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Old 11-21-2020, 01:41 PM   #15
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Originally Posted by tap4154 View Post
Thanks, they actually didn't want to turn anyway so I didn't try to force them. I read that thread that you linked, that's interesting. It is a fact that most of the noise is coming down through the bottom. Mine is on the two cantilevers as well and I was also thinking about putting some kind of insulation board across underneath them.

I removed that U bolt and it didn't make any difference at all. I get 75db inside the motor home and a little over 80 outside. I took a piece of thick folded up piece of cardboard I was laying on and when I lift it up at an angle underneath the generator it really cuts down the noise.

I'm thinking some kind of collapsible rectangular bucket that could be put underneath it might be a solution in blocking sound both to the left and to the right. Maybe it could "catch" the noise?

Or even something that just flipped up on two sides to block noise to the left and the right, with some sound absorbing material on it. When folded down it would be easy to store.

To me it seems the worst noise is not coming from the exhaust, it's from the mechanical racket made by the engine itself.
wow seems loud 75 .. 80 db... I know guys complain but whoa.... I gonna fire mine in the AM to let it run a bit,, I will test as it sets in driveway, been a year or 2 since mods..
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Old 11-21-2020, 04:33 PM   #16
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Originally Posted by sibe View Post
wow seems loud 75 .. 80 db... I know guys complain but whoa.... I gonna fire mine in the AM to let it run a bit,, I will test as it sets in driveway, been a year or 2 since mods..
I figured out what microquiet means. It means it's just a little teeny tiny bit quieter than a farm tractor. If it was a megaquiet generator, it might actually be quiet
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Old 11-21-2020, 08:02 PM   #17
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The problem with the way mine is mounted, and probably many others are the same way, is it's just mounted on cantilever brackets, and there really is no compartment, there is no back wall at all.

I was just out looking at it and there's about 5 1/2" between the top of the generator housing, and the floor of the motorhome. And I can see through that to the other side of the motor home because there's no back to the area.

I was just thinking if I could get some heavy dense foam and put a piece in there, and wedge it between the top of the generator and the bottom of the motorhome floor, that would sort of block at least part of the opening. There are no vents on the top of that generator housing, it's just flat.

Then I got to thinking, what if I build sort of a temporary dam on the front, side and back of the generator housing out of cardboard, then fill the area between top of the generator and the underneath of the motorhome floor with expanding foam?

Not only would that insulate the top of the generator and the motorhome floor directly above it, but it would partially close the opening to the other side of the motorhome, maybe reducing noise transmitted to the other side of the motorhome?

I dunno, just kicking around ideas...
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Old 11-21-2020, 11:37 PM   #18
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I think I just found why I'm getting so much vibration and noise from the generator in the motorhome. The insulated hanger bracket on the exhaust is touching the U-bolt that protects it. The rubber hangers are also very rotted, so I'm going to have to replace those too, but I'm pretty sure this bracket clamp touching that big U bolt is the reason I'm getting all the vibration.

I'll take that U bolt off tomorrow and run it and see what happens. In fact I could turn it around and that would give it some room between the bracket and U bolt.
The exhaust hanger in the pic is a standard Onan part. It appears to be nearly broken. The Onan p/n is 0155-2174

A good aftermarket exhaust hanger would probably work also. I had one of the Onan hangers on my Bigfoot travel trailer with a built in 2500LP Onan and it had broken (prior to my owning the trailer) and the previous owner had "fixed" it with a piece of rubber, but it was TOO flexible and allowing the pipe to be stressed and cracked it at the 90 degree coming out of the bottom of the generator. I had the pipe's cracks welded up, we installed Onan resonator p/n 0155-2449 by cutting out a section of the tailpipe and welding the resonator in, and I installed a new Onan exhaust hanger 0155-2174

You might consider installing the exhaust resonator and possibly additional hangers to support it. Most certainly gain clearance between the pipe/clamp and the U bolt which is a safety bracket in case the pipe cracks or the hanger fails.

The exhaust resonator makes a huge difference on my 2500LP but I have seen Youtube videos where they installed it on a 4000 and it did not make a lot of difference, yet, the people on the Winnebago View/Navion forum several years ago raved about how well it worked on their 3600LP (which is the same as the 4000 gas except for the fuel)

If you do not want to buy the Onan exhaust hanger, NAPA has several "universal" hangers and I have found the 732-1009 to work well for me on a full size exhaust pipe https://www.napaonline.com/en/p/BK_7321009



The lower part of the hanger that the clamp passes thru also swivels, rather tightly, on a large rivet that holds the very bottom to the next piece. It also swivels some on the rubber attachment.

