Pondicheey University MEEE61 Automobile Engineering

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Sri Ganesh College of Engineering and Technology
Department of Mechanical Engineering
MEE61-Automobile Engineering
2 MARK AND 11 MARK QUESTION AND ANSWERS
UNIT –IV
PART A (2 MARKS)
1. What is the function of brake? State its type.
The function of brake is to stop the vehicle within a short distance.
Types:
1. Mechanical brakes
a. Drum brakes
b. Disc brakes
2. Hydraulic brakes
3. Power brakes
a. Air brakes
b. Air-hydraulic brakes
c. Vacuum brakes
d. Electric brakes
2. What is a self energizing brake?
A brake is called self-energizing if it uses the rotational force of the wheel to help stop the
automobile.
3. What is disc brake?
These brakes are different from drum brakes in that the drum is replaced by a circular plate
and the brake shoes are replaced by a calliper which supports a pair of friction pads, one on each
side of the disc. These pads are forced inward by the operating force and so retard the disc.
4. What is meant by electric brake?
In an electric brake, the current from the battery is utilized to energize an electromagnet
within the brake drum. This actuates a cam to expand the brake shoes. When the current is not
supplied, the cam and brake shoes are returned to the release position by retractor springs.
5. What is regenerative braking?
A regenerative brake is an energy recovery mechanism, which slows a vehicle by converting
its kinetic energy into another form, which can be either used immediately or stored until needed.
This contrasts with conventional braking systems, where the excess kinetic energy is converted to
heat by friction in the brake linings and therefore wasted.
6. Define bleeding.
The operation of removing trapped air from the hydraulic braking system is known as bleeding.
7. What is the main function of brake fluid?
The main function of the brake fluid is power transmission. Brake fluid is used for power
transmission.

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8. How the parking brakes employed in vehicles are operated?
The parking brakes employed in vehicles are operated mechanically.
9. What is the main function of a master cylinder?
The main function of a master cylinder is to convert brake pedal force into hydraulic pressure.
10. What is meant by bleeding of brakes?
The process of removing air from the hydraulic brakes is known as bleeding of brakes. This is
known as bleeding of brakes.
11. What are the benefits of anti-lock brake system?
• Preventing the wheel from locking at the time of braking
• Keeping the wheel rotating
• Due to rotating wheel, it helps you to steer away the vehicle from the object, while
applying brakes at the same time.
• It is even more effective in sand, snow, water, and mud where loss of traction is even
higher, as on these surfaces, with normal braking system, it is even easier to
12. List out the various materials used in the construction of chassis frames.
Low Carbon Steel - 0.18 or 0.20 % carbon content
High Carbon Steel - 0.25 % carbon content
Alloy Steel – With alloying elements like Ni & Cr
13. What are the functions of frames in automobile?
1. To form the base for mounting engine and transmission system.
2. To withstand the engine and transmission thrust and torque stresses as well as accelerating
and braking torque.
3. To accommodate suspension system.
4. To carry the other parts of the vehicle and its passengers or goods.
5. To resist the effect of centrifugal forces when cornering a curve.
6. To withstand bending and twisting stresses due to the fluctuating or rear and front axle.
14. List out the various loads acting on the chassis frame?
1. Load of short duration
2. Combined loads of moment any duration
3. Inertia loads
4. Impact loads
5. Loads due to road camber
6. Loads due to wheel impact
7. Static loads
8. Overloads
15. What is meant by anti-lock braking system (ABS)?
The anti-lock braking system (ABS) monitors wheel speeds and releases pressure on individual
wheel brake lines, rapidly pulsing individual brakes to prevent lock-up. During heavy braking,
preventing wheel lock-up helps the driver maintain steering control. Modern ABS has an
individual brake line for each of the four wheels, enabling different braking pressure on different
road surfaces. Monitors wheel speeds and releases pressure on individual wheel brake lines,
rapidly pulsing individual brakes to prevent lock-up. During heavy braking, preventing wheel
lock-up helps the driver maintain steering control. Modern ABS has an individual brake line for
each of the four wheels, enabling different braking pressure on different road surfaces.

