ae lecture - 2

8/14/2019 AE Lecture - 2

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Frames

A. Prasanna

8/14/2019 AE Lecture - 2


Frame

The frame or under body is the main skeleton of

the vehicle.

The remaining parts of the chassis are mounted

on it.Chassis frames are made of “steel Section”

They are strong enough to withstand the load

and also light in weight to reduce dead weight onthe vehicle.

8/14/2019 AE Lecture - 2


Location of major parts on the chassis:

The engine is mounted in the front end of the frame and is connected to the clutchand transmission unit to form a complete

power assembly.

The rear axle housing is attached throughthe real spring at the rear end of the

frame.

Contd

8/14/2019 AE Lecture - 2


The wheel and the tyre assembliessupport the frame

The steering system has some partsattached to the frame and the body

The petrol tank is fastened to therear of the frame.

8/14/2019 AE Lecture - 2


Functions of the frame

To carry the weight of the vehicle andpassenger.

To withstand the engine and transmission

torque.To bear thrust, acceleration and braking

torque.

To resist the centrifugal forces whencornering.

To withstand bending and twist

Contd

8/14/2019 AE Lecture - 2


8/14/2019 AE Lecture - 2


Types of frame

Conventional frame

Semi – Integral frame

Integral or Unitized frame

The chassis frames are pressed steelmembers and are easily attached toeach other by riveting or welding.

Contd

8/14/2019 AE Lecture - 2


The frame basically consists of twolongitudinal members of mils steel with

channel section.

These two members are connected

cross - wise by cross members of tubular or box like cross section.

8/14/2019 AE Lecture - 2


Construction

8/14/2019 AE Lecture - 2


Conventional frame

8/14/2019 AE Lecture - 2


It is called as non – load carrying frame

The loads on the vehicle are transferredto the suspension by this type of frame.

The total frame is mounted on the wheelaxle by means of springs.

Mostly used in heavy vehicles like trucks.

The cross sections of the frame areusually channel, tubular or box type.

8/14/2019 AE Lecture - 2


Semi-Integral frame construction

The rubber body mountings are usuallyreplaced by relatively stiff mountings.

This arrangement transfers a part of the

frame load to the body structure also.This type is mainly used in European cars

and American cars.

This construction is heavy when comparedto the previous type.

8/14/2019 AE Lecture - 2


Integral frame construction or frameless

construction

This is also called as Chassisless, Unitary ormonocoque construction.

There is no separate frame.

This used in passenger cars.

This construction provides a stiff lightconstruction suitable for mass producedvehicles.

Contd

8/14/2019 AE Lecture - 2


8/14/2019 AE Lecture - 2


All the assembly units are attached to the

body.

Heavy side members are eliminated and

cross members are combined with the floorof the body.

This type of construction led to muchreduction of weight.

Contd

8/14/2019 AE Lecture - 2


The members are welded together asone assembly.

In this type the stresses are evenlydistributed throughout the structure.

A strong structure with goodtorsional rigidity and resistance inbending is provided by this type.

Contd

8/14/2019 AE Lecture - 2


SUB FRAME

A frame is attached to the body framein the front of the body shell.

The engine and the gear box aresupported on these frames at thefront suspension using independentrear suspension.

These are simple in construction andmounted in rubber blocks.

Contd

8/14/2019 AE Lecture - 2


Front Sub-Frame

8/14/2019 AE Lecture - 2


Rear Sub-Frame

8/14/2019 AE Lecture - 2


This frame supports the main frameat three points.

This is to isolate the components from

twisting and flexing effects.

In turn protect the body from engine

vibrations.

Contd

8/14/2019 AE Lecture - 2


ADVANTAGES OF SUB - FRAMES

1. It helps to dampen the vibration.

2. It simplifies the production process while

assembling.

3. It facilitates repair, service and overhaul.

8/14/2019 AE Lecture - 2


Types of sections of frames

Channel section

This is used in long members of theframe. It is good in bending and tubular in

torsion.

8/14/2019 AE Lecture - 2


8/14/2019 AE Lecture - 2


Box section

This is used in short member of theframe. It is good in bending and torsion.

8/14/2019 AE Lecture - 2


Box Type

8/14/2019 AE Lecture - 2


Tubular section

This is used in three-wheeler, scooters,matadors and pick-ups

8/14/2019 AE Lecture - 2


8/14/2019 AE Lecture - 2


BACK BONE FRAME

A central longitudinal steel tube is called

back bone.The section below uses single arm parallel

type of suspension.

8/14/2019 AE Lecture - 2


8/14/2019 AE Lecture - 2


The engine gear box unit is accommodated at theforked front end of the frame.

The driving shaft is made to pass through theinside of the central tubular portion of the frame.

8/14/2019 AE Lecture - 2


This frame is build up of two channelsections, which are pressed andwelded together.

This type of frame is used inindependent suspensions.

8/14/2019 AE Lecture - 2


Frame

Members

8/14/2019 AE Lecture - 2


8/14/2019 AE Lecture - 2


It consists of two longitudinal or side

members A and B.These are made in the form of

pressings of channel section.

8/14/2019 AE Lecture - 2


The side members are generallyarranged to be closer at the front.

The side members are brazed by anumbers of cross members C.

Dump irons-D are provided at thefront and rear ends.

8/14/2019 AE Lecture - 2


Springs are connected to brackets ‘E’ which are provided to support therunning boards.

Brackets ‘F’ are used to support theengine, gear box, brakes shafts,…..

The frames are stiffened with cross

pressing for independent suspension andare stiffer at the front end.

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X - Frame

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8/14/2019 AE Lecture - 2


The side members and cross members

are rigidly attached to each other by

riveting or welding.

Heavy side members are eliminated and

cross members are connected with the

floor of the body.

8/14/2019 AE Lecture - 2


‘X’ member may be of channel or box

section.

This type of frame imparts rigidity to the

frame.

8/14/2019 AE Lecture - 2


DEFECTS IN CHASSIS FRAME

Some of the defects are;

CracksDislocated parts Broken welds Buckling

The chassis is checked for thesedefects and suitably rectified.

8/14/2019 AE Lecture - 2


The following methods are used to prevent

rust formation;

Use of galvanized sheets.Use of zinc enriched primer paint.

Use of plastic coating on panels.

Use of rubberized solution. Avoiding tight corners so that the moisture cannot

get settled.

Providing plenty of drain holes to allow trapped

water to run out.

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It is important that the chassis frame is

properly aligned.

After repair is carried out on the frame, the

alignments should be checked with the

original measurements.

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Materials for Frame

The various tools used are Mild Sheet Steel,Carbon Sheet Steel and Sheet nickel alloy steel.

The composition of sheet nickel alloy is;

Carbon - 0.25 to 0.35 % Manganese - 0.35 to 0.75 % Silicon - 0.30 % (Max)

Nickel - 3 % Phosphorous - 0.05 % (Max) Sulphur - 0.5 % (Max)

ae lecture - 2

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