ANNA UNIVERSITY EXAM PAPER
B.E. DEGREE EXAMINATION
IV Semester Automobile Engineering
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A — (10 ´ 2 = 20 marks)
1. Sketch the layout of the power plant and drive line for a 4–wheel drive vehicle and list out its salient features.
2. List out the different types of vehicles frames and sketch a typical ladder type frame.
3. Why an I section at the middle and rounded off square or oval section at the ends are used for the rigid type front axle of commercial vehicles?
4. Define caster and camber. Mention their influence on steering.
5. Derive an equation for true rolling of all the wheels in an Ackerman’s type of steering mechanism.
6. What do you mean by Hotch Kiss drive? How the torque reactions and driving thrust are taken care in this drive.
7. List out the different types of final drives, sketch them and mention their salient features?
8. Sketch the layout of a full floating rear axle and list out its salient features.
9. What are the different types of spring system used in the suspension of automobiles? How their spring rate differs?
10. A vehicle traveling at a speed of 80 km/hr. is stopped in a distance of 72 meters after application of brake. Assuming uniform deceleration for the vehicle find out the efficiency of the brakes.
PART B — (5 ´ 16 = 80 marks)
11. A car with a wheel track of 147.2 cm and wheel base of 274 cm is fitted with an Ackerman’s steering mechanism. The distance between the axis of the pivot pins is 122 cm and the tie–rod is 110.6 cm long. The track arm is 15.25 cm long. Find the turning circle radius of the car, so that true rolling motion is there for all the wheels.
12. (a) Explain how the torsional stiffness and bending rigidity of ladder type vehicle frame may be tested in the laboratory. Supplement your answer with sketches of the test set–up.
(b) With the aid of sketches explain the constructional details and working of a linear spool valve type hydraulically assisted steering system.
13. (a) Design a propeller shaft for a vehicle whose engine produces a maximum of 36 BHP at 1500 rpm. The first gear ratio is 3 : 2 : 1. The inner diameter of the tube is 2.75 cm and its length is 1.2 meters. The safe shear stress for mild steel used for the tube is 562.5 kg/cm2. The tube should withstand whirling as well as shear stresses.
(b) (i) Sketch and explain the constructional details of a Rzeppa type constant velocity joint. (8)
(ii) Explain the working of a typical differential unit used in automobiles. (8)
14. (a) List out the different types of independent front suspension system and write down the merits of this system. With the aid of sketch explain the constructional details of a Mc.pherson strut type suspension system.
(b) A truck spring has 12 number of leaves two of which are full–length leaves. The spring supports are 1.05 metres apart and the central band holding the leaves is 85 mm wide. The total load acting on the spring is 5.4 kN and the permissible stress is 280 N/mm2. Determine the thickness, width and the length of each spring leaf. The ratio of total depth to the width of the spring is 3. Also determine the deflection of the spring under this load. Take E = 0.21 ´ 106 N/mm2.
15. (a) A motor car has a wheelbase of 264 cm and its center of gravity is
0.61 meter above the ground and 112 cm in front of the rear axle. If the car is traveling at 40 KMPH on a level road, determine the distance in which the car may be stopped when (i) front wheels alone are braked
(ii) rear wheels alone are braked (iii) all the wheels are braked. The co–efficient adhesion between the tyre and the road surface may be taken as 0.6. Prove the formulas used.
(b) Write notes on the following :
(i) Double acting telescopic type a shock absorber.
(ii) Steering of crawler tractor.