Machine Dynamics Questions and Answers – Balancing of Coupled Locomotives & Secondary Forces of Multi-cylinder Inline Engines

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This set of Machine Dynamics Questions and Answers for Entrance exams focuses on “Balancing of Coupled Locomotives & Secondary Forces of Multi-cylinder Inline Engines”.

1. In a coupled locomotive, the driving wheels are connected to the leading and trailing wheels by a/an __________
a) Outside coupling rod
b) Inside coupling rod
c) Backside coupling rod
d) Frontend coupling rod
View Answer

Answer: a
Explanation: In a coupled locomotive, the driving wheels are connected to the leading and trailing wheels by an outside coupling rod.
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2. For a coupled locomotive, the driving wheels and the leading and trailing wheels are connected by an inside coupling rod.
a) True
b) False
View Answer

Answer: b
Explanation: In a coupled locomotive, the driving wheels are connected to the leading and trailing wheels by an outside coupling rod.

3. On connecting a wheel through outside coupling rod, which utility comes of use?
a) Tractive
b) Swaying
c) Hammer
d) Piston
View Answer

Answer: a
Explanation: For a coupled locomotive, the driving wheels and the leading and trailing wheels are connected by an outside coupling rod. A significantly greater portion of the engine mass is utilized by tractive purposes.
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4. In coupled locomotives, the coupling rod cranks are placed diametrically opposite to the adjacent ________
a) Driving cranks
b) Driving rods
c) Driving piston
d) Driving valves
View Answer

Answer: a
Explanation: In coupled locomotives, the coupling rod cranks are placed at a position which is diametrically opposite to the adjacent driving cranks which are also known as the main cranks.

5. Coupling rods with connecting rods and pins can be treated as ________
a) Rotating masses
b) Masses in linear motion
c) Reciprocating masses
d) Massless
View Answer

Answer: a
Explanation: The coupling rods together along with cranks and pins can be treated as rotating masses, and completely balanced by masses in the respective wheels i.e trailing, driving and leading.
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6. The variation of pressure between the wheel and the rail (i.e. hammer blow) may be reduced by _______
a) Equal distribution of balanced masses
b) More mass towards driving wheel
c) More mass towards trailing wheel
d) More mass towards leading wheel
View Answer

Answer: a
Explanation: The variation of pressure between the wheel and the rail also known as hammer blow, it can be reduced by equal distribution of the balanced mass between the three wheels i.e driving, leading and trailing wheels respectively.

7. In coupled locomotives, where are the coupling rod cranks placed with respect to the main crank?
a) Diametrically opposite
b) At 90 degrees
c) At 60 degrees
d) At 120 degrees
View Answer

Answer: b
Explanation: In coupled locomotives, the coupling rod cranks are placed at a position which is diametrically opposite to the adjacent main cranks (i.e. driving cranks).
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8. If the connecting rod is not too long, then which of the following phenomenon occurs?
a) Secondary disturbing forces
b) Primary disturbing forces
c) Secondary stabilizing forces
d) Primary stabilizing forces
View Answer

Answer: a
Explanation: When the connecting rod isn’t too long or in other words when the obliquity of the connecting rod is taken into consideration, then the secondary disturbing force due to the reciprocating mass arises.

9. When the connecting rod is too long, secondary forces arise due to reciprocating masses.
a) True
b) False
View Answer

Answer: b
Explanation: When the obliquity of the connecting rod is taken into consideration which means that the long is not too long, then the secondary disturbing force due to the reciprocating mass arises.
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10. Which of the following is the correct expression for secondary force?
a) mω2r.cos2θ/n
b) mω2r.sin2θ/n
c) mω2r.tan2θ/n
d) mω2r.cosθ/n
View Answer

Answer: a
Explanation: The secondary force depends on the following factors:
mass, rotating speed, radius of crank and the cosine of the crank angle.

11. In a multicylinder inline engine, each imaginary secondary crank with a mass attached to the crankpin is inclined to the line of stroke at which angle?
a) Twice the angle of crank
b) Half the angle of crank
c) Thrice the angle of crank
d) Four times the angle of crank
View Answer

Answer: a
Explanation: In multi-cylinder in-line engines, each of the imaginary secondary crank with a mass attached to the crankpin is inclined to the line of stroke at twice the angle of the actual crank.

12. The numerical values of the secondary forces and secondary couples couples may be obtained by considering the ___________
a) Revolving mass
b) Reciprocating mass
c) Translating mass
d) Rotating mass
View Answer

Answer: a
Explanation: Each imaginary secondary crank with a mass attached to the crankpin is inclined to the line of stroke at two times the angle of the actual crank. The values of the secondary forces and couples can be obtained by considering the revolving mass.

13. For the secondary balancing of the engine, which of the condition is necessary?
a) Secondary force polygon must be close
b) Secondary force polygon must be open
c) Primary force polygon must be close
d) Primary force polygon must be open
View Answer

Answer: a
Explanation: In order to achieve the secondary balancing of the engine. The sum (algebraic ) of the secondary forces must be equal to zero. In other words, the secondary force polygon must close.

14. For the secondary balancing of the engine, which of the condition is necessary?
a) Secondary couple polygon must be close
b) Secondary couple polygon must be open
c) Primary force polygon must be close
d) Primary force polygon must be open
View Answer

Answer: a
Explanation: In order to achieve the secondary balancing of the engine. The sum (algebraic ) of the secondary couples must be equal to zero. In other words, the secondary couple polygon must close.

15. If the secondary couple polygon is open and the force polygon is closed then stability is achieved.
a) True
b) False
View Answer

Answer: b
Explanation: In order to achieve stability, the sum of secondary forces and secondary couples must be zero and their respective polygons must be closed.

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