Balancing of Rotating Masses
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Questions and Answers

Why is it essential to balance rotating and reciprocating parts in engines and machines?

  • To decrease the stresses in various members
  • To minimize pressure on main bearings and reduce vibrations (correct)
  • To increase the loads on bearings
  • To produce unpleasant vibrations

    • What happens if rotating and reciprocating parts are not properly balanced?

  • Decrease in stresses in various members
  • No impact on the machinery
  • Increase in loads on bearings and stresses in members (correct)
  • Reduction in vibrations

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

  • To balance the effect of the centrifugal force of the first mass (correct)
  • To increase the effect of centrifugal force
  • To produce more vibrations
  • To prevent bending of the shaft

    • What is the process called when providing a second mass to counteract the effect of the centrifugal force of the first mass?

    <p>Balancing of rotating masses</p> Signup and view all the answers

    In balancing a single rotating mass by a single mass rotating in the same plane, what is the objective?

    <p>To balance out the centrifugal forces</p> Signup and view all the answers

    What are some consequences of unbalanced rotating masses?

    <p>Dangerous vibrations and increased loads on bearings</p> Signup and view all the answers

    What is the purpose of attaching a balancing mass in the same plane as the disturbing mass?

    <p>To counteract the effect of the centrifugal force exerted by the disturbing mass.</p> Signup and view all the answers

    What condition must be satisfied for static balancing of a system with two balancing masses in different planes?

    <p>The centre of masses of the system must lie on the axis of rotation.</p> Signup and view all the answers

    What does dynamic balancing refer to in the context of attaching two balancing masses?

    <p>Keeping the system in complete balance.</p> Signup and view all the answers

    In dynamic balancing, what is required for the net couple due to dynamic forces on the shaft?

    <p>To be zero.</p> Signup and view all the answers

    What is one possibility when attaching two balancing masses for a disturbing mass lying in between them?

    <p>The plane of the disturbing mass may lie on the left or right of the two planes containing the balancing masses.</p> Signup and view all the answers

    What is required for static balancing of a system with two balancing masses for a disturbing mass lying between them?

    <p>The centroids must align vertically.</p> Signup and view all the answers

    What is necessary to achieve dynamic balancing when attaching two balancing masses for a disturbing mass lying between them?

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

    What does aligning centroids vertically achieve in static balancing?

    <p>It helps balance out centrifugal forces and put the system in equilibrium.</p> Signup and view all the answers

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

    <p>The algebraic sum of the secondary forces must be equal to zero and the algebraic sum of the couples must be equal to 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

    What is the relationship between the direct crank OC and the reverse crank OC'?

    <p>They rotate in opposite directions.</p> Signup and view all the answers

    How can the mass (m) of reciprocating parts at P be replaced for primary effects according to the text?

    <p>By dividing it into two parts, each equal to m/2 placed at primary direct and reverse cranks.</p> Signup and view all the answers

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

    <p>At D and D' such that OD = OD' = r/4n</p> Signup and view all the answers

    What is the rotational speed of the secondary reverse crank OD' according to the text?

    <p>$2p/n$ rad/s</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 centrifugal force on the disturbing mass must be equal to the sum of the centrifugal forces on the balancing masses.</p> Signup and view all the answers

    In order to find the magnitude of balancing force in plane L, which point should moments be taken about?

    <p>Point P</p> Signup and view all the answers

    Which method involves finding the centrifugal force exerted by each mass on the rotating shaft?

    <p>Analytical method</p> Signup and view all the answers

    How is the resultant centrifugal force calculated analytically?

    <p>$\tan(θ) = S_V / S_H$</p> Signup and view all the answers

    What does the balancing force equal according to the analytical method?

    <p>The resultant force but in opposite direction</p> Signup and view all the answers

    In order to balance several masses rotating in the same plane, what angles are used to calculate the horizontal and vertical components of centrifugal forces?

    <p>$1, 2, 3, 4$</p> Signup and view all the answers

    To determine the magnitude and direction of the balancing mass analytically, what step is taken after calculating the horizontal and vertical components of centrifugal forces?

    <p>$tan(θ) = S_V / S_H$</p> Signup and view all the answers

    What does tan(θ) represent when calculating the resultant centrifugal force analytically?

    <p>$S_V$ divided by $S_H$</p> Signup and view all the answers

    What role does taking moments about specific points play in determining balancing forces?

    <p>Balancing static and dynamic forces</p> Signup and view all the answers

    What is a key requirement for achieving balance when considering multiple masses in rotation?

