Gears mcq

Gears
MCQ
Dr. L.K. Bhagi
Associate Professor
School of Mechanical Engineering
Lovely Professional University

29-11-2019
Design of Machine Elements II MEC306
(Dr. L K Bhagi)
2
Q1. Tooth interference in an external involutes spur gear pair can be
reduced by
(a) Decreasing centre distance between gears
(b) Decreasing module
(c) Decreasing pressure angle
(d) Increasing number of teeth
Question 1

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(Dr. L K Bhagi)
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Q1.
Increasing the number of teeth on the gear can also eliminate the chances of
interference.
However, if the gears are to transmit more power, more teeth can be used only
by increasing the pitch diameter, otherwise the smaller-sized teeth may break in
transmitting more loads. This makes the gear larger for a given module.
Question 1» Solution
Decrease Pressure Angle means larger
base circle i.e. less portion of the tooth
profile becomes involute.
Use Long and Short Addendum Gearing

29-11-2019
(Dr. L K Bhagi)
4
Q1.
Increasing the number of teeth on the gear can also eliminate the chances of
interference.
However, if the gears are to transmit more power, more teeth can be used only
by increasing the pitch diameter, otherwise the smaller-sized teeth may break in
transmitting more loads. This makes the gear larger for a given module.
Decrease Pressure Angle means larger
base circle i.e. less portion of the tooth
profile becomes involute.
Use Long and Short Addendum Gearing

29-11-2019
(Dr. L K Bhagi)
5
Q2. Two mating spur gears have 40 and 120 teeth respectively. the
pinion rotates at 1200 rpm and transmit a torque of 20N-m. The
torque transmitted by the gear is?
(a) 6.6 Nm
(b) 40 Nm
(c) 20 Nm
(d) 60 Nm
Question 2

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(Dr. L K Bhagi)
6
Q2.
Tgear = 60 Nm
( )
( )A
B
A
B
A
B
B
A
Torque
Torque
N
N
D
D
RatioGear ====



29-11-2019
(Dr. L K Bhagi)
7
Q3. Large speed reductions (greater than 20) in one stage of a gear train
are possible through
a) spur gearing
b) worm gearing
c) bevel gearing
d) helical gearing
Question 3

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(Dr. L K Bhagi)
8
Q3. Worm and worm wheel gear is famous for high speed reduction
ratio. bcz worm having very high spiral angle and very less diameter
and worm wheel having very less spiral , very high diameter.
Gear ratio is around 20:1 to 50:1. ‘X’ rotation of worm will cause 1
rotation in Worm wheel.

29-11-2019
(Dr. L K Bhagi)
9
Q3. Worm and worm wheel gear is famous for high speed reduction
ratio. bcz worm having very high spiral angle and very less diameter
and worm wheel having very less spiral , very high diameter.
Gear ratio is around 20:1 to 50:1. ‘X’ rotation of worm will cause 1
rotation in Worm wheel.

29-11-2019
(Dr. L K Bhagi)
10
Q4. The minimum number of teeth on the pinion to operate without
interference in standard full height involute teeth gear mechanism
with 20°pressure angle is
a) 14
b) 12
c) 18
d) 32
Question 4

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(Dr. L K Bhagi)
11
Q4. (C)

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(Dr. L K Bhagi)
12
Q5. A 1.5 kW motor is running at 1440 rev/min. It is to be connected to
a stirrer running at 36 rev/min. The gearing arrangement suitable
for this application is
(a) differential gear
(b) helical gear
(c) spur gear
(d) worm gear
Question 5

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(Dr. L K Bhagi)
13
Q5.

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(Dr. L K Bhagi)
14
Q6. In spur gears, the circle on which the involute is generated is called
the.
(a) Pitch circle
(b) clearance circle
(c) Base circle
(d) addendum circle.
Question 6

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(Dr. L K Bhagi)
15
Q6.

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(Dr. L K Bhagi)
16
Q7. Interference in a pair of gears is avoided, if the addendum circles of
both the gears intersect common tangent to the base circles within
the points of tangency.
(a) True
(b) False
(c) Insufficient data
(d) None of the above
Question 7

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(Dr. L K Bhagi)
17
Q7.

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(Dr. L K Bhagi)
18
Q8. In Match List I with List II and select the correct answer using the
codes given below the lists:
List I (Terminology) List II (Relevant terms)
A. Interference 1. Arc of approach, arc of recess, circular pitch
B. Dynamic load on tooth 2. Lewis equation
C. Static load 3. Minimum number of teeth on pinion
D. Contact ratio 4. Inaccuracies in tooth profile
Codes: A B C D A B C D
(a) 3 4 1 2 (b)1 2 3 4
(c) 4 3 2 1 (d) 3 4 2 1
Question 8

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(Dr. L K Bhagi)
19
Q8.
(d)

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(Dr. L K Bhagi)
20
Q9.
Question 9

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(Dr. L K Bhagi)
21
Q9.

