Vibration control of an engine hood on a medium-sized tractor

Generally, engine is a main vibration source for a tractor. Under its excitation, engine hoods on tractors may vibrate seriously, because most hoods are connected rigidly to tractor bodies or frames. As a result, some accessories and lights equipped on the hoods may be damaged or can not work well. In order to control the hood vibration, an engine hood on a wheeled medium-sized tractor is investigated here. At first, the vibration transmission path was studied. Then the hood vibration was tested and analyzed with the technique of frequency analysis. And the natural vibration characteristics analysis of the hood was also conducted with the technique of experimental modal analysis. The vibration spectra showed us that the highest peak was located at the second order frequency of the working engine, which indicated that the second unbalanced inertial force and/or the explosive combustion force are the dominant exciting source for the engine hood. The experimental modal analysis shows that the third and the forth vibration modes of the hood may be one of the main factors which affect the vibration of the engine hood. Considering the characteristics of the exciting forces and the natural properties of the engine hood, some measures for reducing the vibration could be applied. But for economy and convenience, a kind of special elastic supporting members (vibration insulating structures) was designed. The further tests indicated that the specially designed supporting structures work well, and the hood vibration was reduced obviously, and its vibration situation was improved noticeably.