PTU Punjab Technical University B-Tech May 2019 Question Papers 4th Semester Automobile Engineering
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Roll No.
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech. (AE) (2011 Onwards) (Sem.?4)
MECHANICS OF MACHINES
Subject Code : BTAE-402
M.Code : 54123
Time : 3 Hrs. Max. Marks : 60
INSTRUCTIONS TO CANDIDATES :
1.
SECTION-A is COMPULSORY consisting of TEN questions carrying T WO marks
each.
2.
SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3.
SECTION-C contains T HREE questions carrying T EN marks each and students
have to attempt any T WO questions.
SECTION-A
1. Write briefly :
a. Distinguish between lower pair and higher pairs giving examples.
b. What is Kutzback's criterion for degree of freedom of plane mechanisms?
c. What is meant by the term "Crowning of Pulleys"? Why is it done?
d. What is the difference between simple and compound mechanism?
e. Why cycloidal motion of follower is preferred for high speed engines?
f. Distinguish bet www.FirstRanker.com
ween the working of a flywheel and a governor.
g. Define coefficients of fluctuation of energy and speed.
h. Is it possible to give the same equilibrium speed as in case of porter governor, balls of
smaller mass will be required in proell governor?
i. Differentiate between completely constrained motion and successfully constrained
motion with the help of suitable example.
j. State D'Alembert's principle and its significance.
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SECTION-B
2. The crank length of a petrol engine is 50 mm and the connecting rod is 175 mm long and
the crank rotates at a uniform speed of 400 r.p.m. calculate the velocity and acceleration of
the piston at different positions of the piston along its stroke and plot the curves. Also find
the crank position at which the piston's acceleration is zero.
3. Four masses A, B, C and D are carried by a rotating shaft at radii 80 mm, 100mm, 160mm
and 120mm respectively are completely balanced. Masses B, C, D are 8kg, 4kg and 3 kg
respectively. Determine the mass A and the relative angular positions of the four masses if
the planes are place 500mm apart.
4. A belt 100 mm wide and 10 mm thick is transmitting power at 1000 m/min. The net driving
tension is 1.8 times the tension on slack side. If the safe permissible stress on the belt
section is 1.6 N/mm2, calculate the max. power that can be transmitted at this speed.
Assume density of the leather as 1 kg/m3. Calculate the absolute max. power that can be
transmitted by this belt and the speed at which this can be transmitted.
5. What is meant by Inversion of a mechanism? Describe any one Inversion of slider crank
chain mechanism with the help of neat diagram.
6. A cast iron flywheel is fitted to a punch press to run at 90 r.p.m and must supply 12000 N-
m of energy during 1/5th revolution and allow 15% change of speed. The ring speed is
limited to 350 m/min. Find the mean diameter, mass of flywheel and the motor power.
Assume overall efficiency as 80%.
SECTION-C
7.
The length of the connecting road of a gas engine is 500 mm and its centre of gravity lies at
165 mm from the crank pin centre. The rod has a mass of 80 kg and radius of gyration of
182 mm about an axis through the centre of mass. The stroke of the piston is 225 mm and
the crank speed is 300 rpm. Determine the Inertia forces on crankshaft when the crank has
turned 30? and 135? from the inner dead centre.
8.
An offset translating roller follower is driven by a cycloidal motion cam rotating at 600
r.p.m. The maximum follower rise is 3 cm during 150? of cam rotation. If the amount of
offset is 0.5 cm, the www.FirstRanker.com
pressure angle 14? for the offset follower at a cam angle of 60?, find
the prime circle radius. Also determine the maximum velocity and acceleration.
9.
In a Hartnell governor, the radius of ball is 60 mm at the minimum speed of 300 r.p.m. The
length of the ball arm is 140 mm and the sleeve arm is 90 mm. The mass of each ball is 5
kg and the sleeve is 8 kg. The stiffness of spring is 32715 N/m. Determine :
a) Speed when the sleeve is lifted by 50 mm
b) Initial compression of the spring
c) Governor effort
d) Power
NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any
page of Answer Sheet will lead to UMC against the Student.
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This post was last modified on 04 November 2019