Soundproofing on a trailer

[ToddT]

I know soundproofing diesel generators has been bounced around a bit before and I've already learned quite a bit from this forum. I have three "Changfa style" single cylinder water-cooled generators that I want to use in different settings. One will be for emergency power, mounted on a small trailer. Another may end up in a cube van for work. And the other... probably at my shop where I run my small business off the grid.

I understand most of the sound from a diesel is mechanical rather than just the exhaust. Mounted on a trailer, shouldn't that help a lot of the lower level thump sounds? Beyond that, I'm thinking of a plywood box, caulked seams plus some sort of sound deadening material. I can't afford the high end stuff so I'm looking for cheaper alternatives such as "brown board" used for house sheathing. What about leaving a space between the brown board and the exterior wall?

Products like Lizardskin are good for stopping metal to metal sound. I understand that wouldn't do much good. But what about heavy mass material like Dynamat. Again, it isn't attached to a metal floor or body... would it do that much good?

Creative ideas?

My plan is to do sound level readings before, during and after the project, seeing how each treatment cuts a bit more of the sound. Of course, I'll report back as I go.

[mobile_bob]

there is also significant noise from the intake,  so you might also consider some sort of resonator or muffler? to attenuate that noise.

the diesel knock is also significant, and i have considered using some heavy gauge aluminum foil, such as those turkey roaster throw away pans, set off the block a half inch or so and foamed in with some of the blow foam you get at the hardware store.

the major engine manufactures use similar methods to good effect.

also before i forget the gear train noise is also a heavy contributor, so the foamed on shielding might well abate a good part of that noise.

i know these engine's are quite noisy however i am not sure which aspect is the largest contributor. i am not aware of anyone doing any analysis on the noise so as to find out which facet of noise production is the largest contributor.

fwiw
bob g

[BruceM]

+1 for Bob's suggesting re: foam in a can and/or spray foam.  I've been impressed with it as a sound deadener for sheet metal. 

[ToddT]

Are y'all talking about the "Great Stuff" type expanding foam? I hadn't thought of that... figuring that it would compromise the cooling. But, as a water cooled engine, I guess not. What about the heavy stuff they put as sound-proofing for cars? Dynamat and Hushmat are two big names in that field. It can be molded to the surface and sticks to metal.

[quinnf]

If you really want to do it right, consider lining your engine enclosure with this stuff:
http://www.jamestowndistributors.com/userportal/product.do?part=109526&engine=adwords!6456&keyword=product_ad&gclid=CODZoOvtmMECFQWUfgodRIoAKQ

I replaced a gas engine with a 3-cylinder Kubota-based marine diesel on our 34' sailboat years ago and lined the engine compartment with this stuff.  It's expensive, but it's amazing how it absorbs engine sound.  There's a layer of foam, then a layer of heavy soft dense plastic, then another layer of a heavier foam, faced with aluminized mylar sheet.  Once installed with contact cement and fasteners, tape the seams with aluminized mylar tape and be sure to seal up all holes, because a surprising amount of noise can escape through the smallest crevice.

Quinn

[DanG]

The dense single-ply EPDM roofing material attenuates sound well, a lot of hobbyist 'adventure van' conversions are sneaking in layers of it for both in-motion and while-camped sound damping. The downside is given enough heat and fresh airflow it will burn until consumed, getting true fire-rated products is expensive....