Universal Joint

In this Article, we will learn about What is Universal Joint ? It’s Application Advantage, Disadvantage and It’s working with Figure.

what is universal joint ?

A Universal Joint is a mechanical device which is used to joint or coupling the connecting rigid shafts whose axes are inclined to each other.

Universal joint

Note : It is also called U-joint or a Universal Coupling.

A universal-joint, or U-joint, is a mechanical device used to connect two rotating shafts at an angle. It offers flexibility by accommodating misalignment and compensating for axial and radial movements. Universal joints efficiently transmit torque and rotational power, but they can introduce backlash, vibration, and noise. Despite these limitations, they are widely used in various industries for their versatility, cost-effectiveness, and ability to transmit power between non-aligned shafts.

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universal joint cross or coupler

A universal joint coupler, also known as a U-joint coupler or universal joint cross. Function of UJ Cross is to maintain uniform motion between the rotating shafts by coupling the stiff metal rods and allowing shaft to move flexibly in angular directions.

universal joint diagram

Universal joint diagram

parts of universal joint

Parts of universal joint

It is composed of several key parts that work together to enable its function effectively. The main parts of a universal joint include:

  1. Driving Yoke: This is the component attached to the driving shaft or main shaft of the system. It receives the rotational input and transfers it to the universal joint.
  2. Driven Yoke: The driven yoke is connected to the driven shaft or output shaft. It receives the rotational motion from the universal-joint and transfers it to the driven shaft.
  3. Crossed Spider: The crossed spider, also known as the cross-shaped component or cross, forms the central part of the universal-joint. It consists of four arms that intersect at right angles. Each arm contains a trunnion or bearing surface.
  4. Trunnions: The trunnions are the bearing surfaces located at the end of each arm of the crossed spider. They allow the smooth rotation of the spider and facilitate the transfer of torque between the driving and driven yokes.
  5. Bearings: The universal joint incorporates bearings that surround the trunnions. These bearings reduce friction and enable the smooth rotation of the crossed spider and the associated yokes.
  6. Retaining Clips: Retaining clips or circlips are used to secure the bearings in place, ensuring they remain in the correct position within the universal-joint assembly.

These parts work together to allow the universal-joint to accommodate misalignment, transmit torque, and enable angular motion between the driving and driven shafts.

how does universal universal joint works

It consists of a cross-shaped component with bearings at the end of each arm.

When one shaft, referred to as the input shaft, rotates, it causes the cross-shaped component to rotate as well. As the component rotates, the bearings allow it to pivot and accommodate the misalignment between the input shaft and the output shaft.

The rotational motion from the input shaft is transferred to the output shaft through the cross-shaped component and the bearings. As a result, the output shaft rotates at a different angle or orientation than the input shaft.

The design of the universal joint allows it to compensate for angular misalignment between the shafts and also absorb small amounts of axial and radial movements. This flexibility enables the universal-joint to maintain a constant velocity ratio between the input and output shafts, even when they are not aligned in a straight line.

By utilising this mechanism, universal-joints are able to transmit power and torque between non-aligned shafts, making them suitable for applications where flexibility and efficient power transmission are required.

working of Universal joint in automobile with figure

Working of universal joint in automobile

The universal joint, depicted in the diagram above, comprises a driving yoke ‘1’ connected to the gearbox’s main shaft, while a driven yoke ‘3’ is connected to the propeller shaft.

These two yokes are linked through a crossed spider ‘2’, which possesses four arms referred to as trunnions. As the driving shaft rotates, it imparts rotation to the driven shaft while allowing for angular motion. Consequently, power is transmitted from the gearbox to the propeller shaft at an inclined angle.

In essence, these joints serve to establish a flexible connection between two rigid shafts positioned at an angle to each other. They facilitate the transmission of power not only at an angle but also during the continuous variation of this angle.

why does universal joint required in propeller shaft

When a vehicle travels on an uneven road, the differential experiences fluctuations in its position, causing the propeller shaft to also adjust its angle as it rotates.

In such situations, universal joints play a crucial role by enabling the propeller shaft to accommodate these angle changes without interrupting the transmission.

If the differential were directly connected to the gearbox without a universal joint, the connection would fail during the movement of the rear axle. This is because without a universal joint, the system lacks the necessary flexibility to handle the adjustments caused by the uneven road surface.

Universal Joint types

(a)Cross or spider joint (variable velocity joint).

(b) Ball and trunnion joint (variable velocity joint).

(c) Constant velocity joints.

A. Cross or spider joint

The universal joint is composed of two Y-shaped yokes and a crosspiece, commonly referred to as the spider. One yoke is connected to the driving shaft, while the other is connected to the driven shaft.

The crosspiece features four arms, known as trunnions, which are attached to the ends of the yokes. Each arm of the crosspiece is equipped with a needle bearing, allowing the yoke to pivot around the trunnion when the driving and driven shafts rotate together at an angle.

b. ball or trunnion joint

A ball trunnion joint is a unique assembly that combines both universal and slip joints. It consists of a ball-type head securely attached to one end of the propeller or drive shaft.

The assembly includes a pin or cross shaft that is pressed through the shaft end, creating a ‘T’ shape. Within this pin, two steel balls are firmly fitted. This joint enables rotational motion through the interaction of the balls and the pin, allowing for smooth movement. Additionally, the balls have the capability to move axially in a specific direction. It’s important to note that ball and trunnion joints also function as variable velocity joints.

c. Constant velocity joints

A Constant Velocity Joint (CV joint) is a specific type of universal joint that enables both the driving and driven shafts to maintain a constant velocity. This is achieved by positioning the two joints at the same angle.

