Definition and Function

Definition: The upper rudder support is an important component of the ship's rudder system, located at the upper part of the rudder stock. It is mainly used to support the weight of the rudder stock and withstand the radial and partial axial forces generated by the rotation of the rudder stock, ensuring that the rudder stock can rotate stably and achieve precise steering of the ship.

Function:

Support function: bear the weight of the rudder stock itself, prevent the rudder stock from sinking due to gravity, and ensure the stability of the rudder stock in the vertical direction.

Radial force bearing function: When the rudder blade rotates to change the ship's heading, the rudder stock will be subjected to radial forces from water flow, etc. The upper rudder bearing can effectively bear these forces and prevent excessive radial displacement of the rudder stock.

Axial force auxiliary bearing function: Although the axial force in the ship's rudder system is mainly borne by the lower rudder bearing, the upper rudder bearing also shares a part of the axial force, especially when the rudder blades are subjected to axial thrust under special working conditions, the upper rudder bearing can assist in maintaining the axial stability of the rudder stock.

Structural composition

Bearing section:

Rolling bearing type: If it is a rolling rudder bearing, it mainly consists of an inner ring, an outer ring, rolling elements (such as balls or rollers), and a cage. The inner ring is closely matched with the rudder stock, and the outer ring is installed inside the rudder seat. The rolling elements roll between the inner and outer rings to reduce friction when the rudder stock rotates. The retaining frame serves to separate and fix the rolling elements, ensuring even distribution and smooth rolling. The advantage of this structure is its low friction coefficient, which can adapt to higher rotational speeds and certain combinations of radial and axial loads.

Sliding bearing type: For sliding upper rudder bearings, it usually includes bearing shells and bearing seats. The bearing shell is generally made of wear-resistant materials (such as Babbitt alloy, copper alloy, etc.), and its internal surface is in contact with the rudder stock. The bearing seat is used for installing and fixing the bearing shell, and is connected to the ship structure to provide stable support for the rudder stock. Sliding bearings can withstand large radial loads and have a simple structure and low cost.

Lubrication system:

The lubrication system is crucial for both rolling and sliding rudder bearings. The lubrication system can be a simple oil cup, oil tank, or a more complex centralized lubrication system. The function of lubricating oil is to form an oil film between the rudder stock and the bearing, reduce the friction coefficient, minimize wear, and also serve as a cooling and corrosion prevention agent.

Sealing device:

The sealing device of the upper rudder bearing is mainly used to prevent lubricating oil leakage and prevent external impurities (such as seawater, dust, etc.) from entering the interior of the bearing. Common sealing forms include rubber seals and labyrinth seals. Rubber seals fill the sealing gap through their elastic deformation, providing a direct sealing effect; Maze seal uses a series of complex channels to prevent the entry of liquids and impurities, and has a good sealing effect.

working principle

Working principle of rolling rudder support: When the rudder stock rotates, the inner ring rotates together with the rudder stock, and the rolling elements roll between the inner and outer rings, while the outer ring remains stationary and fixed on the rudder support seat. The rolling motion of the rolling element converts the sliding friction between the rudder stock and the rudder support into rolling friction, greatly reducing the frictional force. At the same time, the lubricating oil provided by the lubrication system forms an oil film between the rolling elements and the inner and outer rings, further reducing friction and wear. The sealing device prevents lubricating oil from flowing out and impurities from entering.

Working principle of sliding rudder support: The rudder rotates inside the bearing shell, and lubricating oil forms an oil film between the rudder and the bearing shell, making the friction between the rudder and the bearing shell liquid friction or mixed friction (a combination of boundary friction and liquid friction), thereby reducing friction. The bearing shell is fixed to the ship structure through the bearing seat and bears the force transmitted by the rudder stock. The sealing device ensures the sealing of the lubricating oil and the cleanliness of the interior of the bearing.

advantage

Advantages of rolling rudder bearings:

Low friction loss: The low rolling friction coefficient reduces the power required for the rudder to rotate, effectively reducing the load on the servo, improving its efficiency, and reducing wear on the rudder and bearing components, thus extending its service life.

