VIBRATIONAL BEHAVIOR OF TRACTOR ENGINE HOOD

The main source of vibration in agricultural tractors is the engine. Engine vibration results from the combustion process itself and the mass asymmetry in engine rotating elements. The vibration is transmitted from the engine to the tractor hood. The objective of this study is to record and analyze the vibration patterns on the hood under different operational engine speeds (800 - 2200 rpm). Two different wheeled tractors were used for the experiments. The hood of the first tractor was made from steel sheet. The new hood design of the second tractor was made from fiber reinforced plastic material. The following instruments were used: the PSV-400 scanning laser vibrometer (Polytec), and the 4500A piezoelectric accelerometer (Bruel & Kjaer) that served as reference accelerometer. The experimental data showed significant deflection of the hood surface. Vibration analysis between the two types of engine hoods showed that the steel sheet was indeed very stiff; in contrast to the fiber reinforced plastic hood, which better absorbed the mechanical vibration due to the increased damping.