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Posted Date: 23 Jul 2009 Posted By: phanidra Member Level: Gold
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2009 Jawaharlal Nehru Technological University Mechanical Engineering Jntu Hyderabad,Code No: R05320304 , III B.Tech II Semester Regular Examinations, Apr/May 2009 ,DYNAMICS OF MACHINERY Question paper
Code No: R05320304 Set No. 1
III B.Tech II Semester Regular Examinations, Apr/May 2009
DYNAMICS OF MACHINERY
( Common to Mechanical Engineering, Mechatronics, Production
Engineering and Automobile Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. (a) Differentiate between natural precision and forced precision.
(b) Locomotive moving at a speed of 100 km/hr turns round a curve of 500m
radius to the right. The pair of driving wheels is 2m in diameter and along
with the axle weigh 20KN. The radius of gyration of wheels together with the
axle may be taken as 0.6m. Find the gyro effect on the pair of driving wheels.
[6+10]
2. (a) What is meant by film or viscous friction? Describe Tower’s experiment on
Journal bearing friction to explain film or viscous friction.
(b) A screw jack is used to lift a load of 30kN. The screw of the screw jack is square
threaded with two threads to 1.2 cm. If the coefficient of friction between the
nut and screw is 0.09 and the outer diameter of the screw is 6 cm, find the
force required at the end of the handle of length 60 cm to lift the load.[6+10]
3. (a) Derive the expression for the torque transmitting capacity of a single plate
clutch by considering uniform wear.
(b) A clutch has disk plates with outer radius 120mm. An axial force of 4KN is
acting on them. The disc plates are new and having coefficient of friction 0.7.
Assuming uniform pressure and uniform wear, find the torque transmitted.
i. When the disc plates are solid.
ii. When the disc plates are hallow outer radius 120mm and inner radius
60mm. [6+10]
4. A vertical engine of 14.25 cm stroke has a connecting rod 31.5 cm long between
centers and weighing 27.5 N. the mass center is 9.75 cm from the big end center and
when suspended from the gudgeon pin axis the rod makes 21 complete oscillations
in 20 seconds.
Determine
(a) The radius of gyration of the rod about an axis through the mass center.
(b) The inertia torque exerted on the crank shaft when the crank is 40 degrees
from the TDC and is rotating at 1500 rpm. [16]
5. The particulars of a Hartnell type governor are the following
m=1.4kg
a=0.1m, b=0.05mr1=0.075m, N1=300 rpm
r2=0.1125m, N2=318 rpm
The axis of rotation is 0.09m from the fulcrum. Determine the rate of spring and
equilibrium, speed when radius of rotation of the ball is 0.09m. [16]
6. Two weights of 8kg and 14kg rotate in the same plane at radii of 1.5 and 2.25 m
respectively. The radii of these weights are 600 apart. Find the position of the
third weight of the magnitude of 12kg in the same plane which can produce static
balance of the system. [16]
7. The following data refer to a four coupled wheel locomotive with two inside cylin-
ders:
pitch of cylinders = 600 mm
reciprocating mass/cylinder = 315 kg
revolving mass/cylinder = 260 kg
Distance between driving wheels = 1.6 m
Distance between coupling rods = 2 m
Diameter of driving wheels = 1.9 m
Revolving parts for each coupling rod crank = 130 kg
Engine crank radius = 300 mm
Coupling rod crank radius = 240 mm
Distance of centre of balance mass in planes of driving wheels from axle
center = 750 mm
Angle between engine cranks = 900
Angle between coupling rod crank with adjacent engine crank = 1800
The balance mass required for the reciprocating parts are equally divided between
each pair of coupled wheels. Determine:
(a) The magnitude and position of the balance mass required to balance 2/3 of
reciprocating and whole of the revolving parts.
(b) The hammer blow and the maximum variation of tractive force when the
locomotive speed is 80 kmph. [16]
8. A 1200 kg machine mounted on four identical springs of total spring constant K
and having negligible damping. The machine is subjected to a harmonic external
force of amplitude F0 = 490 N and frequency 180 rpm. Determine the amplitude if
motion of the machine and maximum force transmitted to the foundation because
of the unbalanced force when K = 1.96×106 /m.
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