Chassis

Chassis is the main support structure of the vehicle which is also known as ‘Carrying Unit’. It bears all the stresses on the vehicle in both static and dynamic conditions.”

1. ER. PEEYUSH CHAUHAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING

3. “Chassisisthemainsupportstructureof thevehiclewhichisalso
knownas‘CarryingUnit’.Itbearsallthestressesonthevehiclein
bothstaticanddynamicconditions.”
“Chassis”a French term which means theComplete
Automobiles without Bodyand it includes all the systems like
power plant, transmission, steering, suspension , wheels
tyres , auto electric system etc. without body. It is made of
dropforgedsteel.

5. Inanautomobilefunctionof chassisareasfollows–
1.Supportsorbearstheloadof thevehiclebody.
2.Provide the space and mounting location for various
aggregatesof vehicle.
3.Supports the weight of various systems of the vehicle
suchasengine,transmissionetc.
4.Supportsaloadof passengersaswellastheluggage.
5.Withstandsthestressesarisingduetobadroadconditions.
6.Withstands stresses during braking and acceleration of
thevehicle.

6. Inanautomobilechassisconsiststhefollowingcomponents.
1.Frame
2.FrontAxle
3.Steeringsystem
4.Suspensionsystem
5.Rearaxles
6.Transmission
7.Brakesystem
8.Engine
9.Electricalsystem

7. Inanautomobilechassissubdividedinto:
1.Powerplant
2.Runninggear
1.Powerplant:-Itsincludetheengineassembly&power
transmissionassembly.
2.Running Gear:-Its include frame, steering system,
suspensionsystem,brakes,wheels&tyres.
*Theelectricalsystemispartof bothchassis&body.

8. TheautomobileChassisarefollowingtypes:-
1.Accordingtoitscontrol
1.Conventionalchassis
2.Semiforwardchassis
3.Fullforwardchassis
2.Accordingtofittingof engine
1.Engineatfront
2.Enginefittedinfrontbutcrosswise
3.Enginefittedatthecentreof thechassis
4.Enginefittedatback

9. 3. According to the number of wheelsfittedinvehicle
&numberof drivingwheels.
1.4x2drivechassisvehicle
2.4x4drivechassisvehicle
3.6x2drivechassisvehicle
4.6x4drivechassisvehicle
3.Accordingtowheelbasesize
1.Shortwheelbasesizechassisvehicle
2.Longwheelbasesizechassisvehicle

10. 1. Conventional chassis:-In this type of chassis engine is
fittedinfrontofthedrivercabinordriverseatsuchasin
cars & previous models of Tata trucks. The driver seat
behindtheengine&suchashecan’tseetheroadjustinfront
of front tyres. This type of chassis can’t be utilized for
carryingpassengers&goods.
2. Semi forward chassis:-In this type of chassis half
portionof theengineisindrivercabin&remaininghalf is
outsidethecabin.Thistypeof chassisisutilizedforcarrying
extrapassengers.

13. 3. Full forward Chassis:-In this type of chassis complete
engineismountedinsidethedrivercabin.
In this arrangement floor area is increased to the extent of
accommodating 3 extra seats. Also driver seat is just above
the front wheels he can see full front road right from front
wheels.

15. 1.Engineatfront:- (1)Inthistypeof chassisengineisfitted
infront&driveisgiventothewheelsfromtherear.
Itshasfollowingadvantages:- 
Enough space is available for the luggage behind the rear
seat.

Theweightof thevehicleiswellbalancedonallwheels.

Adequatespaceisavailableforsteeringthefrontwheels.
(2)Engine is fitted in front & drive is also given to the front
wheelsonly.

21. 2. Engine fitted in front but crosswise:-In this
arrangementengineisfittedinfrontnotinconventionalway
but crosswise as inMaruti, B.M.Cetc & drive is given to
frontwheelsonly.
3.Enginefittedatcentreof chassis:-Inthisarrangement
engineisfittedincentreof thechassisasinRoyaltigerworld
masterbuses(DTCbusses)etc&driveisgiventofrontwheels
only.
4. Engine fitted at back of chassis :- Inthisarrangement
engineisfittedinbackof thechassisasinRenault,volksvegon
etc&driveisgiventofrontwheelsonly.

