MdId Gtu Paper

Seat No.: ________ Enrolment No.
___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER–IV(New) • EXAMINATION – WINTER 2016
Subject Code:2141907 Date:23/11/2016
Subject Name:Machine Design & Industrial Drafting
Time: 02:30 PM to 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 Short Questions 14
1 What is Machine design? Why the study of machine design
is necessary?
2 Differentiate among shaft, spindle and axle.
3 Write any two applications of knuckle joint.
4 Why nut is manufactured from phosphor bronze in case of
power screws?
5 Define lead and state the relation between lead and pitch in
case of threaded screws.
6 What is the function of cotter in cotter joint? Where it is
used?
7 What is the difference between rigid coupling and flexible
coupling?
8 Differentiate between crushing stress and bearing stress.
9 “As the value of tolerances increases i.e. more precise
tolerances, the cost of manufacturing the product is
increases”, Justify the statement.
10 Draw the neat sketch of any two types of geometric

tolerances and explain the meaning of each.
11 List the types of riveted joints.
12 What is the criterion of design of fulcrum pin in levers?
13 State the Rankine’s formula in the design of columns.
14 Differentiate between strut and column.
Q.2 (a) What are the reasons for using factor of safety? Why its 03
values are different for different applications?
(b) What is stress concentration? Explain any two methods of 04

reducing of it with neat sketches.
(c) The load on a bolt consists of an axial pull of 10 kN together 07
with a transverse shear force of 5 kN. Find the diameter of
bolt required according to (i) maximum principal stress
theory, (ii) maximum principal shear stress theory,
(iii) maximum distortion energy theory.
Take permissible tensile stress at elastic limit as 100 MPa
and poison’s ratio as 0.3.
OR
(c) Design a right angled bell crank lever to raise a load of 6 kN 07

at short arm. The lengths of short and long arms of a lever
1
are 90 mm and 540 mm respectively. The lever and the pins
are made of steel. The permissible stresses of steel are 80
N/mm2 in tension, 40 N/mm2 in shear and 10 N/mm2 in
bearing. Assume the cross section of the lever as rectangular
with depth as three times the thickness.
Q.3 (a) Classify the couplings. 03

(b) Compare the strength of square key and rectangular key, if 04
the diameter of the shaft is 80 mm and length of key is 50
mm.
(c) Design a shaft supported by two bearings placed 1 m apart. 07
A 600 mm diameter pulley is mounted at a distance of 300
mm to the right of left hand bearing and this drives a pulley
directly below it with the help of belt having maximum
tension of 2.25 kN. Another pulley 400 mm diameter is
placed 200 mm to the left of right hand bearing and is driven
with the help of electric motor and belt, which is placed
horizontally to the right. The angle of contact for both the
pulleys is 180° and μ = 0.24. The allowing working stress of
63 MPa in tension and 42 MPa in shear for the material of
shaft. Assume that the torque on one pulley is equal to that
on the other pulley.
OR
Q.3 (a) Define: basic size, tolerance and deviation. 03
(b) Explain with neat sketches hole basis and shaft basis system 04
of fits.
(c) Design a cast iron protective type flange coupling to transmit 07

15 kW at 900 r.p.m. from an electric motor to a compressor.
The service factor may be assumed as 1.35. The shaft, bolt
and key are made from steel having yield point stress and
crushing stress of 160 N/mm2. The ultimate tensile strength
of cast iron is 32 N/mm2. Assume the shear stress is half of
the normal stress and factor of safety of 2.
Q.4 (a) Explain with neat sketches failures in knuckle pin. 03

(b) Find the tolerances, maximum interference and type of fit for 04
the data as Hole ϕ 50 +0.25 -0.10 and Shaft ϕ 50 +0.20 -0.20.
(c) Calculate the dimensions of the socket end of a cotter joint 07
used to connect two rods, made of plain carbon steel 40C8
having yield point strength 380 N/mm2. The diameter of
each rod is 50 mm and the cotter is made from a steel plate
of 15 mm thickness. Assume (i) the yield strength in
compression is twice of the tensile yield strength, (ii) the
yield strength in shear is 50 % of the tensile yield strength,
(iii) the factor of safety is 6.
OR
Q.4 (a) State the assumptions presume for the derivation of Euler’s 03
formula.
(b) An I-section 400 mm x 200 mm x 10 mm and 3 meter long 04
is used as a strut with both ends pinned. Find Euler’s
crippling load. Assume Young’s modulus of elasticity foe
the material of the section as 200 kN/mm2.
2
(c) Find the suitable size of 300 mm long push rod of a petrol 07
engine carrying a maximum load of 1400 N. It is hollow in
section having the outer diameter 1.25 times the inner
diameter. Spherical seated bearings are used for the push
rod. The modulus of elasticity for the material of the push
rod is 210 kN / mm2. Assume factor of safety of 2.5.
Q.5 (a) Explain different form of threads used in power screws. 03
(b) Explain the phenomenon of self locking and overhauling of 04
power screws.
(c) A power screw having double start square threads of 25 mm 07
nominal diameter and 5 mm pitch is acted upon by an axial
load of 10 kN. The outer and inner diameters of screw collar
are 50 mm and 20 mm respectively. The coefficient of thread
friction and collar friction may be assumed as 0.2 and 0.15
respectively. The screw rotates at 12 rpm. Assuming uniform
wear condition at the collar and allowable thread bearing
pressure of 5.8 N/mm2, find: (i) the torque required to rotate
the screw; (ii) the stress in the screw; and (iii) the number of
threads of nut in engagement with screw.
OR
Q.5 (a) What are the advantages and disadvantages of threaded joints? 03
(b) A steel plate 100 mm wide and 10 mm thick is welded to 04

another steel plate by means of double parallel fillet welds as
shown in figure given below. The plates are subjected to a
static tensile force of 50 KN. Determine the required length
of the welds if the permissible shear stress in the weld is 94
N/mm2.
(c) A bracket is attached to a steel channel by means of nine 07

identical rivets as shown in figure given below. Determine
the diameter of rivets, if the permissible shear stress is 60
N/mm2.
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Seat No.: ________ Enrolment No.

10 Draw the neat sketch of any two types of geometric

(b) What is stress concentration? Explain any two methods of 04

(c) Design a right angled bell crank lever to raise a load of 6 kN 07

Q.3 (a) Classify the couplings. 03

(c) Design a cast iron protective type flange coupling to transmit 07

Q.4 (a) Explain with neat sketches failures in knuckle pin. 03

(b) A steel plate 100 mm wide and 10 mm thick is welded to 04

(c) A bracket is attached to a steel channel by means of nine 07

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