Modified ball-type automatic balancer for rotating shafts: Analysis and experiment

The automatic balancer is a passive device with masses that are free to move in a shaft-concentric race. At supercritical shaft speeds, the masses automatically re-align to counteract imbalance and reduce vibration. This phenomenon is caused by the phase shift of the shaft bending response that occurs through resonance. The conventional automatic balancer (dual-ball, single race) reduces or eliminates vibration at supercritical speeds given a frictionless race, but increases vibration at subcritical and critical speed transitions. In this work, a fully passive, partitioned-track, automatic balancer with centrifugal clamps is proposed to improve performance during suboptimal operation. Both analysis and experiment are presented to support the novel design. Experimentally, a partitioned-race balancer reduced vibration by 7% during spin up, 83% at supercritical steadystate, and 65% during spin down – a complete improvement over conventional balancers. Model predictions are within 14% of experimental data at steadystate. Additionally, the use of centrifugal clamps reduced vibrations by up to 95% during critical speed transitions in analysis. The vibration reduction capability presented in this research outside of supercritical steadystate operation is a necessary advancement for the practical application of passive balancing devices.