22. 1. 4x2 drive chassis vehicles:- Its consists of 4 wheels out
of 2wheelsaredrivingwheels. 2. 4x4 drive chassis vehicles:-Its consists of 4 wheels and all
wheelsaredrivingwheels.
3. 6x2 drive chassis vehicles:-Its consists of 6 wheels out of 2
wheelsaredrivingwheels.
4. 6x4 drive chassis vehicles:-Its consists of 6 wheels out of 4
wheelsaredrivingwheels.

25. Itshasfollowingadvantages:- 
Low floor is available since there is no propeller shaft &
differentialatback.

The clutch, gear box & differential are made as one unit,
therebycostisreduced.

Atrear,luggagespaceisspacious.
Itshasfollowingdisadvantages:-

Whileacceleratingoronangradienttheweightof vehicle
shift to the rear wheels which is not desirable for better
adhesion.

Tractioneffortreducedongradient.

26. 1. Long wheel base chassis vehicles:-Its consists a long
wheelbasechassis.Itsalsofourtypes-
(a)LongFrontOverhang (c)LongRearOverhang
(b)ShortFrontOverhang (d)ShortRearOverhang
2. Short wheel base chassis vehicles:-Its consists a long
wheelbasechassis.Itsalsotwotypes-
(a)LongFrontOverhang (c)LongRearOverhang
(b)ShortFrontOverhang (d)ShortRearOverhang

29. “A frame is the main structural component of the chassis of a
motor vehicle. All other remaining components of chassis
are fastening to it; a term for this design is body-on-
frameconstruction.”
It is the supporting component or called under-bodyof the
automobile. The automobile frame is the skeleton(structural
backbone) of any vehicle chassis. It is the foundation for
carrying the engine, transmission system, steering system,
brakesbymeansof spring,axle,rubberpadsetc.

30. Inanautomobilefunctionof Frameareasfollows–
1.Tocarryloadof thepassengers,goodsorcargocarriedin
thebody.
2.Tosupporttheloadof thebody,engine,gearboxetc.
3.Towithstandtheforcescausedduetothesuddenbraking
oracceleration.
4.To withstand the stresses caused due to the bad road
condition.
5.Towithstandthecentrifugalforcecausedbycorneringof
thevehicle.
6.Towithstandtensionalvibrationcausedbythemovement
of thevehicle.

31. The frame is narrow in the front for providing short
turning radius to front wheels. It widens out at the rear
side to provide larger space in the body. The frame is
supportedonthewheelsandtyreassemblies.Itismadeup
of drop forged steel. And all the parts related to
automobilesareattachedtoitonly.
TheframeisnarroweddownatthefrontcalledInswept,to
have a better steering lock which provides space for
pivoting&swingingof thefrontwheels,whichalsogivesa
smallerturningcircle.TheframeisUpsweptattherearand
front to accommodate the vertical movement of the axles
duetospringingasittravelsoverroadbumps&otherroad
inequalities.Italsokeepsthechassisheightlow.

33. The frames for these have only straight members without
taper towards the front or upsweep at the front or
rear. F are the brackets supporting the body. i.e. called as
aBodybrackets.Darethedumbironstoactasbearingsfor
leaf springShackles. They also take the Bumper
brackets. Brackets E are meant for mounting the
springs. Spring brackets are provided for mounting the
bodyof thevehicle.
Extensionofthechassisframeaheadofthefrontaxleis
called‘Front Overhang’.Extension of the chassis frame
beyondtherearaxleiscalled‘RearOverhang’.

34. TheautomobileFramearefollowingtypes:-
1.ConventionalFrame
2.LadderFrame
2.Semi-integralFrame
3.IntegralFrame(orframelessorunitframeorunibody)
4.PerimeterFrame
5.Space
6.SubFrame

35. 1.ConventionalFrame:-
The conventional frame is also known asNon-load carrying
frame. In these types of frame, the loads on the vehicle are
transferred to the suspension by the frame which is the main
skeletonof thevehicle.
The body is made of flexible material like wood, aluminum sheet
metaland isolated frame by inserting rubber mountings in
between.Example:-UsedonoldDaimlervehicles.
2.LadderFrame:-
Aladderframeisoneof theoldestformsof automotiveframe.It
is thebody-on-frameconstruction. It is clear from its name that
ladderchassisframeresemblesashapeof ladderhavingtwolong
longitudinal rails inter linked by lateral and cross bars.
Examples:-Trucks,LongBuses&SUV’s.

