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Answers to Sb01box
"The sprung clutch just absorbs some of the initial shock but does nothing for the harmonics" 100% true statement. The sprung clutch helps reduce the shock of clutch engagement from being transferred to the gearbox. A dual mass flywheel makes the sprung clutch redundant. Never use a sprung clutch with a dual mass flywheel and don't use an unsprung clutch with a single mass flywheel.
"I've read somewhere where a secondary counter rotating shaft with weight is use to counter harmonics for straight 4 cylinder engines - patented by Mitsubishi??? but these were basically directly driven via chain." There is inherent unbalance that takes place at 2x the RPM of the crank rpm based on the weight of the rod ends attached to the crank in in-line 4 cylinder engines (not horizontally opposed engines nor V6 or V8 engines ...they have different issues). These 4 cyl engines use the timing chain to also spin two shafts that are intentionally out of balance ...and they spin it at 2x the crank RPM and a little above the centerline of the crank. This unbalance directly offsets the mechanical unbalance that takes place due to the positions of the 4 crank journals.
"is my understanding that DMFW has some sort of spring/elastomer coupling the two disks." Answer: Yes, and that is what acts as the damper or the shock absorber. The elastomer is positioned so it doesn't just allow the outside weighted ring to just bounce unrestrained like a spring, but rather it must overcome some friction like a shock absorber being expanded and compressed. It is less like a spring and more like a shock.
"Question, with direct coupling, is the harmonics cancellation accomplished independent of engine rpm." Answer: with direct coupling there is no harmonics cancellation, regardless of engine rpm.
"Question, with spring between the two, taking out harmonics from 700 rpm to 7000 rpm, 10x range would need spring to become 10x stronger??" No the harmonics are not due to the rotating mass or the RPM of the engine, but rather due to the power generated by each explosion of the firing cycle of the engine. While this does changes in force at different rpms, the damper is "tuned" to do the most damping at the specific frequency that the crank needs the most assistance. (if you ever saw the video of the tacoma narrows bridge, you have seen an example of something reasonably rigid that needed assistance at a specific frequency. Tuning of the harmonic damper is done by adding or subtracting mass from the outside rotating mass or by adding stiffness to removing stiffness from the elastomer ...In both cases this must be done equally 180 degrees opposite each other and with the same amount of weight (or elastomer stiffeners) or unbalance will be added to the crank assembly.
-Gregg
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