![]() ![]() The torsional vibration of the crankshaft forces the fluid through narrow passages that dissipates the vibration as heat. Viscous dampers consist of an inertia ring in a viscous fluid.There are two main types of torsional dampers. This potentially damaging vibration is often controlled by a torsional damper that is located at the front nose of the crankshaft (in automobiles it is often integrated into the front pulley). Therefore, and to ensure that the coupling is not damaged due to this (temperature could be very high, depending on the load), this is verified through torsional vibration calculation. The couplings turn the vibration energy into heat. If torsional vibration is not controlled in a crankshaft it can cause failure of the crankshaft or any accessories that are being driven by the crankshaft (typically at the front of the engine the inertia of the flywheel normally reduces the motion at the rear of the engine). There is inherently little damping in a crankshaft to reduce the vibration except for the shearing resistance of oil film in the main and conrod bearings.2 Stroke Engines generally have smaller bearing overlap between the main and the pin bearings due to the larger stroke length, hence increasing the flexibility of the Crankshaft due to decreased stiffness.Engines with six or more cylinders in a straight line configuration can have very flexible crankshafts due to their long length. ![]() The motion of the piston mass and connecting rod mass generate alternating torques often referred to as "inertia" torques.The slider-crank mechanism does not output a smooth torque even if the pressure is constant (e.g., at top dead centre there is no torque generated).The cylinder pressure due to combustion is not constant through the combustion cycle.Alternating torques are generated by the slider-crank mechanism of the crankshaft, connecting rod, and piston. ![]() Causes of the torsional vibration are attributed to several factors. Torsional vibration is a concern in the crankshafts of internal combustion engines because it could break the crankshaft itself shear-off the flywheel or cause driven belts, gears and attached components to fail, especially when the frequency of the vibration matches the torsional resonant frequency of the crankshaft.
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