Tom: There are many different approaches to damping / isolation / energy transfer. When one concentrates on a specific approach, all of the benefits can be achieved. At the same time, there is nothing left to counter the drawbacks that any "less than perfect" approach brings along with it. Since not all energy can be transferred or absorbed at 100% efficiency, either method will leave you with some drawbacks. By using a combination approach, one can minimize drawbacks of any single approach and gain the benefits of each IF properly implimented.
As a side note, what happens to the energy that isn't transferred from the component to the shelf or from the shelf to the rack or from the rack to the floor when working with coupling ? I have yet to see a design that can honestly claim 100% energy transfer at any / all points of contact. Since there IS residual energy left behind and / or possibly stored due to lack of transference and / or passed back into the component, why would "coupling" be any better than any other "half-fast" approach ? Given the sentiments and attitudes that you expressed above, it would appear that we should chuck such a system out the window. Right ?
The key here is to transfer as much self produced or air-borne energy away from the device as possible, minimize energy transfer from the support structure back into the component and dissipate any residual energy that could not be transferred in an efficient manner. In order to do that, you'll have to incorporate some type of "damping" or self-absorbing" device somewhere in there. If the "damping device" is properly designed, it will "eat up" the residual energy by being as "lossy" as possible. Since energy can be consumed via thermal losses, mechanical vibrations that are converted to thermal losses are not subject to the "rebound effect" that most "damping devices" produce.
The trick here is how to impliment all of this technology with one simple to use structure. Since the meeting point between the support structure and the component is typically some type of shelf or platform, that is where the majority of "work" must be done. The shelf must be rigid enough to transfer energy away from the component and support it, but at the same time, it needs to be able to "eat up" any residual energy that is not transfered and "damp" vibrations that try to come up through the support structure itself. Obviously, the material used for the shelf and how the shelf mates to the support structure and component are where most of us are "tweaking". I hope that this explanation somewhat explains why that is to those that aren't familiar with the "science" ( or is it "art" ??? ) of "tweaking".
Other than that, one can minimize the "rebound effect" of a damping device if the damping device is quite large in size and / or phenomenally "lossy". The effect of dropping a rock into a fish tank can be seen as ripples and the associated repurcussions that travel throughout the entire tank and then back towards the point of origin. Taking that a step further, one can increase the "vibration making device" to the size of a boulder and drop it into the ocean. In effect, the same thing takes place, but since there is so much more area to absorb the shock or "energy" of the boulder drop, it is barely noticed except for the surrounding area. Since the energy has been consumed ( efficiently damped ) before it can rebound, the side effects of "damping" have been minimized due to the lack of rebounding repurcussions. The drawback to this type of approach ? BIG size and a lot of weight.
As such Tom, you never thought "BIG enough" when thinking about damping and isolation. You answered your own question when you said "can the rack you are speaking of, isolate equipment from airborne as well as self induced electro-mechanical noise and vibration? If the answer is yes then how does this rack dissipate said captured energy? If it is sitting on a absorbent surface can this resting surface capture and disapate said vibrations as quick as it is refilled? If this rack captures quickly and cannot disapate as fast then you have a new storage medium!!!". By making the devices BIG, there is enough surface area to dissipate pretty much whatever you throw at it, so there is no storage or "rebound" effect. The energy is "consumed" via calculated thermal losses in the damping / isolation base. According to Joe's literature, he had help from several different engineers on this project.
For those that are interested, these "damping & isolation" shelves / platforms are 50+ lbs apiece ( from what i can tell by picking one up ). On top of that, each shelf / platform is specifically "fine tuned" for the actual device that you will be placing on it. While i can't even begin to fathom a guess at what a multi-component rack would weigh ( or cost ), according to Joe's test results published in his literature, a 3 Hz system shows a reduction of vibrational resonance in the component by 97% when "bombarded" with a 25 Hz signal !!! He provides a chart as a "rough estimate" of what to expect out of the various isolation devices that he offers when confronted with various frequencies.
Needless to say, i was impressed with the system that i saw but i still think that there might be a few tricks that can take it a step further. Sean
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PS... I have NO affiliation with these devices or the individual(s) making them. I met Joe and talked to him for the first time at the CAS meeting that he displayed these at. I'm working on contacting him. Hopefully, i'll be able to catch him on Friday and see if he can post information here.
