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With a very low firing frequency of a 2-cylinder diesel engine with 180° phase difference, control of Idle-shake of a pick up vehicle became a challenging task. It was reduced with all 3 engine mounts focused on a Torque-roll axis of the power train. Simulation of rigid body dynamics determined specific mount stiffness in compression and shear. Decoupled engine mount system resulted into also smooth key off of the vehicle. Nonlinear force deflection characteristics of all the rubber mounts ensured optimum design for vibration isolation of the frame, controlled motion of the power train in panic braking and adequate fatigue life of the rubber mounts on Torture Tracks. Sensitivity of front mount position, balance of all 6 rigid body modes and influence of exhaust system flexibility were found to be critical parameters for consistency in performance of production vehicles.

A reactive type of muffler of a 4-stroke Auto-Rickshaw was modeled using a commercially available Acoustic Finite Element Analysis (FEA) software like Sysnoise. Design sensitivity of different geometry parameters of mufflers to its Insertion Loss over a wide frequency range was studied. The analytical results were validated by the Laboratory Speaker test. But in the presence of a hot gas flow, the Insertion Loss characteristics of the muffler were far different. As the flow speed increased, negative attenuation was found in some frequency bands. The second part of the paper studies the software prediction of structure borne noise from a transmission cover of a Motorcycle. The sound power level was predicted by uncoupled fluid-structure analysis of Boundary Element Method (BEM). To reduce the sound power radiated from its top surface, a ribbed pattern and increase in thickness were proposed.

High idling vibrations of a single cylinder Diesel engine proved to be a cause of discomfort for passengers of an Auto-Riksha (3-wheeler). Extensive vibration measurements identified rolling resonance of the engine-mount system. This paper presents mathematical and experimental work to seek directions of the vibration control with low cost passive engine mounts. The work covered study of 1) use of softer rubber mounts at the engine-base 2) placing stiff rubber mounts closer to the Principal Roll-Axis of the engine 3) separate use of a Tie-Rod and Hydraulic Dampers between the engine and chassis 4) limitations of a Decoupled engine-mount configuration. Overall assessment of these methods was carried out by Eigen Analysis of a Lumped Mass Model of the engine-mount system as well as by measurement of the vehicle vibrations over a wide speed range.