Deck 4: Mechanical Balancing of Rotating Systems: Calculations and Principles

Question 1

In balancing of single-cylinder engine, the rotating unbalance is ____________

A)completely made zero and so also the reciprocating unbalance
B)completely made zero and the reciprocating unbalance is partially reduced
C)partially reduced and the reciprocating unbalance is completely made zero
D)partially reduced and so also the reciprocating unbalance

Answer 1

completely made zero and the reciprocating unbalance is partially reduced

Question 2

Let the disturbing mass be 100 kg and the radius of rotation be 10 cm and the rotation speed be 50 rad/s, then calculate the centrifugal force in kN.

A)50
B)25
C)50000
D)25000

Answer 2

25

Question 3

Which of the following statement is correct?

A)In any engine, 100% of the reciprocating masses can be balanced dynamically
B)In the case of balancing of multicylinder engine, the value of secondary force is higher than the value of the primary force
C)In the case of balancing of multimass rotating systems, dynamic balancing can be directly started without static balancing done to the system
D)none of the mentioned

Answer 3

In the case of balancing of multimass rotating systems, dynamic balancing can be directly started without static balancing done to the system

Question 4

If all the masses are in one plane, then what is the maximum no. of masses which can be placed in the same plane?

A)3
B)4
C)6
D)No limitation

Question 5

Which of the following statements is correct about the balancing of a mechanical system?

A)If it is under static balance, then there will be dynamic balance also
B)If it is under dynamic balance, then there will be static balance also
C)Both static as well as dynamic balance have to be achieved separately
D)None of the mentioned

Question 6

In a locomotive, the ratio of the connecting rod length to the crank radius is kept very large in order to

A)minimize the effect of primary forces
B)minimize the effect of secondary forces
C)have perfect balancing
D)start the locomotive conveniently

Question 7

Secondary forces in reciprocating mass on engine frame are

A)of same frequency as of primary forces
B)twice the frequency as of primary forces
C)four times the frequency as of primary forces
D)none of the mentioned

Question 8

For a V-twin engine, which of the following means can be used to balance the primary forces?

A)Revolving balance mass
B)Rotating balance mass
C)Reciprocating balance mass
D)By the means of secondary forces

Question 9

The primary unbalanced force is maximum when the angle of inclination of the crank with the line of stroke is

A)0°
B)90°
C)180°
D)360°

Question 10

From the following data of a 60 degree V-twin engine, determine the minimum value for primary forces in newtons:Reciprocating mass per cylinder = 1.5 Kg Stroke length = 10 cm Length of connecting rod = 25 cm Engine speed = 2500 rpm

A)7711
B)4546
C)2570
D)8764

Question 11

From the following data of a 60 degree V-twin engine, determine the maximum value for primary forces in newtons:Reciprocating mass per cylinder = 1.5 Kg Stroke length = 10 cm Length of connecting rod = 25 cm Engine speed = 2500 rpm

A)7711
B)4546
C)2570
D)8764

Question 12

From the given data, find the balancing mass's inclination in degrees if r=0.2m required in the same plane.Masses = 200kg, 300kg, 240 kg, 260Kg,

A)201.48
B)200.32
C)210.34
D)202.88

Question 13

Which of the following statements are associated with complete dynamic balancing of rotating systems?
1) Resultant couple due to all inertia forces is zero.
2) Support reactions due to forces are zero but not due to couples .
3) The system is automatically statically balanced.
4) Centre of masses of the system lies on the axis of rotation.

A)1, 2, 3 and 4
B)1, 2, and 3 only
C)2, 3 and 4 only
D)1, 3 and 4 only

Question 14

A V-twin engine has the cylinder axes at 90 degrees and the connecting rods operate a common crank. The reciprocating mass per cylinder is 11.5 kg and the crank radius is 7.5 cm. The length of the connecting rod is 0.3 m. If the engine is rotating at the speed is 500 r.p.m. What is the value of maximum resultant secondary force in Newtons?

A)736
B)836
C)936
D)636

Question 15

Let the centrifugal force in kN be 25 and the radius of rotation be 20 cm and the rotation speed be 50 rad/s, then calculate the mass defect in Kg.

A)50
B)25
C)50000
D)25000

Question 16

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

Question 17

In order to achieve stability, the sum of secondary forces and secondary couples must be ------- and their respective polygons must be …......

A)Zero, Closed
B)one, Open
C)Zero, open
D)one, closed

Question 18

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

Question 19

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

Question 20

Which of the following is the correct expression for secondary force?

A)m?^² r.cos2?/n
B)m ?^² r.sin2?/n
C)m?^² r.tan2?/n
D)m?^² r.cos?/n

Question 21

A V-twin engine has the cylinder axes at 90 degrees and the connecting rods operate a common crank. The reciprocating mass per cylinder is 23 kg and the crank radius is 7.5 cm. The length of the connecting rod is 0.3 m. If the engine is rotating at the speed is 500 r.p.m. What is the value of maximum resultant secondary force in Newtons?

A)7172
B)1672
C)1122
D)1272

Question 22

A V-twin engine has the cylinder axes at 90 degrees and the connecting rods operate a common crank. The reciprocating mass per cylinder is 34.5 kg and the crank radius is 7.5 cm. The length of the connecting rod is 0.3 m. If the engine is rotating at the speed is 500 r.p.m. What is the value of maximum resultant secondary force in kN?

A)2.238
B)2.508
C)2.754
D)2.908

Question 23

From the given data, find the balancing mass in Kg if r=0.2m required in the same plane.Masses = 200kg, 300kg, 240 kg, 260Kg, corresponding radii = 0.2m, 0.15m, 0.25m and 0.3m.Angles between consecutive masses = 45, 75 and 135 degrees.

A)116
B)58
C)232
D)140

Question 24

Let the disturbing mass be 200 kg and the radius of rotation be 20 cm and the rotation speed be 50 rad/s, then calculate the centripetal force in kN.

A)-50
B)-25
C)-100
D)-2500