I too, based upon a recommendation posted here a couple of years ago, put a FluidDamper on my engine. (Which has yet to run, so no experience points.)
Even though the FluidDamper is not necessarily tuned to the engine (although it is marketed for the 292) I was comfortable with that sugggestion as it seemed to me that the FluidDamper would be more universally applicable to a modified engine.
My reasoning:
The conventional damper is a tuned mass/spring, and as such will resonate to particular frequencies. The period of the crank resonant frequency absolutely cannot match the damper resonant frequency or they would couple and uncontrolably add. The conventional damper elastic medium doesn't consume (generally) energy; it adsorbs and returns vibrational energy from and to the crank, but at a different time and rate than the cranks natural period. In other words, it would seem that the damper isn't really a 'damper' but a vibrational reflector that scatters the energy pulses over time to prevent build up at certain frequencies.
As mentioned previously; any changes to the engines design rotating assembly is inevitably going to change the resonant periods of the crank, and it would seem to be pretty much a crap shoot whether that change is going to move the resonant frequency of the rotating assembly away from or closer to the resonant frequencies of the damper..
The FluidDamper on the other hand, is not a 'tuned' damper as I understand it. It is simply a fairly large mass buffered by a viscous fluid. When vibration excites movement of the mass relative to the housing, the fluid shears, and actually consumes energy; it doesn't return energy to the crank. Consequently, it seemed to me that it should act as a non-frequency-specific broadband damper that should continue to work regardless of changes to the resonant frequencies of the rotation assembly.
Since buying and installing the FluidDamper, I've heard of some failures that now have me wondering, although TLowe's crank snout wallowing failure might actually be an indication that the FluidDamper was so successfully consuming energy that the wallowing might have been a side effect of saving the crank... Difficult to know.
I've read through the recorded processes needed to flight-qualify the Wright and P&W twin row radials prior to WWII. Crank dyanmics are increadibly convoluted, and that was on short two-throw cranks. Our relatively limber and long cranks are no doubt spectacularly difficult.
