I am going to need to build a generator compartment for my new WRICO 12.5 KW generator. Where can I find some guidelines for building a generator compartment to make it quiet?
I want this to be at least as quiet as my Powertech enclosed generator is now. I have found some Youtube videos of bus conversion diesel generators running and they are loud compared to my Powertech.
Here's where I got the material I used to replace the soundproofing on my coach.
https://www.soundproofcow.com/
They have a few how-to videos and blog entries about this. Poke around their site and see what you can glean from it.
My experience says that there are three aspects to reducing the sound from a generator.
1) Engine noise.
2) Engine vibration.
3) Air flow noise from radiator/cooling system.
You have to address all three to make this work.
The air intake makes the most noise,lead lined sheet rock makes the best sound proofing but you need to cover it to prevent damage,Sun Down is ok but all foam will deteriorate over time.I used the egg crate lead foam on my bus and after so long I was always removing pieces from my air cleaner on the generator
It has to be isolated from the bus, and sometimes the existing isolator pads are not compliant enough. McMasterCarr sells a wide variety of isolators.
Jim
Quote from: Jim Blackwood on October 13, 2020, 08:15:56 AM
It has to be isolated from the bus, and sometimes the existing isolator pads are not compliant enough. McMasterCarr sells a wide variety of isolators.
Jim
He can buy the gel or air bags from Dick they work really well
The Marathon Prevost has air bags on the 17 kw Martin diesel. On a slide out.
Quote from: luvrbus on October 13, 2020, 08:13:09 AM
The air intake makes the most noise,lead lined sheet rock makes the best sound proofing but you need to cover it to prevent damage,Sun Down is ok but all foam will deteriorate over time.I used the egg crate lead foam on my bus and after so long I was always removing pieces from my air cleaner on the generator
Isn't drywall really heavy for a bus? How you stop it from cracking?
People use sheet rock all the time on the interior and it doesn't crack,all depends on how you attach it.The people I know that has used the lead lined sheet rock covered it with FRP and hose the compartment out without problems one for 20+ years and yes it is heavy but so is Granite counter tops
I am looking for where to find design principles like how to design air intakes to reduce sound transmission.
A no-restrictions design would have a well muffled and insulated exhaust which exits above the roof, possibly contained in an air stack with an open bottom and top. Triple-wall stainless stove pipe comes to mind, with the exhaust running up the center.
There have been advances in fans in recent years to reduce sound levels, that would also be a good place to look.
Jim
Custom Coach used lead sheeting on the floor of the bus, with a layer of cork over the top of it. Both were done to provide a sound barrier to the generator below it.
They lined the generator compartment itself with a multi-layered material - heavy vinyl layer between two layers of foam, with a metallic layer facing the generator. All of this is held in place with expanded steel mesh (which protects the foam and also keeps the sound from penetrating.)
The air flow comes in from the driver's side, across the bay in a sound-protected channel, and then through the radiator which is mid-ships. The air is then sucked across the genset and out through the floor of the generator bay with a large squirrel fan moving the air. You can see the intake in the photo, with the radiator at the back of the intake tunnel.
I did install new vibration isolation mounts when I got the bus as the old ones were collapsing. They come in both two-directional and three-directional dampening. I got the three-directional ones. Just upgrading the mounts made a big difference.
Quote from: Jim Blackwood on October 13, 2020, 11:17:09 AM
A no-restrictions design would have a well muffled and insulated exhaust which exits above the roof, possibly contained in an air stack with an open bottom and top. Triple-wall stainless stove pipe comes to mind, with the exhaust running up the center.
Unfortunately, I probably won't be able to run the exhaust to the roof in an already built interior. What sound benefit is provided by doing this? Is there a possibility of too much back pressure?
Here is what I am dealing with for a generator compartment. My bay is 57" wide, 32" deep, and 36" high. Door opening is 49" wide. The rest of the luggage bay behind the generator is full of fresh water and waste tanks.
I have heard that if air makes a turn it will be quieter, but I am trying to find something that actually states that. I tried searching here, but I gave up after a while as I wasn't finding anything useful.
The answer is that it depends on the configuration. You have to get into sonic wave transmission formulas to really nail it down and it is very dependent on frequency. But because a generator runs at a more or less fixed speed that effort can pay off. Essentially what you would be trying to do is create a sound trap where the wave bounces off a wall and cancels out the next incoming wave, then you would put your intake or exit at the cancellation point which is somewhere back up the duct or tube. Sort of like waveguide theory. That's about the limit of my ability to help with this, but yes, it is possible to get some benefit. How much I couldn't say, and I don't know how large this structure would have to be. Again, pretty much dependent on frequency, but also on air flow requirements.
