(Write your roll no. immediately here in the space provided) Roll No……………….. ……… ………….

B. Tech (MAE) – VI Sem

First Term Exams – Feb-March 2017
ETAT 302 (Machine Design)
Max Marks : 30 Time : 1½ Hours

Note: Q. No. 1 is compulsory. Do any 2 more from the rest.

Q1. Briefly answer all the following questions.

a.) State 2 advantages of using standardization in a good mechanical design? (1)
b.) Mention two main considerations in the design of parts requiring casting?

in
(1)
c.) Why are clearances provided between cotter and spigot / socket? (1)
d.) What is the advantage of using a jib in a jib and cotter joint for a square joint? (1)
e.) How is a hollow shaft superior to a solid shaft? Even then, why is a hollow shaft not commonly

.
used? (1)
f.) Define ‘Endurance Strength’ of a non-ferrous material using log S-log N curve? (1)

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g.) For what purpose a rigid coupling is used? How is rigidity achieved here? (1)
h.) Show, by drawing sketches, the methods of reducing stress concentration (i) due to a circular
hole at centre and (ii) due to V-notches at top and bottom centers of a plate carrying tensile
load.? (1)
i.) Suggest two methods to improve the fatigue strength of parts. (1)
t.
j.) Write the formula for finding the diameter d of a keyed solid shaft subjected
moment M and a torque T. Use Km and Kt as combined fatigue and shock load factors in
bending and torsion respectively. τ is the allowable shear stress in shaft material.
to bending
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(1)

Q2. Design a knuckle joint subjected to a tensile load of 41 KN. The ultimate tensile strength in
the 55C6 material of joint is 660 N/mm² and the factor of safety is 8. The allowable shear
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stress may be taken as 0.75 times the permissible tensile strength and the allowable
compressive stress may be taken as 1.25 times the allowable tensile strength. Check the safety
of the knuckle pin in bending and draw a proportionate sketch of the joint. (10)

Q3. Design a bushed pin flexible coupling for joining two shafts of diameter 45 mm. The shafts are
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rotating at 1440 rpm while transmitting a power of 25000 Watts. The allowable bearing
pressure is 0.375 N/mm². The allowable stress in the pins is 63 N/mm². For the key, the
allowable shear stress is 46 N/mm² and the allowable crushing stress is 80 N/mm². Assume any
other data suitably. Also draw an appropriate diagram of the coupled assembly. (10)

Q4. (a) Calculate the maximum and minimum sizes of shaft and hole for a 25 mm diameter shaft
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and hole pair designated as H7/d6. The 25mm size lies in the diameter range of 18 - 30mm.
The value of standard tolerance factor i=0.45(cube root of D)+0.001D microns.
The upper deviation of ‘d’ shaft = - 16D0.44 .
IT6=10i , IT7=16i.
Also state the type of fit. (2+2+1)

(b) A steel rod is subjected to a torsional load that varies from -100 Nm to 400 Nm. Find the
diameter of the rod using a factor of safety of 1.75. Use Soderberg line criteria for design. For
the material of the rod, take Ultimate Tensile Strength =490 MPa, Yield Point Stress= 315
MPa. The load factor is 0.58, surface finish factor is 0.68 and size factor is 0.85, with room
temp, 50% reliability and no stress concentration. (5)
 (Write your roll no. immediately here in the space provided) Roll No……………….. ……… ………….

B. Tech (MAE) – VI Sem

Second Term Exams – April 2017
ETAT 302 (Machine Design)
Max Marks : 30 Time : 1½ Hours

Note: Q. No. 1 is compulsory. Do any 2 more from the rest.

