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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Darkspeed on November 11, 2015, 10:29:02 AM

Title: Quiet Generator Box Build
Post by: Darkspeed on November 11, 2015, 10:29:02 AM
Im going to be building a quiet generator box and I had a few people ask me to document it, so im starting this thread for that, but you are welcome to comment.

This will take some time as I can only work on it part time at the moment..

Is it overkill? depends on what you dont like hearing.. or how good your hearing is..

I will be testing each step of the build with a USB Decibel meter.

I banged up a stainless Dry exhaust to replace the wet marine exhaust manifold and fitted the test muffler > Walker 21479 Quiet-Flow Stainless Steel Muffler

Muffler will eventually be remote mounted.

Two cooling circuits - Generator will have a remote mounted radiator and the box will have its own remote mounted radiator because it will be a sealed enclosure.

Honda Civic fan & 3 row performance aftermarket aluminum radiator ($60) for cooling the box (environmental heat trapped in the sealed box)

Same type radiator will be used for cooling the block except it will have a shroud and a Spal 30103202 12" Curved Blade Puller Fan.

The enclosure will be a box in box design like a soundproof room.

The bay will be partitioned and dampened to create the outer box and there will be an air gap between it and the inner box.

To service the generator you will have to slide out the inner box on its sliders and remove the cover to the inner box.

Generator is isolated from inner box by air springs mounted at 30 deg cradle configuration.

Outer box is isolated from inner box by low durometer rubber captured mounts.

Refrence > http://www.mh-audio.nl/acalculators.asp (http://www.mh-audio.nl/acalculators.asp)

Coolant line quick disconnects > Snap-tite 72 Series #16AN 1" 4GPM

Exhaust / air intake disconnect > Torctite Stainless Lap Joint Band Exhaust Clamp TTOEM200SS

Green Glue > http://www.greengluecompany.com/ (http://www.greengluecompany.com/)

Rubber mat > http://www.tractorsupply.com/tsc/product/rubber-mat-black-4-ft-x-6-ft?cm_vc=-10005 (http://www.tractorsupply.com/tsc/product/rubber-mat-black-4-ft-x-6-ft?cm_vc=-10005)

Dynamat Xtreme > http://www.dynamat.com/automotive-and-transportation/automotive-restoration/dynamat-xtreme/ (http://www.dynamat.com/automotive-and-transportation/automotive-restoration/dynamat-xtreme/)

Lead Sheet > http://www.rotometals.com/lead-sheet-and-shielding-s/31.htm (http://www.rotometals.com/lead-sheet-and-shielding-s/31.htm)
Title: Re: Quiet Generator Box Build
Post by: Scott & Heather on November 11, 2015, 11:37:40 AM
So cool. Todd you're contributing so much to the bus community in such a short time. Thanks for being awesome. How are you transferring the environment box heat to the remote radiator?
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 11, 2015, 11:47:28 AM
So cool. Todd you're contributing so much to the bus community in such a short time. Thanks for being awesome. How are you transferring the environment box heat to the remote radiator?

Thanks Scott!

The block circuit will use the mechanical water pump to feed the external radiator.

There will be a radiator and puller fan inside the enclosure connected to an external radiator and puller fan. The little Honda racing radiators are awesome!

The box cooling circuit will be fed by a small electric water pump like a webasto pump or I have the option of using the accessory belt driven pump that is on the generator.

The accessory pump is a 3/4 pump that was originally to run coolant through the marine exhaust manifold - as this was a marine generator package.

Title: Re: Quiet Generator Box Build
Post by: Scott & Heather on November 11, 2015, 12:21:57 PM
Ok so for the enclosure radiator to radiator heat exchange...cool.
Title: Re: Quiet Generator Box Build
Post by: RJ on November 11, 2015, 03:06:40 PM
Todd -

You've left out a minor point:

Where in the chassis are you installing the genset?

FWIW & HTH. . .

 ;)
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 11, 2015, 03:34:21 PM
Todd -

You've left out a minor point:

Where in the chassis are you installing the genset?

FWIW & HTH. . .

 ;)

Hi RJ, my current plan is to use the passenger side bay between the front wheel well and the diesel tank.

