Answer ALL
questions
PART A –
(10×2=20 marks)
1.
Differentiate
between static and dynamic equilibrium.
2.
Define inertia
force.
3.
Can a single
cylinder engine be fully balanced? Why?
4.
What are the
effects of hammer blow and swaying couple?
5.
What are the
various types of damping?
6.
Define
magnification ratio.
7.
What is meant by
sensitivity of a governor?
8.
What is the
effect of friction on the governors?
9.
Define gyroscopic
couple.
10.
What is meant by
automatic controls?
PART B –
(5x16=80 marks)
11.
(a) A machine weighing 75 kg is mounted on
springs and is fitted with dashpot to damp vibrations. There are three springs each of stiffness 10
kg / cm and it is found that the amplitude of vibration diminishes from 3.84 cm
to 0.64 cm in two consecutive oscillations.
Assuming damping force varies as the velocity, determine the resistance
of the dashpot at unit velocity and compare the frequency of damped vibration
with the frequency when the dashpot is not in operation.
(or)
(b) A vertical single cylinder gas engine has a bore
of 8 cm and a stroke of 10 cm. the
connecting rod length is 20 cm and the reciprocating parts weigh 1.5 kg. The gas pressure on the piston is 6 kg/cm2
when it has moved 1.5 cm from the inner dead centre on its power stroke. Determine the net load on the gudgeon pin
when engine runs at 2000 rpm. At what
speed this load will be zero?
12 (a). The turning moment curve for an engine
is represented by the equation, T = (20000 + 9500 sin 2q - 5700 cos 2q) N-m, where q is the rotation of the
crank. If the resisting torque is
constant, find
i. Power
developed
ii. M.I of
the flywheel; and
iii.
angular acceleration of the flywheel at 450 of crank rotation from
I.D.C
iv. the
speed of the engine is 180 r.p.m and total fluctuation of speed is 1%.
(or)
(b). The four cylinders A, B,
C, D of a vertical engine are spaced at 24 cm, 11 cm and 24 cm centers. The reciprocating masses of cylinders A and D
each weigh 160 kg and their cranks are 900 to one another. The stroke is 12 cm and connecting rod length
is 20 cm. Determine the weights of
reciprocating masses for B and C and their crank position relative to A if all
the primary forces and couples are balanced one another. Calculate maximum unbalanced secondary force
when the engine is running at 450 r.p.m.
13 (a). A, B, C and D are four masses carried
by a rotating shaft at radii 100, 125, 200 and 150 mm respectively. The planes in which the masses revolve are
spaced 600 mm apart and the masses of B, C and D are 10 kg and 4 kg
respectively. Find the required mass A
and the relative angular settings of the four masses so that the shaft shall be
in complete balance.
(or)
(b). Determine the natural
frequency of oscillations of the system by energy method and also by Newton’s
method.
14 (a) The two equal masses of 500 kg and
radius of gyration 37.5 cm are keyed to
opposite ends of a shaft 60 cm long. The
shaft is 7.5 cm dia for the first 25 cm and 12.5 cm dia for the next 10 cm and
8.75 cm dia. For the remainder of its length.
Find the natural frequency of the free torsional vibration of the system
and the position of the node. Take G = 8
x 106 N/cm2.
(or)
(b). A motor cycle with its
rider weighs 250 kg., the centre of gravity of the machine and the rider
combined being 60 cm above the ground level when the machine is standing
upright. Each road wheel has a moment of
inertia of 8 kg – m and rolling diameter of 60 cm. the engine rotates six times the speed of the
road wheels in the same sense. The
moment of inertia of engine is 1.5 kg m2. Determine the angle of wheel necessary if the
motor cycle is traveling at a speed of 15 m/sec in a curve of 30 m.
15 (a) The controlling force FC and
radius of rotation of a spring controlled governor is given by the
expression.
FC = 2000r – 76
The mass of the ball is 5 kg and
extreme radii of rotation of the ball are 0.1m and 0.175m respectively for max.
and min speeds. If the friction on the
governor is 5 N at each ball find the coefficient of insensitiveness of the
governor at extreme radii.
(or)
(b) A governor of the proell type has
each arm 250mm long. The pivots of the
upper and lower arms are 25 mm from the axis.
The central load acting on the sleeve has a mass of 25 kg and them each rotating ball has a mass of 3.2 kg. When the governor sleeve is in mid –
position, the extension link of the lower arm is vertical and the radius of the
path of rotation of the masses is 175 mm.
The vertical height of the governor is 200 mm.
If the governor speed is 160 r. p. m
when in mid – position, find : 1.
length of the extension link; and 2. tension in the upper arm.
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