How does "BVX 2 vertical axis Bivortix"

The first prototype on which Bivortix was mounted was a model of a tugboat, having a length of about 1.70 m, called NEMO.

This model could be remotely controlled and was used to test the functionality of Bivortix; some tests of static bollard pull and some captive tests, to verify its manoeuvre capabilities, have been made in the hydrodynamic laboratories of the University of Trieste.

The results obtained were positive and gave useful information for the future development.

The second prototype was a propeller having an outer diameter of 500 mm, fitted with 12 blades, 6 of which on the outer impeller and 6 on the inner one; the propeller was driven by an external Diesel engine, through an oleodynamic system. The engine and the Bivortix propeller are installed on a boat, called Proteus, designed specifically for the purpose of testing and experiencing the new propulsion system. Proteus was designed specifically to accommodate the Bivortix in three different arrangements and i.e.: stern, bow and a combined configuration.

The main features of Proteus are:

Length over all (m) : 5.430

Breadth (m) : 1.870

Draft (m) :0.34


The propeller can protrude below the hull for a maximum of 0.235 m and it is protected by a flap on the bottom.

An important aspect of the project involved the definition and dimensioning of the mechanical components, that affect respectively :

a) The transmission power from the external axis to the impellers;

b) The contra-rotation of the two crowns, bearing the blades;

c) The joint orientation of the blades on the two crowns

These operations are carried out with the engine running, even at variable speed, and should allow to vary the intensity and direction of thrust.

Increasing the engine power and rpm, the power transmission system had to be redesigned, by removing the causes which produce the greatest clearances between the mechanical components.

During the presentation took place on Thursday, April 28, 2016 at the Auditorium of the Molo IV Trieste, they were present the results achieved by "BVX_2 - Naval vertical axis propeller Bivortix".

It was also performed a demonstration by "PROTEUS" in the basin of the same pier, which highlighted the qualities of manovlabilità of the propulsion system.

With it is possible to move the ship in all directions or to make it rotate on the spot without the aid of the rudder.

It also highlighted the significant reduction of operating time and maneuvering, aimed, in particular, the application in the field of offshore, but also tugs and boats for sailing in shallow water, as water buses and ferries.

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