I am going to build a 36" slide out frame and attach the bay door to it so it slides out with the frame.

I will run the four coolant hoses across and back into the bay with the mesh door.
Title: Re: Quiet Generator Box Build
Post by: RJ on November 11, 2015, 05:33:49 PM
Todd -

Ok, the old HVAC service access bay, got it.  I know another 4106 owner who also used that bay for the genset, same fellow that used a 140hp Corvair muffler that he hung on the rear baggage bin bulkhead, exhausting out the passenger side wheelwell.  Unfortunately his coach was involved in an accident that totaled the bus, so it's now Coke cans. . .

When you stripped the coach, did you save the water pump which hung from the ceiling of that bay?  That pump is/was wired to the defroster fan circuit, it provided boost to the defrost heat exchanger when needed.

What else are you planning for the old A/C condenser compartment besides the genset radiators?

FWIW & HTH. . .

 ;)
Title: Re: Quiet Generator Box Build
Post by: TomC on November 11, 2015, 07:31:54 PM
For remote radiator, that 12v fan will be noisy. I used a single inlet squirrel cage blower from Graingers belt driven with a 1/2hp 2spd totally enclosed fan cooled motor pulling air through the radiator exiting through the blower to the side of the bus. On high it cools to 117 degrees (hottest I've been in). On low, nearly silent night running.
To ventilate the enclosure, I use a 250cfm 8" inline bathroom ventilator also from Graingers. Good Luck, TomC
Title: Re: Quiet Generator Box Build
Post by: luvrbus on November 12, 2015, 01:53:25 AM
Yep you want a 3 speed 110v squirrel fan that only comes on with generator running,the folks I know with the 12v automotive fan seem to be always shut down here in the AZ heat 
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 12, 2015, 02:59:20 AM
Good point about the exterior fan noise, its all about decibel vs cfm.

My limitation may be space but I will give it some thought.

I know because of the enclosure of a caged blower they in general radiate less sound.

The spal is my fall back because it will produce 1800cfm in a very small space and is very quiet at lower speeds, but I have not tested one at full tilt with the decibel meter.

Most generic automotive 12v fans are very noisy and highly inefficient.

Looks like most of the 1/2hp caged blowers have a comparable or greater cfm but they dont provide db specs so i may have to call dayton.

I also did not see 3 speed but they did have three phase which I could use with a VFD and have infinite speed control from a 4-20ma signal or depending on the type of single phase AC motor I could use a PWM.

Ok did some more research and found a 4 speed 115v Dayton that should work.

Title: Re: Quiet Generator Box Build
Post by: TedCalvert on November 12, 2015, 02:40:21 PM
Darkspeed;
 
Many VFDs will accept single-phase input, and give you 3-phase out.
Just curious, where you gonna get 4-20 mA?  Analog out card on a PLC or standalone controller?

Ted.
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 12, 2015, 03:32:03 PM
Darkspeed;
 
Many VFDs will accept single-phase input, and give you 3-phase out.
Just curious, where you gonna get 4-20 mA?  Analog out card on a PLC or standalone controller?

Ted.

Hi Ted, true! I did some Hitachi single to three phase vfd's for machine motor controllers before.

I am doing a Direct Logic Productivity 2000 PLC for the bus with a C-more HMI in the dash. I built a lot of mobile automation systems around the DL260s with good results, even some canbus interface stuff.. Nothing like having your bus send you a text that it is too cold and wants to start the tank heaters or someone bumped it while you were away.

Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 13, 2015, 05:48:28 AM
Put my ear protection on and my respirator and spent some quality time with my generator running looking at what parts make the most noise.

1. Exhaust
2. Intake
3. valve train
4. Case
5. Output Alternator

The civic radiator seems to do a great job!

Things I need to solve..

I need to fireproof the exhaust manifold and enclosure bulkhead - combination of wet wrap and 2k  aluminum faced ceramic to keep heat in the exhaust until it leaves the box.

I need a simple way to disconnect the equipment outside the box so it can be slid out for service, or have all of the equipment slide out with the box.

Need to silence the intake - an engineer friend uses a stainless muffler for his generator intake, I have done the same on a compressor, may have to try that.


