What causes vibrations?
There are five principal causes of vibrations in combustion engines: • Unbalanced rotating parts • Unbalanced reciprocating parts • Combustion cyclic variations • Cyclic variations in the inertial force of reciprocating parts • Variations in torque and torque reaction Vibrations require a restoring force. This is provided by Hook’s law where strain creates a stress. Vibrations do not continue forever because there is a certain amount of internal dampening called “hysteresis”. Hysteresis represents the error in “Hook’s law”. During normal operation, the chief cause of vibrations is fluctuating engine torque -more so on four cylinder engines than six cylinder engines since the torque impulses are further apart on four cylinder engines. The turning force (torque) imposed on the crankshaft occurs on each power stroke and causes uneven torque loading because internal combustion engines are pulsating flow devices. Torque vibrations are transmitted to the engine frame primarily from the cylin