CV joints are commonly utilised in front-wheel drive vehicles, where maintaining a consistent speed between the driving and driven shafts is crucial. Without the use of CV joints, the speed variation between these shafts would pose challenges to the steering system and lead to excessive tire wear.

a universal joint is used to transmit

universal joint is used to connect two shaft whose axes are inclined to each other.

application of universal joint ?

Universal joints have a wide range of applications across different industries and fields. Some of the key applications of universal joints include:

  1. Automotive Industry: Universal joints are commonly used in the automotive industry, particularly in the drivetrain system. They are found in the drive shafts, propeller shafts, and axle shafts of vehicles. Universal-joints allow for the transfer of rotational power from the engine to the wheels, even when the shafts are misaligned due to suspension movement or steering.
  2. Industrial Machinery: Universal-joints are utilized in various industrial machinery applications, such as conveyors, pumps, mixers, and power transmission systems. They enable the transmission of torque between shafts that are not perfectly aligned, accommodating angular misalignment and compensating for axial and radial movements.
  3. Agriculture: Universal-joints are employed in agricultural equipment, including tractors, combines, and harvesters. They facilitate the transfer of power and torque from the power source to the various components of the machinery, allowing for efficient operation even when the equipment is on uneven terrain.
  4. Marine and Offshore: Universal-joints find application in the marine industry, particularly in propulsion systems, steering mechanisms, and marine engines. They enable the transmission of power between the engine and the propeller shaft, allowing for flexible movement and compensating for the misalignment caused by waves and vessel motion.
  5. Aerospace: Universa-joints are utilized in aerospace applications, such as aircraft control systems, helicopter rotor systems, and spacecraft mechanisms. They enable the transmission of rotational motion between components that may be at different angles or orientations, facilitating maneuverability and control.
  6. Robotics and Automation: Universal joints are employed in robotics and automation systems, where they allow for flexible movement and transmission of rotational motion between different components. They are used in robotic arms, manipulators, and articulated systems, providing the necessary flexibility and range of motion.

These are just a few examples of the diverse applications of universal joints. Their ability to accommodate misalignment and transmit power between non-aligned shafts makes them invaluable in many industries, where flexibility and efficient power transmission are required.

advantages of universal joint

Universal joints offer several advantages that make them widely used in various applications. Some of the key advantages of universal joints include:

  1. Flexibility: Universal joints provide flexibility by allowing the transmission of rotational motion between non-aligned shafts. They can accommodate angular misalignment, making them suitable for applications where the shafts are not perfectly aligned or need to move in different directions.
  2. Compensation for Misalignment: Universal-joints can compensate for axial and radial movements between the connected shafts. This ability to absorb misalignment helps to reduce stress and wear on the shafts and other components, resulting in smoother operation and extended equipment lifespan.
  3. Power Transmission: Universal-joints are capable of transmitting significant amounts of torque and rotational power. They efficiently transfer power from one shaft to another, even when the shafts are at different angles. This makes them suitable for applications that require the transmission of high torque, such as in automotive drive shafts or industrial machinery.
  4. Simple Design: Universal joints have a relatively simple design, consisting of a cross-shaped component with bearings at the end of each arm. This simplicity makes them easy to manufacture, assemble, and maintain. Additionally, their compact size allows for integration into various systems and equipment.
  5. Cost-Effective: Due to their simple design and widespread usage, universal-joints are generally cost-effective compared to other complex power transmission mechanisms. They offer a practical and reliable solution for transmitting rotational motion, making them a popular choice in many industries.
  6. Versatility: Universal joints are versatile and can be used in a wide range of applications. They find use in automotive, industrial, agricultural, marine, aerospace, and robotics industries, among others. Their ability to accommodate misalignment and transmit power between non-aligned shafts makes them adaptable to various mechanical configurations.

While universal joints offer numerous advantages, it’s important to consider their limitations as well. They can introduce some backlash, vibration, and noise due to their design, and they may not be suitable for applications that require constant velocity or very precise motion control. In such cases, alternative mechanisms like constant velocity joints (CV joints) or flexible couplings may be more appropriate.

disadvantages of universal joint

Disadvantages of universal joints:

  1. Backlash: One disadvantage of universal-joints is the presence of backlash, which refers to the slight play or movement between the components. This can result in decreased precision and accuracy in applications that require tight tolerances.
  2. Vibration and noise: Universal-joints can introduce vibration and noise during operation. This can be a concern in applications where smooth and quiet operation is desired, such as precision machinery or noise-sensitive environments.
  3. Limited precision: Universal joints are not as precise as some other power transmission mechanisms. They may exhibit some degree of variability or inconsistency in the transmitted motion, which can be a drawback in applications that require high precision and repeatability.
  4. Speed limitations: Universal joints have speed limitations, especially in high-speed applications. At higher rotational speeds, the centrifugal forces acting on the rotating components can cause additional vibration and stress, potentially leading to failure or reduced performance.
  5. Maintenance requirements: Universal-joints require regular maintenance, including lubrication and inspection, to ensure proper functioning and longevity. The need for periodic maintenance can add to the overall cost and time investment in using universal-joints.
  6. Size constraints: Universal-joints tend to have a bulkier design compared to some other power transmission mechanisms. This can be a limitation in applications where space is limited or where compact and lightweight designs are desired.

It’s important to note that while universal-joints have these disadvantages, they are still widely used in many applications due to their flexibility, cost-effectiveness, and ability to accommodate misalignment. However, in certain specialised applications where precision, high speeds, or low noise levels are critical, alternative mechanisms may be preferred.

Source : Wikipedia

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