Improvements in the Economical Propulsion of Twin-screw Vessels when Working at Low Speeds.
Year: 1891

page_text: Date of Application, 28th Dec., 1891
Complete Specification Left, 27th Sept., 1892-Accepted, 29th Oct., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Economical Propulsion of Twin-screw Vessels
when Working at Low Speeds.
I, MAGNUS SANDISON, of Elswick Shipyard, Newcastle on Tyne, in the
County of Northumberland, Engineer, do hereby declare the nature of this inven-
tion to be as follows:-
The invention consists in the application to the vessel, in addition to the main
engines and propellers which are required for propelling the vessel at full speed, of
a special compound or triple expansion engine and a propeller both of such
dimensions as to develop when working at full power no more than the power
required to propel the vessel at low and economical speeds. The sizes and ratios
of the cylinders and the arrangement of the steam distribution valves are to be
such as to utilise the steam admitted to the cylinders to such advantage that the
requisite quantity would be generated from less coal than would be necessary were
one or both of the main engines used to develop this low power.
This additional engine may be fitted in any convenient position in the vessel and
the additional propeller is to be placed near the stern of the vessel between the
twin screws.
When the small propeller is being used the shafts of the main engines may be
disconnected.
The invention is intended to apply chiefly to cruisers and other vessels of war
where the full power of the main engines is only required at intervals.
Dated this 28th day of December 1891.
CARPMAEL & CO.,
Agents.
COMPLETE SPECIFICATION.
Improvements in the Economical Propulsion of Twin-screw Vessels
when Working at Low Speeds.
I, MAGNUS SANDISON, of Elswick Shipyard, Newcastle on Tyne, in the County
of Northumberland, 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 :-
The invention consists in the application to the vessel, in addition to the inain
engines and propellers which are required for propelling the vessel at full speed, of
a special compound or triple expansion engine and a propeller both of such
dimensions as to develop when working at full power no more than the power
required to propel the vessel at low and economical speeds. The sizes and ratios
of the cylinders and the arrangement of the steam distribution valves are to be
such as to utilize the steam admitted to the cylinders to such advantage that the
requisite quantity would be generated from less coal than would be necessary were
one or both of the main engines used to develop this low power.
This additional engine or "cruising engine as it is preferably called may be
fitted in any convenient position in the vessel and the additional propeller is to
be placed near the stern of the vessel between the twin screws.
When the small propeller is being used the propeller shafts of the main engines
may be disconnected.
The invention is intended to apply chiefly to cruisers and other vessels of war
which are only occasionally propelled at full speed.

page_text: Figure 1 shews in diagram an elevation and Figure 2 a plan of the arrangement.
AA are the main engines driving the twin-screws A¹Â¹. B is the "cruising
engine" driving the propeller B¹!
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
In ships the combination of two sets of main engines driving twin screws with a
third set of engines of small size driving a screw placed between the twin screws,
such auxiliary engine being adapted when working 'at full power to propel the ship
economically at a low rate of speed while the main engines are at rest.
Dated this 29th day of August 1892.
MAGNUS SANDISON.