Jim
Brian don't worry about running the stack up thru the finished interior of your coach just build one of the removable stacks that slides on it when parked the guys you haul out to the desert build rockets so a simple exhaust stack ought to be a piece of cake for them to do in a short time while sitting around bs'ing about the days activities!
;D BK ;D
Well turning the sound up (vertical) is one way to deal with it. I've seen some of those vertical stacks that also draw up additional air, Venturi effect?
I watched this when I was insulating my bedroom https://www.youtube.com/watch?v=pABvTWSxOes . Turns out heavy dense material works the best. I know some of the professional panels in hushboxes are just shredded and compressed denim.
Cover that with a fire retardant layer and you're set.
this is the stack for my diesel boiler . no more stinky smell and it made the noise a lot less
https://photos.app.goo.gl/X8XHXNtCGjQT5jq97
dave
I don't think that the exhaust is a major contributor to noise if it runs through a muffler. My focus would be on engine noise & vibration, air flow noise next.
Those diesel boilers can have noisier exhaust than a well-tuned generator with their blast furnace sound.
you are right about the noise but the heat is fast and unlimited unless I run out of diesel
dave
Yes, Brian, you remember correctly.
Making the air intakes and exhaust turn corners is a big part of silencing the noise.
There are also "hospital grade" mufflers available to quiet the engine exhaust.
On the first, creating a cavity with plywood up the centre, to force it to go in, 'round the corner, and back to the originating side, and then into the generator space knocks down a lot of noise. If there's room, lining some of that with sound absorbing material prevents sound bouncing.
On the mufflers, they aren't cheap, i haven't looked at them in many years now...
Some rubber isolators under the unit, or small air bags, help reduce sound and vibration transmission to the chassis.
Happy coaching!
Buswarrior
Longer runs on exhaust piping works better than mufflers you need to be careful sizing to small it creates back pressure to large you get a echo affect.Now some parks require a spark arrester on generators.We were in a park in Utah this past trip they prohibited the use of diesel fired boilers I had use the electric heating elements on my AquaHot on their dime though
Lead lined plywood is also available. It works good for deadening sound and reducing radiation. In a previous life I used it to shield the public from ionizing radiation. Lead bricks work good too, but they get too heavy quickly!
QuoteWe were in a park in Utah this past trip they prohibited the use of diesel fired boilers I had use the electric heating elements on my AquaHot on their dime though
Geez, that's a new one - no diesel powered hydronics allowed? Hummm.. need to sort out how to stay warm in the winter in one of these places, maybe, just stay elsewhere.
The only electric in my water circulation system is the hot water heater and I think it is plumbed into the hydro heating system, primarily to heat the hot water and engine block. It is a lot less powerful than the Webasto but in an emergency it could work on a couple radiators if I redirect the flow to them. A couple electric space heaters would work too.
Since you have a Wrico, call Dick, I took his seminar on hush box's at Bus'N' USA & purchase all material from them.
Quote from: silversport on October 13, 2020, 10:53:06 PM
Since you have a Wrico, call Dick, I took his seminar on hush box's at Bus'N' USA & purchase all material from them.
I don't have a WRICO yet, but I am mailing the check today. I talked to Dick on Friday and emailed him dimensions and pictures of my generator bay. Dick has yet to call me or email me. I talked to Justin and he tried to get Dick to call me, but nothing. I don't really expect to ever hear back from Dick.
Justin made a up a CAD drawing for me of his suggested way to mount the radiator and generator. I noticed it doesn't have any turns in the air intakes. I have attached his drawing.
Interesting that he has the air being drawn in through the floor and out through the side. Opposite of mine. Wouldn't there be concern about drawing all kinds of dust, grass, and other assorted crapola through the radiator sucking the intake air from the floor like that?
Dick doesn't stay around the office Brian he stays at home taking care of Genie,he will call you
The amount of suction depends on the surface area of the opening. Made big enough it wouldn't be able to pick up a leaf. Also since hot air rises it is more efficient that way.
Jim
Quote from: Jim Blackwood on October 14, 2020, 07:07:53 AM
The amount of suction depends on the surface area of the opening. Made big enough it wouldn't be able to pick up a leaf. Also since hot air rises it is more efficient that way.
Jim
With the amount of air the fan moves, whether hot air rises or falls is really irrelevant and won't make much of a difference.
Don't know about the premise that it won't pick up a leaf - my intake is on the side of the bus, and it's quite large. Probably twice the size of the output. Even on the side of the bus, if there is loose grass or leaves in the air it will pull them against the intake. Same for dust. Can't quote you a stitch of scientific formula or theory on this, but I can tell you what I see happening when we're parked in a grassy or wooded area and the generator runs. It only makes sense that it will be worse if the intake is closer to the debris.
