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TRADE OF HEAVY VEHICLE

MECHANIC

PHASE 2

Module 4

Transmission

UNIT: 3 & 4

Drive Shafts and Axles

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Module 34 Unit 3 & 4 Drive Shafts & Axles

Table of Contents

1.0 Learning Outo!e...........................................................1

1.1 "e# Learning $oints......................................................1

%.0 Drive Shafts and Universal oints.....................................%

%.1 'untion.......................................................................%%.% (onstrution................................................................%%.3 O)erating $rini)le......................................................4%.4 $ro)eller*Shaft +i,ration..............................................-%.- Divided $ro)eller Shafts and heir Su))ort.................-%./ nter!ediate $ro)eller*Shaft Su))ort earings...........2

3.0 Drive Arrange!ent........................................................10

3.1 ear*heel Drive.......................................................103.% 5oth6iss O)en*#)e Drive.......................................1%3.3 (onstant +eloit# oint...............................................13

4.0 (ornering.......................................................................14

-.0 ear Axle.......................................................................14

/.0 5alf Shafts.....................................................................1-

2.0 Se!i*'loating.................................................................1-

7.0 hree*8uarter 'loating..................................................12

9.0 'ull# 'loating.................................................................12

10.0 'ront*heel Drive........................................................%0

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Module 4 Unit 3 & 4 Drive Shafts and Axles

1.0 Learning Outcome

By the end of these units each apprentice will be able

to:

Remove a drive shaft and change a carrier bearing and universal

joint

Refit drive shaft aligning flanges

State the function and principle of operation of the universal

joints, CV joints (constant velocity), carrier bearings and drive

shafts of:

a) rear wheeled drive truc

b) front wheeled drive vehicle using CV joints

Remove!refit a constant velocity joint rubber on a light

commercial vehicle drive shaft i"e" bench unit)

State the function and principle of operation of a fully floating,

three#$uarter and semi floating rear a%le

&ismantle a fully floating hub assembly, e%amine and report on

the condition of the bearings and reassemble the hub and adjust

to manufacturer's specifications

Report on the condition of the bearings of the hub

1.1 Key Learning Points

Unit 3

Lu,riation )roedure of drive shaft o!)onents

(ondition of :oints and gaiters he6ed

Aligning of shaft flanges ;

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Unit 4

Safe :a6ing )roedure use of axle stands

$rini)le of o)eration of different t#)es of axle hu,s

Dis!antle and asse!,ling )roedure of hu,o!)onents

earing t#)es and ad:ust!ent )roedure of hu,

,earings

Method of lu,riation of hu, ,earings @hen fitted

Use of lo6ing devies and he6ing ,earing ondition

Sealing !ethods and he6ing ondition of seals

$re*load on ,earings reason for )re*load and !ethod

of setting )reload

he relationshi)s ,et@een engine s)eed gear ratio@heel dia!eter and vehile s)eed

e)ort on the ondition of the ,earings and seals

.0 !ri"e #hafts andUni"ersal $oints

2.1 Function

he )ur)ose of the drive shaft and universal :oints is totrans!it the drive fro! the gear,ox to the ,a6 axle @ith as!ooth trans!ission of torBue even though the gear,ox and)inion shaft are never in exat align!ent.

2.2 Construction

he shaft is a hollo@ tu,ular steel unit @ith a hoo6 :oint ateah end. he :oint onsists of t@o u sha)ed C#o6es @hihare onneted at 90E to eah other ,# a four*legged ross orCs)ider. Feedle roller ,earing !a# ,e used to su))ort thes)ider legs in the #o6es.

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2.3 Operating Principle

hen universal :oints are used to onnet t@o units ;e.g.gear,ox and ,a6 axle= the driven shaft does not rotate @ithunifor! veloit# i.e. it does not turn at the sa!e s)eed

during eah )art of a revolution. n one revolution the drivenshaft is aelerated t@ie and deelerated t@ie. his effet,eing inreases as the angularit# is inreased. hese veloit#differenes an ,e anelled in the )ro)eller shaft ,# the useof t@o orretl# aligned :oints the aeleration of one ,eingneutralised ,# the deeleration of the seond. A sliding :ointis used to allo@ the drive shaft to hange its length as itrotates to o!)ensate for the s!all ,a6@ard and for@ard!ove!ent of the rear axle aused ,# the ation of thesus)ension s#ste!. t is si!)l# a s)lined tu,ular )ortion ,uilt

onto the for@ard universal :oint and it slides in s)lines on thegear,ox !ainshaft.


