Search Results

In today’s automotive scenario, noise vibration and harshness (NVH) has become a synonym for quality perception. This paper evaluates the problem of vibration and noise experienced in M2 category 40 seat bus and suggests the counter measures. Severe vibration is experienced on the bus floor, predominantly towards rear part of the bus. Vibration along with acoustic boom occurs prominently in 4th gear wide open throttle operating condition between 1300-1600 rpm of the engine. This paper focuses on reducing NVH levels by working on the transfer path with little modifications on power-train. Preliminary torsional measurements conducted on powertrain indicated high torsional excitation in the driveline during the problematic rpm zone. Further, Operational Deflection Shape (ODS) analysis revealed that the transfer path to the cabin is rear differential unit and suspension links. The dominant frequencies were identified along the transfer path and suitable modifications were done.

This paper establishes quick and accurate methods to experimentally determine the rigid body properties of a powertrain unit namely, the centre of gravity, the moment of inertia and the torque roll axis and also the rigid body dynamics of mounting system such as the rigid body modes, kinetic energy distribution, and elastic roll axis. The centre of gravity is determined using single point suspension and laser pointer to locate the axis passing through the centre of gravity. A special unifilar pendulum test rig is developed for determining the moment of inertia where an accelerometer measures the rotational oscillations for a given time period and the moment of inertia is determined by solving a set of inertial ellipsoid equations. An easy method of reorienting the powertrain is demonstrated in this paper.