Reduction of Rattle Noise of a Direct Engine-PTO Driveline of Agricultural Tractors: Part III. Reduction of PTO Rattle Noise by a Torsional Damper

The PTO rattle noise of the direct engine-PTO driveline was caused by the collisions between the driving and driven gears in the PTO gearbox due to their velocity variations induced by the torque fluctuations transmitted from the engine (Part II, companion article). This indicated that the speed variation must be reduced to reduce the PTO rattle noise. In this study, a torsional damper was used to reduce the speed variations in the PTO driveline. A torsional damper comprised of two helical coil springs was installed on the engine flywheel to reduce the torque fluctuations causing the speed variations and gear collisions in the PTO gearbox during idling. The effects of design parameters of the torsional damper on the speed variation were investigated, and their optimum values were found by using an 11-degree of freedom, non-linear model of the damped PTO driveline. Under a constant hysteresis torque, the speed variation increased with the torsional stiffness of the damper. When the optimum values of the first spring were used, the sound pressure level of the rattle noise was reduced, resulting in a reduction of 15 dBA. The optimum torsional damper also reduced the velocity variation of the driving gear in the PTO gearbox, resulting in a noise reduction of 15 dBA. The torsional damper performed well in reducing the rattle noise caused by velocity variation in the direct engine-PTO driveline.