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Two universal joints connected in series

2.4 Propeller-Shaft Viration

Due to the high s)eeds the drive shaft reahes in to) gearits .$.M. is the sa!e as the engine the shaft !ust ,e,alaned to avoid vi,ration. f vi,rations our in the driveshaft it !a# ,e due to @orn or ,ro6en needle rollers in theuniversal :oint. his !a# ,e he6ed ,# turning the driveshaft ,# hand to he6 for free )la# a sei?ed :oint !a# not,e deteted this @a# so re!oval of the shaft !a# ,eneessar# for further he6s.

S!all ars and short vans and tru6s are a,le to use a single)ro)eller shaft @ith a sli)*:oint at the front end @ithoutex)eriening an# undue vi,ration. 5o@ever @ith vehiles oflonger @heel,ase the longer )ro)eller shaft reBuired @ouldtend to sag and under ertain o)erating onditions @ouldtend to @hirl and then set u) s#!)atheti resonantvi,rations in the ,od# of the vehile * that is ause the ,od#to Cdru! or vi,rate as the shaft @hirls.

Simple one-piece propeller shaft with one slip-joint and twouniversal joints

2.! "i#i$e$ Propeller Shafts an$ %heirSupport

@o*)iee drive*lines @ith t@o shafts and an inter!ediatesu))ort ,earing are generall# used on tru6s @ith @heel

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,ases fro! 3.4 to 4.7 ! ,ut there is so!e overla)de)ending on the vehiles @or6 role.

Two-piece drive-line with single intermediate supportbearing

he t@o*)iee )ro)eller shaft has three universal :oints andthe )ri!ar# )ro)eller shaft is of the fixed*:oints*and*tu,e*asse!,l# t#)e ,ut the seondar# )ro)eller shaft has a sli)*:oint at the su))ort*,earing end to ao!!odate an#

elongation due to sus)ension !ove!ent. Usuall# the)ri!ar# shaft is in line @ith the gear,ox !ainshaft axis ,utthe seondar# )ro)eller shaft is inlined slightl# so that itintersets the rear*axle final*drive )inion shaft.

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Three-piece drive-line with two intermediate supportbearings

'or vehiles @ith @heel,ases over 4.7 ! a three*)ieedrive*line @ith t@o inter!ediate su))ort ,earings !a# ,eneessar#. here are four universal*:oints and it an ,e seenthat the inter!ediate shaft lies )arallel to the out)ut shaft ofthe gear,ox. Again onl# the rear )ro)eller shaft inor)oratesa sli)*:oint to o!)ensate for shaft length hange.

2.& 'nter(e$iate Propeller-ShaftSupport )earings

nter!ediate )ro)eller*shaft ,earing*and*!ount asse!,liesare )rovided to )osition and su))ort the divided or s)lit)ro)eller shafts. he su))ort*,earing asse!,lies are of t@o,asi t#)esG

;i= self*aligning ,earing su))orts

;ii= flexi,le*!ounted ,earing su))orts.

Self*aligning inter!ediate*,earing su))orts have !ostl#,een used on heav#*dut# tru6s. One t#)e of self*aligning,earing su))ort is a dou,le*ro@ ,all*,earing @ith a dee)*grooved inner rae and an internall# se!iirular outer raeH'ig ;a=. ith this arrange!ent an# shaft defletion isao!!odated ,# the inner rae and ,alls tilting a,out thefixed outer*rae s)herial seat.

!i"ided propeller shaft support%bearing assemblies


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Commercial vehicle double-row self-alignment bearingsupport


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A seond !ethod of )roviding self*align!ent for the s)litshafts is ahieved ,# a single*ro@ dee)*grooved ,all*,earing@ith a s)herial )rofile on the )eri)her# of the outer raes.he ,all rae is then reeived in a steel su))ort ring @hih

has an internal )rofile to !ath the outside of the ,earingH'ig. ;,=. f there is an# !isalign!ent in servie relative!ove!ent of the ,earing and the ring an ta6e )lae@ithout i!)osing strains on the ,earing asse!,l#. otharrange!ents disussed need to ,e lu,riated )eriodiall#and oil*seals are )rovided to retain the grease and 6ee) dirtout of the ,earing tra6s.

Commercial vehicle single-row self-alignment outer bearingrace

'lexi,le*!ounted inter!ediate*,earing su))orts for dividedshafts !a# ,e used for ,oth light and heav# vehiles. Allthese t#)es tend to have a single*ro@ dee)*grooved ,all*,earing @hih fits diretl# over one of the divided shafts andsurrounding this ,earing is a ru,,er !e!,er @hih isenlosed in a steel fra!e. he inter!ediate shafts are thengiven su))ort ,# ,olting this asse!,l# to the hassis or ,od#shell. his ru,,er !ounting )rovides a flexi,le su))ort for

the ,earing so that a slight tilt of theshaft an ,e ao!!odated. naddition the flexi,le ru,,er ats as avi,ration da!)er and isolates an#)ro)eller*shaft vi,rations fro! the,od# !e!,ers.