    <p>Balancing static and dynamic forces</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 and direction</p> Signup and view all the answers

    What is the balancing force equal to?

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

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

    <p>To eliminate vibrations caused by shaking force and couple</p> Signup and view all the answers

    What does the unbalanced force or shaking force result from in a reciprocating engine?

    <p>Resultant of all forces acting on the engine body</p> Signup and view all the answers

    In balancing reciprocating masses, what does adding appropriate balancing mass help achieve?

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

    What is the angle that the balancing mass makes with mass m1?

    <p>$180° + 21.48°$</p> Signup and view all the answers

    How are the horizontal component of FB and FI related in the reciprocating engine mechanism?

    <p>They are equal in magnitude but opposite in direction</p> Signup and view all the answers

    What is the purpose of balancing reciprocating masses by adding balancing mass?

    <p>To reduce unbalanced forces caused by reciprocating parts</p> Signup and view all the answers

    What is the effect of reciprocating parts on an engine according to the text?

    <p>$The$ $effect$ $is$ $to$ $produce$ $a$ $shaking$ $force$ $and$ $a$ $shaking$ $couple$</p> Signup and view all the answers

    What is the magnitude of the balancing mass required for a given radius of rotation if m1 = 200 kg, r1 = 0.2 m and r = 0.2 m?

    <p>40 kg-m</p> Signup and view all the answers

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

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

    What happens when the horizontal component of FB (FBH) is unbalanced?

    <p>It causes objectionable vibrations</p> Signup and view all the answers

    What is the primary unbalanced force in a reciprocating engine considered equivalent to?

    <p>Centrifugal force due to mass m at crank radius r</p> Signup and view all the answers

    How is the primary unbalanced force balanced in a reciprocating engine?

    <p>By having a mass B at radius b diametrically opposite to crank pin C</p> Signup and view all the answers

    Why are locomotives usually equipped with two cylinders placed at right angles to each other?

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

    In inside cylinder locomotives, where are the cylinders usually placed?

    <p>Inside the driving wheels</p> Signup and view all the answers

    What is the purpose of having coupled locomotives?

    <p>To connect driving wheels to leading and trailing wheels</p> Signup and view all the answers

    How does adding appropriate balancing mass help reduce shaking force and shaking couple?

    <p>By partially balancing the reciprocating masses</p> Signup and view all the answers

    What does m represent in a reciprocating engine mechanism?

    <p>Mass of the reciprocating parts</p> Signup and view all the answers

    What is the effect of an unbalanced primary force along the line of stroke?

    <p>Swaying couple</p> Signup and view all the answers

    What results from an unbalanced primary force perpendicular to the line of stroke?

    <p>Variation in pressure on the rails</p> Signup and view all the answers

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

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

    In multi-cylinder in-line engines, what must be satisfied to achieve primary balance of the reciprocating parts?

    <p>Primary force polygon must close</p> Signup and view all the answers

    What are the two conditions that must be satisfied to give the primary balance of reciprocating parts in a multi-cylinder engine?

    <p>Primary force polygon closes and couples sum to zero</p> Signup and view all the answers

    What is essential for secondary disturbing force due to reciprocating mass to arise?

    <p>Obliquity of connecting rod considered</p> Signup and view all the answers

    How can the secondary forces in multi-cylinder in-line engines be equivalent to centrifugal forces?

    <p>By inclined imaginary secondary cranks to line of stroke</p> Signup and view all the answers

    What is the angle at which the tractive force is maximum or minimum?

    <p>$135^{<br /> ho}$ or $315^{<br /> ho}$</p> Signup and view all the answers

    What does it mean when it is said that 'primary couple polygon must close'?

    <p>The algebraic sum of couples around any point is zero.</p> Signup and view all the answers

    What does a multi-cylinder in-line engine refer to?

    <p>Engines with cylinders in same plane and on same side of crankshaft.</p> Signup and view all the answers

    What is the main reason for balancing rotating and reciprocating parts in engines and machines?

    <p>To minimize pressure on the main bearings and reduce vibrations</p> Signup and view all the answers

    What is the term used to describe the process of adding a second mass to counteract the effect of the centrifugal force of the first mass in balancing rotating masses?

    <p>Balancing couple polygon</p> Signup and view all the answers

    In order to balance a single rotating mass by a single mass rotating in the same plane, what is the objective?

    <p>To equalize and oppose the centrifugal forces of both masses</p> Signup and view all the answers

    Why is it important to attach a second mass to a rotating shaft in terms of balancing rotating masses?