Adapt to various working conditions: able to withstand a certain combination of radial and axial loads, suitable for rudder support of different types of ships under various navigation conditions, including complex force systems generated during ship turning.

High precision: The rolling motion of the rolling elements is relatively stable, allowing the rudder to have high precision during rotation, which is beneficial for accurate control of the ship's heading.

Advantages of sliding upper rudder support:

Strong bearing capacity: By designing the size and material of the bearing shell reasonably, it can withstand large radial forces and has good applicability for large ships or steering poles that bear large radial loads.

Simple structure and low cost: Compared with the rolling upper rudder bearing, the sliding upper rudder bearing has a simpler structure, no complex rolling components, relatively simple manufacturing process, and lower cost. It is more suitable for some cost sensitive ship application scenarios.

High reliability: With appropriate lubrication, the sliding upper rudder support can work stably and has good adaptability to some small amplitude vibrations and impacts during ship navigation, making it less prone to failures caused by loose components.

Disadvantages and countermeasures

Disadvantages and countermeasures of rolling rudder bearings:

High requirements for lubrication and cleaning: The gap between the rolling elements and the inner and outer rings is small, and high requirements are placed on the cleanliness and supply of lubricating oil. If the lubricating oil is insufficient, the oil quality deteriorates, or impurities enter, it may lead to increased wear and jamming of the rolling elements. The response measures include regular inspection and maintenance of the lubrication system to ensure the quality and supply of lubricating oil, installation of lubricating oil level monitoring devices and fault alarm devices, and timely detection and handling of lubrication problems. At the same time, strengthen the design and maintenance of sealing devices to prevent impurities from entering.

Complex structure and high cost: Compared to sliding upper rudder bearings, rolling upper rudder bearings have a complex structure, including multiple precision components, with higher manufacturing and installation costs. In the design and procurement process, costs can be reduced through optimization of design and bulk procurement.

Disadvantages and countermeasures of sliding rudder bearings:

High friction loss: The sliding friction coefficient is relatively high compared to the rolling friction coefficient, resulting in significant friction loss during the rotation of the rudder stock. In order to reduce friction losses, special attention should be paid to the maintenance of the lubrication system, ensuring the quality and supply of lubricating oil. Bearing materials with good self-lubricating properties should be used, and the wear of the bearing should be regularly checked. Severely worn components should be replaced in a timely manner.

There are certain requirements for installation accuracy: although the sliding upper rudder support structure is simple, there are also certain requirements for installation accuracy to ensure good contact and lubrication between the rudder stock and the bearing shell. During installation, it is necessary to ensure the concentricity between the rudder stock and the bearing shell, otherwise it may lead to increased local wear. During the installation process, appropriate tools and methods should be used to ensure installation accuracy.

Application scenarios

Rolling up rudder bearing application scenarios:

High speed vessels: For high-speed passenger ships, speedboats, and other vessels that require high steering accuracy and response speed, the low friction and high-precision characteristics of rolling rudder bearings can meet their needs, ensuring that the vessel can quickly and accurately turn when traveling at high speeds.

Precise control of ships: For ships such as warships and ocean research vessels that require precise heading control, the stability and accuracy advantages of rolling rudder bearings make them a suitable choice.

Application scenarios of sliding upper rudder support:

Large cargo ships and oil tankers: The rudder of these ships is subjected to significant radial forces, and the high load-bearing capacity of the sliding rudder can effectively support the rudder. Moreover, due to the sensitivity of these ships to cost, the economic advantages of sliding rudder bearings are also quite obvious.

Inland vessels and small vessels: For inland vessels and small vessels, the load borne by their rudder system is relatively small. The simple structure and reliability of the sliding upper rudder support can meet their basic steering support requirements, while the low cost also meets their economic applicability requirements.