Mechanical Engineering (Semester 5)
Total marks: 80
Total time: 3 Hours
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.
Solve any FIVE
State the different types of governors
Explain the term critical speed of rotating shaft.
Explain Gyroscopic Couple
Discuss the effect of damping on vibratory system.
Why is balancing necessary for rotors of high speed engines?
Explain in details condition monitoring and fault diagnosis.
The length of the arms of a Porter governor is 300mm long. The upper and lower
arms are pivoted to links at 50mm and 60mm, respectively, from the axis of the
rotation. The mass of each ball is 5kg and the sleeve is of mass 60kg. The frictional
force on the sleeve is 35N.Determine speed range for extreme radii of rotation of
120mm and 150mm.
The total mass of a four wheel trolley car is 1800kg. The car runs on rails of 1.6m
gauge and round a curve of 24m mean radius at 36 km/hr. The track is banked at
10°. The diameter of the wheels is 600mm. Each pair of wheels with axle has a mass
of 180kg and radius of gyration of 240mm. The height of the CG. of car above the
wheel base is 950mm. Determine the pressure on each rail.
Explain Dynamically Equivalent System and correction Couple.
In a damped vibrating system, the mass having 20kg makes 40 oscillations in 25sec.
The amplitude of natural vibrations decreases to one eighth of the initial value after
i. the logarithmic decrement
ii. damping factor & damping coefficient
iii. spring stiffness
How to convert multi-springs, multi dampers into a single spring and damper with
linear or rotational coordinate system?
A machine part having a mass of 2.5kg vibrates in a viscous medium. A harmonic
exciting force of 30N acts on the part and causes a resonant amplitude of 14mm
with a period of 0.22 sec. Find the damping coefficient. If the frequency of the
exciting force is changed to 4Hz, determine the increase in amplitude of forced
vibrations upon the removal of the damper.
Determine the natural frequency of oscillation of a half solid cylinder of mass ‘m’
and radius ‘r’ when it is slightly displaced from mean position and released.
How does the force transmitted to the base change as the speed of the machine
increases? Explain using an equation and the corresponding graph.
Explain the principle of vibration measuring instruments and working principle of
any one amplitude measuring instrument.
Each crank and connecting rod of a four crank in-line engine are 200mm and 800mm
respectively. The outer cranks are set at 120° to each other and each has a
reciprocating mass of 200kg. The placing between adjacent planes of cranks are
400mm, 600mm and 500mm. If the engine is in complete primary balance,
determine the reciprocating masses of the inner cranks and their relative angular
positions. Also find the secondary unbalanced force if the engine speed is 210rpm.