motor resonance

[Oli]

Anyone heard a similar comment:
"It is normal that resonances get lower with a stiff mount."
I have always beleived it was the other way around. Olov

[MH]

I believe that would depend on where or which side of the resonance peak the natural being excited is. There have been times I have seen resonance amplitudes increased with stiffening. The Fn was on the lower side of the spectral peak. In stiffening the frequency natural was raised into the forcing frequency. I believe the impact test would reveal the Fn with the information on whether or not to stiffen or add mass to lower the Fn away from the forcing frequency. So, yes stiffening always raises the Fn but could also increase the the resonant peak dependant upon position of the Fn's relationship to the Forcing Frequency.