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UNIVERSAL JOINT

By

Avanish Rai

Brihaspati Singh

Md. Movazzif

Shahbaz Alam

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Overview

What is universal joint

History

Why universal joint is needed

Construction

Working

Types of universal joint

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What is Universal Joint

Universal joint is the joint which enables the driver shaft to transmit power at varied angles.

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History

The original Universal joint was developed in the sixteenth century by a French mathematician named Cardan.

In the seventeenth century, Robert Hooke developed a cross-type Universal joint, based on the Cardan design.

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Then in 1902, Clarence Spicer modified Cardan and Hooke’s inventions for the purpose of transmitting engine torque to an automobile’s rear wheels. By joining two shafts with Y-shaped forks to a pivoting cruciform member, the problem of torque transfer through a connection that also needed to compensate for slight angular variations was eliminated.

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Why universal joint is needed

In automobiles the rear end of propeller shaft is constantly rising & falling due to flexing of road spring.

Usually the power has to transmit at an angle

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FIG:-

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Construction

A universal joint consist two y shape yokes one on the driving shaft and other on the driving shaft and other on the driven shaft

The four arms of spider are known as trunions

These are assembled into bearing in the end of two shaft yoke

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The driving shaft and driven shaft are at an angle to each other, the bearing in the yoke permits the yoke to swing around on the trunions with each revolutions

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Working

When the driving shaft is rotating the driven

shaft also rotates. At the same time the

universal joint permits angular motion and

propeller shaft can rotate at any angle. Thus the

power is transmitted from gearbox to propeller

shaft at any particular angle.

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Location

One universal joint is attached to the driveshaft at each end.

The front u-joint is also attached to a slip yoke which fits into the tailstock of the transmission.

Some heavy duty vehicles with a two-piece shaft have three u-joints. These vehicles will also have a hanger bearing which may require service at the same time.

Some older 4 wheel drive vehicles have a u-joint at each front wheel also.

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Types of universal joint

Variable velocity joint

i. Cross or spider type

ii. Ring type

iii. Ball & trunion type

Constant velocity joint

Rzeppa

Bendix weiss

Tracta

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Speed variation

As a U-joint transmits torque through an angle, its output shaft speed increases and decreases twice on each revolution.

If a U-joint’s input shaft speed is constant, the speed of the output shaft accelerates and decelerates to complete a single revolution at the same time as the input shaft.

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The greater the angle of the output shaft, the more the velocity will change each shaft revolution.

The input yoke rotates at a steady or constant speed through a complete 360-degree rotation.

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Canceling Angles

o The operating angle of the front U-joint is offset by the one at the rear of the drive shaft.

o When the front U-joint accelerates, causing a vibration, the rear U-joint decelerates causing an equal but opposite vibration.

o The correct angle must be maintained to minimize vibration.

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These vibrations created by the two joints oppose each other and dampen the vibrations from one to the other. The use of canceling angles provides smooth drive shaft operation.

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Reasons for Universal Joint Failure

Lack of lubrication

Pushing another car

Towing a trailer

Changing gears abruptly

Carrying heavy loads

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APPROXIMATE COST OF REPAIR

Depending on vehicle design and load capability, u-joints are relatively cheap.

Usually between $20 - $50 each, it is recommended to replace all u-joints at the same time.

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1-2 hours labour to diagnose and replace 2/3 u-joints.

Special skills and procedures are needed to replace a u-joint without damaging the drive shaft.

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