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(Dr. L K Bhagi)
22
Q10. Match the following
Type of gears Arrangement of shafts
P. Bevel gears 1. Non-parallel off-set shafts
Q. Worm gears 2. Non-parallel intersecting shafts
R. Herringbone gears 3. Non-parallel non-intersecting shafts
S. Hypoid gears 4. Parallel shafts
(a) P-4 Q-2 R-1 S-3
(b) P-2 Q-3 R-4 S-1
(c) P-3 Q-2 R-1 S-4
(d) P-1 Q-3 R-4 S-2
Question 10

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(Dr. L K Bhagi)
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Q10. (b)

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(Dr. L K Bhagi)
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Q11. Twenty degree full depth involute profiled 19-tooth pinion and 37-
tooth gear are in mesh. If the module is 5 mm, the centre distance
between the gear pair will be
(a) 140 mm
(b) 150 mm
(c) 280 mm
(d) 300 mm
Question 11

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(Dr. L K Bhagi)
25
Q11. (a)

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(Dr. L K Bhagi)
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Q12. For full depth of involutes spur gears, minimum number of teeth
of pinion to avoid interference depends upon
(a) pressure angle
(b) Speed ratio
(c) circular pitch
(d) pitch diameter
Question 12

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(Dr. L K Bhagi)
27
Q12. (a)

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(Dr. L K Bhagi)
28
Q13. A pair of spur gears with module 5 mm and a centre distance of
450 mm is used for a speed reduction of 5:1. The number of teeth
on pinion is_______.
Question 13

29-11-2019
(Dr. L K Bhagi)
29
Q13. m = 5 mm and a = 450
speed reduction 5:1
Speed reduction = Np/Ng=Zg/Zp= 5
Centre distance =
2
z
2
z
22
2121 mmdd
a +=+=
( )
pg
pg
ZZ
ZZ
+=
+
= 180
2
5
450
305180 =+= ppp ZZZ

29-11-2019
(Dr. L K Bhagi)
30
Q14 A spur pinion of pitch diameter 50 mm rotates at 200 rad/s and
transmits 3 kW power. The pressure angle of the tooth of the pinion is
20°. Assuming that only one pair of the teeth, the total force exerted by
tooth of pinion on the tooth on the mating gear
Question 14

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(Dr. L K Bhagi)
31
Q14. 638.5 N

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(Dr. L K Bhagi)
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Q15 A spur A 20° full depth involute spur pinion of 4 mm module and
21 teeth is to transmit 15 kW at 960 rpm. Its face width is 25mm.
Q.15.1 The tangential force transmitted (in N) is
(A) 3552 (B) 2611
(C) 1776 (D) 1305
Q. 15.2 Given that the tooth geometry factor is 0.32 and the combined
effect of dynamic load and allied factors intensifying the stress
is 1.5; the minimum allowable stress (in MPa) for the gear
material is
(A) 242.0 (B) 166.5
(C) 121.0 (D) 74.0
Question 15

29-11-2019
(Dr. L K Bhagi)
33
Q15.1 (a)
( )
T&
mzdiacirclepitchd&
2
2
60
N
P
t
d
T
F

=
==
( ) N35523554.36N
1084
2
9602
1015602
3-
3
2
60
=




==


mz
F N
P
t

29-11-2019
(Dr. L K Bhagi)
34
Q15.2 (b)
mYbF bt = 
equationLewisFrom
33
10432.01025
3552
−−

=

=
mYb
Ft
b
MPab 111=
MPa5.1661115.1
stress)(workingallowableMinimum
bw ===  vC

29-11-2019
(Dr. L K Bhagi)
35
Q16 A spur gear has a module of 3 mm, number of teeth 16, a face
width of 36 mm and a pressure angle of 20°. It is transmitting a
power of 3 kW at 20 rev/s. Taking a velocity factor of 1.5 and a
form factor of 0.3, the stress in the gear tooth is about.
(A) 32 MPa (B) 46 MPa
(C) 58 MPa (D) 70 MPa
Question 16

29-11-2019
(Dr. L K Bhagi)
36
Q16 (B)
( )
T&
mzdiacirclepitchd&
2
2
60
N
P
t
d
T
F

=
==
( ) N995
16103
2
12002
103602
12006020sec/20
3-
3
2
60
=




==
===


mz
F
rpmrpmrevN
N
P
t

29-11-2019
(Dr. L K Bhagi)
37
Q16 (B)
mYbF bt = 
equationLewisFrom
MPa30.70Pa107.30
1033.01036
995
6
33
==

=

=
−−mYb
Ft
b
MPa06.4670.305.1
stressworkingePermissibl
bw ===  vC

29-11-2019
(Dr. L K Bhagi)
38
Q17 A gear set has a pinion with 20 teeth and a gear with 40 teeth. The
pinion runs at 30 rev/s and transmits a power of 20 kW. The teeth
are on the 20° full-depth system and have a module of 5 mm. The
length of the line of action is 19 mm.
Question 17

