"Gordon Arnaut" wrote

This means that as soon as the springs kick in, the system is no longer in
resonance because its resonant frequencies are now quite a bit lower, due
to the added flexibility of the entire system. So the oscillations stop.
You yourself alluded to this in your remarks about overall system
stiffness.

For pete's sake, give it a rest. Your incomplete knowledge is showing in
spades.
--
Jim in NC