DOM QUESTION PAPER - 5

QUESTION PAPER – 5

DYNAMICS OF MACHINES

   QUE NO 1:-

    (A) EXPLAIN THE IMPORTANCE OF FREE BODY DIAGRAMS IN CASE OF STATIC FORCE ANALYSIS.

    (B) HOW IS THE INERTIA TORQUE ON THE CRANK SHAFT OF A VERTICAL I.C. ENGINE DETERMINED ANALYTICALLY? STATE CLEARLY THE VARIOUS LOADS ACTING ON THE ENGINE.

   QUE NO 2:-

           (A) EXPLAIN CLEARLY THE USES OF CRANK EFFORT DIAGRAM.

     (B) A CAST IRON FLY WHEEL USED FOR A FOUR STROKE I.C. ENGINE IS DEVELOPING 18.75 KW AT 250 RPM.THE TANGENTIAL STRESSES DEVELOPED IN THE FLY WHEEL IS 5.2 MPA. THE TOTAL FLUCTUATION OF SPEED IS TO BE LIMITED TO 3% OF THE MEAN SPEED. IF THE WORK DONE DURING THE POWER STROKE IS 1/3 TIMES MORE THAN THE AVERAGE WORK DONE DURING WHOLE CYCLE, FIND THE MEAN DIAMETER AND MASS OF THE FLYWHEEL. THE DENSITY OF CAST IRON MAY BE TAKEN AS 7220 KG/M³.

   QUE NO 3:-

       (A) DETERMINE THE MINIMUM NUMBER OF TEETH ON PINION FOR INVOLUTE RACK IN ORDER TO AVOID THE INTERFERENCE.

         (B) DEFINE PRESSURE ANGLE AND BACKLASH IN GEARS.

    (C) A 20⁰ INVOLUTES PINION WITH 20 TEETH DRIVES A GEAR HAVING 60 TEETH.MODULE IS 10 MM.

(i)     STATE WHETHER INTERFERENCE OCCURS ON NOT, GIVE REASONS.

(ii)   FIND THE LENGTH OF PATH OF CONTACT, ARC OF CONTACT, NUMBER OF PAIRS IN CONTACT AND ANGLE TURNED BY PINION AND GEAR.

   QUE NO 4:-

         (A) EXPLAIN THE CONSTRUCTION OF DIFFERENTIAL AND SHOW HOW THE TWO  REAR WHEELS WILL ROTATE AT DIFFERENT SPEEDS WITH ITS HELP WHEN ROUNDING A CURVE.

       (B) WHAT IS MEANT BY INTERFERENCE IN INVOLUTES PROFILE GEARS? HOW THIS CAN BE AVOIDED? EXPLAIN.

   QUE NO 5:-

        (A) DERIVE AN EXPRESSION FOR THE RATIO OF TIGHT SIDE AND SLACK SIDE TENSIONS IN BAND AND BLOCK BRAKE.

     (B) DESCRIBE WITH NEAT SKETCH THE PRINCIPLE OF OPERATION OF AN INTERNAL EXPANDING SHOE BRAKE AND DERIVE EXPRESSIONS FOR BRAKING TORQUE AND MOMENTS.

   QUE NO 6:-

         (A) EXPLAIN THE EFFORT OF GOVERNOR AND DERIVE ITS EXPRESSION PORTER GOVERNOR.

          (B) FOLLOWING DATA REFER TO THE HARTNELL GOVERNOR:

         LENGTH OF BALL ARM                        =15 CM

         LENGTH OF SLEEVE ARM                   =10 CM

         MASS OF EACH BALL                              =4 KG

         MASS OF SLEEVE                                     =40 KG

         STIFFNESS OF SPRING                           =245 N/CM

         SLEEVE LIFT                                             =6 CM

         FRICTION FORCE                                    =29.43 N

                                                                                                                                                                            

     AT LOWER EQUILIBRIUM SPEED OF 300 RPM. THE RADIUS OF ROTATION OF BALL IS 8 CM.DETERMINE THE UPPER EQUILIBRIUM SPEED, EFFORT AND POWER OF GOVERNOR.

   QUE NO 7:-

      (A) PROVE THAT INTRODUCTION OF A FEEDBACK DEVICE IN AN OPEN LOOP CONTROL SYSTEM REDUCES THE TRANSFER FUNCTION AND INTRODUCES THE POSSIBILITY OF INSTABILITY. ALSO DISCUSS THE MERITS OF INTRODUCING THE FEEDBACK IN THE SYSTEM.

       (B) EXPLAIN RESPONSE, STABILITY AND SENSITIVITY IN CONNECTION WITH A CONTROL SYSTEM.

          (C) DETERMINE THE TRANSFER FUNCTION FOR HYDRAULIC RELAY SYSTEM.

   QUE NO 8:-

      (A) FIND THE ANGLE OF INCLINATION WITH RESPECT TO THE VERTICAL OF A TWO WHEELER NEGOTIATING A TURN. GIVEN: COMBINED MASS OF VEHICLE WITH ITS RIDER 250 KG; MOMENT OF INERTIA OF THE ENGINE FLYWHEEL 0.3 KG-M²; MOMENT OF INERTIA OF EACH ROAD WHEEL 1 KG-M², SPEED OF ENGINE FLYWHEEL 5 TIMES THAT OF ROAD WHEELS AND IN THE SAME DIRECTION; HEIGHT OF CENTRE OF GRAVITY OF RIDER WITH VEHICLE 0.6 M; TWO WHEELER SPEED 90 KM/HR; WHEEL RADIUS 300 MM; RADIUS OF TURN 50 M.

       (B) EXPLAIN THE GYROSCOPIC EFFECTS ON AIRCRAFT.