THEORY EXAMINATION (SEM–VI) 2016-17 DESIGN OF AUTOMOTIVE COMPONENTS

DESIGN OF AUTOMOTIVE COMPONENTS – NAU603

B.Tech (SEM VI) | Section-wise Solved Answers

SECTION – A

(10 × 2 = 20 marks)

(a) Camber and Castor

Camber is the inclination of the front wheel from the vertical when viewed from the front of the vehicle. It helps in uniform tyre wear and stability.
Castor is the inclination of the steering axis from the vertical when viewed from the side. It improves straight-line stability and steering self-centering.

(b) Double Declutching

Double declutching is a gear-shifting technique used mainly in non-synchromesh gearboxes. The clutch is operated twice to match gear speeds before engagement, reducing gear clash.

(c) Necessity of Gearbox

A gearbox provides different speed and torque ratios so that the engine can operate efficiently under various driving conditions such as starting, climbing, and cruising.

(d) Tractive Effort

Tractive effort is the force available at the driving wheels to propel the vehicle forward. It must overcome road resistance, air resistance, and gradient resistance.

(e) Need of Clutch

A clutch allows smooth engagement and disengagement of power from the engine to the transmission system, enabling smooth starting and gear changing.

(f) Sprag Clutch

A sprag clutch is a one-way clutch that transmits torque in one direction only. It is commonly used in automatic transmissions and starter motors.

(g) Cushioning Springs in Clutch Plate

Cushioning springs absorb shock during clutch engagement, ensuring smooth power transmission and reducing wear on transmission components.

(h) Material for Clutch Facing

Clutch facing materials include asbestos-free organic materials, sintered bronze, ceramic, and Kevlar-based composites due to their high friction and heat resistance.

(i) Use of Propeller Shaft

The propeller shaft transmits power from the gearbox to the differential, especially in rear-wheel-drive vehicles.

(j) Final Drive

The final drive reduces speed further and increases torque before transmitting power to the wheels through the differential.

SECTION – B

(Attempt any five – 10 marks each)

(a) Synchromesh Gearbox

A synchromesh gearbox uses synchronizer rings to match the speed of gears before engagement. This allows smooth and noiseless gear shifting. It consists of hub, sleeve, synchronizer rings, and dog teeth.

(b) Multi-Plate Clutch Numerical

Given power, speed, friction coefficient, and pressure limits, axial force is calculated using torque equations. The number of friction discs is determined based on torque capacity, and actual pressure is verified to be within safe limits.

(c) Torque Transmission in Multi-Plate Clutch

The torque transmitted depends on axial force, coefficient of friction, number of friction surfaces, and effective mean radius. Expressions vary depending on uniform pressure or uniform wear assumptions.

(d) CAD of Leaf Spring

Computer-aided design of leaf springs involves stress analysis, deflection calculation, and optimization using software tools. CAD improves accuracy and reduces design time.

(e) Steering Behavior

Steering behavior describes how a vehicle responds to steering input. Vehicles may exhibit under-steer, over-steer, or neutral steer depending on design and load conditions.

(f) Ackermann Steering Gear

Ackermann steering ensures that all wheels roll without slipping during turning. It satisfies the condition that inner wheel turns at a greater angle than the outer wheel.

(g) Total Resistance to Vehicle Motion

Resistances include rolling resistance, air resistance, gradient resistance, and acceleration resistance, all of which must be overcome by tractive effort.

(h) Loads on Front Axle

The front axle experiences bending stress, shear stress, and torsional stress due to vehicle weight, braking, and road shocks.

SECTION – C

(Attempt any two – 15 marks each)

(3) Correct Steering Geometry

Correct steering ensures that the axes of all wheels intersect at a common instantaneous center during turning.
Using given wheelbase, track width, and lock angle, expressions are derived to calculate turning circle radius and lock angles.

(4) Sliding Mesh Gearbox Design

Given gear ratios and speed reductions, the number of teeth on clutch gear, lay shaft gear, and main shaft gears are calculated using gear ratio relations.

(5) Final Drive and Full Floating Rear Axle

The final drive provides speed reduction and torque multiplication.
A full floating rear axle supports vehicle weight independently of the axle shaft, improving strength and reliability.