Lee J., Kim W., Park W.

Vibration Reduction using modal testing techniques is accomplished with respect to three-cylindered engine driven tractor having 38 horse power. Unlike four-cylindered engine which have 2nd harmonics of rotating speed, three-cylindered engine have 1.5th harmonics of the rotating speed including the other harmonics of the integers. Unlike other passenger vehicle, tractor structures do not have suspension in order to sustain their rigidity under the severe ground loading conditions, therefore, vibration resonance avoiding measure is the best way in reducing the vibration level of the present tractor. Order tracking analysis is performed with each engine rotating speed in order to investigate resonance phenomena and modal testing is performed with each important components, especially to the drivers, to extract the natural frequencies and mode shapes. The structure modifications and vibration isolations with respect to the important components, such as handle, seat and foot rest, without modifying engine itself, are performed and, finally, the authors confirmed that the vibration level of the present new modified tractor are improved significantly compared with the previous one.