Honda 2000 quiet box, I'm back!!

[jjrbus]

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28956619/srt/pa/pging/1/page/1.cfm

Getting rid of the Toyota and bought a Roadtrek. First thing I did was take out the Onan and sell it. Starting a new box from scratch, reading the net and trying to gather as much info as I can before I take out the tools. I'm very fond of my collection of presidents pictures so the first consideration is to keep as many of them as I can.

The composite foams are nice, I have used them before. So wondering about the newer mass loaded vinyl's. The composite foams are usually 1 inch think and the mass loaded vinyl are 1/8 to 1/4" thick.

[ProjectMon]

Looks like very nice work!!!

[jjrbus]

Moving along at a snails pace on this. My cobbled together exhaust baffle for testing seems to be a sucess, will be trying to make it smaller. Picked up some 1 inch ductboard possibly to use as the exhaust baffle.

Finding a aluminum box was a challenge, I had an idea and my good budd the super craftsman Rick showed up and we chopped the bottom off the box, he did it with a circular saw freehand! Better job than I could have done on a table saw. We cut the bottom into strips and using that to raise the height of the box 3 inch to 20".

Taking everything into consideration I ordered the 1" Soundown. $74 sheet but a whopping $55 shipping!!

[jjrbus]

Thanks, I am not overly concerned but would not be surprised. I will not leave it unattended.

[ProjectMon]

If you are truly concerned that you might catch the cardboard on fire, you can make homemade fire-retardant and spray your flammable materials, let them dry and then move forward.

Here is a quick link to some mixes you might consider:
Flame Retardant Mixes

[jjrbus]

Thanks for the response. My picture did not post. The prototype is made from cardboard, masking tape and the cheap white open cell foam. Osha would have a fit.

[ProjectMon]

The 1st box I built did not catch on fire but did fall off the back of the trailer while driving down the road... Grin. Luckily it was wired on, so it was destroyed but did not fall into traffic.

[jjrbus]

I am experimenting with the baffle for the exhaust. Using what I have laying around for a prototype. I am skeptical this will work, as I only have 18 sq in of exhaust, but have seen it done with less, looking at one online with no dimensions with about a 6 sq in exhaust. I am waiting for a thermometer I ordered which I should be able to use to monitor oil temperature before testing. I suspect I should have a fire extinguisher handy also.

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[jjrbus]

Thanks for the response. Soundown in on my list of options. What I am spending too much time on is trying to figure how the official Honda sound box and others use such small intake and exhaust?

A combination of something to dampen the metal, mass loaded vinyl and duct board is effective but construction gets complicated. Plus duct board can be used to fabricate intake and exhaust baffles. Do not have an unlimited budget for this!!

A "quiet" generator in an urban area is ok, in a wooded rural campsite is very loud!

[ProjectMon]

Call these guys. https://soundown.com/

They can specify a product they sell that will be thinner and provide similar sound absorption to the rockwool based on material testing (nice folks to talk to). They are also located in FL so in most cases, you will get one-day shipping for free.

Foam board is mostly worthless for sound absorption as it has insufficient mass. Drywall needs to be isolated from itself and other materials to get its full benefits using something like viscoelastic glue. Drywall also has a tendency to fail when it gets wet so unless you can keep it 100% dry it is a non-starter.

Sheets of metal have a tendency to resonate with the vibrations of a generator so make sure to use some product to dampen the resonation (you can put your foam/wool against it). On the plus side, metal has great mass versus its thickness and mass is what absorbs sound.

If you want to copy a working model so you know what you end up with will provide real benefit use the generator enclosures built for boats as your model. Specifically copy the ones built for Kohler 5e marine generators (sound shield). The Kohler units are gas motors running at 3600 rpm and are noisy as all get out. With the sound shield, you can actually seep in your boat. Their basic design is a metal box lined with sound-deadening foam (not the garbage you can get from homedepot or lowes).

