UNIT- 4 PPT

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  • Introduction Balancing Why Balance? Rotating components experience significant quality and performance improvements when balanced. Balancing is the process of aligning a principal inertia axis with the geometric axis of rotation through the addition or removal of material. By doing so, the centrifugal forces are reduced, minimizing vibration, noise and associated wear.Balancing The process of providing the second mass in order to counteract the effect of the centrifugal force of the first mass, is called balancing of rotating masses. To eliminate all shaking forces and shaking moments Any link or member that is in pure rotation can, theoretically, be perfectly balanced to eliminate all shaking forces and shaking moments.A rotating member can be balanced either statically or dynamically. The amount and location of any imbalance can be measured quite accurately and compensated for by adding or removing material in the correct locations..

  • Types of Balancing Balancing Static Balancing: Static balancing is a balance of forces due to action of gravity.A body is said to be in static balance when its centre of gravity is in the axis of rotation.An other name for static balance is single-plane balance, which means that the masses which are generating the inertia forces are in, or nearly in, the same plane.Some examples of common devices which meet this criterion, and thus can successfully be statically balanced, are: A single gear or pulley on a shaft, A bicycle or motorcycle tire and wheel, A thin flywheel, An airplane propeller, An individual turbine blade-wheel (but not the entire turbine)

  • Types of Unbalancing Balancing

  • Types of Balancing Balancing Static Unbalancing:A condition of static unbalance exists when the mass center does not lie on the axis of rotation. Static unbalance is also known as Force Unbalance. As defined, static unbalance is an ideal condition, it has the additional condition that the axis of rotation be parallel to the central principal axis . no couple unbalance.

  • Types of Balancing Balancing Static Unbalancing:A condition of static unbalance exists when the mass center does not lie on the axis of rotation. Static unbalance is also known as Force Unbalance. As defined, static unbalance is an ideal condition, it has the additional condition that the axis of rotation be parallel to the central principal axis . no couple unbalance.

  • Types of Balancing Balancing Balancing

  • Types of Balancing Balancing Dynamic balancing:Dynamic balance is a balance due to the action of inertia forces.A body is said to be in dynamic balance when the resultant moments or couples, which involved in the acceleration of different moving parts is equal to zero.The conditions of dynamic balance are met, the conditions of static balance are also met.Any rotating object or assembly which is relatively long in the axial direction compared to the radial direction requires dynamic balancing for complete balance. Dynamic balance is sometimes called two plane balance It require that two criteria to be met The sum of forces must be zero And the sum of moments must also be zero

  • Types of Balancing Balancing

  • Types of Balancing Balancing Dynamic balancing:Some examples of devices which require dynamic balancing are: Rollers Crank-shafts Camshafts Axles Clusters of multiple gears, motor rotors, turbines, propeller shafts.COUPLE UNBALANCE: Is a specific condition that exists when the central principal axis of inertia is not parallel with the axis of rotation. Couple unbalance is often presented as dynamic unbalance in engineering classes,. As defined, couple unbalance is an ideal condition. It carries the additional condition that the mass center lie on the axis of rotation . no static unbalance.

  • Types of Balancing Balancing Dynamic Unbalancing:The most general case of unbalance in which the central principal axis is not parallel to and does not intersect the axis of rotation.Dynamic unbalance is also referred to as two plane unbalance, indicating that correction is required in two planes to fully eliminate dynamic unbalance.

  • Balancing of Rotating Masses.. Balancing Balancing involves redistributing the mass which may be carried out by addition or removal of mass from various machine membersBalancing of rotating masses can be ofBalancing of a single rotating mass by a single mass rotating in the same plane.Balancing of a single rotating mass by two masses rotating in different planes.Balancing of several masses rotating in the same planeBalancing of several masses rotating in different planes

  • Balancing of Rotating Masses.. Balancing Balancing of a single rotating mass by a single mass rotating in the same plane.

  • Balancing of Rotating Masses.. Balancing THE PLANE OF THE DISTURBING MASS LIES IN BETWEEN THE PLANESOF THE TWO BALANCING MASSES.

  • Balancing of Rotating Masses.. Balancing Balancing of several masses rotating in the same plane.

  • Balancing of Rotating Masses.. Balancing Balancing of several masses rotating in the different plane.When several masses revolve in different planes, they may be transferred to a reference plane (briefly written as R.P.), which may be defined as the plane passing through a point on the axis of rotation and perpendicular to it.

  • Balancing of Rotating Masses.. Balancing Balancing of several masses rotating in the different plane.When several masses revolve in different planes, they may be transferred to a reference plane (briefly written as R.P.), which may be defined as the plane passing through a point on the axis of rotation and perpendicular to it.

  • Balancing of Rotating Masses.. Balancing Balancing of several masses rotating in the different plane.When several masses revolve in different planes, they may be transferred to a reference plane (briefly written as R.P.), which may be defined as the plane passing through a point on the axis of rotation and perpendicular to it.Reference plane: the plane passing through a point on the axis of rotation and perpendicular to it. In order to have a complete balance of the several revolving masses in different planes, the following two conditions must be satisfied : The forces in the reference plane must balance, i.e the resultant force must be zero.The couples about the reference plane must balance, i.e. the resultant couple must be zero.

  • Balancing of Rotating Masses.. Balancing Balancing of several masses rotating in the different plane.

  • Balancing of Reciprocating engine Balancing Effect of the reciprocating parts is to produce a shaking force and a shaking couple. Since the shaking force and a shaking couple vary in magnitude and direction during the engine cycle, therefore they cause very objectionable vibrations. but it is usually not practical to eliminate them completely. In other words, the reciprocating masses are only partially balanced.

  • Balancing of Reciprocating engine Balancing The primary unbalanced force is maximum, when = 0 or 180. Thus, the primary force is maximum twice in one revolution of the crank. The secondary unbalanced force is maximum, when = 0, 90,180 and 360. Thus, the secondary force is maximum four times in one revolution of the crank. From above we see that secondary unbalanced force is 1/n times the maximum primary unbalanced force.

  • Shaking force, F x21 = m B A B Shaking couple , T = x F41F21=t Balancing of Reciprocating Masses

  • Shaking force, F x21 = m B A B Shaking couple , T = x F41Forces on the frame of the engine

  • Shaking force, F x21 = m B A B Shaking couple , T = x F41shaking forceForces ofshaking couple

  • 21=tmBmB r 2b B r B 2

    b B r B 2 cos t

    b B r B 2 sin t

    mB r 2cos t

    Primary disturbingforcebalancing forcethis force to line of stroke not balancedb B r B= mB r for 100 %Balancing along the line of stroke

  • MULTI CYLINDER IN-LINE ENGINES:

    Common crank shaft driven by number of connecting rods

    Angular interval between successive cranks ,

    (2 / n) in the case of 2-stroke engine

    (4 / n) in the case of 4-stroke engine

    Where n is the number of cylinders

    firing order influences balancing condition

  • *ratna kUseless EducationChanakya Neetisays thatEducation will be considered useless until it is not put to some practical use. The life of an uneducated person is a total waste. Similar is the case with an army without a commander

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