Balancing of Rotating Masses
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Questions and Answers

What is the purpose of balancing rotating and reciprocating parts?

  • To bend the shaft and produce vibrations
  • To minimize pressure on main bearings and reduce vibrations (correct)
  • To increase the loads on bearings
  • To set up dynamic forces

    • Why is it important to balance rotating masses in engines?

  • To maximize the loads on bearings
  • To increase the effect of centrifugal force
  • To produce dangerous vibrations
  • To balance out dynamic forces and reduce stresses (correct)

    • What is the purpose of attaching a second mass to a rotating shaft?

  • To amplify the effect of centrifugal force
  • To increase vibrations in the shaft
  • To bend the shaft further
  • To counteract the centrifugal force of the first mass (correct)

    • What are the consequences of not properly balancing rotating parts?

    <p>Increase in bearing stresses and production of dangerous vibrations</p> Signup and view all the answers

    What is meant by balancing of rotating masses?

    <p>Counteracting the centrifugal force of one mass by another</p> Signup and view all the answers

    How does balancing a single rotating mass by a single mass in the same plane help?

    <p>It minimizes pressure on main bearings when an engine is running</p> Signup and view all the answers

    What does the closing side ae represent as per the polygon law of forces?

    <p>Resultant force in magnitude</p> Signup and view all the answers

    In the context of balancing masses, why is the balancing force equal to the resultant force?

    <p>To maintain equilibrium</p> Signup and view all the answers

    What is the magnitude of the balancing mass required at a radius of rotation of 0.2 m in the given scenario?

    <p>21.6 kg-m</p> Signup and view all the answers

    What is the purpose of balancing reciprocating masses in an engine mechanism?

    <p>To reduce unbalanced forces</p> Signup and view all the answers

    How are the forces FR and FI related in a reciprocating engine mechanism?

    <p>Equal in magnitude but opposite in direction</p> Signup and view all the answers

    Why do reciprocating masses cause objectionable vibrations in engine mechanisms?

    <p>Due to shaking force and couple variations</p> Signup and view all the answers

    What is the purpose of adding appropriate balancing mass in reciprocating mechanisms?

    <p>To reduce shaking force and couple</p> Signup and view all the answers

    What is the purpose of balancing the reciprocating masses in an engine mechanism?

    <p>To reduce the shaking force and shaking couple</p> Signup and view all the answers

    What is the correct relationship between the mass of the reciprocating parts (m), connecting rod length (l), and crank radius (r) in a reciprocating engine mechanism?

    <p>$m &lt; l + r$</p> Signup and view all the answers

    How is the primary unbalanced force in a reciprocating engine related to centrifugal force?

    <p>Balanced by centrifugal force</p> Signup and view all the answers

    In locomotives, what is the reason for having cranks placed at right angles to each other?

    <p>To improve uniformity in turning moment diagram</p> Signup and view all the answers

    What is the effect of adding appropriate balancing mass to reciprocating masses in mechanisms?

    <p>Reduces shaking force and shaking couple</p> Signup and view all the answers

    What is the primary purpose of balancing the reciprocating masses in engines?

    <p>To reduce vibrations</p> Signup and view all the answers

    Why are locomotives classified into inside cylinder and outside cylinder types?

    <p>To have uniformity in turning moment diagram</p> Signup and view all the answers

    Which statement best describes the effect of reciprocating parts on engine mechanisms?

    <p>Reciprocating parts generate shaking forces and couples.</p> Signup and view all the answers

    What is the main reason for partially balancing reciprocating masses in engines?

    <p>Practicality of complete elimination.</p> Signup and view all the answers

    How do locomotives differ based on coupling?

    <p>Single locomotives transmit effort to one pair of wheels only.</p> Signup and view all the answers

    What conditions must be satisfied to achieve a complete secondary balance of an engine?

    <p>Algebraic sum of the secondary forces is zero, algebraic sum of the couples is zero</p> Signup and view all the answers

    What is the method used in balancing radial or V-engines with connecting rods connected to a common crank?

    <p>Direct and reverse cranks method</p> Signup and view all the answers

    Which crank is known as the direct crank in a reciprocating engine mechanism?

    <p>OC</p> Signup and view all the answers

    What happens when the direct crank rotates in a clockwise direction?

