Bussin 2009, Generator Sound Reduction and Cooling Seminar

[edroelle]

This will show on both boards.

I am putting together a seminar for Jack's Bussin 2009 rally, on generators.  It will focus on some of the discussions/questions on the BBs.  Particularly, I will address noise reduction and efficient cooling.

Now to my point.  If anyone coming to the Bussin rally, is interested in offering their generator installation as an example of very quiet installation, let me know.   This is NOT a contest.   What I would like to do is give all of us an opportunity to learn additional techniques to minimize noise.

Ed Roelle

[bobofthenorth]

If you need an example of the noisiest SOB east of the Pacific Ocean then I'm your guy but quiet - can't help you there.

Don't worry - I'll be in your audience.  If the SuperUke ever gives me back my Kubota then task #1 is to build a hush box for it.

[Blacksheep]

Hi Ed and hope your enjoying this Florida weather which is a little rare for us but goon none the less. You can use my bus for anything you want. My Wrico is seemingly quiet but could be quieter. (can't they all) When I installed it, I had no idea I could make it quieter by means of a box but I DID have to get it in in a hurry because of 3 hurricanes back to back to back! LOL
You know I'll be there so if you need the bus, it's yours!

Ace

[grantgoold]

I would like to ask whomever steps up to provide the presentations that they somehow capture the various strategies and provide those of us that will not be in Florida a chance to see the different efforts. I am ready to get my box built and would like to see what you all come up with. 

Thanks

Grant

[uncle ned]

You are welcome to use "huggy" It has a box and is sorta quiet but could stand to be quieter.

uncle ned

[white-eagle]

Ed, since we are a vendor and we'll be at our usual spot, you are welcome to use ours.  I don't think it is exceptionally noisy or quiet.  We have a 12k, holes in the the door and floor for vents, padding all around the compartment.

then we can all finish my brake install and illustrate smi's methods.  (just joking.)

[Dreamscape]

I would like to ask whomever steps up to provide the presentations that they somehow capture the various strategies and provide those of us that will not be in Florida a chance to see the different efforts. I am ready to get my box built and would like to see what you all come up with. 

Thanks

Grant

I agree with Grant, Please share information and pictures for those of us who cannot make it. Sounds like lots of fun to be had, ENJOY!

Paul

[blue_goose]

Ed
I will be there for sure, because I own the generator from He--.   Been working on it for over 20 years and it still wants to run hot and make lots of problems.

Jack

[edroelle]

Thanks everyone.

I will look you up down there. 

I will try to transmit the information for those who are unable to come to the rally. 

Jack, we will take a look at yours and see what ideas everyone can come-up with so that it runs cool.

Ed

[JohnEd]

Not trying to upstage anyone...truly.  I made this post in another thread without seeing this one.  My post is, IMHO, pertinent to this one even more than its first position.  There have to be a ton of info beyond what I have offered and I would attend that seminar if I were there.

I would ask that someone at the seminar measure the noise level 10 feet from the bus with a DBM meter so there is a real baseline for comparison between the various approaches to the problem.


I see only some that go the full yard with the soundproofing.

As I understand it and auto makers build it the air intake is silenced with a VERY carefully crafted filter resonator cavity.  Mine even has chambers built on the side of the pipe feeding the engine that have no obvious utility but are intricate in design.  I suggest you get a inlet filter and box from a small displacement Honda or Toy and modify it for your genset motor.  That would also give you a cheap and effective air filter alternative.

The muffler is also an acoustical engineering item.  They are designed around the "frequency" of the exhaust that they want to silence.  Cars are a compromise but the more spendy the car the more silent the muffler so a 4 cylinder Accord would have a more silent muf than a Civic "maybe".  You can listen to them at the dealer's location.  Remember that you are only interested in the mufs perf at the rpm at which the gen operates.  I think you have a ton of choices from the Jap stuff and their mufs last the longest for some reason that you want to take advantage of.  They also all use a resonator and you could also put one downstream of the muffler.

Sound energy will travel thru the enclosure wall....no matter what you do but you can attenuate it greatly.  Rubber is good cause it doesn't like to move quick and it absorbs some of the energy in that manner.  Additionally, it is dense and difficult to get moving and that is a significant factor in its sound deadening performance.  The thicker the better but size and weight are a factor.

Lead is great stuff because it is heavier by dimension(density) than anything you can use.  I wouldn't pass up using lead as part of my design.  It is safe to live with lead as long as it isn't being converted to something that the body can absorb. 

Hard and light plywood is inferior as a sound block to soft plywood.  Think about the comparison between a drum skin and a piece of cardboard.  Scratch the drum head/skin with your finger nail and it almost seems to amplify the sound.  There is a particle board that is far denser than the usual stuff.  Pattern makers and others use it and it is commonly available and not expensive.  Any home depot type shop can point it out to you.  Even common particle board would be superior to plywood of any kind for soundproofing.  Look at your spendy speaker enclosures and just try to lift one.....200 pounds is not rare for woofers.

You can "spend" the sound energy by passing it thru a light material many times.  Acoustic tile operates on that principle.  Sound readily enter it as a medium and bounces of the underlying wall and travels back thru the tile.  The tile material absorbs the sound but not so much for the sound going thru the wall.  Still its attenuation is worth going after in the final design.  In "quiet rooms" they use a acoustic material that is built up into little cones.  I don't know where you could get that but that material would be optimum for application to the interior surface. Common acoustic tile would work pretty well to reduce the energy of the sound that reaches the wall.

You can dramaticall reduce the sound trans-missability of any wall by just gluing a weight to the center of the wall.  Your propane furnace can be significantly silenced by gluing heavy washers to the center of all the flat sheet metal.  Like wise the cabnet in which it is mounted can be improved by gluing 1 X 2s to the center of big walls. 

The coolant fan contributes greatly to the gen noise output.  You can eliminate almost all of that noise by plumbing you gen coolant into your engine radiator.  Many do this without a hitch.  With the engine off the rad has a thermo controlled electric fan to handle the gen and with the rad capacity even that would have a duty cycle.

Even without the gen rad load you still have to have cooling air flow for the generator windings and misc motor heat.  That flow must be thru carefully designed and sized baffles.  Point the air flow at the ground insted of out the side of the bus.

Lexus seems to be the only car I have ever encountered that can be driven away from me and I can hear absolutely no exhaust sound whatsoever.  You can't get there so yours will have "some" noise.  Even the quietest of exhaust will still be poison and objectionable to anyone immediately down wind.  To relieve that the Genny exhaust is run thru a pipe that is hung on the exterior wall of the bus to get the fumes 13 feet up in the air.  That works to eliminate a component of the noise.  PVC pipe will deaden more noise than rain spout metal tubing.  Plumb the exhaust into a larger diameter PVC/ABS pipe and the air flow caused by parasitic convection will keep the pipe cool enuf.

No box will isolate the low frequency hammering that is in the motor block if the gen is hard mounted to the wall/floor.  The gen must be mounted on rubber pillow isolators that are sized for the weight that will rest on each isolator.

I don't think roofing felt would contribute much to the sound absorbing performance of a wall.


Sooooo.....  From the outside:  1/4" particle board, 1/8" rubber sheet, 1/8 lead sheet, 1/8 rubber sheet and 1/4 " particle board layer of acoustic tile.  You can increase the various thicknesses to your application.  Air cooled gen sets will need more isolation and Chinese gens will require an 8 inch thick wall.
YMMV

My thoughts and I hope for some constructive crit.HTH

John