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. “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.”
“Chassis” a French term which means the Complete
Automobiles without Body and it includes all the systems like
power plant, transmission, steering, suspension , wheels
tyres , auto electric system etc. without body. It is made of
drop forged steel.

5. In an automobile function of chassis are as follows–
1. Supports or bears the load of the vehicle body.
2. Provide the space and mounting location for various
aggregates of vehicle.
3. Supports the weight of various systems of the vehicle
such as engine, transmission etc.
4. Supports a load of passengers as well as the luggage.
5.Withstands the stresses arising due to bad road conditions.
6.Withstands stresses during braking and acceleration of
the vehicle.

6. In an automobile chassis consists the following components.
1. Frame
2. Front Axle
3. Steering system
4. Suspension system
5. Rear axles
6. Transmission
7. Brake system
8. Engine
9. Electrical system

7. In an automobile chassis subdivided into:
1. Power plant
2. Running gear
1. Power plant:- Its include the engine assembly & power
transmission assembly.
2.Running Gear:-Its include frame, steering system,
suspension system, brakes, wheels & tyres.
* The electrical system is part of both chassis & body.

8. The automobile Chassis are following types:-
1. According to its control
1. Conventional chassis
2. Semi forward chassis
3. Full forward chassis
2. According to fitting of engine
1. Engine at front
2. Engine fitted in front but crosswise
3. Engine fitted at the centre of the chassis
4. Engine fitted at back

9. 3. According to the number of wheels fitted in vehicle
& number of driving wheels.
1. 4x2 drive chassis vehicle
2. 4x4 drive chassis vehicle
3. 6x2 drive chassis vehicle
4. 6x4 drive chassis vehicle
3. According to wheel base size
1. Short wheel base size chassis vehicle
2. Long wheel base size chassis vehicle

10. 1. Conventional chassis:- In this type of chassis engine is
fitted in front of the driver cabin or driver seat such as in
cars & previous models of Tata trucks. The driver seat
behind the engine & such as he can’t see the road just in front
of front tyres. This type of chassis can’t be utilized for
carrying passengers & goods.
2. Semi forward chassis:- In this type of chassis half
portion of the engine is in driver cabin & remaining half is
outside the cabin. This type of chassis is utilized for carrying
extra passengers.

13. 3. Full forward Chassis:- In this type of chassis complete
engine is mounted inside the driver cabin.
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. Engine at front:- (1) In this type of chassis engine is fitted
in front & drive is given to the wheels from the rear.
Its has following advantages:-
 Enough space is available for the luggage behind the rear
seat.
The weight of the vehicle is well balanced on all wheels.
Adequate space is available for steering the front wheels.
(2) Engine is fitted in front & drive is also given to the front
wheels only.

21. 2. Engine fitted in front but crosswise:- In this
arrangement engine is fitted in front not in conventional way
but crosswise as in Maruti, B.M.C etc & drive is given to
front wheels only.
3. Engine fitted at centre of chassis :- In this arrangement
engine is fitted in centre of the chassis as in Royal tiger world
master buses (DTC busses) etc & drive is given to front wheels
only.
4. Engine fitted at back of chassis :- In this arrangement
engine is fitted in back of the chassis as in Renault, volksvegon
etc & drive is given to front wheels only.

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

25. Its has following advantages:-
 Low floor is available since there is no propeller shaft &
differential at back.
The clutch, gear box & differential are made as one unit,
thereby cost is reduced.
At rear, luggage space is spacious.
Its has following disadvantages:-
While accelerating or on an gradient the weight of vehicle
shift to the rear wheels which is not desirable for better
adhesion.
Traction effort reduced on gradient.

26. 1. Long wheel base chassis vehicles:- Its consists a long
wheel base chassis. Its also four types-
(a) Long Front Overhang (c) Long Rear Overhang
(b) Short Front Overhang (d) Short Rear Overhang
2. Short wheel base chassis vehicles:- Its consists a long
wheel base chassis. Its also two types-
(a) Long Front Overhang (c) Long Rear Overhang
(b) Short Front Overhang (d) Short Rear Overhang

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-
frame construction.”
It is the supporting component or called under-body of 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,
brakes by means of spring, axle, rubber pads etc.

30. In an automobile function of Frame are as follows–
1. To carry load of the passengers, goods or cargo carried in
the body.
2. To support the load of the body, engine, gear box etc.
3. To withstand the forces caused due to the sudden braking
or acceleration.
4. To withstand the stresses caused due to the bad road
condition.
5. To withstand the centrifugal force caused by cornering of
the vehicle.
6. To withstand tensional vibration caused by the movement
of the vehicle.

