Two machines of identical geometry on the same base, or platform, is not a good design, especially if one is mostly in a standby mode. The problem is that the working machine transmits vibration to the standby machine and causes damage. The housing of the standby machine vibrates in sympathy with the operating machine particularly when resonances are involved. One needs to stiffen the machines such that motion is restricted. This decreases the forces transmitted through the bearings as the housing oscillates against the inertia of the rotor. The other alternative is to break the transmission path by cutting the common support on base.
This experiment shows how the vibration is transmitted from one machine to near by machine. Experiment can be done with and without common base for these machines and its effects on vibration level can be experimented.