Aux 1 Unit 9 Q1

A two-ram steering gear is a type of hydraulic steering system commonly used on larger vessels, including superyachts. It utilizes two hydraulic cylinders (rams) to generate the mechanical force necessary to move the rudder and control the vessel’s direction.  

1. Steering Gear Hydraulic Systems – TSPS Engineering Manual – Massachusetts Maritime Academy

Key Components:

1. Hydraulic Rams:
   • Two hydraulic cylinders, typically mounted horizontally on either side of the tiller or rudder stock.
   • Each ram consists of a piston and a cylinder barrel.
   • The piston is connected to the tiller or rudder stock via a crosshead.
2. Hydraulic Power Unit (HPU):
   • Supplies pressurized hydraulic fluid to the rams.
   • Consists of a pump (often a variable displacement pump), a reservoir, valves, and other control components.
3. Control System:
   • Includes a steering wheel or joystick on the bridge, a control unit, and various valves and sensors.
   • Transmits the helmsman’s steering commands to the HPU and rams.
4. Tiller or Rudder Stock:
   • The tiller is a large lever arm connected to the rudder stock, which in turn is connected to the rudder.   1. Tillers | CJR Propulsion www.cjrprop.com
   • The rams act on the tiller or directly on the rudder stock to move the rudder.
5. Feedback System:
   • Sensors provide feedback on the rudder’s position to the control system, allowing for accurate steering and autopilot functionality.

Operation:

1. Steering Command: The helmsman turns the steering wheel or moves the joystick, sending a signal to the control system.   1. Steering Gear in Ship — Working , Applications and it’s Types, Construction – Medium medium.com
2. Control Signal: The control system processes the signal and directs the HPU to pump hydraulic fluid to the appropriate side of the rams.
3. Ram Movement:
   • Fluid pressure causes the piston in one ram to extend, pushing the tiller or rudder stock in one direction.
   • Simultaneously, fluid is drained from the other ram, causing its piston to retract.
4. Rudder Movement: The movement of the tiller or rudder stock turns the rudder, causing the vessel to change direction.
5. Feedback: Sensors monitor the rudder’s position and send feedback to the control system, ensuring the rudder moves to the commanded angle.
6. Hydraulic Lock: When the steering wheel or joystick is held steady, the control system stops the flow of fluid to the rams, effectively locking them in place and holding the rudder at the desired angle.

Advantages of Two-Ram Steering Gear:

• High Power and Torque: Can generate significant force to move large rudders on bigger vessels.
• Precise Control: Offers accurate and responsive steering control.
• Redundancy: The presence of two rams provides some level of redundancy in case one ram fails.
• Compact Design: Relatively compact compared to other steering gear systems.

Disadvantages:

• Complexity: More complex than some other systems, requiring specialized maintenance and knowledge.
• Potential for Leaks: Hydraulic systems are prone to leaks, requiring regular inspection and maintenance.

Applications:

• Commonly used on larger vessels, including superyachts, commercial ships, and tankers.

In summary, two-ram steering gear systems are a reliable and powerful solution for controlling the direction of large vessels. Their ability to provide precise control and handle significant loads makes them well-suited for demanding marine applications.

Spherical bearings, also known as spherical plain bearings or self-aligning bearings, are a type of bearing that allows for rotational movement in multiple directions. They consist of an inner ring (or ball) with a spherical outer surface that fits into a spherical housing, enabling angular misalignment between the shaft and the housing.  

1. Spherical bearing – Wikipedia

2. Spherical plain bearings for flexible movement | ASKUBAL

Key Features:

• Multi-directional Movement: Spherical bearings accommodate both rotational and angular movement, meaning the shaft can rotate freely while also tilting or swiveling within a certain range.   1. Understanding Features and Applications of Spherical Bearings (Also Known As Ball Joint Bearings) | ISK BEARINGS iskbearing.com
• Self-Aligning: This self-aligning capability is crucial in applications where misalignment or shaft deflection is likely to occur. It prevents excessive stress and wear on the bearing and surrounding components.   1. Self-Aligning Ball Bearings: Exploring Applications and Recent Innovations – PIB Sales pibsales.com2. How Spherical Bearings Improve Equipment Longevity in Harsh Environments www.metcocal.com
• High Load Capacity: Spherical bearings can handle both radial (perpendicular to the shaft) and axial (along the shaft) loads, making them suitable for a variety of applications.   1. Spherical roller bearings | SKF www.skf.com
• Low Friction: They offer low friction during operation, contributing to smoother movement and reduced energy losses.   1. Spherical Roller Bearings Reduce Friction and Allow Smoother Rotation www.bmcbearing.com

