1.0 INTRODUCTION

1.1 HISTORY AND DEVELOPMENT OF SHAFTS

A careful examination into the modern drive these days most

especially in a front wheel drive (FWD) through critical analysis of the

causes of failure of front shaft drive was as a result of either

mechanical fault or lack of proper maintenance and environmental

factors.

The reason that necessitated this research cannot be over

emphasized as it has become apparent that 21st century automobile

cars are driven using front wheel drafts.

A drive shaft also referred as a propeller shaft or cardan shaft is a

mechanical part that translates the torque generated by a vehicles

engine into usable motive force to propel the vehicle. Physically a

drive shaft is tubular in design with an outside metal housing that

protects an interior metal cylinder which spins at a frequent governed

by engine output. Depending on the engine and drive configuration of

a vehicle be it automobile boat or motor cycle one or more drive

shafts may work cooperatively to turn engine power into motion.

In a Front Wheel Drive (FWD) vehicle two drive shafts emanate from

the transmission connecting to each front wheel. As opposed to

Universal - joints drive shafts on FWD cars usually have

constant-velocity or CV joints that allow for articulation of the wheels.

CV joints are generally more flexible and require less frequent

maintenance than U-joints making them suitable for FWD

applications where the wheels that receive power are also the ones

responsible for steering.

In general front wheel drive shafts in vehicle transfer the drive

directly from the differential to the front wheels. A short inner stub

shaft is splined to the differential side gear and an outer stub shaft is

splined to the front wheel lub. Each stub shaft has a yoke or housing

to accommodate a universal joint at end of a connecting intermediate

shaft. Universal joint let the shaft keep rotating while allowing for

changes due to suspensions movement such as shaft length and

horizontal angle and shaft angle as the steering turns.

Constant-velocity universal joints are normally used to transfer power

smoothly between the components. The inner universal can be a

plunger or tripod type joint. The tripod is splined to the intermediate

shift and held by a circlip. A ball supported on needle roller bearing is

fitted to each post of the tripod and these slide in torsion inside the

yoke. This caters for changes in shaft length to horizontal angle. The

drive is transferred through the torsion and balls to rotate the shaft.

The outer universal joint allows greater angular changes but not

changes in shaft length. It is normally a ball and cage type with an

inner race splined to the intermediate shaft. An outer race is formed

in the yoke. The cage retains the balls in location in grooves in both

races. The balls transfer the drives from the shaft to the lub and allow

for changes in horizontal angle and for a wide steering angle to be

achieved. A flexible rubber boot fitted to each joint retains grease and

keeps out dirt and moisture. Where the differential is not located in

the center line of the vehicle an intermediate shaft can be fitted to

maintain equal length drive shaft on each side. This keeps drive shaft

angles equal on both sides and helps prevent steering irregularities

and vibration. The outer end of the intermediate shaft is supported by

a bearing secured to the transaxle case and a universal joint assists

with alignment. In some cases a longer drive shaft is used on one

side. A rubber dynamic damper may be fitted to absorb vibration.

1.2 Statement of the Problem

The failure of Front Wheel Drive shaft (FWD) in a vehicle observed

during visitation and interaction we had with “Mr Chinazo and Co. at

Pantaker Express located by Bye Pass Nnamdi Azikwe way revealed

clearly that front wheel drive shaft has become the most serious

problem in vehicle as far as shaft drive is concerned.

1.3 Aim of the Study/Analysis

The principal aim of this analysis is to investigate into the primary

causes of the failure in a Front Wheel Drive shaft (FWD) in a vehicle

and to recommend possible solutions to them.

1.4 Objectives of Analysis

The objectives hoped to be attained at the end of the analysis

includes:

1. To verify if the material used for the design of the drive shaft is

of sub-standard or not.

2. To investigate the causes of failure of the shaft.

3. To examine the causes of failure due to environmental factors.

1.5 Scope of Study

The scope of this research is limited to physical observation of the

shafts questionnaires and interview of the users of vehicles with front

wheel shafts.

1.6 Limitation of the Research

The study is a case study based on interview questionnaires and

observation of vehicles within Kaduna town.