Commercial Lawn Tractor Driveline Torsional Vibration

Problem: A commercial lawn tractor manufacturer contacted Roush to analyze a problem with one of its products. The vehicle was exhibiting a premature failure of a driveshaft that coupled the engine flywheel to the transmission input. Roush was asked to identify the source of this failure, and develop the modifications required to eliminate it.

Solution: After installing the tractor on a dynamometer, Roush instrumented it with accelerometers, strain gauges and torsional sensors. Test results identified a high torsional response caused by a torsional resonance in the driveshaft. Roush recommended an increase in shaft diameter to shift the torsional resonance beyond the normal operating speed range.

Result: The driveshaft torsional response was reduced over the entire operating speed range. At the high operating speeds where the failure occurred, the torsional response was reduced by a factor greater than two.