(SEM.VII) THEORY EXAMINATION 2018-19 AUTOMOBILE ENGINEERING

AUTOMOBILE ENGINEERING (NME-702)

B.Tech – Semester VII

SECTION A

(Attempt all questions)

(a) Automobile and classification of automobiles

An automobile is a self-propelled vehicle designed for transportation of passengers or goods on roads. Automobiles can be classified on different bases such as type of fuel, purpose, number of wheels, and transmission system. Based on fuel, automobiles may be petrol, diesel, electric, hybrid, or CNG powered. Based on purpose, they are classified as passenger vehicles, commercial vehicles, and special-purpose vehicles. Such classification helps in understanding vehicle design, performance, and application.

(b) Important events in the history of automobile

The history of the automobile began with the invention of the steam engine, followed by the development of internal combustion engines. Karl Benz introduced the first practical petrol automobile in 1885. Henry Ford revolutionized automobile manufacturing by introducing mass production through the assembly line. The later introduction of diesel engines, automatic transmissions, electronic fuel injection, and emission control technologies marked major milestones in automobile development.

(c) Reason for using bigger tyres at the rear of vehicles

Bigger tyres are used at the rear of vehicles because the rear wheels usually carry more load and are responsible for transmitting driving torque to the road. Larger tyres provide better traction, improved load-carrying capacity, and enhanced vehicle stability. This arrangement also reduces tyre wear and improves overall vehicle performance, especially in rear-wheel-drive vehicles.

(d) Defects in clutch

Clutch defects arise due to wear, improper adjustment, or overheating. Common defects include clutch slipping, dragging, grabbing, and excessive noise. These defects affect smooth power transmission from engine to gearbox and may lead to reduced efficiency and poor drivability if not rectified in time.

(e) Stability and safety in modern cars

Stability and safety in modern cars have greatly improved due to advancements in vehicle design and technology. Features such as anti-lock braking systems, electronic stability control, airbags, crumple zones, traction control, and improved suspension systems enhance vehicle control and protect occupants during accidents. These innovations have significantly reduced road fatalities and injuries.

(f) Periodic observations and replacements in automobiles

Regular maintenance of automobiles involves periodic inspection and replacement of engine oil, filters, brake fluid, coolant, and transmission oil. Tyre pressure, battery condition, brake wear, and suspension components are also checked. Periodic maintenance ensures smooth operation, improved fuel efficiency, and longer vehicle life.

(g) White exhaust smoke during engine start

White exhaust smoke during cold start is mainly due to condensation of water vapour in the exhaust system. It may also indicate coolant leakage into the combustion chamber. Proper engine warm-up and timely inspection of cooling system components help prevent this issue.

(h) Significance of BS-III and BS-IV engines

BS-III and BS-IV engines represent Bharat Stage emission standards aimed at reducing vehicular pollution. These standards limit harmful emissions such as carbon monoxide, hydrocarbons, and nitrogen oxides. Adoption of BS-IV engines led to cleaner fuel, advanced engine technology, and reduced environmental impact.

(i) Kingpin offset

Kingpin offset is the horizontal distance between the center of the tyre contact patch and the point where the kingpin axis meets the ground. Proper kingpin offset improves steering stability, reduces steering effort, and enhances directional control of the vehicle.

(j) Comparison between Hotchkiss drive and torque tube drive

Hotchkiss drive transmits driving torque through the leaf springs and is widely used due to its simplicity and ease of maintenance. Torque tube drive encloses the propeller shaft within a tube that absorbs torque reaction, providing smoother operation but increased complexity. Hotchkiss drive is more common in modern vehicles due to its practicality.

SECTION B

(Attempt any three)

Preventive maintenance and overhauling system

Preventive maintenance involves regular inspection, servicing, and minor repairs to prevent major failures. It reduces breakdowns, enhances safety, and lowers operating cost. Overhauling, on the other hand, involves complete dismantling, inspection, repair, and replacement of worn-out components to restore vehicle performance. Both systems are essential for efficient vehicle operation.

Transmission system and its importance

The transmission system transmits power from the engine to the driving wheels while allowing variation of speed and torque. It includes clutch, gearbox, propeller shaft, differential, and axles. Proper transmission ensures smooth acceleration, fuel efficiency, and adaptability to different driving conditions.

Suspension system and its function

The suspension system absorbs road shocks and vibrations, ensuring ride comfort and vehicle stability. It maintains tyre contact with the road surface, improves handling, and protects vehicle components from damage. Modern suspension systems are designed to balance comfort and control.

SECTION C

(Attempt any one)

Resistances encountered by a moving vehicle

A moving vehicle experiences several resistances that oppose motion. Road resistance occurs due to tyre deformation and surface irregularities. Air resistance increases with vehicle speed and depends on shape and frontal area. Gradient resistance acts when a vehicle moves uphill due to gravitational force. These resistances can be minimized through proper tyre inflation, aerodynamic design, and efficient route planning.

Ackermann steering geometry

Ackermann steering geometry ensures that all wheels roll without slipping while turning. It achieves this by making the inner front wheel turn through a greater angle than the outer wheel. Proper steering geometry reduces tyre wear and improves vehicle control during cornering.