38. 3.Semi-integralFrame:-
In some vehicles half frame is fixed in the front end on
whichengine,gearboxandfrontsuspensionismountedand
anotherhalf isinunder-body.Ithastheadvantagewhenthe
vehicleismetwithaccidentthefrontframecanbetaken
easilytoreplacethedamagedchassisframe.
Inthiscasetherubbermountingsusedinconventionalframe
between frame and suspension are replaced by more stiff
mountings. Because of this some of the vehicle load is
shared by the frame also. This type of frame is heavier in
construction.Application:-FIAT cars and some of the
EuropeanandAmericancars.

40. 4.IntegralFrameorFrame-lessConstruction:-
In this type of construction, there is no frame. It is also
called unitized frame-body construction or
sayUnibody.Inunitconstruction,thebodyshellandunder-
bodyareweldedorboltedtogetherintosingleunitassembly.
Uni-bodyconstructionassembledbyweldsmajorbodypanels
together to form the frame for attaching the engine, drive
train,suspension,andotherparts. Thistypeof construction
is commonly used on cars. This type of body construction
thatdoesn't require a separate frame , it provide structural
strength or support for the car's mechanical components.
Application-Mostof Moderncars.

42. 4.SpaceFrame:-
Spaceframehasaparticularkindof tubeframethatconsists
exclusively of relatively short, small diameter tubes. The
tubesareweldedtogetherinaconfigurationthatloadsthem
primarily in tension and compression. A metal body
structurecoveredwithanouterskinof plasticorcomposite
panels.Showingbyextrudedviewinfigure.
Roof and quarter panels may be attached with mechanical
fastenersoradhesives.Thespaceframechassisframehasall
components attached to a skeletal frame of tubes and the
body panels have limited structural function.Example:-
Audi A8, Audi R8, Ferrari 360, Lamborghini Gallardo and
theMercedesSLSAMG.

45. 4.PerimeterFrame:-
Similar to a ladder frame, but the middle sections of the
frame rails sit outboard of the front and rear rails just
behindtherockerpanelsorsillpanels.Thistypeofframe
offerlowerfloorpanandbettersafetyintheeventof aside
impact.
Perimeter frames used in passenger cars in the U.S. but not
in the rest of the world, until the Uni-body gained
popularity and is still used on US full frame cars. These
types of frames see a lot of 1950s sales of U.S. passenger
cars.

47. 5.SubFrame:-
Asub-frameisastructuralcomponentof avehicle.Thesub-
frame is bolted to basic structure of the vehicle along with
rubber bushings or springs to dampen vibration. A sub-
frame reduces forces generated by the engine and
transmissionanditcanbedampedenoughthattheywillnot
disturbpassengers.
Sub-framesaremostlyusedonCarswhichhavingframeless
orunibodyconstruction.Thevariouschassiscomponentsare
mounted on sub-frame. These sub-frames are supported by
main frame or unibody.Example:-Austin Mini (1959),
ChevroletCamaro(1967–1981).

50. Threetypesof steelsectionsaremostcommonlyusedformaking
frames:
1.Channelsection
2.Tubularsection
3.Boxsection. 
Channelsectionisusedinlongmemberof frame.Itsgood
inbending.

Tubularsectionisusedthreewheeler,scoters,&matadors.
Itsgoodintorsion.

Boxsectionisusedinshortmemberof frame.Itsgoodin
bending&torsion.

51. Compositionof nickelalloysheetsteelhavingcontentcarbon
0.25-0.35%,Manganese0.35-0.75%,Silicon0.30%max,Nickel
3%,Phosphorous0.05%max.,Sulphur0.5%max.
‘
Alpax’is an Aluminum alloy has also been used for frame
material. While material used for different frame brackets
are;mildsteel,mediumcarbonsteel,hardsteel,1%nickel,softsteel,
Iron(blackheart).