Types:

• Radial Spherical Plain Bearings: These bearings support primarily radial loads and allow for angular misalignment. They typically consist of a spherical inner ring and an outer ring with a concave spherical race.   1. Radial Spherical Plain Bearings | Bushings – The Timken Company www.timken.com2. Radial spherical plain bearings – SKF www.skf.com
• Spherical Roller Bearings: These bearings also accommodate radial and axial loads and misalignment but use rolling elements (rollers) between the inner and outer rings, further reducing friction and increasing load capacity.

Materials:

• Inner and Outer Rings: Commonly made from steel alloys for strength and durability.
• Rolling Elements (if present): Also made from hardened steel.
• Bearing Liners: May be lined with self-lubricating materials like PTFE or composite materials to reduce friction and wear.

Applications on a Vessel:

• Engine Mounts: Accommodate engine movement and misalignment due to vibrations and structural flex.
• Steering Systems: Used in rudder linkages and other steering components to allow for angular movement while supporting loads.
• Deck Machinery: Found in cranes, winches, and other deck equipment where misalignment and articulation are required.
• Stabilizer Systems: Enable the movement and adjustment of stabilizer fins.
• Shaft Couplings: Compensate for misalignment between shafts.

Advantages:

• Accommodate Misalignment: Their self-aligning capability is essential in situations where perfect alignment between the shaft and housing is difficult to achieve or maintain.   1. Self-Aligning Ball Bearings: Exploring Applications and Recent Innovations – PIB Sales pibsales.com
• High Load Capacity: They can handle substantial loads, both radial and axial.   1. Spherical roller bearings | Schaeffler medias medias.schaeffler.us
• Low Friction: They offer smooth movement with minimal friction and wear.   1. Spherical Roller Bearings Reduce Friction and Allow Smoother Rotation www.bmcbearing.com
• Versatility: Suitable for a wide range of applications requiring multi-directional movement.

Disadvantages:

• Limited Speed: They are generally not suitable for high-speed applications due to the sliding contact between the inner and outer rings.
• Maintenance: Require regular lubrication and inspection to ensure proper function and prevent wear.   1. Spherical plain bearings requiring maintenance – SKF www.skf.com

In conclusion, spherical bearings are valuable components in marine applications where misalignment, articulation, and high load-carrying capacity are required. Their ability to accommodate movement in multiple directions while minimizing friction makes them ideal for various systems on board vessels, contributing to their smooth and reliable operation.

In a two-ram steering gear system with spherical bearings, the arrangement of rams and tiller focuses on efficient power transmission while accommodating the necessary movement and flexibility for steering. Let’s break down this arrangement and the associated fittings:

Arrangement of Rams and Tiller:

• Rams:
  • Two hydraulic cylinders (rams) are positioned horizontally, typically on either side of the tiller.
  • They are mounted securely to the vessel’s structure, often on sturdy foundations or bedplates.
  • Each ram consists of a piston rod connected to a crosshead.
• Crossheads:
  • The crossheads are attached to the ends of the piston rods.
  • They provide a connection point between the rams and the tiller.
• Spherical Bearings:
  • These bearings are located at the connection points between the crossheads and the tiller.
  • They allow for angular movement (tilting or swiveling) between the crossheads and the tiller, accommodating any misalignment or deflection that might occur during rudder movement.
• Tiller:
  • A large, sturdy lever arm, usually made of cast or forged steel.
  • It’s keyed or otherwise securely attached to the rudder stock, which in turn is connected to the rudder.   1. Rudderstock – Wärtsilä www.wartsila.com
  • The tiller’s arms extend outward, with spherical bearings mounted at their ends to connect to the crossheads.

