Compound Mounting Systems That Incorporate Dynamic Vibration Absorbers

The transmissibility across novel compound or two-stage mounting systems is discussed, and representative calculations of transmissibility are compared for systems with intermediate stages that comprise either (1) a rigid mass plus a dynamic vibration absorber, (2) dual beams loaded symmetrically by equal lumped masses, or (3) dual beams to which multiple dynamic vibration absorbers are attached. In the first case, the undesirable secondary resonance of the compound system can be suppressed effectively by the dynamic vibration absorber, for which appropriate design data are given. In the latter two cases, lumped masses or dynamic vibration absorbers are applied to each intermediate beam of the compound system at the locations of the four upper mounts that support the vibrating item from below. In turn, the beams are supported at each end by single antivibration mounts on a rigid foundation. The “secondary” resonance of the compound system that incorporates the multiple dynamic absorbers can be suppressed heavily by them; and it is shown how the excitation of a high-frequency resonance of the intermediate beams can be avoided, at the same time, by judicious choice of upper mount location. Design data for the multiple absorbers, which have relatively small mass, are tabulated.