JSPM’S

Bhivrabai Sawant Polytechnic,Wagholi

Department of Mechanical Engineering

Result Improvement Program

A.Y -2023-24

Subject: Automobile Engineering (22656)

Class: TY
Name of Subject Teacher: Mali S.M

DAY: 01

1) Name the various components mounted on the chassis frame. ( 2 Marks)

Ans: Components mounted on the chassis frame:

(i) Engine (Power plant) (ii) Clutch (iii) Gear Box (iv) Differential (v) Wheels & Tyre
assembly (vi) Suspension system (vii) Braking System (viii) Steering System (ix) Front and
Rear axle assembly

2) Compare front engine front wheel drive (FEFWD) with front engine rear wheel drive
(FERWD) (Any Four Points). ( 2 Marks)
 3. List different frames used in automobile construction. ( 2 Marks)

Types of Frames used in Automobiles:

(A) According to Construction:

(i) Conventional frame

(ii) Integral Frame (Unitized Body/Frameless construction/Monocoque construction)

(iii) Sub/Half Integral frame

(B) According to Engine Position:

(i) Full Forward Chassis Frame

(ii) Semi Forward Chassis Frame

(iii) Bus Chassis Frame

4. State the function of the propeller shaft. ( 2 Marks)

Function of Propeller Shaft:

The function of the propeller shaft is to transmit torque from the gearbox to the Differential through
the universal joints. The differential then transmits the torque to the rear axle to which the rear wheels
are connected.

5. State working principle of the clutch. ( 2 Marks)

Working principle of clutch:

A clutch works with two rotating shafts, one that is typically driven by a motor or pulley and one
that drives another device. The clutch connects the two shafts so they can either be locked together
and spin at the same speed or be decoupled and spin at different speeds.

6. State working principle of a centrifugal clutch. ( 2 Marks)

The centrifugal clutch operates on a principle of centrifugal force, instead of spring force for keeping it
in the engaged position. The force acting away from the center; is known as a Centrifugal force.
Centrifugal clutch does not require a clutch pedal for operation. The clutch is operated automatically
depending on the engine speed. The vehicle can be stopped in gear without stalling the engine. Similarly,
the vehicle can be started in any gear by pressing the accelerator pedal. This makes the driving operation
very easy.

7. State need of universal joint and slip joint used in the propeller shaft. ( 2 Marks)

Need for Universal Joint: A universal joint is a particular type of connection between two shafts,
whose axes are inclined to each other. It is used where two shafts are connected at an angle to transmit
the torque. The purpose of the universal joint in an automobile is to absorb the angular changes
brought about by changes in relative positions of the differential in relation to the transmission and in
this way to smoothly transmit power from the transmission to the differential. U joints take care of the
variation in the inclination of the propeller shaft during the up-and-down movement of the vehicle.
Need of Slip (Sliding) Joint: Depending upon the type of drive, one slip joint may be there in the
shaft. This serves to adjust the length of the propeller shaft when demanded by the rear axle
movements. Slip joint used to accommodate the change in length due to road irregularities.

8. Describe various types of alternative fuels for auto engines. ( 2 Marks)

Answer: Types of Alternative fuels for auto engines:

[1] Biodiesel used for Diesel Vehicles:

It refers to any diesel equivalent processed fuel, derived from biological sources. Therefore, it is a
processed fuel that is ready to be used in common diesel engine vehicles.

[2] Ethanol used for Flex Fuel Vehicles:

It is derived from crops. It can be used as a fuel either alone in a special engine or as an additive to
gasoline.

[3] Natural Gas used for Natural Gas Vehicles:

Natural gas is a mixture of hydrocarbons consisting of approximately more than 80 percent methane
used in two forms; CNG (compressed natural gas) and LNG (liquefied natural gas).

[4] Methanol:

Also known as Methyl Alcohol. It might be an alternative to petrol especially because it is very easy
to manufacture it from methane.