The OEM rubber mounts transmit a lot of noise and vibration into the steel workbench - but the are 27 years old so they may be a little stiff -

I found a perfect goodyear pneumatic spring that has a 2" installed height and a 580lb rating > 1S3-013

And a 4 speed 115v Dayton blower > 1XJY2 that will do 2000cfm and runs at 1100rpm so it should be fairly quiet.

I am thinking about putting a 200F automatic 50CF extinguisher in the outer box..just in case..
Title: Re: Quiet Generator Box Build
Post by: RJ on November 13, 2015, 07:29:05 AM
Todd -

Are your plans to run the exhaust to the rear axle and dump it out the passenger side?  If so, do what that other 4106 owner I know did and pick up a 140 hp Corvair muffler  (Walker #17908, $33 at O'Reilly's) and mount it on the rear bulkhead in front of the axle pumpkin between the brake pots.  Made his exhaust noise virtually non-existent.

FWIW & HTH. . .

 ;)
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 13, 2015, 08:04:45 AM
Thanks RJ, that is almost what I am using now, im using the walker quietflow on the exhaust (and possibly the intake) http://www.walkerexhaust.com/products/mufflers-muffler-assemblies/quiet-flow-ss (http://www.walkerexhaust.com/products/mufflers-muffler-assemblies/quiet-flow-ss) it is very similar to what you suggested.

I have not decided where im exhausting yet, still trying to make all this fit in my reduced height bays safely.

BTW I got a chance to test one of the Fujitsu Ductless Mini-Split systems I want and the outdoor unit running on high was 43 dB  ;D ;D ;D NINJA!

If anyone wants to learn about the proper use of materials, this is a good reference > http://www.sounddeadenershowdown.com/products (http://www.sounddeadenershowdown.com/products)

and....  https://books.google.com/books?id=AF_AYLaJNNIC&printsec=frontcover#v=onepage&q&f=false (https://books.google.com/books?id=AF_AYLaJNNIC&printsec=frontcover#v=onepage&q&f=false)
Title: Re: Quiet Generator Box Build
Post by: OneLapper on November 14, 2015, 12:56:02 AM
Todd,

I'm really enjoying this project of yours!  At my job I get to see all different types of generators installs.  Without doubt, the quietest are sets that are in a sound enclosure within another box. 

Remote mounting the mufflers and the intake filter, as well as the radiator really help, too. 

Keep up the great work! 
Title: Re: Quiet Generator Box Build
Post by: 86102A3 on November 14, 2015, 02:16:53 AM
Todd,
Thanks for sharing your build. I plan to also build my own enclosure as well.  What brand, size etc is your generator?
Also I thought I was reading my own ideas in your post about having a PLC on board, with the Cmore HMI, that is exactly what I am planning as well. I have been looking at the less expensive Click series PLC just to get me started. I am an industrial electrician and mostly deal with the field end of installs, so I will be on a bit of a learning curve for the programming end. Hopefully you can post some of your work on the PLC install, would like to see what you have planned.

Jeff
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 14, 2015, 03:29:30 AM
Thanks Mark! Sounds like a cool job!

Thanks Jeff, it is a 8kw 1800rpm Quicksilver marine diesel.

I have never used the Click series before but I am sure it would work, I think it just has fewer features (most you may not need) and is memory address location based vs tag name based programming.

If you do some creative thinking the PLC can replace a lot of expensive systems in a bus.

I have a girl I hire to do voice over work who has an obscenely sexy voice and she records all of the touch screen alerts/messages as .wav files then I load them into the Cmore.

I have had companies refuse to let anyone else do plc work because the guys who operate the machines have developed an attachment to their touch screen lol.

Title: Re: Quiet Generator Box Build
Post by: digesterman on November 14, 2015, 03:31:05 AM
Count me in on that too Jeff,  reading this thread with great interest
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 14, 2015, 08:12:01 AM
Making some modifications for adding a thermostatic remote oil cooler to give it every fighting chance to not overheat in a sealed box.

Thinking about doing inline cooling with the Dayton blower:   Baffle In > Blower > Enclosure Radiator > Oil Cooler > Engine Radiator > Baffle Out

The Dayton needs a minimum of 1" water static pressure or it will spin too fast and go into overload - it is designed that way

Tested the stainless exhaust on the intake side and it made a significant improvement.

