🔍 Key Concepts

• Torsional vibration in rotating shafts and drive trains • How a marine propeller load varies during each revolution • Differences between steady imbalance forces and cyclic torque changes

💭 Think About

• Ask which component in a geared turbine drive produces a cyclic twisting load on the shaft once each revolution or in a repeating pattern • Consider which option is most closely tied to changes in torque rather than changes in radial or unbalanced forces • Think about which effect is present under normal conditions, not only during a fault or unusual operating condition

✅ Before You Answer

• Distinguish torsional (twisting) vibration from lateral or radial vibration • Identify which choice is directly related to cyclic torque variations in the shaft line • Consider which source acts continuously with the propeller load in the water rather than only at certain critical speeds