How will vibration change if the sheaves are eccentric?

When sheaves are eccentric, the resulting vibration will be influenced primarily through the unbalanced centrifugal forces that are generated during operation. This unbalance results in vibrations that can manifest at various frequencies related to the operational speed of the machinery.

Choosing to focus on the impact of this imbalance, it is understood that the primary frequency of vibration (often called the 1X frequency, which is directly related to the rotational speed of the sheave) will increase due to the additional forces acting on the system. As the eccentricity increases, the imbalance will cause greater amplitude vibrations at this fundamental frequency.

While harmonics can be present (for example, at 2X, which corresponds to twice the operational speed), the significant effect of eccentric sheaves is predominantly on the fundamental frequency (1X) of vibration. This leads to increased levels at this fundamental frequency, making it the most notable change when assessing the vibration characteristics of the machinery in question.

In this context, consequently, the correct option reflects the substantial increase in vibration at 1X due to the eccentric nature of the sheaves.