When the better decibel meter ( A Weight ) shows up I will get some good numbers.

Going to try to drag everything below human hearing (20hz) and the left over I will convert to heat.

Mostly using decoupling layers and lead sheet as the damper materials ( like dynamat ) loose almost all of their damping ability at a heat higher than a car interior.

The best damper for higher heat is fiberglass resin mixed with small gauge lead shot and painted on to the metal panel - as long as you are below the melting point of the lead  ::)


Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 17, 2015, 05:58:43 AM
I spent a lot of time watching the youtube videos , googling how-to's, talking to "car audio experts" just to get a feel for what the rv/bus/mobile home community does for generator sound control of the enclosure.... and I cant find anyone doing it to the known best practices. - with the possible exception of custom prevost -

The boat/marine folks seem to be doing it right but there is a disconnect to the on the road guys.. ( THAT I HAVE FOUND - NOT ALL IM SURE )

A lot of the on the road guys are making three mistakes  ( not judging or point fingers it is just an unqualified generalization )

#1 connecting the barrier layer directly to the enclosure  = screwing the lead or MLV to the plywood or to the aluminum bay = no decoupling layer

#2 relying solely on higher frequency absorption = foam / fiberglass / foil pads, panels = not absorbing anything below 8-4khz

#3 using dampening material full coverage as only solution = dynamat the whole box = no sound blocking only frequency reduction.

#4 big holes for venting the box - not really an error just the alternative to box cooling = inadvertently turning the box into a port tuned speaker.

We should be aiming for good isolation in the 80hz-500hz range for an 1800 rpm 3 cylinder

1800 rpm = 30 cycles per second ( 30hz ) and 3 cylinders (3 x 30 = 90hz) so we should see problems at those frequencies, plus the resonant cavity size of the cylinder, resonant length of the valve train components, etc... Most of this is going to be low frequency hot spots.

If we can drag all of the low frequency noise below 20hz we will no longer hear it.

Butyl dampening material is not going to be usable because it looses almost all of its properties at these temperatures.

MLV blocking material is not going to be usable because it looses almost all of its properties at these temperatures.

2 decoupled layers of 1/64 lead sheet is much more effective than one layer of 1/32 lead sheet.

-30dB layer @125hz (when attached to enclosure)= 1/8 EPDM decoupler layer > 1/64 lead sheet > 1/8 EPDM decoupler layer > 1/64 lead sheet > 1/8 EPDM decoupler layer.

This should reflect anything in the high range and give about 30dB reduction in the 125hz range, and up to -70dB in the 2khz+ range.

Internal box ( generator box )  -30dB layer on the outside of the enclosure
Outer box ( the bay ) -30dB layer on the inside of the enclosure
0.5 air gap between boxes ( a good -10B )
Generator on pneumatic isolators
Inner box on low durometer isolators.
Inside of inner box would have ceramic batting in corners to turn high frequency waves into heat.

If the generator was say 100dB @ 1 foot then the box should attenuate 70dB @ 1 foot minus anything transferred through the cooling hoses as longitudinal waves, for a total 30dB @ 1foot.

So in a perfect world you could have a 8kw Diesel running at full tilt and not hear it ( at 30 dB ) standing beside it, because a library is 40 dB.

This would take 155# of lead sheet and 15# of EPDM/Neoprene foam sheet.

The EPDM/Neoprene foam allows each sheet of lead to vibrate independently and a lead sheet has a very low resonant frequency so it will convert the frequency of the sound waves down as it passes through it as well as converting a lot of the sound wave into heat, essentially using up the sound pressure before it can get to your ears / body.

The sound from the exhaust can be absorbed, canceled to a degree with a good non flow through exhaust and the  remainder directed in an acceptable direction, preferably straight up ( unless parked under trees where it would be reflected back down to you )

The noise from the cooling fan , radiator , etc can easily be absorbed because they will be a much higher frequency range. A filter on the cooling fan inlet and exhaust will also help this.


