Jawaharlal Nehru Technological University Kakinada 2009-2nd Sem B.Tech Code No: Q0302/R05 III Supplementary s, / DYNAMICS OF MACHINERY ( Common to Mechanical Engineering, Mechatronics, Product

Code No: Q0302/R05
III B.Tech II Semester Supplementary Examinations, Nov/Dec 2009
DYNAMICS OF MACHINERY
( Common to Mechanical Engineering, Mechatronics, Production
Engineering and Automobile Engineering)
Time: three hours
Max Marks: 80
ans any 5 ques.
All ques. carry equal marks

1. (a) Write short notes on "Gyroscopic couple" as to how they are produced, their
magnitude and direction with respect to the spin and torque axes.
(b) A horizontal axle AB 200cms long is pivoted at its centre. It carries a weight
of 42N at B & a rotor weighing 100N at A. The rotor rotates at 1200 rpm in
clockwise direction looking from the front. compute the angular velocity of
precision taking the radius of gyration of the rotor to be 60cms. [6+10]

2. write short notes on the following:
(a) Friction circle
(b) Friction axis
(c) Coulombs laws of dry friction.
[16]

3. (a) define with neat sketch the fottinger torsion dynamometer.
(b) A simple band brake is operated by a lever of length 500mm. The brake
drum has a diameter of 500mm and the brake band embraces 5/8th of the
circumference. 1 end of the band is attached to the fulcrum of the lever
while the other is attached to a pin on the lever 100mm from the fulcrum. If
the effort applied to the end of the lever is 3kN and the coefficient of friction
is 0.25, obtain the maximum braking torque on the drum. [6+10]

4. (a) Derive the expression for the acceleration of the piston of a reciprocating
engine.
(b) A punching machine is needed to punch two cm diameter holes in 1.5cm thick
plates having ultimate shear stress of 3200kg/sq.cm. If 30 holes are to be
punched per minute and if punching operation requires 1/10th of a second, obtain
moment of inertia of a suitable flywheel in order that the speed lies ranging from
141 and 159 rpm.
[6+10]

5. A Porter governor carries a central load of 30 kgf and every ball weighs 4.5 kgf.
The upper links are 20cm long and the lower links are 30 cms long. The points of
suspension of upper and lower links are 5cms from axis of spindle. Calculate:
(a) The speed of the governor in rpm if the radius of revolution of the governor
ball is 12.5 cm and
(b) The effort of the governor for increase of speed of 1%. [16]

6. 4 masses m1, m2, m3 and m4 having 100, 175, 200 and 25 kg are fixed to cranks
of 20 cm radius and revolve in places 1, 2, three and 4. The angular position of the
cranks in planes 2, three and four with respect to the crank in plane one are 750 , 1350 and
2000 taken in the identical sense. The distance of planes 2, three and four from plane one are
60 cm, 186 cm and 240 cm respectively. Determine the position and magnitude of
the balance mass at a radius of 60 cm in plane L and M located at middle of the
plane one and two and the middle of the planes three and four respectively. [16]

7. A 4 coupled-wheel locomotive with 2 inside cylinders has reciprocating and
revolving parts per cylinder as 300 kgf and 250 kgf respectively. The distance
ranging from planes of driving wheels is 150 cms. The pitch of cylinders is 60cms. The
diameter of tread and driving wheels is 190 cms and the distance ranging from planes
of coupling rod cranks in 190 cms. The revolving parts for every coupling rod crank
are 125 kgf. The angle ranging from engine cranks is 900 and the length of coupling
rod crank 22 cms. The angle made by coupling rod crank with adjustment crank
is 180. The distance of center of gravity of balance weights in planes of driving
wheels from a scale center is 75 cms. Crank radius is 32 cms. Determine:
(a) The magnitude and position of balance weights needed in leading and trailing
wheels to balance 2/3 of reciprocating and whole of revolving parts if half of
the needed reciprocating parts are to be balanced in every pair of coupled
wheels.
(b) The maximum variation of tractive force and hammer blow when locomotive
speed is 100kmph.
[16]

8. A machine mounted on springs and fitted with a dashpot has a mass of 60 kg.
There are 3 springs, every of stiffness 12 N/mm. The amplitude of vibrations
decreases from 45 to eight mm in 2 complete oscillations. Assuming that the damping
force varies as the velocity. Determine:
(a) The damping coefficient.
(b) The ratio of frequencies of damping and undamped vibrations and
(c) The periodic time of damped vibrations.
[16]

Earning:   Approval pending.