Azimuth thruster

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There are two major variants, based on the location of the motor:{{cn|date=November 2014}}

1. Mechanical transmission, which connects a motor inside the ship to the outboard unit by gearing. The motor may be diesel or diesel-electric. Depending on the shaft arrangement, mechanical azimuth thrusters are divided into L-drive and Z-drive. An L-drive thruster has a vertical input shaft and a horizontal output shaft with one right-angle gear. A Z-drive thruster has a horizontal input shaft, a vertical shaft in the rotating column and a horizontal output shaft, with two right-angle gears.
2. Electrical transmission, more commonly called pods, where an electric motor is fitted in the pod itself, connected directly to the propeller without gears. The electricity is produced by an onboard engine, usually diesel or gas turbine. Invented in 1955 by Friedrich W. Pleuger and Friedrich Busmann (Pleuger Unterwasserpumpen GmbH), ABB Group's Azipod was the first product using this technology.

The most powerful podded thrusters in use are the four 21.5 MW Rolls-Royce Mermaid units fitted to {{RMS|Queen Mary 2}}.{{cite web| url=https://www.wartsila.com/encyclopedia/term/mermaid-propulsion-unit| title=Mermaid propulsion unit| publisher=Wärtsilä| access-date=1 February 2020}}

Mechanical azimuth thrusters can be fixed installed, retractable or underwater-mountable. They may have fixed pitch propellers or controllable pitch propellers. Fixed installed thrusters are used for tugboats, ferries and supply-boats. Retractable thrusters are used as auxiliary propulsion for dynamically positioned vessels and take-home propulsion for military vessels. Underwater-mountable thrusters are used as dynamic positioning propulsion for very large vessels such as semi-submersible drilling rigs and drillships.

File:BPC Dixmude.jpg Mistral-class amphibious assault ship Dixmude manoeuvering in Jounieh bay; the wake at the stern is perpendicular to the ship, indicating the use of her azimuth thrusters.]]

Primary advantages are maneuverability, electrical efficiency, better use of ship space, and lower maintenance costs.{{Citation needed|date=October 2010}} Ships with azimuth thrusters do not need tugboats to dock, though they may still require tugs to maneuver in difficult places.{{citation needed|date=October 2020}}

The major disadvantage of azimuth drive systems is that a ship with azimuth drive maneuvers differently from one with a standard propeller and rudder configuration, necessitating specialized pilot training.{{citation needed|date=October 2020}} Another disadvantage is they increase the draught of the ship.{{citation needed|date=October 2020}}

English inventor Francis Ronalds described what he called a propelling rudder in 1859 that combined the propulsion and steering mechanisms of a boat in a single apparatus. The propeller was placed in a frame having an outer profile similar to a rudder and attached to a vertical shaft that allowed the device to rotate in plane while spin was transmitted to the propeller.{{Cite book|title = Sir Francis Ronalds: Father of the Electric Telegraph|last = Ronalds|first = B.F.|publisher = Imperial College Press|year = 2016|isbn = 978-1-78326-917-4|location = London}}

The modern azimuth thruster using the Z-drive transmission was invented in 1951 by Joseph Becker, the founder of Schottel in Germany, and marketed as the Ruderpropeller. Becker was awarded the 2004 Elmer A. Sperry Award for the invention.{{cite web |url=http://www.sperryaward.org/awardbooklets/2004%20Sperry%20Award%20Booklet.pdf|title=Presentation of The Elmer A. Sperry Award for 2004|publisher=Sperryaward.org|access-date=24 November 2014}} This kind of propulsion was first patented in 1955 by Pleuger.{{cite web|url=https://patents.google.com/patent/US2714866|title=Patent US2714866 - Device for propelling a ship|access-date=24 November 2014}}

In the late 1980s Wärtsilä Marine, Strömberg and the Finnish National Board of Navigation developed the Azipod thruster with the motor located in the pod itself.{{cn|date=November 2014}}

• {{annotated link|Pleuger rudder}}
• {{annotated link|Cyclorotor}}
• {{annotated link|Voith Schneider Propeller}}
• {{annotated link|Saildrive}}
• {{annotated link|Z-drive}}
• {{annotated link|Outboard motor}}

{{commonscat|Azimuth thrusters}}

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Category:Marine propulsion