Author Topic: Sound deadening ideas, suggestions?  (Read 8110 times)

Todd T

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Sound deadening ideas, suggestions?
« on: June 27, 2011, 12:12:36 AM »
I run my small chemical company off the grid using a diesel generator for most of my power. Right now, I'm using a 6kw light plant with a Mitsubishi 3 cyl diesel. It isn't too loud. I have a 12kw Changfa clone that runs great but is so loud that I've been waiting to put it into service until I could do some work on sound deadening. Here are some ideas I've gleaned from here and elsewhere:

Mount the generator on a trailer- Use the tires as an insulator for the low end "thumps". Or make a sand bed to place the genset on. The idea is to isolate the generator from the surrounding ground.

Build a doghouse around the generator- This is my ultimate plan. I want to relocate the radiator outside this box. I can get some insulated panels like they use in making walk-in freezers. These panels are 24" or 30" wide, 3" or so thick, sheet metal on exteriors with "styrofoam" in the middle. With a solid surface on the interior, I wonder how much it will drop the sound. Sound rooms (for hearing exams) usually have perforated wall panels. Would a solid metal interior wall just create an echo chamber? At minimum, I'll use some of the foam insulating panels from Home Depot. They have 1/2", 3/4" and 1".

Run a larger diameter exhaust and have it pass through a drum of sand- I've heard of folks running the exhaust in a drum of gravel buried in the ground. Do they have the pipe run through the gravel or does it just exhaust into the ground? Before doing anything, I'm going to check the exhaust back pressure. I've read that 1.5psi at idle and no more than 3psi at 2000rpm is a target.

Change the intake system- I've ordered a plastic air intake housing. It looks like what is on a Kubota diesel air compressor I have. This air cleaner is designed for a much larger engine than my Changfa so I'm hoping it will give more room for the pulsation of the air.

Recently, I ran across a paintable/sprayable coating from the manufacturer of undercoating material. This sounds promising. What about applying it to the valve cover, engine cases, etc? With water cooling, it shouldn't cause the engine to run hotter, should it? I would add an oil temp gauge, adding an external oil cooler if necessary.

Other ideas? Warnings?

veggie

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Re: Sound deadening ideas, suggestions?
« Reply #1 on: June 29, 2011, 06:46:02 AM »
Hi Todd,

The Changfa 1115 (12kw) does not have any low level thumps because it has internal counterbalance shafts to negate a thump.
It's actually a very smooth engine. Therefore tires won't make much difference.
What the Changfa's do have is a very loud ignition knock and lots of internal gear clatter because of the straight cut gear teeth driving the counterbalance shafts.
Here's a few of the things that help to tame a Changfa....

- A good (low back pressure) exhaust muffler
- An inlet air muffler (not critical but you will get a pop...pop...pop...without it)
- An enclosure (small box or full shed) lined with acoustical foam. Be careful to keep adequate air flow for cooling.
- RPM....The noise drops substantially below 1800 rpm (if you don't need the full HP output of the engine).

I got the best results when the engine was slowed down and an exhaust muffler added.
Here's a link to discussion and video of my Slow Speed Changfa project on the MicrCogen forum.
http://www.microcogen.info/index.php?topic=477.0

If it's any consolation, I've heard they quite down somewhat after about 1000 hrs. of running  :) so you can look forward to that.
(I don't have anywhere near that much time on my Changfa yet.)

veggie

- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- JiangDong R165 Air cooled - 2 kw
- Changfa S195 (Waiting for a project)

38ac

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Re: Sound deadening ideas, suggestions?
« Reply #2 on: June 29, 2011, 01:37:54 PM »
I am a bit limited in experiance with them but our 1115/ 15KW combo is mounted on an old boat trailer fame with suspension and we get none of the ground punding we can feel from the 6/1 Lister ground mounted on a slab. . However the exhaust and intake noise needs addressing as Veggie stated.  I have built a shed for the trailer and plan to leave it dirt floor and insulate it heavily with blue board. Not sure what we will do with the exhaust yet.

Collector and horder of about anything diesel

Combustor

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Re: Sound deadening ideas, suggestions?
« Reply #3 on: June 29, 2011, 01:47:37 PM »
Hello Todd T,
                 If your location allows it, you can reflect most of the noise away in another direction using solid brick or masonry  walls a foot or 2 higher than the power unit.  Place it within a vee or 3 sided solid wall and very little sound will penetrate through a structure rhat has substantial mass. Fine if you don't have near neighbours,
 Regards,  Combustor.
Toys include- Lister CS 8/1, Lister VA SOM plant and some Aussie engines.
   "Old iron in the Outback" Kimberley, West Australia.

veggie

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Re: Sound deadening ideas, suggestions?
« Reply #4 on: June 29, 2011, 02:41:44 PM »
Here's a couple of examples of what others have done with exhaust systems and enclosures...

http://www.youtube.com/watch?v=GsMAdspwRUY

http://www.youtube.com/watch?v=9Z1lWrOTgPg&feature=mfu_in_order&list=UL


veggie
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- JiangDong R165 Air cooled - 2 kw
- Changfa S195 (Waiting for a project)