Balancing of single cylinder engineAim: Find the primary balancing force, balancing mass radius and residual un balanced force when crank has at 600 or 1200 from inner dead centre.

Observation

Note:

Reciprocating mass are only partly balanced.

The masses rotating with crankshaft are normally balanced and they do not transmit any un balanced forces on the body of the engine

The acceleration of reciprocating mass

aP = (2 r (cas(+cos 2(/n)

Inertia force due to reciprocating parts

Ft or FR = mass ( acceleration

= m ((2 r (cas(+cos 2(/n))

= (m (2 r cas() + (m (2 r cos 2(/n)

= FP + FS

Where FP and FS are primary and secondary unbalanced forces.

FP = m (2 r cas( NFS = m (2 r cos 2(/n N The secondary unbalanced force will be 1/n times the primary unbalanced forces. In moderate speed, the secondary unbalanced force is small and that can be neglect. The un balanced force due to reciprocating mass varies in magnitude but constant in direction

The unbalanced force due to revolving masses, the unbalanced force is constant in magnitude but varies in direction. The primary un balanced force may be considered as the component of the centrifugal force produced by a rotating mass m placed at the crank radius r.

The primary force acts from O to P along the line of stroke m be the equivalent balancing mass is placed at the crank radius r. this is balanced by mass B at the radius b placed directly opposite to the crank pin. The primary unbalanced force acts along the line of stroke, the secondary un balanced force acts along perpendicular to line of stroke.There fore we can write

B b = (m1 + c m ) rWhere c is the component of reciprocating mass to be balanced i.e., 50% (i.e., 0.5)or 75% (i.e., 0.75)m1 is the mass of revolving massm is the mass of reciprocating massObservations

N = rpm (at that instant)

( = 2( N/60 = rad/sec

Stroke = 60 mm

Wt of the connecting rod +piston (m) = 740 grams

Wt of revolving = grams

Radius of revolving mass (crank radius r) = 30 mm

c is the component of reciprocating mass = 0.5

Calculation

1. Primary balancing force = m (2 r cas ( N2. Balancing mass radius (b) i.e., B b = (m1 + c m ) r (insufficient data)3. Residual unbalanced force = m (2 r NTabular columnSl NoSpeed

N rpmAngle (Primary balancing

force at that instant NResidual un balanced

force at that instant N

deg rad

60

120

60

260

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