Edit: Actually, with my initial response below, I think I misinterpreted your intention when you mentioned using the "trailer air". I guess you are still looking to dampen the generator itself by placing the airbags "under the generator" to help isolate it from the trailer itself. Correct?
Correct.
So yes, when doing any sort of slow speed maneuvering, the corners of the deck on the trailer overlap with the truck (and some trickier terrain causes rubbing...), so the current center-line location is the only spot, as tested with a cardboard box, that doesn't risk crushing the generator.
So to give you guys some ideas of what I've tried and done:
Noise Dampening
The inside wall of the container is sprayed with closed-cell foam (well over 2") so that 2x4 studs, laid flat, and the voids in between, are completely filled and cut flat. The voids have more than 4" of foam. Then, blue insulating 1" foam has been installed on the flat of the studs, and plywood mounted atop that, fastened through to the studs using screws. The studs are "floating" and encapsulated in the spray foam.
I've fabricated a 1 1/2" exhaust flange to go over top the end of the muffled MEP 831A. The flange, all stainless, makes an immediate 90 degree turn and goes vertical with stainless flexible line. The single "soft mount" to hold the weight of my exhaust is bolted to doubled horse-stall mats, creating a 1 1/2" thick rubber "tab". These tabs (1 per side of the pipe) are then through-bolted to metal tabs welded on the container. There is an Indian motorcycle muffler (OEM) that tops it off. The exhaust is supported by the conex box but is not bolted directly to the trailer- it floats via the horse mat. There's not
too much noise audibly on this side. I need to get my meter back out, but if you stand a few feet back from the generator, it was in the neighborhood of 65 decibels and exponentially fell off as you backed away (which makes sense). Up close, the generator was louder through the box then the exhaust.
Vibration
The skids are tacked down to the deck of the trailer. The skids were utilized because the generator has a pair of mounting "skids" and one side would have hung off the front of the trailer and wouldn't have been supported. I originally mounted a pair of marine engine (rubber) heavy duty mounts to the skids and the generator box atop that. The meter reading inside the container was roughly 90 decibels. It changed depending on distance to the front wall with the trailer having a harmonic "hot spot" about 2/3 of the way back.
I then removed the mounts and put in a set of onan-cummins soft generator mounts. They reduced the noise to roughly 80 decibels inside. I attempted doubled-horse mat in addition to the soft generator mounts and had mixed readings between 75-80 decibels.
I don't mind a bit of "white noise" and expect it, but you can't/shouldn't sleep next to 75 or 80 decibels. One thought (just occurred to me) is to take the tractor, and using the skids, hold the generator just above the deck of the trailer (but not touching) and see what the noise does. That alone should decide what vibration is doing with the trailer. I have attempted removing the exhaust mount point from the trailer (so it was totally supported temporarily by the generator) and that didn't produce much difference (1-3 decibels).