Fittings:

• Hydraulic Connections:
  • Each ram has hydraulic connections for supplying and returning pressurized hydraulic fluid.
  • These connections typically involve high-pressure hoses or pipes with appropriate fittings to ensure leak-free operation.
• Seals and Gaskets:
  • Seals are used on the piston rods and other moving parts to prevent fluid leakage from the rams.
  • Gaskets are used at the flange connections between the rams and the piping to ensure a tight seal.
• Position Sensors:
  • Sensors, often linear transducers or rotary encoders, are mounted on the tiller or rudder stock to measure the rudder angle and provide feedback to the control system.
• Limit Switches:
  • Switches may be installed to detect the maximum rudder angle (hard-over) in both port and starboard directions, preventing overtravel and potential damage.
• Relief Valves:
  • Pressure relief valves are incorporated into the hydraulic system to prevent excessive pressure buildup, protecting the rams and other components from damage.
• Filters:
  • Hydraulic filters are used to remove contaminants from the hydraulic fluid, ensuring the longevity and smooth operation of the system.   1. The Essential Guide to Hydraulic Filters chasefiltercompany.com

Benefits of this arrangement:

• Efficient Power Transmission: The two rams, acting on opposite sides of the tiller, provide balanced and efficient power transmission for moving the rudder.
• Accommodates Misalignment: The spherical bearings allow for angular movement, compensating for any misalignment or deflection in the system and preventing excessive stress on the components.
• Compact Design: This arrangement is relatively compact, making it suitable for installation in limited spaces.

Operational Considerations:

• Regular Maintenance: Regular inspection and maintenance of the rams, bearings, seals, and other components are essential to ensure the system’s reliability and prevent leaks or malfunctions.
• Hydraulic Fluid Quality: Using the correct type and viscosity of hydraulic fluid and maintaining its cleanliness are crucial for optimal performance and longevity of the system.

In conclusion, the arrangement of rams and tiller in a two-ram steering gear with spherical bearings is designed for efficient power transmission, flexibility, and reliability in controlling the vessel’s rudder. The use of spherical bearings and other key fittings contributes to the system’s ability to handle heavy loads and accommodate misalignment, ensuring safe and responsive steering even in challenging conditions.

Spherical bearings are required on the ram ends of a two-ram steering gear system for the following reasons:

1. Accommodate Misalignment:

• Structural Flex: As the vessel moves through waves and encounters various forces, the ship’s structure experiences some degree of flex and deformation. This can lead to slight misalignment between the rams and the tiller.
• Thermal Expansion: Temperature changes can also cause components to expand or contract, potentially creating misalignment in the system.
• Wear and Tear: Over time, wear and tear in the system can lead to slight changes in alignment.
• Prevent Binding and Stress: Spherical bearings allow for angular movement (tilting or swiveling) between the ram’s crosshead and the tiller, accommodating this misalignment and preventing binding or excessive stress on the components. This ensures smooth and efficient operation of the steering gear.

2. Allow for Rudder Movement:

• Angular Displacement: As the rudder moves from side to side, the tiller also experiences angular displacement.
• Smooth Articulation: Spherical bearings allow for this angular movement, ensuring the rams can push and pull the tiller effectively throughout the rudder’s full range of motion.

3. Reduce Friction and Wear:

• Low Friction: Spherical bearings have a low coefficient of friction, minimizing friction between the moving parts and reducing wear and tear. This contributes to the longevity and reliability of the steering gear system.

4. Compact Design:

• Space Efficiency: Spherical bearings are relatively compact, allowing for a more space-efficient design of the steering gear assembly. This is especially important in the confined spaces often found on board vessels.

Alternative Solutions:

While other types of bearings, like plain bearings or roller bearings, could theoretically be used, they lack the multi-directional movement capability of spherical bearings. This would make them less effective in accommodating misalignment and could lead to increased stress, wear, and potential binding in the system.

In Summary:

Spherical bearings are essential components in two-ram steering gears because they:

• Accommodate misalignment caused by structural flex, thermal expansion, and wear and tear.
• Allow for smooth articulation of the tiller during rudder movement.
• Reduce friction and wear, improving system efficiency and longevity.
• Contribute to a compact and space-efficient design.

By enabling these functions, spherical bearings play a crucial role in ensuring the reliable, efficient, and safe operation of the steering gear system, allowing for precise control of the vessel’s direction even in challenging conditions.