Originally Posted by magnakansas
imagine a box around your gen set. that box has thousands of 1/8 holes in it.
Now place fiberglass insulation around the box..no paper just fiberglass. Now put a second box around the outside of this. the holes allow sound pressure into the fiber area that calms the noise down.
use rock wool, instead of fiberglass -- does not absorb water or any fluids really and is non flamable. If that gen set goes off for some reason this will help contain fire. watch air pathways The fan air flow may be used to air cool other parts of the system. Try to see how this was originally installed so as to evaluate air flow.
use as system that isolates gen set from bus by rubber mounts. These are usually best under compression... other words weight of the gen set sits on mounts, not hang from them. The looser you can float the parts the less vibration will transmit.
most engines, the air intake makes more noise than the exhaust. Same for piston type air compressors.
hope this helps
I was going to place rockwool aka mineral wool in between the "floor supports" underneath, then add a sheet of aluminum across the supports/wool, then heat mat over that.
Do you think I'd be better to drill holes into the aluminum to allow the sound to enter/disappate into the insulation? Would you still apply heat mat then with the holes drilled into it?
Genny will have 2 12" fans pulling air from in the compartment through the radiator, and vented to the exterior. The bottom will be open/grated so that is where the supply air will come from. The original APU had a similar setup, but it vented the hot air towards the driveshaft. That works in a semi because the space around the driveshaft is open at the top. In a bus however, I felt that this method would trap heat and any fumes underneath the floor between the skirting.
For vibrations, I've scavenged the mounts off the old apu, I also have shock absorber mounts that I've scavenged as well that I plan on using. Vibrations shouldn't be an issue.
I'll second the intake making more noise. During test running, I didn't install the air filter or muffler. After installing the intake it's noticeably quieter, I'll install the muffler when the whole works is mounted.