'or extra*heav# dut# a solid ru,,erring ,lo6 fitting over a ,earing hu,!a# ,e usedH'ig. ;=. t an ,e seenthat the inner ,earing rae is held in

)osition ,# the universal*:oint flangeand that the outer ,earing rae is loated ,# a shi!!ed


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sleeve. egular lu,riation is neessar# @ith this asse!,l#.Most light*and heav#*dut# inter!ediate*,earing asse!,liesno@ use )re*greased and sealed*for*life dee)*groove,earings.

&ea"y%duty rubber bloc' bearing mount

3.0 !ri"e (rrangement

3.1 *ear-+heel "ri#e

orBue reationHCo ever# ation there is an eBual ando))osite reation. his state!ent !eans that ever#o!)onent that )rodues or hanges a torBue @ill also exertan eBual and o))osite torBue tending to turn the asing. 'orexa!)le @hen the engine ran6shaft exerts a torBue in alo6@ise diretion the #linder ,lo6 @ill tend to rotate inan antilo6@ise diretion.

A further exa!)le of torBue reation is sho@n in @hih atrator @ith its rear driving @heels lo6ed in a dith. n this

situation the driver !ust ,e areful ,eause torBue reationis li6el# to lift the front of the trator rather than turn therear @heels.


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Lever action of wheel

hen the la@ stated a,ove is a))lied to rear axles #ou @ill

see that so!e arrange!ent !ust ,e )rovided to )revent theaxle asing turning in the o))osite diretion to the driving@heels.


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3.2 ,otchiss Open-%ype "ri#e

@o rear leaf s)rings longitudinall# !ounted are onnetedto the fra!e ,# a Cfixed )ivot at the front and s@inging

sha6les at the rear. At eah end of the ex)osed or Co)ent#)e )ro)eller shaft is fitted a universal :oint @ith )rovision!ade for alteration in shaft length @hih ours @hen thes)rings are defleted.

orBue reation is resisted ,# la!)ing the axle to thes)rings ,# !eans of CU ,olts. Under heav# driving onditionsthe s)rings @ill deflet u) at the front and do@n at the rearand vie versa during ,ra6ing.

&otsh'iss dri"e and suspension

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3.3 Constant Velocity oint

+ehiles @ith front @heel drive reBuire a s)eial universal:oint to !aintain torBue at the @heel @hilst turning a orner.

he :oint is alled a onstant veloit# :oint. his :oint doesnot have the disadvantage of the 5oo6es t#)e :oint @heret@o :oints are neessar# to !aintain unifor! veloit#. n this:oint a !ehanis! is inor)orated ,et@een the I#o6esJ@hih auto!atiall# align itself @hen the angle is for!ed ,#the t@o shafts. he align!ent !a# ,e o,tained through the!ove!ent of steel ,alls in grooves or through the defletionof ru,,er o!)onents * these defletions neutralising theveloit# variation.

)*racta+ type constant%"elocity uni"ersal ,oint fitted to afront wheel dri"e a-le


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4.0 ornering

As the vehile turns a orner the inner @heel !oves through

a s!aller distane than the outer the @heels @ill ta6e thesa!e ti!e to turn the orner so the outer @heel !ust !ovefaster to over the greater distane. f a differential @as note!)lo#ed a lot of t#re sru,,ing @ould ta6e )lae and thevehile @ould ,e hard to ontrol.

n the differential asse!,l# the differene in road resistaneon eah side of the vehile auses the sun @heel to rotatethe )lanet gears @hih inreases the s)eed of the outer@heel dereases the s)eed of the inner @heel at the sa!e)ro)ortion @hile !aintaining an eBual torBue at ,oth

@heels.

/ote:UneBual rear t#re )ressure ,ad road onditions also,rings in the differential asse!,l# into o)eration.

.0 ear (-le

he rear axle is @here the final inrease in torBue andderease in engine s)eed ta6es )lae. eause of the large*

dia!eter @heels reBuired to arr# the heav# loads a ver#high torBue is reBuired at the end of the half shaft to turnthe @heels and )ro)el the vehile. he axle asing is usuall#a ,an:o*t#)e asting @ith su))ort ,earings for the rear@heels at eah end and a detaha,le asting @hih housesthe differential gears and ro@n @heel asse!,l#.


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On light o!!erial vehiles a onventional s)iral ,evel ofh#)oid*t#)e rear axle onstrution is used. As the load*arr#ing a)ait# of the vehile inreases the axle ratio alsohas to ,e inreased to give the reBuired torBue at the rear

@heels. hen this ratio reahes a))roxi!atel# 7G1 the single,evel gear axle gives @a# to a @or! and @heel arrange!entor uses a dou,le redution arrange!ent to give the desiredratio @ithin reased strength.