Q1. Briefly answer all the following questions.

a) Why is a butt joint preferable to a lap joint in a riveted joint?? (1)
b) Why are the weldments designed for shear strength instead of principal stress?

in
(1)
c) What are the necessary conditions for the self locking and irreversibility for the screw of a
screw jack? (1)
d) Why are the soft metal bushes inserted in the eyes of levers? (1)

.
e) State two applications of springs? (1)
f) If in a pair of gears, the velocity ratio is integer, how is the wear made uniform? (1)

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g) Why are the arms of gears tapered from large size near hub to a smaller size near the rim.
(1)
h) State the McKee’s equation used in the design of Journal bearings along with the meaning of
the symbols used. (1)
i) A ball bearing has a life of 320 million revolutions at 90% reliability. What will be its life if the

j)
t.
equivalent load on the bearing is doubled?
Show the variation of pressure along the circumference of a journal bearing?
(1)
(1)
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Q2. Design a closed coiled helical spring for an engine. The following data is given.
Length of spring when valve is open = 50mm and spring load =575 N.
Length of spring when valve is closed = 56mm and spring load =850 N.
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Maximum inside diameter of spring = 28 mm.

The maximum permissible shear stress for the spring material is 480 N/mm² and its modulus
of rigidity is 80 GPa. (10)

Q3. (a) Find the module, face width and pitch circle diameters of a spur gear reducer for
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transmitting a power of 48 kW at 2100 rpm of pinion containing 20 teeth. The velocity ratio is
2.5:1. The allowable static stress for both pinion & gear material (cast steel) is 120 N/mm².
The pressure angle is 20° full depth involute.
Take Velocity Factor c = 4.5 / (4.5+v) ,where v = pitch line velocity.
Form Factor y = 0.154-(0.912/z) where z = no. of teeth. (7)
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(b) Design the fulcrum pin only of a bell crank lever to carry a load of 12 KN at the end of a
vertical arm. The mechanical advantage is 3.5 and the effort is to be applied in vertical
direction at the end of a horizontal arm 350 mm in length. The allowable stresses in tension
and shear pin materials are 71 and 43 N/mm² respectively and allowable bearing pressure is
14 N/mm². (3)

Q4. (a) Write the steps to design the screw of a Screw Jack. (5)

(b) How will you select a ball / roller bearing from a manufacturer’s catalogue (say SKF) for a
particular application. Write down the necessary steps to be followed. (5)
(Write your roll no. immediately) Roll No……………….. ……… ………….

B. Tech (MAE) – VI Sem

First Term Exams – Feb-March 2017 (Reappear)
ETAT 302 (Machine Design)

Max Marks : 30 Time Allowed : 1½ Hours

Note: Q. No. 1 is compulsory. Do any 2 more from the rest.

Q1. Briefly answer all the following questions.

a) Why is knuckle pin designed as the weakest part? (1)

in
b) Highlight the importance of ergonomic considerations in design activity? (1)
c) State any two considerations for parts requiring machining? (1)
d) Why is taper provided on one side of cotter? (1)
e) Define ‘Fatigue Limit’ of a material?

.
(1)
f) What arrangement ensures flexibility is a bushed pin flexible coupling? (1)

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g) How do size and surface finish effect the endurance strength of a material? (1)
h) State any two methods to improve fatigue strength of materials. (1)
i) Why do shafts need to be joined by couplings? (1)
j) What is indicated by 30 E7/h5? Mention the type of fit. (1)
k) What does the symbol 40C7 represent as material specification. (1)
t.
Q2. A steel shaft 1m long carries 1000N pulley at a distance of 500 mm from left bearing. The pulley is
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keyed to the shaft and receives 20KW at 900rpm. The belt drive is horizontal and the ratio of belt
tensions is 2:1. The diameter of pulley on steel shaft is 600mm.The load is applied with moderate
shocks. Calculate the necessary diameter of the solid shaft. (10)
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Q3. Design a protected type rigid flange coupling for joining two shafts of diameter 70mm transmitting a
power of 50 kW at 1800 rpm.. The allowable shear stress in the shaft, hub, bolts material is 52
N/mm². For the key, the allowable shear stress is 48 N/mm² and the allowable crushing stress is 88
N/mm². Assume ant other data suitably. (10)
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Q4. Design a spigot & socket Cotter joint subjected to a tensile load of 35 KN. The allowable tensile
strength in the 50C5 material of joint is 70 N/mm², the allowable shear stress is 50 N/mm² and the
allowable crushing stress is 100 N/mm². Also check the safety of the cotter in bending and state the
reason for its strength or weakness. Draw a proportionate sketch of the joint. (10)
m