus be prevented from being a drag on the ship. The
two propellers may be both alike as regards the inclination of their
blades, and be driven in the same direction, or one may be left-handed
and the other right-handed, the two being then driven in opposite
directions. The engines or coupling gearing may be arranged so as to
be capable of making the two propellers propel in opposite directions
when this may be desirable to facilitate the manoeuvring of the ship in
narrow waters or in an engagement in the case of a war steamer. In
ordinary circumstances I intend that both propellers shall be used and
be driven by all the available engine power to ensure the maximum
speed.

page_text: In the event of accident to either set of engines, to either shaft, or to
either propeller, the propeller or engine thereby disabled may be instantly
disconnected and the propelling of the steamer be continued with the
other propeller; and this will admit of the voyage being prosecuted
independently of any assistance from masts and sails or from other
vessels.
My Invention is especially applicable to war ships and floating
batteries from the additional security afforded against complete dis-
ablement of the propelling apparatus, and to the larger class of ocean
steamers of the merchant service engaged in carrying passengers from
the greatly increased speed, security, and comfort which its adoption
will necessarily ensure.
Having thus particularly described my said Invention, and the manner
in which the same is to be performed, I have to state that I do not
restrict myself to the precise details herein described or delineated; but
that what I believe to be novel and original, and claim as the Invention
secured to me by the herein-before in part recited Letters Patent is, the
fitting of a screw steamer with two propellers, both in the vertical plane
of the keel and one immediately in front of the other and below its
shaft, as and for the purposes herein-before described.
In witness whereof, I, the said Thomas Henderson, have hereunto
set hand and seal, this Fifteenth day of August, in the year
my
of our Lord One thousand eight hundred and seventy-two.