Title: Re: Quiet Generator Box Build
Post by: oltrunt on November 17, 2015, 03:19:56 PM
Exactly!  Too much fun and you are right on!  I wish I had taken the time to go the extra effort on sound proofing--but I got lazy and in a hurry.  But then I'm old and I was afraid I wouldn't get the bus done before I was to frail to use it.  Keep up the effort and the fine posts.  I got as far as the double box, lead and bitumen, and dense rubber but i still have air noises your remote cooling scheme would have solved.  I've only achieved 58 db with my little 3K gas genny.  I should add that fiberglass and foam rubber seem only capable of lowering high frequency sound and your camping neighbors probably have already lost the ability to hear that anyway.  Also, plywood is best used as a sounding board--not a sound deadening material.  Jack
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 17, 2015, 04:30:05 PM
Thanks Jack! 58dB is still pretty good!
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 18, 2015, 09:59:27 AM
The good dB meter came in today and I got some good base line numbers

@ full speed 1800rpm
@ Injection Pump : 100dB
@ open exhaust : 107dB
@ muffler out : 94dB
@ crank case : 102dB
@ 1 meter distance 86dB

@ half speed - around 900rpm
@ Injection Pump : 94dB
@ open exhaust : 101dB
@ muffler out : 91dB
@ crank case : 97dB
@ 1 meter distance 82dB

My generator is a fixed speed unit - full throttle 1800rpm

The rpm setting affects cycles per second so 1800rpm is in the 240v / 60hz range.

Running it at half speed was significantly quiter but it would give me around 100v / 30hz which ac systems would be unhappy with.

But..... it gave me an idea.. allow me to digress into madness..

If I did a full bridge diode bank on each leg of my AC output to rectify it to a half wave DC, and combined that into a buffer capacitor, I would end up with around 80VDC / 40A which could happily feed a MPPT battery charger like a wind generator or solar would use.

So I could have two modes for my generator:

Mode A = 1800rpm AC 240V/120V @ 8kw
Mode B = 900rpm battery charging @ around 3kw - may be closer to 2.5kw - would need to test.

I would just need a contactor to switch loads and a solenoid to push the throttle from 1/2 to full throttle.

The result would be a quitter more fuel efficient way to recharge the house batteries when direct AC loads were not needed.

I wonder if there is any issue running this diesel at near idle for extended periods of time... the lower the rpm the more vibration.

BTW, totally impressed that muffler took 13dB out of the exhaust.

As a side note some of the new inverter chargers will accept some fairly funky ac inputs like the Victron Quatro for example:

Input frequency range 45 - 65 Hz
Input voltage range 180 - 265 VAC

and the Magnum:

Input frequency range 50- 70/ 40-60 Hz
Input voltage range 60 - 140/120-280 VAC

If the Magnum would actually accept 120v @ 40hz I could skip the rectifiers and capacitor for low rpm battery charging.

Title: Re: Quiet Generator Box Build
Post by: eagle19952 on November 18, 2015, 04:14:22 PM
 :o  well after reading this i have come to the conclusion that you exceed every requirement to be in the top 2% of nuts...  ;D

good nuts but still nuts  :o
Title: Re: Quiet Generator Box Build
Post by: Darkspeed on November 18, 2015, 04:37:50 PM
Haha thanks...
Title: Re: Quiet Generator Box Build
Post by: Scott & Heather on November 19, 2015, 03:59:34 PM
No really.....Todd, you're a certified busnut... :o


You are spot on. I've done years of research on soundproofing and most people have no clue how complex it is. Carpet and foam the walls and you have a home recording studio....they think....sigh.

There is a special caulk out there that you can use between layers too. Super effective for acoustic projects. You can layer two sheets of drywall using the caulk between them and it does an excellent job of creating an acoustic barrier. Another weapon in the arsenal.
Title: Re: Quiet Generator Box Build
Post by: TomC on November 20, 2015, 05:03:29 AM
If you use a belt driven squirrel cage blower, you don't have to worry about overspeeding. I have a 2spd 1/2hp totally enclosed fan cooled GE motor. Granted, you can get a thumping sound from the belt at times, but the slower speed of the belt driven fan is much quieter than direct drive squirrel cage. Good Luck, TomC
Title: Re: Quiet Generator Box Build
Post by: OneLapper on November 20, 2015, 01:03:24 PM
Can't what to see the results of this project!