Perhaps there is a good reason for putting the intake on the bottom, and that's partly why I asked. Just seems to go against what I've observed.
I dunno. May not be practical to make the intake large enough to keep from pulling stuff in. It's something I'd like the answer to also.
Jim
All the generators with the factory quite box the suction is on the bottom ,the generator has fan between the engine and the head that needs fresh air also sucking from the bottom helps with noise level.I relocated my air cleaner with another 90 bend and dropped my DB from 58 to 51 dba
Quote from: windtrader on October 13, 2020, 08:46:45 PM
Geez, that's a new one - no diesel powered hydronics allowed? Hummm.. need to sort out how to stay warm in the winter in one of these places, maybe, just stay elsewhere.
The only electric in my water circulation system is the hot water heater and I think it is plumbed into the hydro heating system, primarily to heat the hot water and engine block. It is a lot less powerful than the Webasto but in an emergency it could work on a couple radiators if I redirect the flow to them. A couple electric space heaters would work too.
The EGT (exhaust Temp) on those are around 600F they will start a fire .I saw a guy at Bus'n USA park his car in front of his and it melted the plastic bumper ,they limit the length on the exhaust to get rid of the heat my manual says 47 inches max
Quote from: luvrbus on October 14, 2020, 07:56:20 AM
All the generators with the factory quite box the suction is on the bottom ,the generator has fan between the engine and the head that needs fresh air also sucking from the bottom helps with noise level.I relocated my air cleaner with another 90 bend and dropped my DB from 58 to 51 dba
Interesting. My current Powertech blows out the bottom and air for the radiator come from the side. Justin from WRICO said he suspects my Powertech generator if run at full load in high temps would overheat just due to not enough airflow. I have run it in 107 degrees at 4,000 feet without overheating and I had a fair bit running on it.
Quote from: luvrbus on October 14, 2020, 07:56:20 AM
All the generators with the factory quite box the suction is on the bottom ,the generator has fan between the engine and the head that needs fresh air also sucking from the bottom helps with noise level.I relocated my air cleaner with another 90 bend and dropped my DB from 58 to 51 dba
Are you talking about the Onan QD generators?
I don't doubt what you're saying about them all drawing from the bottom, but that still leaves the question of why? I'd first have to know if it's for convenience of manufacture or if it's truly the best location to place the intake for cooling performance.
What I mean is, many of the units that come with factory quiet boxes are built to be somewhat universal and suitable for installation in a variety of coaches. Nearly every coach will have access for intake air from the bottom, either through the floor of the bay or by being installed in a bay without a floor.
If they had the intake on the side of a factory-built unit, it would require custom intake ducting built for each unique type of install. For us doing conversions that would be okay, but not for a manufacturer hoping to install the same genset in a variety of models.
Also, many of the coaches being built with factory quiet boxes have fiberglass/plastic on the sides. Not sure but would suspect that it makes for a cleaner look for high-end coaches to leave the intake venting on the bottom rather than cutting into the siding.
I talked to Justin at WRICO again and he said the air doesn't have to come from below for the radiator for sure, and probably not for the generator compartment either.
As far as enclosed diesel generators for motorhomes, is anybody using anything besides Powertech or Cummins Onan? It seemed like for a time a lot of motorhomes had the Powertech enclosed generators. Overall, Cummins Onan is much bigger in the market.
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I had a 20kw ESP generator in a quite box it was vented from the bottom never caused a problem,the Onan the generator radiator is layed flat in the bottom of the enclose case it does blow a lot of dust on gravel roads I don't care for that but it never overheats or shuts down even at 127F heat this summer
Quote from: luvrbus on October 14, 2020, 10:07:13 AM
I had a 20kw ESP generator in a quite box it was vented from the bottom never caused a problem,the Onan the generator radiator is layed flat in the bottom of the enclose case it does blow a lot of dust on gravel roads I don't care for that but it never overheats or shuts down even at 127F heat this summer
Clifford I learned a trick for that from a friend that ran a fleet of MCI's he took a mud flap and used angle iron and a piece of flat stock to pinch it on both ends then hung the ends on 3 small chains per end under the blowers about 5-6" below the bus, his buses were always nice an shiney and his drivers never had to turn off the A/C on gravel roads an parking lots like a bunch of us had too!
(until I learned this trick too!) ;D BK ;D
Lots of MCI with the flap under the AC discharge.
Might be a factory option?
A good consideration for the bottom discharge generator crowd too.
Happy coaching!
