THEORY EXAMINATION (SEM–VI) 2016-17 AUTOMOTIVE CHASSIS AND SUSPENSION

AUTOMOTIVE CHASSIS AND SUSPENSION (NAU601)

Time: 3 Hours  Max Marks: 100

SECTION – A (Short Answer Questions)

(10 × 2 = 20 Marks)

(a) Over steering and under steering

Over steering: When the vehicle turns more sharply than intended, causing the rear wheels to skid outward.

Under steering: When the vehicle turns less than intended, causing the front wheels to skid.

(b) Hotchkiss drive

Hotchkiss drive is a rear-wheel drive system in which the propeller shaft transmits torque to the 
differential, and the leaf springs take driving and braking thrust.

(c) King pin inclination

King pin inclination is the angle between the king pin axis and the vertical line when viewed from the front of the vehicle. It helps in self-centering of wheels and reduces steering effort.

(d) Torque capacity

Torque capacity is the maximum torque that a clutch or transmission component can transmit without slipping.

(e) Functions of gearbox

Main functions of gearbox are:              Provide variable speed and torque

Allow reverse motion                             Enable neutral position

(f) Wheel track

Wheel track is the distance between the centers of the left and right wheels on the same axle.

(g) Function of differential

A differential allows rear wheels to rotate at different speeds while taking turns and transmits torque to both wheels.

(h) Slip joint

Slip joint allows axial movement of the propeller shaft to accommodate changes in distance due to suspension movement.

(i) Function of vibration dampers

Vibration dampers (shock absorbers) control oscillations of springs, providing ride comfort and vehicle stability.

(j) Purpose of stub axles

Stub axles support the front wheels, allow steering movement, and transmit load from the wheels to the front axle.

SECTION – B (Long Answer Questions)

(Attempt any FIVE – 5 × 10 = 50 Marks)

2(a) Chassis frame – functions, types, and loads

Functions of chassis frame:                Support vehicle components

Carry loads                                            Maintain alignment

Withstand shocks and vibrations

Types of frames:                                 Ladder frame

Box frame                                             Tubular frame

Backbone frame

Loads acting on frame:                      Static load

Dynamic load

Torsional load                                      Bending load

2(b) Torque converter and its application

A torque converter is a hydrodynamic device that transmits and multiplies torque using fluid.

Components:                                     Impeller

Turbine                                                Stator

Applications:

Automatic transmission vehicles         Heavy-duty vehicles

Buses and luxury cars

2(c) Air bleeding and master cylinder

Air bleeding:
It is the process of removing air bubbles from hydraulic brake lines to ensure effective braking.

Master cylinder construction:         Reservoir

Piston                                                 Return spring

Seals                                                   It converts pedal force into hydraulic pressure.

2(d) Steering gear boxes & rack and pinion

Types of steering gear boxes:        Worm and wheel

Worm and sector                              Rack and pinion

Recirculating ball

Rack and pinion working:
Rotational motion of steering wheel is converted into linear motion, providing precise steering and less effort.

2(e) Epicyclic gearbox

An epicyclic gearbox consists of:   Sun gear

Planet gears                                   Ring gear

Working:
By holding different elements stationary, different speed ratios are obtained. Used in automatic 
transmissions.

2(f) Power brake and servo system

Power brake:
Uses external power to reduce driver effort.

Servo system:
Uses vacuum or hydraulic pressure to multiply braking force, improving braking efficiency.

2(g) Wheel balancing and tubeless tyre

Wheel balancing:
Process of equalizing weight distribution to avoid vibration.

Tubeless tyre vs normal tyre:                    No inner tube

Reduced air leakage                                     Better heat dissipation

Improved safety

2(h) Short notes

(i) Independent suspension system
Each wheel moves independently, improving ride comfort and handling.

(ii) Fluid coupling
Hydrodynamic device that transmits power smoothly without mechanical contact.

SECTION – C (Very Long Answer Questions)

(Attempt any TWO – 2 × 15 = 30 Marks)

3. Clutch – need, requirements, and types

Need of clutch:                                           Engage/disengage engine from transmission

Smooth starting                                           Gear shifting

Requirements of good clutch:                   High torque capacity

Smooth engagement                                    Good heat dissipation

Minimum wear

Types of clutches:                                       Single plate clutch

Multi-plate clutch                                         Centrifugal clutch

Cone clutch

4. Transfer gearbox and propeller shaft

Purpose of transfer gearbox:                    Distribute power to all wheels

Provide high and low gear ratios                 Used in four-wheel-drive vehicles.

Propeller shaft functions:

Transmit power from gearbox to differential Accommodate angular and length variations

5. Suspension system elements and vehicle motions

Elements of suspension system:               Springs

Shock absorbers                                          Control arms

Stabilizer bars

Suspension movements:                            Bouncing: Vertical movement

Rolling: Sideways tilting during turns          Pitching: Forward/backward tilting during braking or acceleration

Suspension improves comfort, safety, and road handling.