The oar, the helix, and the paddle-wheel constitute at present the means
of propulsion that are exclusively employed when one has recourse to a
motive power for effecting the propulsion of a boat. The sail
constitutes an entirely different mode, and should not figure in our
enumeration, considering the essentially variable character of the force
utilized.
In all these propellers, we have only an imitation, very often a rude
one, of the processes which nature puts in play in fishes and mollusks,
and the mode that we now wish to make known is without contradiction
that which imitates these the best.
Hydraulic propulsion by reaction consists, in principle, in effecting a
movement of boats, by sucking in water at the bow and forcing it out at
the stern. This is a very old idea. Naturalists cite whole families of
mollusks that move about in this way with great rapidity. It is probable
that such was the origin of the first idea of this mode of operating.
However this may be, as long ago as 1661 a patent was taken out in
England, on this principle, by Toogood & Hayes. After this we find the
patents of Allen (1729) and Rumsay (1788). In France, Daniel Bernouilli
presented to the Académic des Sciences a similar project during the last
century.
Mr. Seydell was the first to build a vessel on this principle. This
ship, which was called the Enterprise, was of 100 tons burden, and was
constructed at Edinburgh for marine fishery. The success of this was
incomplete, but it was sufficient to show all the advantage that could
be got from the idea. Another boat, the Albert, was built at Stettin,
after the same type and at about the same epoch; and the question was
considered of placing a reaction propeller upon the Great Eastern.
About 1860 the question was taken up again by the house of Cokerill de
Seraing, which built the Seraing No. 2, that did service as an excursion
boat between Liége and Seraing. The propeller of this consisted of a
strong centrifugal pump, with vertical axis, actuated by a low pressure
engine. This pump sucked water into a perforated channel at the bottom
of the boat, and forced it through a spiral pipe to the propelling
tubes. These latter consisted of two elbowed pipes issuing from the
sides of the vessel and capable of pivoting in the exhaust ports in such
a way as to each turn its mouth downward at will, backward or forward.
The water expelled by the elbowed pipes reacted through pressure, as in
the hydraulic tourniquet of cabinets of physics, and effected the
propulsion of the vessel. Upon turning the two mouths of the propelling
tubes backward, the boat was thrust forward, and, when they were turned
toward the front, she was thrust backward. When one was turned toward
the front and the other toward the stern, the boat swung around.
Finally, when the two mouths were placed vertically the boat remained
immovable. All the evolutions were easy, even without the help of the
rudder, and the ways in which the propelling tubes could be placed were
capable of being varied _ad infinitum_ by a system of levers.
The Seraing No. 2 had an engine of a nominal power of 40 horses, and
took on an average 30 minutes to make the trip, backward and forward, of
85 kilometers, with four stoppages.
The success obtained was perfect, and the running was most satisfactory.
It was remarked, only, that from the standpoint of effective duty it
would have been desirable to reduce the velocity of the water at its
exit from the propellers.
Mr. Poillon attributes the small effective performance to the system
employed for putting the water in motion. At time of Mr. Seraing's
experiments, only centrifugal force pumps were known, and the theoretic
effective duty of these, whatever be the peculiar system of
construction, cannot exceed 66 per cent., and, in practice, falls to 40
or 50 per cent. in the majority of cases.
It is probable, then, that in making use of those new rotary pumps where
effective duty reaches and often exceeds 80 per cent., we might obtain
much better results, and it is this that justifies the new researches
that have been undertaken by Messrs. Maginot & Pinette, whose first
experiments we are about to make known.
In order to have it understood what interest attaches to these
researches, let us state the principal advantages that this mode of
propulsion will have over the helix and paddle wheel: The width of
side-wheel boats will be reduced by from 20 to 30 per cent., and the
draught of water will be diminished in screw steamers to that of the
hull itself; the maneuver in which the power of the engine might be
directly employed will be simplified; a machine will be had of a
sensibly constant speed, and without change in its running; the
production of waves capable of injuring the banks of canals will be
avoided; the propeller will be capable of being utilized as a bilge
pump; all vibration will be suppressed; the boat will be able to run at
any speed under good conditions, while the helix works well only when
the speed of the vessel corresponds to its pitch; it will be possible to
put the propelling apparatus under water; and, finally, it will be
possible to run the pump directly by the shaft of the high speed engine,
without intermediate gearing, which is something that would prove a very
great advantage in the case of electric pleasure boats actuated by piles
and accumulators and dynamo-electric machines.
[Illustration: NEW STEAMER PROPELLED BY HYDRAULIC REACTION.]
We now arrive at Messrs. Maginot & Pinette's system, the description of
which will be greatly facilitated by the diagram that accompanies this
article. The inventors have employed a boat 14 meters in length by 1.8
m. in width, and 65 centimeters draught behind and 32 in front. The
section of the midship beam is 70 square decimeters, and that of the
exhaust port is 4. At a speed of 2.2 meters per second the tractive
stress, K, is from 10 to 11 kilogrammes. At a speed of 13.5 kilometers
per hour, or 3.75 meters per second, the engine develops a power of 12
horses. The piston is 19 centimeters in diameter, and has a stroke of 15
centimeters. The shaft, in common, of the pump and engine makes 410
revolutions per minute. It will be seen from the figure that suction
occurs at the lower part of the hull, at A, and that the water is forced
out at B, to impel the vessel forward. C and C' are the tubes for
putting the vessel about, and DD' the tubes for causing her to run
backward. Owing to the tubes, C, C', the rudder has but small dimensions
and is only used for _directing_ the boat. The vessel may be turned
about _in situ_ by opening one of the receiving tubes, according to the
side toward which it is desired to turn.
This boat is as yet only in an experimental state, and the first trials
of her that have recently been made upon the Saône have shown the
necessity of certain modifications that the inventors are now at work
upon.--_La Nature_.
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