    <p>To balance out the centrifugal force exerted by the first mass</p> Signup and view all the answers

    What are the consequences of not properly balancing rotating and reciprocating parts in engines and machines?

    <p>Production of unpleasant and dangerous vibrations</p> Signup and view all the answers

    How does adding a second mass to counteract centrifugal force affect the shaft in a rotating system?

    <p>Reduces bending of the shaft</p> Signup and view all the answers

    What is the balancing force in the reciprocating engine mechanism?

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

    In the reciprocating engine mechanism, what is the effect of the shaking couple?

    <p>FU × x</p> Signup and view all the answers

    What is the angle that the balancing mass makes with the horizontal mass of 200 kg?

    <p>180° + 21.48°</p> Signup and view all the answers

    Which method can be used to solve the problem of balancing masses analytically or graphically?

    <p>Both analytical and graphical methods</p> Signup and view all the answers

    What does the horizontal component of FB along the line of reciprocation balance in the reciprocating engine mechanism?

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

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

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

    What is the unbalanced force or shaking force denoted by in reciprocating engines?

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

    How can vibrations be reduced in engines with reciprocating masses?

    <p>By partially balancing reciprocating masses</p> Signup and view all the answers

    In a reciprocating engine mechanism, what is the effect of adding a shaking couple?

    <p>Introduces a secondary unbalanced force</p> Signup and view all the answers

    What is the purpose of balancing reciprocating masses in engines?

    <p>To eliminate shaking forces and couples</p> Signup and view all the answers

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

    <p>To achieve dynamic balancing</p> Signup and view all the answers

    In static balancing of a system with two balancing masses, what condition must be met regarding the line of action of centrifugal forces?

    <p>They must be parallel to the axis of rotation.</p> Signup and view all the answers

    When balancing a single rotating mass by two masses in two different planes, what is the primary goal in terms of the net dynamic force on the shaft?

    <p>Minimize the net dynamic force</p> Signup and view all the answers

    Which is a key aspect of achieving complete balance when introducing two balancing masses for a single rotating mass?

    <p>Making sure the centre of masses lies on the axis of rotation</p> Signup and view all the answers

    What is a common consequence of using only one balancing mass in the same plane for a single rotating mass?

    <p>Creation of dynamic unbalance</p> Signup and view all the answers

    In balancing a single rotating mass by a single mass in the same plane, what is essential about the centrifugal forces produced?

    <p>They must be equal and opposite</p> Signup and view all the answers

    What role does having two balancing masses play when dealing with a disturbing mass positioned in between them?

    <p>Achieving complete static balance</p> Signup and view all the answers

    When attaching two balancing masses, what condition ensures that the system is in complete balance?

    <p>'The algebraic sum of moments about any point is zero'</p> Signup and view all the answers

    Why are two balancing masses preferred over a single one when balancing a single rotating mass?

    <p>To reduce net centrifugal forces on the shaft</p> Signup and view all the answers

    In terms of static balance, what must be satisfied when dealing with two balancing masses for a single rotating mass?

    <p>The centre of masses must be aligned with the axis of rotation.</p> Signup and view all the answers

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

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

    In locomotives, what characterizes 'outside cylinder locomotives'?

    <p>Cylinders placed outside the driving wheels</p> Signup and view all the answers

    For primary balancing in a reciprocating engine, what is the primary unbalanced force considered equivalent to?

    <p>Centrifugal force due to mass B</p> Signup and view all the answers

    What does adding appropriate balancing mass help achieve in reciprocating engines?

    <p>Eliminate objectionable vibrations</p> Signup and view all the answers

    What is the effect of unbalanced primary force along the line of stroke in a reciprocating engine?

    <p>Introduces objectionable vibrations</p> Signup and view all the answers

    How are locomotives usually equipped in terms of cylinders placement for uniformity in turning moment diagram?

    <p>Two cylinders with cranks at right angles</p> Signup and view all the answers

    What does the primary unbalanced force in a reciprocating engine act along?

    <p>Line of stroke</p> Signup and view all the answers

    'Inside cylinder locomotives' have their cylinders placed where in relation to the driving wheels?

    <p>Inside the driving wheels</p> Signup and view all the answers

    What is the goal of partially balancing reciprocating masses in an engine?

    <p>To reduce but not entirely eliminate shaking forces and couples</p> Signup and view all the answers

    What do secondary unbalanced forces of reciprocating masses form when they are equal and opposite?