    <p>The reverse crank rotates in an anticlockwise direction</p> Signup and view all the answers

    How is the primary force due to the mass of reciprocating parts affected when the mass is divided into two parts?

    <p>Remains the same</p> Signup and view all the answers

    Where are the two masses (each m/2) placed for the secondary effects when replacing the mass of reciprocating parts?

    <p>D and D'</p> Signup and view all the answers

    What is the condition for static balance when the plane of the disturbing mass lies on one end of the planes of the balancing masses?

    <p>The mass m lies in the plane A and the balancing masses lie in the planes L and M.</p> Signup and view all the answers

    How can the magnitude and direction of the balancing mass be obtained analytically?

    <p>Summing both horizontal and vertical components of the centrifugal forces and finding their resultant.</p> Signup and view all the answers

    What must be done to balance a system with multiple masses rotating in the same plane?

    <p>Find the sum of horizontal and vertical components of centrifugal forces.</p> Signup and view all the answers

    In terms of balancing force, what does equation (i) represent?

    <p>The condition for static balance.</p> Signup and view all the answers

    What is required to find out the balancing force in plane L or the dynamic force at bearing Q?

    <p>Taking moments about P.</p> Signup and view all the answers

    What is essential to balance several masses rotating in the same plane?

    <p>Balancing force must be directed in opposite direction.</p> Signup and view all the answers

    How can one obtain the magnitude and position of the balancing mass graphically?

    <p>By drawing vectors representing centrifugal forces of each mass to scale.</p> Signup and view all the answers

    What is represented by tanθ = SV / SH in finding the balancing force?

    <p>'Vertical' divided by 'Horizontal'.</p> Signup and view all the answers

    'Balancing of Several Masses Rotating in the Same Plane' requires finding what quantity analytically or graphically?

    <p>'Centrifugal force'</p> Signup and view all the answers

    What is the purpose of introducing two balancing masses rotating in different planes?

    <p>To satisfy the conditions of equilibrium for complete balance</p> Signup and view all the answers

    What is the main purpose of balancing a single rotating mass with two masses rotating in different planes?

    <p>To eliminate any couple that rocks the shaft in its bearings</p> Signup and view all the answers

    What are the conditions that must be satisfied for dynamic balancing when using two balancing masses in different planes?

    <p>The net couple due to dynamic forces acting on the shaft must be zero</p> Signup and view all the answers

    In what scenario would the plane of the disturbing mass lie between the planes of the two balancing masses?

    <p>When aiming for static balancing only</p> Signup and view all the answers

    What is essential for static balancing when using two balancing masses in different planes?

    <p>The line of action of all three centrifugal forces must be the same</p> Signup and view all the answers

    Which arrangement helps in reducing any tendency for the shaft to rock in its bearings?

    <p>Balancing a single rotating mass with a single mass in the same plane</p> Signup and view all the answers

    Why is it important for the net dynamic force acting on the shaft to be zero?

    <p>To achieve complete balance of the system</p> Signup and view all the answers

    How does introducing two balancing masses in different planes contribute to dynamic balancing?

    <p>By achieving a zero net couple from dynamic forces</p> Signup and view all the answers

    What is the effect of an unbalanced primary force along the line of stroke due to partial balancing of reciprocating parts?

    <p>Formation of a swaying couple</p> Signup and view all the answers

    What is the maximum magnitude of the unbalanced force perpendicular to the line of stroke known as?

    <p>Hammer blow</p> Signup and view all the answers

    In a multi-cylinder in-line engine, what condition must be satisfied to achieve primary balance?

    <p>The algebraic sum of couples must be zero</p> Signup and view all the answers

    What is treated as one of revolving masses when achieving primary balance in a multi-cylinder engine?

    <p>Reciprocating masses transferred to their respective crank pins</p> Signup and view all the answers

    What angle should (cos - sin) be for the tractive force to be maximum or minimum in two-cylinder locomotives?

    <p>$135^{\text{\circ}}$ or $315^{\text{\circ}}$</p> Signup and view all the answers

    What must be done in multi-cylinder in-line engines when balancing secondary forces due to reciprocating masses?

    <p>Attach an equal mass to the imaginary crankpin</p> Signup and view all the answers

    What does it mean for the primary force polygon in a multi-cylinder engine to 'close'?

    <p>Primary forces are balanced and sum up to zero</p> Signup and view all the answers

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