2.0 &alf #hafts

hree !ain !ethods are used to su))ort the half shafts inthe rear axle ase. n all of the! the inner ends of the shaftsare s)lined into and su))orted ,# the sun @heels of thedifferential asse!,l#. he differenes lie in the arrange!entof the hu, ,earing in relation to ,oth the ase and the shaftand in the fores or loads i!)osed u)on the shaft itself.

.0 #emi%loating

he hu, and the half shaft are in effet a one )iee unit

although the# !a# in fat ,e s)lined or fitted together ,#!eans of a ta)er 6e# and lo6 nut. he ,earing is arried onthe shaft and is loated ,# a nut or a sleeve. he outer tra6of the ,earing is fitted into a reess in the axle ase and isloated ,# a retainer )late ,olted to the end flange of theaxle ase. his ,earing is usuall# sealed on one side to)revent exess lu,riant ruining the ,ra6e lining.

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orces acting on the half shaft:

1. Shear fore due to the @eight of the vehile.

%. ending fore due to the @eight of the vehile.

3. orsional or t@isting fores due to the driving and,ra6ing fore.

4. Side thrusts as the vehile turns.

5.0 *hree%6uarter loating

he ,earing is !ounted on the asing and is held against a

shoulder ,# a lo6nut and ta, @asher. he hu, is !ade int@o )arts the inner )art fitting over the ,earing and alsoenlosing a s)ring loaded oil seal. he outer )art !a# ,eintegral @ith the half shaft ,e s)lined and interferene fitu)on it or ,e seured to the shaft ,# a ta)er 6e# andlo6nut. he ,ra6e dru! !a# ,e integral @ith the hu, outerhalf or seured to it ,# ounter sun6headed sre@s. he,a6 )late !ounting flange is nearer to the entre of theaxle than the se!i*floating design. his design is !ainl# onlight o!!erial vehiles.


1. ending fore due to side thrust @hen ornering.

%. orsional ;t@isting= fores due to the driving and,ra6ing thrusts.

7.0 ully loating

his design is !ainl# used on heav# o!!erial vehiles.he hu, is a heav# forging or asting of steel and is arriedon the axle ase ,# t@o heav# dut# o))osed ta)er roller,earings. he tra6s of these ,earings are loated ,#shoulder and a lo6nut and are ad:usta,le. he hu, drive


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)late is integral @ith the shaft and is seured to the hu, ,#radiall# arranged set ,olts a gas6et fitted ,et@een the [email protected] s)ring loaded oil seal is fitted into the inner side of the hu,near the ,a6 )late flange. he half shaft !a# ,e re!oved@ithout re!oving the @heel.


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orsional ;t@isting= fores due to the driving and ,ra6ingthrusts.

/ote: n all of the designs desri,ed the ,rea6ing of a half

shaft @ill result in the loss of driving torBue due to the ationof the differential unit.


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10.0 ront%8heel !ri"e

*rans"erse engine layout

he transversel# !ounted engine is ,olted to a unit alled atransaxle. his unit gets its na!e fro! the t@o @ordstrans!ission ;a ter! used in A!eria for gear,ox= and axle.n the )ast the general ter! Crear axle often a))lied to thegearing as @ell as the axle asing ,ut no@ada#s the variousdrive arrange!ents !a6e it neessar# to restrit the use ofthe na!e Crear axle to the !e!,er @hih )erfor!s the axledut#. he t@o !ain o!)onents inside the axle of a rear*@heel drive vehile are the final drive e.g. ro@n @heel and)inion and the differential.

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he four*s)eed gear,ox has t@o shaftsG an in)ut shaft

s)lined to the luth and a !ainshaft onneted to the finaldrive )inion. A ,evel gear final drive is neessar# @hen theengine is !ounted longitudinall# ,ut in the la#out sho@n theengine )osition allo@s the use of nor!al helial gears. Drivefro! the final drive is trans!itted through the differential tothe t@o drive shafts. S)eed variation due to drive shaftangularit# is )revented ,# using onstant veloit# universal:oints at eah endK the in,oard :oint at eah side ,eing of the)lunge t#)e.

During aeleration or at ti!es @hen the engine is used as a,ra6e torBue reation tends to !a6e the engine rotatea,out the ran6shaft so suita,l# s)aed engine !ountingsare fitted to resist this !ove!ent.

Driving thrust and ,ra6ing torBue are ta6en ,# thesus)ension !e!,ers in )artiular the tie ,ar fitted fro! thetra6 ontrol ar! to the ,od#.

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