An azimuth thruster is a configuration of marine

propeller A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working flu ...

s placed in pods that can be rotated to any horizontal angle (

azimuth An azimuth (; from ) is the horizontal angle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system. Mathematically, the relative position vector from an observer ( origin) to a point ...

), making a

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...

redundant. These give

ship A ship is a large watercraft, vessel that travels the world's oceans and other Waterway, navigable waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research and fishing. Ships are generally disti ...

s better maneuverability than a fixed propeller and rudder system.

Types of azimuth thrusters

There are two major variants, based on the location of the motor: # Mechanical transmission, which connects a motor inside the ship to the outboard unit by

gear A gear or gearwheel is a rotating machine part typically used to transmit rotational motion and/or torque by means of a series of teeth that engage with compatible teeth of another gear or other part. The teeth can be integral saliences or ...

ing. 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. # 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 A gas turbine or gas turbine engine is a type of Internal combustion engine#Continuous combustion, continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas gene ...

. Invented in 1955 by Friedrich W. Pleuger and Friedrich Busmann (Pleuger Unterwasserpumpen GmbH),

ABB Group ABB Group is a Swedish-Swiss multinational electrical engineering corporation. Incorporated in Switzerland as ABB Ltd., and headquartered in Zurich, it is dual-listed on the Nasdaq Nordic exchange in Stockholm, Sweden, and the SIX Swiss Exch ...

'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 . Mechanical azimuth thrusters can be fixed installed, retractable or underwater-mountable. They may have fixed pitch propellers or

controllable pitch propeller Controllability is an important property of a control system and plays a crucial role in many regulation problems, such as the stabilization of unstable systems using feedback, tracking problems, obtaining optimal control strategies, or, simply p ...

s. 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 Semi-submersible may refer to a self-propelled vessel, such as: *Heavy-lift ship, which partially submerge to allow their cargo (another ship) to float into place for transport *Narco-submarine, some of which remained partially on the surface *S ...

drilling rig A drilling rig is an integrated system that Drilling, drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to ...

s and

drillship A drillship is a merchant vessel designed for use in exploratory offshore drilling of new oil and gas wells or for scientific drilling purposes. In recent years the vessels have been used in deepwater and ultra-deepwater applications, equipped ...

Advantages and disadvantages

Primary advantages are maneuverability, electrical efficiency, better use of ship space, and lower maintenance costs. Ships with azimuth thrusters do not need

tugboat A tugboat or tug is a marine vessel that manoeuvres other vessels by pushing or pulling them, with direct contact or a tow line. These boats typically tug ships in circumstances where they cannot or should not move under their own power, suc ...

s to dock, though they may still require tugs to maneuver in difficult places. 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. Another disadvantage is they increase the draught of the ship.

History

English inventor

Francis Ronalds Sir Francis Ronalds Fellow of the Royal Society, FRS (21 February 17888 August 1873) was an English scientist and inventor, and arguably the first History of electrical engineering, electrical engineer. He was knighted for creating the first wo ...

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. 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. This kind of propulsion was first patented in 1955 by Pleuger. 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.

References

{{DEFAULTSORT:Azimuth Thruster Marine propulsion

Types of azimuth thrusters

Advantages and disadvantages

History

See also

References