What is the characteristic of vibrations at running speed if an eccentric sheave is present?

Vibrations at running speed, particularly when an eccentric sheave is present, are primarily influenced at the fundamental frequency known as 1X, which corresponds to the running speed of the machine or component. An eccentric sheave introduces an unbalanced force that generates vibrations at this fundamental frequency as it rotates.

When rotation occurs, the unbalanced mass causes periodic displacement from the center of rotation, resulting in vibration that is directly related to the machine's operational speed (1X). As the speed increases, the amplitude of the vibrations can increase as well, particularly at this 1X frequency. This characteristic is crucial for identifying potential issues with an eccentric sheave, as it often serves as a clear indicator of imbalance within the system.

Other options do not accurately represent the behavior of vibrations in this context. For instance, focusing on harmonic frequencies alone does not account for the specific effects of the eccentric sheave's unbalance, and stating vibrations remain constant overlooks the dynamic nature of how these forces interact during operation. Additionally, vibrations peaking above running speed would not typically be observed due to the direct relationship between the running speed and the resultant 1X vibration frequency.