If a rotor has static unbalance, what is the phase relationship of the two ends of the machine in the vertical direction?

When a rotor has static unbalance, it means that the mass is unevenly distributed relative to its axis of rotation. This condition leads to a consistent displacement pattern as the rotor spins. In a scenario of static unbalance, the two ends of the rotor will experience the same forces and thus respond in a similar manner in terms of vibration amplitude and phase.

Since both ends of the machine experience the same unbalance forces due to the rotor's weight not being evenly distributed, they will oscillate together in the same phase. This means that when one end moves up, the other end also moves up, and when one end moves down, the other end does the same simultaneously. This characteristic phase relationship results from the coupled nature of the rotor's static mass distribution impacting both ends similarly, leading to synchronous motion.

Options that suggest the ends are out of phase, have random phase relationships, or depend on the load do not align with the fundamental understanding of how static unbalance affects rotor dynamics. Static unbalance creates a predictable and consistent vertical lift or drop at both ends of the rotor simultaneously, which will always be in phase.