    <p>Shaking couple of magnitude FN × x or FBV × x</p> Signup and view all the answers

    To achieve static balance in a system with a disturbing mass lying on one end of the planes of the balancing masses, what must be true?

    <p>The centrifugal force on the disturbing mass must be less than the sum of the centrifugal forces on the balancing masses</p> Signup and view all the answers

    What is true about the direction of the balancing force when finding the magnitude of balancing force in plane L analytically?

    <p>The balancing force is directed opposite to the resultant force</p> Signup and view all the answers

    What is the purpose of taking moments about point P when finding the balancing force in plane L?

    <p>To find the dynamic force at the bearing Q</p> Signup and view all the answers

    How is the magnitude of the balancing mass found analytically when balancing several masses rotating in the same plane?

    <p>By calculating sums of horizontal components of centrifugal forces</p> Signup and view all the answers

    What is true about balancing multiple masses rotating in the same plane using the analytical method?

    <p>The balancing mass magnitude equals the sum of horizontal and vertical components</p> Signup and view all the answers

    When finding the magnitude and position of balancing mass graphically, what does ab represent in relation to mass m1?

    <p>Centrifugal force exerted by m1</p> Signup and view all the answers

    In graphical method for finding balancing mass, what is represented by vectors bc, cd, and de?

    <p>'SV' components of masses m2, m3, and m4</p> Signup and view all the answers

    What does resolving centrifugal forces horizontally and vertically help determine when balancing several masses analytically?

    <p>'SH' and 'SV' components required for graphical method</p> Signup and view all the answers

    'Tan θ = S V / SH', this equation is used to find what aspect when determining resultant centrifugal force analytically?

    <p>'SV' components for each mass separately</p> Signup and view all the answers

    'FC = m·r', where does 'm' represent when determining the magnitude of balancing mass analytically?

    <p>'m', balancing mass required for static balance</p> Signup and view all the answers

    What is the effect of an unbalanced primary force along the line of stroke in reciprocating parts?

    <p>Swaying couple</p> Signup and view all the answers

    In a multi-cylinder in-line engine, what must be equal to zero to achieve primary balance of reciprocating parts?

    <p>Primary forces</p> Signup and view all the answers

    What is the condition for the tractive force to be maximum or minimum in a reciprocating engine?

    <p>$135°$ or $315°$</p> Signup and view all the answers

    What is the maximum magnitude of the unbalanced force along the 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 should close to achieve primary balance of reciprocating parts?

    <p>Primary force polygon</p> Signup and view all the answers

    What results from an unbalanced primary force perpendicular to the line of stroke in locomotives?

    <p>Hammering action on the rails</p> Signup and view all the answers

    How is the tractive force calculated in a reciprocating engine?

    <p>$(1-c)m.2.r(\cos - \sin)$</p> Signup and view all the answers

    What is the purpose of balancing the reciprocating parts in a multi-cylinder in-line engine?

    <p>To achieve primary balance</p> Signup and view all the answers

    What happens when considering multiple masses rotating in the same plane?

    <p>Primary forces cancel out each other</p> Signup and view all the answers

    What is the equivalent to the component parallel to the line of stroke of the centrifugal force due to reciprocating masses?

    <p>Resultant centrifugal force due to an equal mass at crankpin</p> Signup and view all the answers

    What must be true in order to achieve a complete secondary balance of an engine?

    <p>The algebraic sum of the couples about any point in the plane of the secondary forces must equal zero.</p> Signup and view all the answers

    What is the role of the direct and reverse cranks in balancing radial or V-engines?

    <p>Balancing primary forces.</p> Signup and view all the answers

    In the reciprocating engine mechanism, what is the relationship between the direct and reverse cranks' rotations?

    <p>The direct crank rotates clockwise while the reverse crank rotates counterclockwise.</p> Signup and view all the answers

    For primary effects due to the mass of reciprocating parts, how is the mass (m) replaced for these effects?

    <p>By splitting m into two masses and placing them at C and C'.</p> Signup and view all the answers

    What are the rotations of the secondary direct and reverse cranks OD and OD' respectively?

    <p>OD rotates at 2π rad/s in a clockwise direction, while OD' rotates at 2π rad/s in a counterclockwise direction.</p> Signup and view all the answers

    What is the purpose of replacing the mass (m) of reciprocating parts by two masses (each m/2) for secondary effects?

    <p>To simplify calculations for secondary forces.</p> Signup and view all the answers

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