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 A Universal Joint is a type of joint or coupling that links rigid rods with bent axes and is typically used in shafts that convey rotating motion. It is made up of a pair of hinges that are near together and connected by a cross shaft that is 90 degrees to each other.

Greetings, friends! You've probably heard of Universal Joint and Slip Joint before. In this essay, we'll go over all there is to know about Universal Joints and Slip Joints. In this article, we will look at the following topics: 

TABLE OF CONTENT

  • What Is Universal Joint
  • Working of Universal Joint
  • Types of Universal Joint
  • Function of Universal Joint
  • Materials Used For Universal Joint
  • Applications of Universal Joint
  • Advantages and Disadvantages
  • Slip Joint
  • Function Of Slip Joint\

WHAT IS A UNIVERSAL JOINT?

In the history of the universal joint, Robert Hooke is credited with developing the 'Hooke's Joint' or 'Universal Joint.' Universal joints are also known as universal couplings, U-joints, Cardan joints, Spicer joints, and Hardy Spicer joints.

Universal Joints are mostly used to link two rigid shafts at an angle in a flexible manner. It allows for the transmission of power that is continually changing. It is used to transmit rotary motion by connecting the propeller shaft to the gearbox shaft.

The transmission of power under varying conditions is impossible without using a flexible device or universal joint. This flexible device is also used in vehicles having coupling shafts between clutch and gearbox, between main gearbox and auxiliary gearbox and also on driving shafts of the driven front axle.


WORKING OF UNIVERSAL JOINT

In the case of a car, the gearbox is fixed in place. The position of the rear axle is constantly modified due to the action of the road springs, and the allowance is supplied if the gearbox is mounted to the rear axle through a propeller shaft.

Two yokes make for a universal joint. Each end of the shaft has a yoke attached to it. A centre or connecting cross piece connects the two yokes. With the change in angularity between shafts, the connecting cross piece will turn the yoke bearings. If the shafts are working at an angle, they do not transmit motion equally.

Therefore, the driven shaft increases to the maximum and then it decreases to the minimum. The rise and fall of the driven shaft occurs twice as the pivot pin rotates through different planes in each revolution.

TYPES OF UNIVERSAL JOINT

1. Variable Velocity Joints

  • Cross or Spider Type
  • Ring Type
  • Ball And Trunnion Type
2. Constant Velocity (CV) Joints

  • Rzeppa
  • Bendix Weiss
  • Tracta

1. Variable Velocity Joints

Even though each component of a revolution is at the same rpm, both the driven and driving shafts do not revolve at the same speed in this scenario. The driven and driving shafts should be aligned in a straight line so that they rotate at the same speed during each revolution. However, it will not be possible in any autos in practise. The drive shaft is slanted at all times.

If the driven and driving shafts are at an angle, the driven shaft will be half a revolution slower than the driving shaft and half a revolution quicker than the driving shaft. As a result, the driven shaft's average speed is the same as the driving shaft's. The speed variation in the driven shaft grows as the universal joint's flex angle increases.

The yoke on the shaft connecting to the universal pairs should not be in different planes if two variable speed universal pairs are utilised in two drive lines. It is responsible for balancing the speed variances.

Variable Velocity Joints are following These Types.

  • Cross or spider type
  • Ring type
  • Ball and trunnion type

Cross or Spider Type :

A cross or spider connects the two yokes in universal joints, one of which is attached to the driving shaft and the other to the driven shaft at right angles to each other. Between the yokes and the cross ends are needle bearings. This sort of joint is commonly seen in driving shafts.

Ring Type :


A flexible ring is used in this sort of joint. Two or three armed spiders adorn the shaft. The arms are bolted to the flexible ring's opposite faces. One spider's arms are positioned in the middle of the other's arms. To give enough strength, the flexible ring is composed of one or more rubber rings. Instead of cloth rings, a number of tiny steel discs are employed. The axial movement of the shaft is sufficient thanks to this joint. It smooths out torque fluctuations and doesn't need to be lubricated. The biggest disadvantage is that the ring does not last for a long time.

Ball and Trunnion Type :

This kind uses a combination of universal and slip joints in a single assembly. In the end of a universal joint shaft, a pin or cross shaft is joined across in a 'T' shape. At each end of the cross shaft, a ball is fixed on the needle bearings. The entire assembly moves freely in grooves drilled into the joint's exterior body. The strong spring prevents the shaft from moving too far in one direction. The trunnion, balls, and cross shaft are used to convey power. Rolling the ball in one direction causes the bending moment. By moving balls lengthwise in trunnion grooves, it can also be done in the opposite direction. The leather or rubber boot covers the open end of the shaft.

2. Constant Velocity Joints

The driven shaft revolves at the same speed as the driving shaft during each segment of the revolution at any degree of flex with this type of joint. These joints are mostly utilised to transmit power over large angles in front drive axles. In the propeller shafts of Cadillac cars, ball and socket constant velocity joints are used.

