LV12 drive shafts issue 1

LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 aLV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1 LV12 drive shafts issue 1

Student Workbook

LV12 Drive Shafts (1)

kap all covers 6/9/03 9:49 am Page 23

Student Workbook for Technical Certificates in

Light Vehicle Maintenance and Repair

MODULE LV12 Drive Shafts (1)

Contents

Page ……… Page

Drive Train Layouts: 3 Drive Shaft Joints: 11 Front engine rear wheel drive 3 Construction of the Hooke’s joint 11 Power transfer 4 Construction of a rubber coupling 11 Front engine front wheel drive 4 Drive shaft joints 12 Mid engine rear wheel drive 5 Tripod joint 13 Four wheel drive (full-time 4WD) 5 Constant velocity joints 13 Non-permanent four wheel drive 6 Drive shaft assemblies 14 Operational requirements of drive

shafts and propeller shafts 7 Drive Shaft Construction: 15

Steering condition 7 Propeller shaft 15 Wheel rebounding 8 Two piece propeller shafts 15 Disadvantages of the simple Front propeller shaft

universal joint 8 (intermediate shaft) 16 Angular velocity 9 Drive shaft layout 16

Fitting Propeller Shafts: 10 Drive Shaft Operation: 17 Propeller shaft alignment 10 Progress check 18

Drive Train Layouts

In this unit we consider the means by which power is transmitted between the power source and the driven wheel

Front e ngine rear wheel drive

Power produced by the engine must be transferred to the driving wheels of

e vehicle This is achieved by a series of shafts and specialised joints

er produced by the engine in this illustration must be transferred from

e fro t to the rear of the vehicle This is achieved by using a propeller shaft

At the rear, the differential and half shafts transfer the power to the rear

wheels within a rigid axle casing

th

The pow

Front engine rear wheel drive

th n

Power transfer

In this example the power is also transferred from the front to the rear of the vehicle, but the differential transmits the power to smaller shafts, generally referred to as drive shafts, before driving the rear wheels This allows each drive shaft to move independently of each other, rather than together in the rigid casing of a conventional rear axle

Front engine front wheel drive

The position of the engine and transaxle close to the driving wheels of this front engine front wheel drive example means that a propeller shaft is not required

Engine power is transferred directly to the differential and from there to the driving wheels by two drive shafts

Mid engine rear wheel drive

the same manner this mid engine rear wheel drive vehicle has an almost entical layout

ar wheel drive systems previously explained

In

id

Four wheel drive (full-time 4WD)

This permanent four wheel drive layout is a combination of the front wheel drive and re

Non-permanent four wheel drive

In this example of a non permanent four wheel drive vehicle engine power is transferred to the rear wheels by a propeller shaft However before leaving the transmission the power is also transferred, via a transfer unit, to a front differential and then to the front wheels

In this layout there is a means by which the front differential can be

disconnected leaving the vehicle in two wheel drive mode Engine power can

be transferred from the differential units to the wheels by either a rigid axle or,

in independent suspension systems, by separate drive shafts

Operational requirements of drive shafts and propeller shafts

The transmission is normally fixed to the vehicle chassis by flexible rubber mountings The rear differential and rear axle are usually supported by the rear suspension Therefore suspension travel, due to vehicle loading and bumps in the road, causes the rear axle and differential to change position in relation to the transmission The propeller shaft must therefore be designed

to constantly change length and transmit power through a variety of angles

teering condition

imilarly in the above illustration of a front engine front wheel drive

rrangement the engine and transaxle are connected to the chassis The ont hubs and wheels are supported by the suspension and move in relation the transaxle

herefore drive shaft operational requirements, to change length and drive rough varying angles, are the same as for the propeller shaft arrangement

he situation is further complicated because the front wheels are also the teering wheels The turning radius of the vehicle is affected by the ability of

e outboard drive shaft joint to deliver power smoothly through an angle of at ast 40 degrees, indicated by symbol Ø in the illustration

To allow changes in length the propeller shaft is usually connected to the transmission by a sliding splined shaft Each end of the propeller shaft is fitted with a universal joint to enable it to absorb changes in drive angle

S

S

a

fr

to

T

th

T

s

th

le

Wheel rebounding

e 0mm

e simple univers l joint

aken to overcome this problem vibration and surge at the wheels would be produced

The angle (usually in the order of 20 degrees) through which the inboard joint needs to transmit power is considerably less The effects of suspension

movement require the drive shaft to change length and in this illustration th

inboard joint can slide in an axial direction The distance is usually 25 – 5

In this illustration a simple universal joint, often referred to as a Hooke’s or

Spider joint, can be seen to have a major draw back Rotating at an angle of

30 degrees the speed of shaft B varies in relation to shaft A This is often

referred to as changing angular velocity If action was not t

Angular velocity

to

Variations in angular velocity are cancelled out by fitting a similar joint to the other end of the shaft The drive and driven shafts are also fitted parallel each other to smooth out variations in rotating speeds and torque