Onan accessories can be found in this accessories catalog. Stuff for one model of a generator may also fit another.

https://mart.cummins.com/imagelibrar...es/0058349.pdf

I found that much of the generator noise was, as you have found, echo and resonance from the pavement, the underside of the motorhome, etc. Experiments I preformed on my Bigfoot trailer found that it was much louder on concrete than on asphalt and quieter still on gravel or dirt. I also found that just standing flattened cardboard boxes alongside the trailer as an experiment, made the unit much quieter outside. Mine hangs under the trailer in the front under the dinette area so there is not a lot of hope for inside noise reduction. As you noted, much of the noise is mechanical and comes out of the cooling exhaust which is the opening where the exhaust exits also.

Here is what mine sounded like with and without the resonator, as an experiment. I think a longer exhaust helps alot also.

https://youtu.be/NQEtWhQr8ps

This next video is about a hard start issue I had, but if you watch the first 30 seconds or so of it you will see how long my exhaust is and the resonator permanently installed in it.

https://youtu.be/pmrSYhydtjg

Hope someone finds some help in this information.

Charles
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Old 11-22-2020, 08:05 AM   #19
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Originally Posted by CharlesinGA View Post
The exhaust hanger in the pic is a standard Onan part. It appears to be nearly broken. The Onan p/n is 0155-2174

A good aftermarket exhaust hanger would probably work also. I had one of the Onan hangers on my Bigfoot travel trailer with a built in 2500LP Onan and it had broken (prior to my owning the trailer) and the previous owner had "fixed" it with a piece of rubber, but it was TOO flexible and allowing the pipe to be stressed and cracked it at the 90 degree coming out of the bottom of the generator. I had the pipe's cracks welded up, we installed Onan resonator p/n 0155-2449 by cutting out a section of the tailpipe and welding the resonator in, and I installed a new Onan exhaust hanger 0155-2174

You might consider installing the exhaust resonator and possibly additional hangers to support it. Most certainly gain clearance between the pipe/clamp and the U bolt which is a safety bracket in case the pipe cracks or the hanger fails.

The exhaust resonator makes a huge difference on my 2500LP but I have seen Youtube videos where they installed it on a 4000 and it did not make a lot of difference, yet, the people on the Winnebago View/Navion forum several years ago raved about how well it worked on their 3600LP (which is the same as the 4000 gas except for the fuel)

If you do not want to buy the Onan exhaust hanger, NAPA has several "universal" hangers and I have found the 732-1009 to work well for me on a full size exhaust pipe https://www.napaonline.com/en/p/BK_7321009



The lower part of the hanger that the clamp passes thru also swivels, rather tightly, on a large rivet that holds the very bottom to the next piece. It also swivels some on the rubber attachment.

Onan accessories can be found in this accessories catalog. Stuff for one model of a generator may also fit another.

https://mart.cummins.com/imagelibrar...es/0058349.pdf

I found that much of the generator noise was, as you have found, echo and resonance from the pavement, the underside of the motorhome, etc. Experiments I preformed on my Bigfoot trailer found that it was much louder on concrete than on asphalt and quieter still on gravel or dirt. I also found that just standing flattened cardboard boxes alongside the trailer as an experiment, made the unit much quieter outside. Mine hangs under the trailer in the front under the dinette area so there is not a lot of hope for inside noise reduction. As you noted, much of the noise is mechanical and comes out of the cooling exhaust which is the opening where the exhaust exits also.

Here is what mine sounded like with and without the resonator, as an experiment. I think a longer exhaust helps alot also.

https://youtu.be/NQEtWhQr8ps

This next video is about a hard start issue I had, but if you watch the first 30 seconds or so of it you will see how long my exhaust is and the resonator permanently installed in it.

https://youtu.be/pmrSYhydtjg

Hope someone finds some help in this information.

Charles
Thank you for all the information Charles. Yes I already ordered a couple Onan hangers, actually they're arriving today..

That resonator made quite a difference on yours. Mine has the muffler up in the right side, then the pipe comes down and runs forward, then out, so it is a fairly long exhaust pipe. But really, I don't hear that much noise from the exhaust itself, I just hear more mechanical noise. As you said, a lot of it is coming out of the cooling exhaust area.

Also, to put a resonator underneath by cutting a section of pipe out, I'd need to weld it and I don't have that capability. I don't know if I'd want to trust just using clamps on an exhaust pipe underneath the motorhome.

I agree about the ground noise, I tried some folded up cardboard underneath the generator and it does cut down the sound to a certain degree. It's parked on brick in the backyard so that amplifies the noise quite a bit.