Buswarrior
That sounds like a good idea might have to implement,
I have bottom discharge
The bottom flap must be a factory option on MCI coaches as I have seen a lot of them over the years. I had no idea what it is for before this thread.
I'd love to see a picture of that.
Jim
I don't think it was a factory option as much as once seen many owners/shops copied it.
I never saw one from the factory, but it's easy to do. I don't have any pics, but I copied the ones Bill had done and it worked out nicely. I had other drivers getting down on their hands and knees taking pics of mine to show their mechanics so they didn't have to turn their A/C off in dusty parking lots!
;D BK ;D
The first picture is whats on a 88 102 A 3 the second picture is a 96 102 D3
Can't quite visualize it. What keeps the flap from dragging the ground?
On the noise cancellation, If you can lay your hands on an audio spectrum analyzer (Hi-Fi hobbyists often have them, or they can be found pretty cheap online) you can isolate the loudest frequency or the most annoying one. Take the center frequency, divide into 1 and multiply by the rate of sound propagation (6xx mph I think) and you can get the wavelength. There are online calculators that can do this for you. Take one quarter that distance and that is what you need for your sound trap. This is a dead end stub coming off the corner of a 90 degree bend and in a straight line with the source of the noise. Car makers do this all the time in intake systems. If you have more than one frequency to cancel out you can step the reflecting wall to different lengths.
Think of a sine wave. One wavelength is a full cycle including top and bottom. From your bend it takes 1/4 wave to hit the reflecting wall and 1/4 wave to get back, putting the reflected wave exactly 180 degrees out of phase and cancelling the incoming wave. That's how passive noise cancellation works. It's also known as a 1/4 wave trap. The distances required should make it quite feasible to build and it can almost completely cancel out the tuned frequency.
Jim
The flap is attached at both ends, and droops in the middle.
Typically with a link or two of chain, air can get out all the way around, but not blast straight down.
Happy coaching!
Buswarrior
Any problems with this either restricting air flow or catching on things while driving?
Richard, I hadn't ever heard of or saw either!
;D BK ;D
I believe the flap underneath were factory installed.
The 3rd picture # 441 with the fan removed, what you see is the flap thru the hole.
It flops around just like a truck mud flap.
I made a deflector for my 12.5 power tech genny that is over sized in width and is like a wedge that sends the exhausted hot air towards the driver side of the coach . helped with the noise and got rid of the dust blowing around .
dave
Quite simply get with Wrico to get sound deadening and use what they provided me-3/4" plywood with sound deandening-expensive though. Good Luck, TomC
Quote from: TomC on October 15, 2020, 02:08:13 PM
Quite simply get with Wrico to get sound deadening and use what they provided me-3/4" plywood with sound deandening-expensive though.
Justin has been too busy to help me much with design of my generator compartment. He did make a drawing of one possibility that I posted here.
I talked to Dick on Friday and emailed him pictures and dimensions. He still hasn't called me back to give me advice about designing a generator compartment.
I finally decided to order just the generator and not order any sound deadening stuff with the generator. Justin said it doesn't make sense to ship the plywood without a generator as the freight is really expensive. There is a place that sells lead lined drywall and plywood locally so I will buy locally if I decide to go that route.
Sound deadening loud generators is old business. Do some research on the materials used in larger towed, portable generators. It is amazing how quiet some are when standing right next to them. They must have it all worked out to a science: intake, exhaust, vibrations, baffles, mufflers, etc.
BW, and Paso,
I don't know about factory installed ones an I suppose they could have been, but I have seen Thousands that had NO FLAPS compared to maybe a hundred that did. But maybe after something happens to the original one they just don't repair/replace most of them.
Or maybe it's northern thing were they have far more gravel roads, I don't know. I just know for a long time I'd never seen one period and one day I was at Bill's picking up some parts and noticed one and told him "Bill you better have your mechanic check that bus there's something hanging underneath it."
He looked and looked and finally asked where so we walked over toward it and I pointed it out. He laughed and said "No I got those on all my buses, it cuts down on dust and debris from blowing everywhere."
I was curious so I got down on my knees an checked it out, an was impressed. I told him I was going to copy that and he told me to go ask his mechanic for an old one to use as a pattern. So I did and what he gave me was an old NAPA mudflap that was worn thin and ragged with 3/4" angle iron bolted on both ends with 3 holes drilled in each for a chain to hang it from.
I am sure his weren't factory, but they might have been at one time.
I do know for a fact they do help a lot!
;D BK ;D
There's only so much space under my bus (maybe 6" at best). How low do these flaps need to hang to not cause a reduction in air flow from the fan?
For that concern Richard, you could use a broom style.