What Is An Ear Stud?

A trunnion is a common supporting and connecting component in mechanical engineering. It is usually used as a fixed pivot point for rotating or vibrating structures. Its core function is to provide stable support, transfer torque and control the motion trajectory. This paper will explain the concept of relay from five aspects: definition, structure, function, application scenarios and design considerations.
I. Definition of a Trunnion
A trunnion is a short shaft or similar shaft structure, usually connected to the main body of the device by bearings or bushing, forming a pair of rotating shaft necks. The word "axon," derived from the French word "tronçon" (meaning "axon joint"), was originally used to describe the support shaft on cannon carriage and later extended into various mechanical fields.
ii. Typical structure of tropical cyclones
Basic forms
The axons are usually cylindrical, with the ends secured to the supporting structure (e.g. valve body, base) by bearings or bushing.
The surface can be hardened, chromed or otherwise treated to improve abrasion and corrosion resistance.
Connection a Rotating Component (as example of interceptor ball valve)
The ball valve has an ear shaft at either end of the ball. The trunnions is connected to the valve body by bearings, allowing the ball to rotate around the ear shaft.
The auricles and balls are usually formed or fixed in their entirety by high-precision coordination, such as interference fit, to ensure synchronous rotation.
Seal and Lubrication Design
Sealing rings (such as O-rings) may be installed between the shaft neck and bearing to prevent liquid leakage;
Fill bearing bearing cavity Lubricating grease or design a lubrication channel to reduce friction and wear.
III. Key Functions a Trunnion
Support and fixation
The center shaft provides a stable fulcrum for rotating components,such as balls or blast furnace body, to prevent movement deviation or vibration.
For example, when steel is used in blast furnace, the shaft neck supports the body of the furnace, which weighs hundreds of tons, ensuring a smooth and stable tilting.
Torque and Load Transmission
The trunnion transfers torque from the operating mechanism,such as a a valve actuator or blast furnace drive, to the rotary component, allowing movement to open, close or oscillate.
Figure: In high pressure ball valves, trunnion design can reduce operating torque by more than 50% and reduce the load on the actuator. Controlling range of motion
The fixed position of the ear shaft determines the maximum rotation angle of the rotating component (e.g., 90° rotation for the ball valve and 360 degrees for the rotary furnace).
Uses: In space, control the nozzle swing of rocket engine nozzles with otolaryngology to flight attitude adjustment.
Reduce friction and wear
The design of bearings and shafts (such as rolling bearings and sliding bearings) greatly reduces friction coefficient and extends the service life of the equipment.
Case study: In offshore platform valves, self-lubricating bearings are used on the trunnions, with maintenance intervals extending to more than five years.
IV. INTRODUCTION Typical application of Trunnion
Valve
Cylindrical ball valve: Cylindrical ball valve is fixed, suitable for high pressure, large diameter (e.g., oil pipelines, LNG terminal, etc.).
Fixed ball valve: The trunnion and valve seat work together to achieve bidirectional sealing, in line with API 6D and other standards.
Metallurgy
Rotary Furnace Trunnion: support for the steelmaking furnace, high temperature resistance (>1600°C), heavy load (hundreds of tons), frequent start and stop.
Electric Arc Furnace Trunnion: control furnace inclination, feed and steel output.
Aerospace
Rocket Engine Nozzle Trunnion: The nozzle swings to adjust thrust direction through hydraulic or electric actuators.
Satellite solar panel configuration mechanism: Relay serves as a hinge for precisely configuring and locking solar panels.
Construction Machinery
Crane boom: Connect boom to rotary platform, transfer crane weight, control boom angle.
Concrete Concrete Pump Boom Trunnion: Supports the rotation and extension of multi-knotted boom with a range of up to 360°.
Energy Equipment
Wind Turbine Yaw System Trunnion: supports the nacelle and controls its horizontal rotation, keeping the blades in line with the wind direction.
Nuclear power plant cooling pump main pipe: in high temperature, high pressure and radiation stable operation to ensure reactor safety. V. Key design considerations for Journal Bearings
Material Selection
High strength materials selected according to conditions of use:
Alloyed steel (e.g. 42CrMo4): suitable for high pressure and heavy loading applications;
Stainless steel (e.g. 316L): suitable for chemical industries with high corrosion resistance requirements;
Heat-resistant alloys (e.g., Inconel 718): used in high-temperature environments (e.g. aerospace).
Structural Optimization
Finite Finite Element Analysis used to optimize the journal bearing shape and reduce stress concentration.
Use hollow structures or light holes to reduce weight (e.g. in aerospace applications).
Lubrication and sealing
Design lubrication channels or use of self-lubricating bearings (e.g., graphite bronze bushings);
Install sealing devices (e.g., labyrinth seals, mechanical seal) to prevent liquid leakage or contamination.
Installation and maintenance
Strict control of clearance between journal bearing and bearing structure (typically H7/h6);
Periodically check bearing wear, lubrication status and sealing performance and replace damaged parts in a timely manner.
VI. INTRODUCTION Differences between Journal Bearings and Similar Components
The Difference betweenTypical Application of Core Function of Component and Journal Bearings
Bearing supports rotating parts and transfers torque valves, rotary kilns, cranes with emphasis on fixed support and bidirectional torque transmission
Hinges connect two parts, allowing for flexible rotation of the relative rotational door, window, and robotic arm joints, usually unaffected by heavy loads
Pins provide fixed connection and transmit axial force Linkage mechanisms, suspension systems is mainly used for fixed connection, rotation angle is limited
Transmission shaft supports rotating parts and conveys torque motor and gearbox focus on torque transmission efficiency, usually without fixed support point