I ordered some Noico sound dampener, it's like Dynamat. I wonder if putting that on the outside of the generator shell itself really helps much? I'm thinking about also extending it up on the back of the generator almost to the motorhome floor, to help block some sound going to the other side of the motorhome. As I said in my previous post there is no back panel behind the generator, so it's wide open to the other side of the motorhome.

By the way I love that second video, very informative. I gave you a thumbs up.
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Old 11-22-2020, 08:28 AM   #20
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Just as a proof-of-concept I made up a little sound block out of my piece of cardboard. The sides don't fold up quite high enough yet, but it actually did knock off 2-3 dB inside the motorhome. I can see you definitely would not 4 sides though, because it would block the warm cooling air from escaping. I think this would be safe because it allows air in from the left to the intake, and the warm air from the right to escape.

75-80 db, I would find that horrible.


Experimenting and mockups, I go through a lot of cardboard! Sound does not like to turn corners. You could actually make a 4 sided box, it would still need entrance and exit for air but would need to be baffled. Hard to explain, the sound would hit a wall and then have to turn to exit, a U turn would be most efficient, lined with a sound absorbing or blocking material would be ideal.
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Old 11-22-2020, 12:28 PM   #21
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I got it down to 67 DB on the interior, just using an old fitness roller. Like I said, there is no back wall behind the generator, so the sound just goes straight through to the other side, and I actually could hear it the loudest near the entry steps when I'm inside.

So I remembered I have this old 6" fiitness roller that I never use because it's too stiff. I cut it at 24 in and then used the other short portion for the right side. I sliced a little bit off so it would fit into the 5 1/2" area between the top of the generator housing, and the bottom of the motorhome floor. Made a huge difference!

Really, a lot of the noise comes from the intake side of this generator. I don't have a vent cut into the door, because it's completely open on the bottom. So when I get that noise dampening material I'm going to double layer it on the door and that should help as well.

But at this point, it's a heck of a lot better!
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Old 11-22-2020, 03:26 PM   #22
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When I experiment with a generator I always use some type of thermometer to monitor temperature
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Old 11-22-2020, 03:43 PM   #23
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When I experiment with a generator I always use some type of thermometer to monitor temperature
That's a smart idea. However I don't think what I did there is going to alter anything, as far as the engine cooling .I have 2 1/2" from the front of the air inlet to the motorhome wall (installation manual says at least 1 1/2" ) and even more than that to the door because it's much thinner.

I just cleaned the back and right side of the genset dog house, both are fairly easy to reach from underneath. When I get the sound absorption material I'm going to put some on the back and the right of it, and on the inside of the cabinet door. Then I'll probably call it a day at that. Also putting the new exhaust hangers on when they arrive.

I've seen people suggest putting a 45 degree tip on the exhaust pipe might help a little bit, but I don't think I'll bother with that.
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Old 11-22-2020, 07:25 PM   #24
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Got the new exhaust hangers installed, and now it's going between 65 and 66 db. I put a little zig-zag bend in the inner clamp strap because it was holding the metal clamp really close to the frame. Now both of the clamps have space. The pipe also feels a lot more secure.
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Old 11-22-2020, 08:11 PM   #25
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Donít cover it so much that it overheats.
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Old 11-22-2020, 09:29 PM   #26
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I did not read through all your replies. I will say that your complaint is very common. Like you indicated, some installations are less noisy than others.

One thing I learned is about the reflected noise bouncing off the pavement. A large piece of carpet laid on the ground under the area of the generator will help. Though it works I can't carry a large sound-deadening carpet. Plan-B is similar to your cardboard, leaning our folding table against the motor home to be a better neighbor.
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Old Yesterday, 09:30 AM   #27
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I did not read through all your replies. I will say that your complaint is very common. Like you indicated, some installations are less noisy than others.

One thing I learned is about the reflected noise bouncing off the pavement. A large piece of carpet laid on the ground under the area of the generator will help. Though it works I can't carry a large sound-deadening carpet. Plan-B is similar to your cardboard, leaning our folding table against the motor home to be a better neighbor.
I'm thinking of cutting a piece of plywood or MDF that will fit up inside the skirt under the generator, and I'll put some of that sound deadening material on it. I have plenty of room to carry something like that on the cross bed shelves. Actually MDF would probably be better because it doesn't tend to resonate like plywood does. It's kind of a dead material, acoustically.
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Old Yesterday, 11:58 PM   #28
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Yup to both, and that rubber subject to sudden failure, so get that ordered too, Locally or Amazon, Wish MINE was so obvious on my 20-yo Emerald Plus (250-HOURS+/-) that sounds like a PISTON SLAP or LIFTER RATTLE. (As the preschool grandson says "You got this", (well, actually, he says "I got this", LOL :-)
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