[5] Liquified Petroleum Gas:

LPG means Liquefied Petroleum Gas. It is also called bottled gas (or) Refinery gas. It is obtained as a
byproduct during the cracking of heavy crude oils or from directly obtained natural gas.
9. Explain the working of a constant mesh type gearbox with a neat sketch. ( 4 Marks)

Answer: Working of Constant Mesh Gear Box:

In this gear box, all the gears on the main (transmission) shaft are constantly connected to the
corresponding gears on counter (lay) shaft. In addition, two dog clutches are provided on the main
shaft. One dog clutch is between the third gear and clutch gear and another is between the first
(Low) gear and second gear. Top or 4th speed gear is obtained when the left dog clutch is shifted
to the left to mesh with clutch gear by using the gear shift lever. In this case, main shaft rotates at
the same speed as that of clutch gear or engine crankshaft speed which is the maximum speed.
Third gear is obtained when dog cutch (left side) meshes with third gear on main shaft. In this way
by sliding the second dog clutch, second and first gears are obtained.

10. Discuss the classification of brakes from different considerations. ( 4 Marks)

The following are the classifications of Brakes

[1] By method of power (according to actuation):

(a) Mechanical brakes

(b) Hydraulic brakes

(c) Air brakes

(d) Vacuum brakes

(e) Power assisted hydraulic brakes

(f) Magnetic brakes

(g) Electrical brakes

[2] By method of application (according to purpose):

(a) Primary or Service or footbrakes

(b) Secondary or Parking or handbrakes

 [3] By method of operation (according to extra braking efforts):

(a) Servo or Power Assisted brakes

(b) Power-operated brakes

[4] By method of Braking contact (according to construction):

(a) Internal Expanding brakes

(b) External Contracting brakes

[5] By Method of Applying Brake Force:

(a) Single Acting brakes

(b) Double Acting brakes.

[6] According to a number of wheels:

(a) Two-wheel brakes

(b) Four-wheel brakes

[7] According to the location:

(a) At Transmission

(b) At the wheel

11.Explain the importance of the aerodynamic shape of a car body. ( 4 Marks)

Answer: Importance of the aerodynamic shape of a car body:

i) It reduces air resistance or air drag.

ii) It prevents undesirable lift.

iii) It improves the fuel economy of the car by reducing fuel consumption.

iv) It increases the stability of the car on the road at higher speeds.

v) It reduces the noise of cars.

vi) It improves the aesthetic appearance of car.

vii) It reduces the driver’s effort to drive the vehicle.

viii) It improves the speed of vehicle.

ix) It reduces the running cost of the vehicle.

12. Explain the working of diaphragm type clutch with a neat sketch. ( 4 Marks)

Working of Diaphragm Type Clutch:

[A] Disengaged condition:

[1] When the driver presses the clutch pedal through a linkages release fork presses the release bearing.
[2] Due to the release Fork presses the release bearing, Release Bearing presses the middle portion of the
diaphragm to move inwards.

[3] Due to the inwards movement of the middle portion of the diaphragm, the outside part of the
diaphragm moves backward as well as pressure plate also moves backward.

[4] Therefore due to the pressure plate’s backward movement, pressure on the friction plate gets
removed. So, there is no friction between the plates & flywheel. Hence no power transmission
takes place. Hence clutch gets disengaged.

[B] Engaged condition:

[1] When the driver releases the clutch pedal, results in diaphragm again comes to its original position.

[2] Hence outside part of the diaphragm moves inside & presses the pressure plate on the friction plate &
flywheel.

[3] Therefore, friction occurs between them. Hence power/torque again starts to transmit from the
flywheel to the clutch shaft. Hence Clutch gets engaged.
 13. Describe the working of the master cylinder with a neat sketch. ( 4 Marks)

Answer: Working of Master cylinder:

The master cylinder consists of the following two sections;

[1] Fluid Reservoir contains the fluid to supply to the brake system. Fluid Reservoir supplies fluid to the
brake system through two parts.

[2] The compression Chamber contains the spring-operated piston and Intake & Bypass port for brake
fluid circulation.