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
supported on the wheels and tyre assemblies. It is made up
of drop forged steel. And all the parts related to
automobiles are attached to it only.
The frame is narrowed down at the front called In swept, to
have a better steering lock which provides space for
pivoting & swinging of the front wheels, which also gives a
smaller turning circle. The frame is Upswept at the rear and
front to accommodate the vertical movement of the axles
due to springing as it travels over road bumps & other road
inequalities. It also keeps the chassis height low.

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
a Body brackets. D are the dumb irons to act as bearings for
leaf spring Shackles. They also take the Bumper
brackets. Brackets E are meant for mounting the
springs. Spring brackets are provided for mounting the
body of the vehicle.
Extension of the chassis frame ahead of the front axle is
called ‘Front Overhang’. Extension of the chassis frame
beyond the rear axle is called ‘Rear Overhang’.

34. The automobile Frame are following types:-
1. Conventional Frame
2. Ladder Frame
2. Semi-integral Frame
3. Integral Frame (or frameless or unit frame or unibody)
4. Perimeter Frame
5. Space
6. Sub Frame

35. 1. Conventional Frame:-
The conventional frame is also known as Non-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
skeleton of the vehicle.
The body is made of flexible material like wood, aluminum sheet
metal and isolated frame by inserting rubber mountings in
between. Example: - Used on old Daimler vehicles.
2. Ladder Frame:-
A ladder frame is one of the oldest forms of automotive frame. It
is the body-on-frame construction. It is clear from its name that
ladder chassis frame resembles a shape of ladder having two long
longitudinal rails inter linked by lateral and cross bars.
Examples: -Trucks, Long Buses & SUV’s.

38. 3. Semi-integral Frame :-
In some vehicles half frame is fixed in the front end on
which engine, gear box and front suspension is mounted and
another half is in under-body. It has the advantage when the
vehicle is met with accident the front frame can be taken
easily to replace the damaged chassis frame.
In this case the rubber mountings used in conventional frame
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
European and American cars.

40. 4. Integral Frame or Frame-less Construction :-
In this type of construction, there is no frame. It is also
called unitized frame-body construction or
say Unibody. In unit construction, the body shell and under-
body are welded or bolted together into single unit assembly.
Uni-body construction assembled by welds major body panels
together to form the frame for attaching the engine, drive
train, suspension, and other parts. This type of construction
is commonly used on cars. This type of body construction
that doesn't require a separate frame, it provide structural
strength or support for the car's mechanical components.
Application- Most of Modern cars.

42. 4. Space Frame :-
Space frame has a particular kind of tube frame that consists
exclusively of relatively short, small diameter tubes. The
tubes are welded together in a configuration that loads them
primarily in tension and compression. A metal body
structure covered with an outer skin of plastic or composite
panels. Showing by extruded view in figure.
Roof and quarter panels may be attached with mechanical
fasteners or adhesives. The space frame chassis frame has all
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
the Mercedes SLS AMG.

45. 4. Perimeter Frame :-
Similar to a ladder frame, but the middle sections of the
frame rails sit outboard of the front and rear rails just
behind the rocker panels or sill panels. This type of frame
offer lower floor pan and better safety in the event of a side
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. Sub Frame:-
A sub-frame is a structural component of a vehicle. The sub-
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
transmission and it can be damped enough that they will not
disturb passengers.
Sub-frames are mostly used on Cars which having frameless
or unibody construction. The various chassis components are
mounted on sub-frame. These sub-frames are supported by
main frame or unibody. Example:-Austin Mini (1959),
Chevrolet Camaro (1967–1981).

50. Three types of steel sections are most commonly used for making
frames:
1.Channel section
2. Tubular section
3. Box section.
 Channel section is used in long member of frame. Its good
in bending.
 Tubular section is used three wheeler, scoters, & matadors.
Its good in torsion.
 Box section is used in short member of frame. Its good in
bending & torsion.

51. Composition of nickel alloy sheet steel having content carbon
0.25-0.35%, Manganese 0.35-0.75%, Silicon 0.30% max, Nickel
3%, Phosphorous 0.05% max., Sulphur 0.5% max.
‘
Alpax’ is an Aluminum alloy has also been used for frame
material. While material used for different frame brackets
are; mild steel, medium carbon steel, hard steel, 1% nickel, soft steel,
Iron (black heart).