Constant Velocity Joints are following These Types.

  • Rzeppa
  • Bendix Weiss
  • Tracta

Rzeppa :


It is made up of internal and external spherical ball races with grooves cut parallel to the shaft. On the spherical raceway, steel balls are put in grooves. The torque is transferred from one race ball to the next. Shafts turn at the same speed due to the circular arrangement of balls.

Bendix Weiss :


This sort of joint works on the basis of driving through balls in a circle around a sphere. In close-fitting yokes, four numbers of driving balls are positioned in machined races. As an inner race, a fifth or centre ball is held between two yokes. In the same way as the Rzeppa joint, the driving balls are placed in a circle. The balls' aligning movement creates a joint with a constant velocity.

Tracta :


This joint is different from the other two. This joint has four yokes, two of which are fastened to shafts and the other two of which float in the joint's centre. The yokes' mating portions are shaped like circle segments. A constant velocity joint is provided by both the circular segments and the floating movement of the two yokes.

FUNCTION OF UNIVERSAL JOINT

Universal joints are used for connecting two shafts inclined to one another at angle and also for transmitting the rotary motion from engine to road wheels throughout the variations in rear axle position with respect to gearbox and chassis.

So the universal joints are used at the front and rear end of the propeller shaft which transmit the power to the wheels even if the heights of transmission and rear axle are different. Also whenever the axle moves up and down due to road irregularities, the angle of drive changes continuously and the universal joint allows transmission of power and rotary motion at a varied angle.

Materials Used For Universal Joints

Universal joints can be made from almost any material depending on the application.

Common materials used include stainless steel, steel, naval brass and other similar alloys to handle greater torque and temperature.

Plastics and thermoplastics are also used to create universal joints as they have greater rust and corrosion resistance as well as electrical and magnetic insulation in applications where this is required.

APPLICATIONS OF UNIVERSAL JOINT

  • Universal joints vary based on their material composition, hub type and the applications for which they are designed, it is a positive mechanical joint that is used for connecting shafts.
  • Universal Joint is most commonly found in the propeller shaft of rear wheel drive cars.
  • Specific applications of universal joints include aircraft, appliances, control systems, electronics, Instrumentation, textile machinery, medical and optical equipment, radios, weapons, sewing machines and tool drives.

Advantages And Disadvantages Of Universal Joint

Advantages

  1. Universal coupling is more flexible than knuckle joint.
  2. It facilitates torque transmission between shafts which have angular misalignment.
  3. It is cheap and cost-effective.
  4. It is simple to be assembled and dismantled.
  5. Torque transmission efficiency is high.
  6. The joint permits angular displacements.

Disadvantages

  1. Wear may occur if the joint is not properly lubricated.
  2. Maintenance is often necessary to avoid wear.
  3. Universal joint produces fluctuating motion
  4. It does not support axial misalignment.

WHAT IS SLIP JOINT

To compensate for this difference in length, a Slip Joint or Sliding Joint is utilised between the propeller shaft and the universal joint connecting the propeller shaft. It also helps to deliver power from the engine to the rear axle at the same time. A slip joint is not required in cars with torque tube drives.

As previously indicated, the propeller shaft is inclined downward from the transmission main shaft to the back axle. When the axle rises as the rear springs are compressed and when the axle returns to its original position, the propeller shaft will be shortened and lengthened again.

The male splined end of the main shaft slides into the appropriate grooves with the female part of the joint to form the joint. The universal joint hub and the feminine part are inextricably linked. The splines allow the slip joint to transmit power while sliding, accounting for any changes in the propeller shaft's length.


FUNCTION OF SLIP JOINT

The spring compresses or expands as the differential with the rear axle housing and the wheel moves up and down if the rear wheel gets in front of the bump. This not only alters the angle of the propeller shaft, but also its length.

As a result of the slip joint, the effective length of the propeller shaft might vary depending on the road conditions. The propeller shaft will buckle or brake if there is no slip joint.

FAQ: What Is Universal Joint?

A universal joint is a joint or coupling that connects rigid rods whose axes are bent to each other, and are commonly used in shafts that transmit rotary motion. It consists of a pair of hinges placed close together, connected by a cross shaft, oriented at 90 ° to each other. A universal joint is not a constant-velocity joint

Q2. What is a universal joint used for?

A universal joint is a type of mechanical device that is used in many applications to propagate rotation through slightly incorrectly shaped shafts. Misalignment correction is limited by the design of the shaft, but can be amplified by the use of multiple universal joints.

Q3. Why is there no need for a slip joint in a torque tube drive

The sliding joint is not necessary because the propeller shaft and pinion shaft will rotate in the same center in the torque tube drive.

Q4. What Is Slip Joint?

A Slip Joint or Sliding Joint is used between propeller shaft and universal joint connecting the propeller shaft to compensate for this change of length and it helps to transmit the power from engine to rear axle at the same time. In cars having a torque-tube drive, a slip joint is not necessary.

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