Arcusaflex® couplings from Ringfeder Power Transmission USA Corp., Westwood, N.J., are used on machines powered by diesel engines and strong pumps, which run less smoothly than electric motors. These soft couplings isolate driven systems from their less-than-steady power sources — particularly helpful where cardan shafts connect the two. Why? Cardan shafts allow shaft displacement and longer distances between driving and driven components, but their torsional flexibility can allow resonant excitation.
As explained by Sarah McChesney, chief engineer at Ringfeder, most isolators (including the Arcusaflex®) don't prevent vibration generation: “Instead, these devices dampen vibration and lower natural machine frequency to below lowest operating speed.” Of course, the other approach to lowering natural frequency is to add mass: “We've helped designers applying reciprocating compressors with tuning by both isolation and mass,” explains McChesney, “because these machines have terrible vibration. Often, a vibrating engine powers the compressor, which compounds the vibration issue with its own excitation. In fact, depending on system specifics, these compressors can only be applied successfully with both isolating couplings and increased mass.”