Q2.
Attempt any THREE of the following (12 Marks):
a) Constant Mesh Gearbox
Working:
- In a constant mesh gearbox, all gears on the main shaft are in constant mesh with
corresponding gears on the lay shaft.
- The gears on the main shaft are mounted on splined shafts, allowing them to rotate
freely.
- Dog clutches are used to engage the required gear.
- For smooth engagement, helical or spur gears are used.
Advantages:
- Less gear damage
- Smooth operation
- Easy shifting with skill
b) Wishbone Type Suspension System
Description:
- A wishbone suspension (also called A-arm suspension) consists of upper and lower arms
shaped like wishbones.
- The wheel hub is placed between them and is connected via ball joints.
- A coil spring or strut is placed between the lower arm and the chassis.
Functions:
- Absorbs shocks
- Maintains wheel alignment
- Improves handling
c) Aerodynamic Forces on Vehicle Body
1. Drag Force: Opposes forward motion; caused by air resistance.
2. Lift Force: Acts perpendicular to motion; can cause instability.
3. Side Force: Acts sideways due to crosswinds; affects vehicle control.
4. Downforce: Pushes the car downward for better tire grip.
d) Starting System
Main Components:
1. Battery
2. Ignition switch
3. Starter motor
4. Solenoid
5. Starter drive (Bendix drive)
Working:
- When the ignition key is turned, the solenoid engages the starter motor.
- The motor rotates the flywheel, which cranks the engine for starting.
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Q3. Attempt any THREE of the following (12 Marks):
a) General Layout of Automobile
- Engine (Front or Rear mounted)
- Clutch
- Gearbox (Transmission)
- Propeller Shaft
- Differential
- Rear Axle
- Suspension System
- Chassis Frame
- Steering Mechanism
- Brake System
b) Hydraulic Braking System
Working:
- When the brake pedal is pressed, it pushes a piston in the master cylinder.
- This creates hydraulic pressure using brake fluid.
- The pressure is transmitted through brake lines to wheel cylinders.
- Wheel cylinders expand brake shoes or pads, which apply friction to brake drums or
discs.
Advantages:
- Equal braking force
- Smooth operation
- Less maintenance
c) MacPherson Suspension System
Construction:
- Uses a strut-type shock absorber as the upper suspension link.
- Lower control arm connects wheel hub to vehicle body.
- A coil spring is mounted over the strut.
- Used in front-wheel drive cars due to compact design.
Advantages:
- Lightweight and simple
- Compact layout
- Cost-effective
d) Bendix Drive
Working:
- Bendix drive is used in starter motors.
- When motor starts, pinion gear moves on threaded shaft to engage with flywheel.
- As engine starts, the gear disengages automatically.
Features:
- Simple and automatic
- Common in old vehicles
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Q4. Attempt any THREE of the following (12 Marks):
a) Importance of Aerodynamic Shape of Car Body
1. Reduces Air Drag: Improves fuel economy.
2. Increases Stability: Reduces lift for high-speed stability.
3. Improves Performance: Lowers engine load.
4. Noise Reduction: Minimizes wind noise.
5. Aesthetic Appeal: Modern, sleek look.
b) Drum Brake
Working:
- Hydraulic pressure pushes brake shoes outward against the rotating drum.
- Friction between the shoes and drum slows the wheel.
Components:
- Brake drum
- Brake shoes
- Wheel cylinder
- Return springs
Advantages:
- Simple design
- Cost-effective
- Reliable in smaller vehicles
c) Tube Tyre vs Tubeless Tyre
Tube Tyre:
- Has a separate inner tube filled with air.
- Prone to puncture when pinched or damaged.
Tubeless Tyre:
- Air is filled directly inside the tyre without inner tube.
- Rim and tyre bead make an airtight seal.
- Safer, lighter, and more efficient.
d) Alternator Construction and Working
Construction:
- Rotor (field winding) and stator (armature winding).
- Rectifier and voltage regulator.
Working:
- Engine drives rotor via belt to produce rotating magnetic field.
- Stator induces AC voltage.
- Rectifier converts AC to DC to charge battery and power electrical systems.
e) Role of AIMV (Advanced Intelligent Mechatronics Vehicle)
- Enhances vehicle automation and safety.
- Integrates AI, sensors, and mechatronics.
- Improves driver assistance, collision detection, and navigation.
- Supports autonomous driving technologies.
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Q5. Attempt any TWO of the following (12 Marks):
a) Six Traffic Symbols
1. Stop Sign (Red octagon)
2. Speed Limit (Circular board)
3. No Entry (Red circle with white bar)
4. School Zone (Children crossing)
5. U-turn Prohibited (U-turn with a cross)
6. Pedestrian Crossing (Walking figure on stripes)
b) Single Plate Clutch
Working Principle:
- Based on friction.
- Clutch plate pressed between flywheel and pressure plate to transmit power.
- Disengaged when pedal is pressed.
Components:
- Flywheel, Clutch plate, Pressure plate, Release bearing, Springs.
c) Steering Geometry
- Camber: Wheel tilt from vertical (front view).
- Kingpin Inclination: Angle between vertical and kingpin axis.
- Toe-In: Front edges of wheels closer than rear edges.
- Caster: Tilt of steering axis (side view).
- Toe-Out on Turns: Ackermann geometry for turning.
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Q6. Attempt any TWO of the following (12 Marks):
a) Wheel Balancing & Alignment
Balancing:
- Mount wheel on balancing machine, detect imbalance, attach weights, recheck.
Alignment:
- Check camber, caster, toe-in/out, adjust to specs, test drive.
b) Lead Acid Battery
Construction:
- Positive plate: PbO■, Negative plate: Pb, Electrolyte: H■SO■, Separators.
Working:
- Electrochemical reaction converts chemical to electrical energy on discharge.
- Reversed during charging.
c) Synchromesh Gearbox
Construction:
- Gears on layshaft and main shaft, syncro units with cones and rings.
Working:
- Synchro unit matches gear speeds before dog clutch engagement for smooth shifts.