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UNIT-IV
PART- B (11 Marks)
1. Explain the Hydraulic braking systems with neat sketch.
Hydraulic Brake System
The pedal force in this system is transmitted to the brake shoes for its actuation through a
confined liquid known as brake fluid. The fluid pressure acting upon positions in the wheel brake
operating causes the brake shoes to expand. A system of force transmission based on Pascal’s law
helps to multiply and transmit the force applied on the pedal to the brake shoes.
A hydraulic braking system essentially consists of:
i. A fluid supply tank for storing the fluid necessary for operating the system.
ii. A master cylinder and piston connected by steel tubing to hydraulic wheel cylinders at each of
the four wheels and brake pedal.
iii. Pipelines and houses for conveying the fluids under pressure to the wheel brake shoe
operating units.
iv. The wheel cylinders whose position moves out for applying the pressure to the wheel brakes.
The main components of the hydraulic brake system are
1. Master Cylinder
2. Wheel Cylinder
Master Cylinder

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Master cylinder is the central unit in the hydraulic braking system. The hydraulic pressure required
to operate the system is produced here. The pressure of the driver’s foot on brake pedal through different
linkage arrangements is transmitted to the master cylinder piston. It can be considered as the heart of the
hydraulic braking system. The Master Cylinder is the heart of the hydraulic brake system.
It consists of two main chambers. The fluid reservoir contains the fluid to supply to the brake
system, and the compression chamber in which the piston operates. The reservoir supplies fluid to the
brake system through two ports. The larger port is called the filler or intake part and is connected to the
hollow portion of the piston between the primary and secondary cups which act as piston seals.
The smaller port is called the relief, bypass or compensating port which connects the reservoir
directly with the cylinder and lines when the piston is in the released position. When the brake pedal is
depressed, the master cylinder piston moves forward to force the liquid under pressure into the system. The
relief port is sealed out of the system. The liquid pressure is conducted to the wheel cylinders, where it
forces the wheel cylinder pistons out wards. These pistons force the brake shoes out against the brake
drums.
2. Explain the Drum type brake with neat sketch.
Drum Brakes:
Construction: The main components of drum brakes are
1. Brake drum
2. Back plate
3. Brake shoes
4. Brake Liners
5. Retaining Springs
6. Cam
7. Brake Linkages

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In this system the wheel is attached to drum. There are brake shoes used to contact the rotating
drum for braking operation. The shoes provide lining on their outer surface. The cam is used to lift the brake
shoes at one end, other end is connected by some method so as to make as the brake sleeve come into
contact in the brake drum. The retaining spring is provided for bringing the brake shoes back to its original
position, after releasing the brake pedal. All these parts are fitted in the back plate and enclosed with brake
drum.
Working:
When the pedal is pressed the cam moves the shoes outwards through linkages, there by coming
in frictional contact with the rotating drum. As soon as the brake pedal is released the retaining springs help
the brake shoes to brought back and release the brakes.

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3. Explain the Disc type’s brakes with neat sketch.
Disc brakes: There are two types of disc brakes:
1. Spot Type
a. Swinging Caliper Type
b. Sliding caliper type
2. Clutch Type
Construction:
The discs are made of gray cast Iron. The brake pressure in case of disc brakes have to be much
lighter than the drum brakes. It consists of rotating disc and two friction pads which are actuated by the four
hydraulic wheel pistons contain in two halves of an assembly is called a caliper.
The calliper assembly is secured to the steering knuckle in a front wheel brakes. The road wheel is
fashioned to the outer surface of the disc. The friction pads rides freely on each side of the discs. They are
in position being the hydraulic systems.
Working:
When the brake is applied hydraulic pressure is supply to the fluid inlet tube, due to which the
wheel cylinder piston force the friction pads against the rotating disc. In the released piston, the spring holds
the piston pads so that they maintain contact with disc surface.

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4. Write short notes on power brakes in automobile.
POWER BRAKES
Brakes operated by power other than physical effort applied at 'brake pedal, are known as Power
brakes. The power may be exerted by air pressure, engine vacuum or electrical energy. There are semi-
power or power assisted brakes too, in which the power assists or supplements the power in
Actuating the brakes, Hydraulic brakes are semi-power brakes in these brakes the engine vacuum assists in
the actuation of hydraulically operated brakes.
Main features
The main features of the power brake system are:
1. "Time-lag" or the time internal between the moment when pedal is pressed down and the Moment
when the brakes are put on must be very small.
2. The force applying the brakes should be closely proportional to the force exerted by the Driver on
the brake pedal.
These days the following systems are predominantly used for actuating the brakes:
1. Air brakes. 2. Air hydraulic brakes.
3. Vacuum brakes. 4. Electric brakes.
5. Write short notes on Air Brake system in detail.
Air Brake System:
The air brake system consists of two-stage air-compressor driven by the crankshaft or gearbox shaft. It
takes air from atmosphere, compresses it and delivers to the air reservoir through un-loader valve. Where
the pressure of the reservoir reaches the maximum degree, the unloader valve opens to the atmosphere.
Then the compressed air is directed in to the atmosphere directly.
Each of the four wheels fitted with brake chambers consists of a diaphragm, and which the air pressure is
applied and pushes it. This force operates the cam actuating lever and applies the brake. Each of the brake
chambers is connected to the brake pedal, and air filter is also fitted between the brake valve and reservoir.
Working:
When the brake pedal is pushed the brake valve opens and compressed air is allowed in to the
brake chamber. The brake valve consists of three passages.
1. Air intake 2. Exhaust 3. Brake chamber