As a pedal is pressed, the push rod moves to the left against the force of the spring,
till it covers the by-pass port. Further movement of the push rod causes the building up of pressure
in the compression chamber. Finally, when sufficient pressure has built up, the inner rubber cup of
the fluid check valve is deflected, forcing the fluid under pressure in the lines. This fluid enters the
wheel cylinder or the caliper and moves the piston thereby applying the brakes. When the brake
pedal is released, the spring pressure in the master cylinder moves the piston to the right extreme
position. This same force of the spring keeps the fluid check valve pressed on its seat for some
time and thereby delays the return of fluid from the lines into the compression chamber again.

14. Explain Rack and Pinion type steering gearbox with a neat sketch. ( 4 Marks)

Rack and Pinion Type Steering Gear Box: In this type of steering gearbox, a
pinion is mounted at the end of the steering shaft. The pinion engages with the rack which
is provided with a ball joint at each end in order to allow for the rise and fall of the wheel.
The rotary motion of the steering wheel is transmitted to the pinion. The circular motion of
the pinion is converted into the linear rack movement, which is further transmitted to tie
rods to the stub axle through the ball joint. This type of steering gearbox provides
sufficiently low gear reduction for cars and it is quite suitable even for heavier motor
vehicles if assisted with power. It occupies very less space and less a number of linkages.
15. State function and need of independent suspension system. ( 4 Marks)

Function of Independent Suspension System:

1. It has light moving parts that help the wheel to follow the road irregularities.

2. The Unsprung weight is low.

3. It absorbs road shocks or impacts due to bumping in the road by oscillation.

4. Tires also provide a spring effect, but to a smaller extent.

5. It set the parameters like camber, caster, and kingpin inclination for better steering Quality.

6. Axle should not tilt and the wheel remains vertical.

7. It reduces the shocks to passengers and gives a comfortable ride, also reducing additional stresses
in the automobile frame body.

8. It requires a more rigid sub frame or chassis frame.

Need for Independent Suspension System:

1. In order to provide a comfortable ride to the passenger and avoid additional stresses in the
vehicle frame.

2. The vehicle should neither bounce nor roll or sway the passengers when cornering nor pitch when
accelerating, braking or suddenly lifting or dropping of the front wheel with respect to the rear
wheel.

3. Although some of the road irregularities and inequalities are absorbed by large tires.

4. It may provide a softer suspension because the low spring rate (stiffness) enables large wheel
movement.

5. In this the engine and chassis frame can be placed relatively lower which means the engine
position can be moved forward so more space for the passenger.

6. The unsprung weight is low.

16. State need of ABS .Draw typical layout of ABS. Write in Brief role different components

( 4 Marks)

Need of ABS

It is also known as anti-skid braking system. Wheels skid when they slow down faster than the
vehicle. To prevent skidding of the vehicle the wheels must not be lock up. This is the purpose of
antilock braking system.

Role of Different Components:-

1. Electronic Control Unit (ECU) It is heart of ABS. It monitors and controls antilock brake
function when required. Its function based on input from wheel speed sensors and hydraulic
unit to decide whether antilock operation is necessary or not

2. Accumulator It is used to maintain high pressure in braking system by storing hydraulic fluid. It
also provides residual pressure for power assisted braking.

3. Wheel Speed Sensor It is mounted on each wheel. It is used to measure speed of wheel. It sends
signal to ECU.

4. Hydraulic Unit the brake lines from the master cylinder are connected to it. It modulates the
brake pressure as per the signals provided by the ECU.

17. Describe the working of the Disc brake. Draw a net sketch. ( 4 Marks)

Working of Disc Brake:

Motor vehicles are now fitted with disc brakes instead of conventional drum brakes. Disc
brakes use friction to create braking power. Disc brakes create braking power by forcing flat
friction pads against the sides of the rotating disc.
Disc brake mainly consists of, (i) Rotor (ii) Caliper, and (iii) Brake pads.
In between each piston & disc, a friction pad is held in position by springs. When the brakes
are applied, hydraulically actuated pistons move the friction pads into contact with the discs,
applying equal and opposite forces on the latter. On releasing the brakes, the rubber sealing
rings act as return springs and retract the pistons and the friction pads away from the disc.