AUTOMOTIVE MECHANICS MODEL QUESTION PAPER AUTOMOBILE ENGG 6TH SEM

MODEL QUESTION PAPER

 

Note;   1.         Question no 1 is compulsory.

2.                  Answer any two full questions from remaining sections A, B & C.

 

Qno: 1.   a.      Fill in the blanks with appropriate word.                                                        1x5=5

 

1.                  The inlet valve is made bigger to increase--------------efficiency of the engine.

2.                  To find the FP by Morse test the speed of the engine is kept---------.

3.                  The formula to find the distance between two shafts in gearbox is-----.

4.                  The distance between two front wheels is called as------.

5.                  The length of the spring, when there is no load on the spring is called as -----.

 

               b.      Derive an expression to find the front right wheel turning circle radius.                   05

 

SECTION-A

 

Qno: 2.   a.      Define the following terms                                                                                         05

1.                  Mechanical efficiency.

2.                  Volumetric efficiency.

 

   b.      A petrol engine working on Otto cycle has a clearance volume of 20% of the stroke volume. This engine consumes 8.1 liters of petrol/ hour, when developing 23.5KW IP. The sp.grvity of petrol is 0.76 and its heating value is 43900KJ/Kg. determine the indicated thermal efficiency of the engine.                                                         10

 

Qno: 3.   a.      Define the term gear ratio.                                                                                          02

 

b.            In a gearbox the clutch shaft pinion has 14 teeth and low gear main shaft pinion has 32 teeth. The corresponding lay shaft pinions have 36 and 18 teeth. The rear axle ratio is 3.7:1 and the effective radius of the rear tyre is 0.355 m. Calculate the vehicle speed in the above arrangement at an engine speed of 2500 rpm.

13

Qn: 4.     a.      State the difference between the Ackerman steering and Davis steering

Mechanisms.                                                                                                               05

 

b.            A truck has pivot pins 1.37 m apart, the length of each track arm is 0.18m and the

Track rod is behind front axle and is 1.27m long. Determine the wheel base which will give true rolling for all wheels, when the car is turning so that inner wheel stub axle is 60 degrees to the center line of the car.                                                    10

 

SECTION-B

Qno: 5.    a.     Derive an expression for stopping distance.                                                               05

b.          Prove that when a passenger car with wheel base equal to five time the height of

Center of gravity above the ground is braked to utilize all the road friction available (µ=0.6), the weight transferred from rear to front wheels is approximately 12% of the weight of the car.                                                                                                      10

Qno: 6    a.      Derive an expression for deceleration when brakes are applied to rear wheels, when

Vehicle is moving on a gradient.                                                                                10

b.            Define the fallowing terms.                                                                                        05

1.                  Pitch of the coil.

2.                  Free length.                                                    

Qno: 7     a.     A motor car weighs 13341.5N and has wheel base of 2.65m. The cg is 1.27 m

Behind the front axle and 0.76m above the ground. Maximum braking on all four wheels on level ground will bring the vehicle uniformly to rest from a speed of 64 km/hour in a distance of 25.9 m. Calculate the value of the adhesion between the tyre and the road.

b.         Under the same road conditions the vehicle descends a hill of gradient 1 in 20 and is braked on front wheels only. Determine the load distribution between front and rear wheels and the distance required to bring the car to rest.                                           15

 

SECTION-C

Qno: 8 a.         What are the advantages of hallow shaft?                                                                  05

b.                  A car with wheel base 2.75m with a cg of 0.85m above the ground and 1.15m behind the front axle has a coefficient of adhesion 0.6 between the tyre and the ground. Calculate the maximum  possible acceleration when vehicle is

1.                  Driven on front wheels.

2.                  Driven on rear wheels.

3.                  Driven on all wheels.                                                                                      10

 

Qno: 9.a.         Explain traction and tractive effort                                                                            05

b.                  An automobile engine develops 28 KW at 1500rpm and its bottom gear ratio is

3.06. If a propeller shaft of 40mm out side diameter is to be used, determine the

Inside diameter of mild steel tube to be used, assuming a safe shear stress of

55X103 KPascal.                                                                                                         10

 

Qno: 10.          A motor car weighs 17795 N including the four road wheels each of which has an

Effective dia of 0.66m, a radius of gyration of 0.28m and a weight of 294N has an engine developing 66 kW at 2400 rpm. The parts which rotate at engine speed weigh 1069N, with a radius of gyration of 0.115m. The transmission efficiency is 90% and the total road and air resistance at this engine in top gear of 3.84:1 is 873N on level.

                        Calculate the acceleration in m/s2, under those conditions and assuming the

Acceleration to be uniform the time required to increase the speed by 32km/hr.      15

 

 

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