Assessment of the Removal of the Crankshaft Balance Weights on Bearing Caps Vibration and Engine Noise

The paper quantifies the vibrational acceleration of the main bearings and engine noise of an 8.2 Litre, six-cylinder, turbocharged diesel engine before and after the removal of the crankshaft balance weights and reviews their properties in both time and frequency domains. The change in the axial vibration of the middle bearing and the corresponding change in the emitted engine noise measured at the RHS (right hand side) of the engine are correlated. A similar correlation is observerd between the change in the axial vibration of the frontal bearing and the corresponding change in the emitted engine noise measured at the engine front.

It is shown that the removal of the balance weights has not resulted any consistent increase of the emitted noise level, in fact at some running conditions the noise level is lower.

The removal of the balance weights tends to reduce the mid and high frequency level of axial vibration.

The increase in amplitude of the second harmonic of the bearing loads at the higher engine speeds could give rise to a deterioration in fatique life of the crankshaft and bearings.