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When the brake pedal is pressed the exhaust passage will be closed and Air intake passage open
and compressed air goes back to the chamber.
During return stroke the exhaust passage opens while intake closes and used air goes to the
atmosphere. This system fitted with an emergency mechanical brake, which can be used when air supply
fails the air brake system, which is called air assisted hydraulic braking system.
Advantages:
1. This system used in heavy vehicles because they are more powerful than hydraulic or mechanical
brakes.
2. It simplifies the chassis design
3. The compressed air is used for purposes like tyre inflation; for horn, windscreen wiper etc.
Disadvantage:
1. If there is any leakage in passage the entire system will be fail.
2. Therefore sealing of air is very difficult.
6. Explain the layout of chassis and main components in detail.
Layout of a Chassis and its main components
Various components of the motor vehicle, i.e. engine car body, wheels e.t.c. are required to be
supported. These are supported on a rigid structure providing a skeleton to hold the components together.
To withstand the shocks, blows, twists and vibrations coming during operation, chassis are provided cross-
bracings to increase rigidity. The whole of the chassis is now fastened to a frame of channel or U-shaped

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section. The engine is mounted in the front portion of frame through rubber cushioned motor mounts or
pads or washer placed between the brackets on the frame and support lugs on the engine.
Layout of Power Assembly and Transmission
To form a compact power assembly and transmission, the engine is connected to the clutch and
transmission which are further connected to final drive gears through the propeller shaft and universal joints.
Layout of Chassis and its main Components:
The following main components of the Chassis are
1. Frame: it is made up of long two members called side members riveted together with the help of
number of cross members.
2. Engine or Power plant: It provides the source of power
3. Clutch: It connects and disconnects the power from the engine fly wheel to the transmission
system.
4. Gear Box
5. U Joint
6. Propeller Shaft
7. Differential

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7. Explain the types of chassis frame in detail
TYPES OF CHASSIS FRAMES:
There are three types of frames
1. Conventional frame
2. Integral frame
3. Semi-integral frame
1. Conventional frame: It has two long side members and 5 to 6 cross members joined together with the
help of rivets and bolts. The frame sections are used generally.
a. Channel Section - Good resistance to bending
b. Tabular Section - Good resistance to Torsion
c. Box Section - Good resistance to both bending and Torsion
2. Integral Frame: This frame is used now days in most of the cars. There is no frame and all the assembly
units are attached to the body. All the functions of the frame carried out by the body itself. Due to elimination
of long frame it is cheaper and due to less weight most economical also. Only disadvantage is repairing is
difficult.
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. It has the advantage when the vehicle is met with accident the front frame
can be taken easily to replace the damaged chassis frame. This type of frame is used in FIAT cars and
some of the European and American cars
8. Explain the Different bodies used in automobile.
DIFFERENT BODIES USED IN AUTOMOBILES:
The Automobile bodies are divided in two groups
According to Chassis design the body can divided into
1. Conventional Type
2. Integral Type
3. Semi- Integral Type
According to other usage:
1. Light vehicle Bodies - cars, jeeps
2. Heavy vehicle Bodies – Busses, Lorries
3. Medium vehicle Bodies - Vans, Matadors
9. Explain the Requirements of bodies for various types of vehicle.
The body of the most vehicles should fulfil the following requirements:
Body
Passenger Body Commercial body

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1. The body should be light.
2. It should have minimum number of components.
3. It should provide sufficient space for passengers and luggage.
4. It should withstand vibrations while in motion.
5. It should offer minimum resistance to air.
6. It should be cheap and easy in manufacturing.
7. It should be attractive in shape and colour.
8. It should have uniformly distributed load.
9. It should have long fatigue life
10. Explain the basic requirements of brakes.
Basic Requirements of a Brake:
1. The brake must be strong to stop the vehicle during emergency within the shortest distance
without skidding.
2. The effectiveness of the brakes should remain constant even with prolonged application, as in
hill descending.
3. It should work efficiently irrespective of road condition and quality.
4. The retardation must be uniform throughout its application.
5. The pedal effort must be within the convenient capacity of the driver.
6. It must be reliable and should not be affected by heat, water and dust.
7. It should be in minimum weight.
8. It should have long life.
9. It should be easy to maintain and adjust.
10. Noise and vibrations are to be minimum.
11. There should be provision for secondary brake or parking brake.