You will still have the vibration transmission issue, but as you pointed out you are starting with a quiet model and it sounds like just trying to get a few more DB off the top.

[jjrbus]

Down to choosing materials. Rockwool 80 board seems to be a popular choice, I cannot find any near me for sale. So adds shipping, getting the cost up towards the $100 area for 1 package. Then need to add some type of sound deadener such as Blue skin and mass such as drywall. I have used duct board and blue skin before and is a contender, light, reasonably inexpensive, does not have the Db reduction of other options. But I am starting with a quiet generator.


I can buy composit foam for $80 sheet, would need 2 and will be hard getting enough coverage from a 32X54 inch sheet.

In the interest of economy I will be trying to use an aluminum box that is not tall enough and somehow modifying it to make it taller.

[jjrbus]

Thanks for the input greatly appreciated. The intake end of the generator is fairly simple and not the greatest source of noise. It is building a exhaust baffle in a limited amount of space and without spending a fortune. For the body of the generator I have done Composite foam with MLV and a lead floor and works very well. I have also done a sound deadener like Blue Skin for the metal box and 1" fiberglass duct board. It works well, not silent but good enough. Similar to what RaD did.

63 to 48 is very impressive even more so if the gen does not burn up!


I need weather proof, secure, as light as possible and not break the bank. jaguston's did a great job with his but I cannot find the link.

One person suspended the genset on rubber straps to stop vibration. Not practical for my application. The Japanese like to make springs for the feet of the genset.

RaD did a good low cost job. https://www.youtube.com/watch?v=kuRd-ZPeaoQ

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/21111126/srt/pa/pging/1/page/1.cfm

[ProjectMon]

Two more studies:
Wood box with a partial baffle and used ~1in think fiber glass insulation ~7db reduction
https://www.ajol.info/index.php/jasem/article/download/135141/124634

FRP panels with `2in Rockwool and no baffle ~18db
https://www.academia.edu/download/67787833/31568.pdf

What no one seems to have done yet is study a panel box built like this:
FRP | Mass loaded vinyl | Rockwool | Metal screen (think bird screen)

And then you would also need a baffle with at least two chambers.
I built a wooden box with a two-chamber baffle for the air intake and one for the output but used a significantly lesser sound absorption product than the Rockwool and got a 5db reduction in noise.

My next project will be built using the panel design above and the baffles. Of course, I need time to do it. 🙂

[ProjectMon]

Great link. I followed the video to their page where they sell the Eco Route Silent Box. For the Yamaha ef2800ise the products costs $1,721.71. Looks like a metal shell with some sound deadening built in. The magic being the sound baffle box they designed for the exhaust end of the generator. If they used mlv on the shell, they could likely knock a few extra DB out of the overall box.

This guy described how a sound baffle works for exhaust nose the best I have seen and shows how he built his box. He also sells some very nice plans for wood generator enclosures and claims up to 5X sound reduction. https://www.youtube.com/watch?v=_qPRIq-9U-4

There is a 2003 study from India titled “Studies On Control Of Noise From Portable Power Generator” by Parvathi and Gopalakrishnan that looks at some unique ways to start deadening sound (should be some better studies since then but I have not yet followed up). I used their bed of sand trick on a whole house generator I had, and it worked as advertised. But the video I posted above appears to be the best homemade project yet.

I did drop the DB in my boat from 63db to 48db by decoupling the generator from the flooring using spring mounts I designed and had built. Since you appear to be wanting to use an inverter generator if you are going to mount it to your RV I would suggest floating the whole box in springs like the ones used in the HVAC industry to quiet hvac equipment. For my project, I used the springs out of a Mason CA-310
Mason CA-310 Spring kit
But you could likely just use valve springs.

Good luck and I would really like to see what you do and learn from your successes and failures.

Moderator edit to fix URL.

[jjrbus]

https://www.youtube.com/watch?v=A8CmaC0jT20