Balancing of reciprocating masses

Balancing is Important in Machineries. Classified in to Balancing of Rotating and reciprocating Masses.

1. Unit 2 Module 2 Balancing of Reciprocating Masses B. VARUN Assistant Professor( Sr.Gr ) Department of Mechanical Engineering

2. Shaking Force 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 2 The resultant of all the forces acting on the body of the engine due to inertia forces only is known as unbalanced force or shaking force

3. Primary and Secondary Unbalanced Forces of Reciprocating Masses 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 3 Considering a reciprocating engine mechanism Let m = Mass of the reciprocating parts, l = Length of the connecting rod PC , r = Radius of the crank OC , θ = Angle of inclination of the crank with the line of stroke PO , ω = Angular speed of the crank, n = Ratio of length of the connecting rod to the crank radius = l / r .

4. Acceleration 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 4 Inertia Force F I = Mass * Acceleration Primary Unbalanced Force = Secondary Unbalanced Force =  

5. Partial Balancing of Locomotives 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 5 The locomotives, usually, have two cylinders with cranks placed at right angles to each other in order to have uniformity in turning moment diagram.

6. Effect of Partial Balancing of Reciprocating Parts of Two Cylinder Locomotives 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 6 Due to the partial balancing of the reciprocating parts, there is an unbalanced primary force along the line of stroke and also an unbalanced primary force perpendicular to the line of stroke . Variation in tractive force along the line of stroke ; Swaying couple.

7. Variation of Tractive Force 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 7 The resultant unbalanced force due to the two cylinders, along the line of stroke, is known as tractive force . T ractive Force=  

8. Swaying Couple 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 8 The unbalanced forces along the line of stroke for the two cylinders constitute a couple about the centre line between the cylinders. This couple has swaying effect about a vertical axis, and tends to sway the engine alternately in clockwise and anticlockwise directions. Hence the couple is known as swaying couple. Swaying Couple=  

9. Hammer Blow 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 9 The maximum magnitude of the unbalanced force along the perpendicular to the line of stroke is known as hammer blow . Hammer Blow =  

10. Problem no 1 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 10 The following data refer to a two cylinder uncoupled locomotive Rotating mass per cylinder : 280 kg Reciprocating mass per cylinder : 300 kg Distance between wheels : 1400mm Distance between cylinder centers : 600mm Diameter of treads of driving wheels : 1800mm Crank radius :300mm Radius of centre of balanced mass = 620 mm Locomotive speed : 50km/ hr Angle between cylinder cranks : 90 Dead load on each wheels : 3.5 tonne Determine : Balancing Mass required in the planes of driving wheels if whole of revolving and 2/3 of the reciprocating mass to be balanced Swaying Couple Variation in the tractive force Maximum and minimum pressure on the rails

11. Problem No 2 8/9/2018 B.Varun,AP(SRG)/Mechanical Engineering 11 The following data apply to an outside cylinder uncoupled locomotive : Rotating mass per cylinder = 360 kg ; Reciprocating parts per cylinder= 300 kg ; Angle between cranks = 90° ; Crank radius = 0.3 m ; Cylinder centres = 1.75 m ; Radius of balance masses = 0.75 m ; Wheel centres = 1.45 m . If whole of the rotating and two-thirds of reciprocating parts are to be balanced in planes of the driving wheels, find : 1. Magnitude and angular positions of balance masses, 2. Speed in kilometres per hour at which the wheel will lift off the rails when the load on each driving wheel is 30 kN and the diameter of tread of driving wheels is 1.8 m, and 3. Swaying couple at speed arrived at in (2) above.

12. B.Varun,AP(SRG)/Mechanical Engineering 12 8/9/2018