Identical unbalanced masses m are secured to disks a in such a way that the resultant of the unbalanced forces acts along an axis perpendicular to the plane of the drawing, or so that a torque is produced with respect to this axis. Frame 2 of the machine is rigidly attached to the structure being tested. When shaft 1 rotates, all disks rotate and a vibrational load is applied to the foundation or support being tested.
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