Fitting

n the top

haft assembly is fitted correctly and the lower assembly is incorrect

ropeller shaft alignment

lignment marks as illustrated should be added before disassembly

Propeller Shafts

It is vital that propeller shafts are fitted correctly Propeller shaft ends must be marked so that they can be refitted in exactly the same location If this is ignored vibration and noise will be the result In the above illustratio

Correct fitting

Incorrect fitting

s

P

A

Drive Shaft Joints

Con

part and eedle roller bearings are installed in bearing cups press-fitted into the yoke ountings The cups are located in some instances by circlips or snap rings

erviced Other versions use shell type bearings instead The cups are crimped in position and this version cannot be

dismantled

onstruction of a rubber coupling

n example of a rubber based flexible propeller shaft joint

struction of the Hooke’s joint

The Hooke’s joint illustrated has the advantage of simple construction One of the yokes is welded to the propeller shaft and the other yoke is an integral

of a splined joint, which when inserted into the transmission output housing provides a sliding joint A forged spider is installed between the yokes

n

m

and can be dismantled and s

C

A

Drive shaft joints

A Birfield joint, sometimes known as a Rzeppa joint, has an inner race fitted

)

ion constant velocity is commonly abbreviated as C.V and a joint

f this type often referred to as a C.V joint The joint is encased in a flexible oot to retain the appropriate lubricating grease

into an outer race between which steel balls are held in position by a steel cage Simple construction and the ability to transmit large torque through a considerable angle means this joint is a common feature of drive shafts fitted

to front wheel drive vehicles Because the intersecting point (0 in the

illustration) of the driving and driven shafts and the centre (P in the illustration

of each ball bearing is constant this is a constant velocity joint The rotational speeds of the drive and driven shafts are identical

The express

o

b

Tripod joint

e

riate

this constant velocity joint an inner race and an outer race have between

em a ball cage As can be seen from the illustration the outer race has a eries of grooves in which the ball bearings run, providing axial movement

he joint is encased in a flexible boot to retain the appropriate lubricating rease Failure of drive shaft joints are usually preceded by failure of the exible boot allowing the loss of lubricant and the ingress of road dirt

The Tripod joint has three trunnion shafts on which three rollers, which hav roller bearings, run The outer casing has a groove in which each of the rollers is located It is a relatively inexpensive joint which usually has axial movement The joint is encased in a flexible boot to retain the approp

lubricating grease Failure of drive shaft joints are usually preceded by failure

of the flexible boot allowing the loss of lubricant and the ingress of road dirt

Constant velocity joints

In

th

s

T

g

fl

Similar constant velocity joint, the major difference being that, as can be seen

in the illustration, the grooves of the outer race are set at an angle

nt is produced in two versions one with axial movement

to those of the inner race The joi

and one without The joint is encased in a flexible boot to retain the

appropriate lubricating grease Failure of drive shaft joints are usually

preceded by failure of the flexible boot llowing the loss of lubricant and the

illustrated

a ingress of road dirt

Drive shaft assemblies

A drive shaft assembly will usually have a combination of two types of joint as

forces Despite a careful balance process, and the ddition of balance weights, a single shaft having a joint at each end can uffer from imbalance and vibration at higher rotational speeds because of its

Tw

hafts Bending and high speed vibration is therefore reduced The nger shaft is often two piece with rubber insulators fitted in between

ecause of these advantages this propeller shaft arrangement is more

ommonly used

e Shaft Construction

Propeller shaft

Propeller shafts are usually made from a high carbon steel tube to prevent torsional and bending

a

s

greater length

o piece propeller shafts

A two-piece shaft having three joints and a centre bearing has the advantage

of shorter s

lo

B

c

Front propeller shaft (intermediate shaft)

To reduce vibration and noise even furt er the centre propeller shaft bearing mounted in rubber

ade increases stiffness to match the rigidity of shorter shafts

h is

Drive shaft layout

Whilst most shorter drive shafts are solid, longer drive shafts are often m from a tube This

Drive Shaft Operation

During sudden acceleration the front of a vehicle tends to rise up If drive shafts of significantly different length are fitted, as in the top illustration, joint angle Ø1 will be much greater than Ø2 This will cause the wheel attached to

st drive shaft

illustration

An illustration of an intermediate drive shaft fitted to maintain straight-line stability during acceleration

the shortest drive shaft to attempt to ‘track or toe in’ further than the wheel attached to the longer drive shaft This will cause the vehicle to veer toward the side with the longe

This can be prevented from occurring, by keeping joint angles and drive shaft length the same An intermediate shaft is often fitted, as shown in the bottom

Progress check

Answer the following questions:

1

4

What is the purpose of a sliding joint on a propshaft?

2 What is cyclic variation?

3 When removing a propshaft it is good practice to mark a line acros

sliding joint Why is this?

If a vehicle is fitted with a two-piece propeller shaft, what advantages would this have over a single piece shaft?