IMPROVEMENTS IN PROPELLING SHIPS OR OTHER VESSELS
Year: 1863

page_text: PROVISIONAL SPECIFICATION left by Robert Griffiths at the Office of
the Commissioners of Patents, with his Petition, on the 16th November
1863.
I, ROBERT GRIFFITHS, of Mornington Road, Regent's Park, in the County
of Middlesex, Engineer, do hereby declare the nature of the Invention for
"IMPROVEMENTS IN PROPELLING SHIPS OR OTHER VESSELS," to be as follows:-
This Invention has for its object improvements in arranging the position of
the screw or screws employed for propelling ships or other vessels, and is
especially applicable to those vessels which have a light draft of water.
There has hitherto been great difficulty in or indeed no possibility of
getting an adequate speed in proportion to the power employed in ships or
vessels of light draft when combined with broad flat bottoms and full ends,
owing to the screw, as at present arranged and employed for propelling, causing
the water to be driven away from the stern of the vessel faster than it can
flow under the "counter" of the ship to take the place of that driven away,
and also owing to the pressure of water per square inch on the screw blade or
blades being so small through the small amount of immersion of the screw
propeller. These causes, separately or combined, have the effect of wasting a
large proportion (in many cases as much as three-fourths) of the power
employed, the part wasted being occupied in what is known as "grinding or
churning the water." Now, my Invention is intended to obviate this difficulty
& loss, and to efficiently use up the power employed however light the draft
of water may be; and for the purpose of carrying out my improvements I
take a screw of suitable diameter, and mount it by suitable means attached

page_text: to the stern post or under the counter at an angle of about 45° (or other
suitable angle of inclination) to the upright stern post, the end of the screw
placed at such angle looking downwards and towards the bow of the vessel.
A short shaft passes through the screw and into the body of the vessel, and
on the end of such short shaft within the vessel suitable gearing is applied to
connect it with the steam engines or other power employed for propelling the
vessel. By placing the screw at an angle, as above described, the water is
drawn more directly from under the vessel, and a screw of much larger
diameter may be employed. I also in some cases employ two screw propellers
placed and arranged to work at an angle, as before described, one on each side
of the stern post and under each "counter," by which means I am enabled to
use larger screws, and thus obtain a much better flow of water under the
"counter" of vessels so propelled. These screws are connected to the steam
engines or other motive power by bevil wheels and other suitable gearing, as
is well understood, for giving motion to screw propellers.
Another method in which I arrange and apply these screws is to take a
vessel fitted with a screw in the ordinary manner in the stern of the ship, and
in addition thereto I fix two of the inclined screws arranged, as above described,
under the "counters" of such vessel, the whole of the three screws being
connected by any suitable gearing, one form of which may be a plate or
forging, having suitable bearings connecting three cranks in the three shafts
with a crank on the main engine shaft, and thus communicating the motion
to the three shafts simultaneously, or each screw may be driven by separate
engines if desired. The effect of this arrangement of screws is to draw the
water from underneath the vessel, and so propel the same by means of the
inclined screws, and also to supply water to the upright or ordinary screw,
which would otherwise, as before stated, be working with a short supply.