If a machine that is not overhung is out of balance, what will the spectrum display?

When a machine that is not overhung is out of balance, it generates vibrations that manifest as peaks in the vibration spectrum. The primary frequency of interest in this situation is the running speed of the machine, known as 1x. This is because the imbalance causes the machine to vibrate at its operating frequency.

In a balanced machine, the forces acting on it are evenly distributed, leading to minimal vibration and a spectrum that displays little to no significant peaks. However, when the machine is out of balance, the imbalance leads to an increase in vibrations due to uneven forces, causing high peaks to appear at 1x. Since the machine is not overhung and typically exhibits vibration in both vertical and horizontal directions, we can expect strong peaks in both orientations.

This understanding aligns with the mechanics of vibration analysis; a significant increase in amplitude at the fundamental frequency indicates imbalance, reinforcing the idea that out-of-balance machines will show high peaks at 1x in both the vertical and horizontal directions in the spectrum.