29-11-2019
(Dr. L K Bhagi)
39
Q17.1 The center distance for the above gear set in mm is
(A) 140 (B) 150
(C) 160 (D) 170
Question 17

29-11-2019
(Dr. L K Bhagi)
40
Q17.2 The contact ratio of the contacting tooth is
(A) 1.21 (B) 1.25
(C) 1.29 (D) 1.33
Question 17

29-11-2019
(Dr. L K Bhagi)
41
Q17.3 The resultant force on the contacting gear tooth in N is
(A) 77.23 (B) 212.20
(C) 2258.1 (D) 289.43
Question 17

29-11-2019
(Dr. L K Bhagi)
42
Q17.1 (B)
( ) ( ) mm
zzmdd gpgp
150
2
40205
22
distanceCentre =
+
=
+
=
+
=

29-11-2019
(Dr. L K Bhagi)
43
Q17.2 (C)
29.1287.1
20cos5
19
mcos
)(LactionofLength
ratioContact ab
=

=

=


29-11-2019
(Dr. L K Bhagi)
44
Q17.3 (C)
cos
tF
F =
N
zm
N
P
d
T
F
pinion
pinion
pinion
pinion
t
14.2123
05.0
157.106
10205
18002
102060
2
2
60
2
2
3
3
==











=










==
−


N1.2258
20cos
14.2123
cos


==

tF
F

29-11-2019
(Dr. L K Bhagi)
45
Q18 In heavy-duty gear drives, proper heat treatment of gears is
necessary in order to:
(a) Avoid interference
(b) Prevent noisy operation
(c) Minimize wear of gear teeth
(d) Provide resistance against impact loading on gear teeth
Question 18

29-11-2019
(Dr. L K Bhagi)
46
Q18 (C)

29-11-2019
(Dr. L K Bhagi)
47
Q19 The overall gear ratio in a 2 stage speed reduction gear box (with
all spur gears) is 12. The input and output shafts of the gear box are
collinear. The counter shaft which is parallel to the input and
output shafts has a gear (Z2 teeth) and pinion (Z3 = 15 teeth) to
mesh with pinion (Z1 = 16 teeth) on the input shaft and gear (Z4
teeth) on the output shaft respectively. It was decided to use a gear
ratio of 4 with 3 module in the first stage and 4 module in the
second stage.
Q. 19.1 Z2 and Z4 are
(A) 64 and 45 (B) 45 and 64
(C) 48 and 60 (D) 60 and 48
Question 19

29-11-2019
(Dr. L K Bhagi)
48
Q19.2 The centre distance in the second stage is
(A) 90 mm (B) 120 mm
(C) 160 mm (D) 240 mm
Question 19

29-11-2019
(Dr. L K Bhagi)
49
Q19.1 (A)
Let N1, N2, N3 and N4 are the
speeds of pinion 1, gear 2, pinion 3
and gear 4.
Given : Z1 = 16 teeth , Z3 = 15
teeth and Z4 = ?, Z2 = ?
Velocity ratio
( )
( )A
B
A
B
A
B
B
A
Torque
Torque
Z
Z
D
D
N
N
RatioGear ==== 12
3
4
1
2
4
1
==
Z
Z
Z
Z
N
N

29-11-2019
(Dr. L K Bhagi)
50
Q19.1 (A)
Velocity ratio
For stage 1
12
3
4
1
2
4
1
==
Z
Z
Z
Z
N
N
4
1
2
2
1
==
Z
Z
N
N
3124
3
4
3
4
==
Z
Z
Z
Z
teethZ
Z
453
15
4
4
==
teethZ
Z
Z
Z
644
16
4 2
2
1
2
===

29-11-2019
(Dr. L K Bhagi)
51
Q 20. Which of the following statements is/are true?
a) Helical gears have high contact ratio than spur gears
b) Axial thrust is created by helical gears on bearings
c) Crossed helical gears are used for power and motion
transmission
d) All of the above
Question 20

29-11-2019
(Dr. L K Bhagi)
52
Q20 (D)

29-11-2019
(Dr. L K Bhagi)
53
Q 21. Angle made by ________ with axis of rotation is called as helix
angle.
a) only helix
b) only teeth
c) helix or teeth
d) none of the above
Question 21

29-11-2019
(Dr. L K Bhagi)
54
Q21 (C)

29-11-2019
(Dr. L K Bhagi)
55
Q 22. What is the axial pitch for helical gears if helix angle is 25° and
normal module is 7?
a) 50.55 mm
b) 52.03 mm
c) 32.15 mm
d) 11.31 mm
Question 22

29-11-2019
(Dr. L K Bhagi)
56
Q22 (b)
( ) mm
mp
pa 03.52
25tan
73.7
tantan
====




mm
m
m n
72.7
25cos
7
cos
=

==


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