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Old 26-05-2018, 05:57   #1
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Noisy generator

Our Dynamica Mini 40 generator makes a lot of noise, most of which seems to be vibration related. Is there a simple way to fix this? Are there standard rubber mounts that could fit under the current mounting board?



We already have a gas / water exhaust separator.

Thanks.
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Old 26-05-2018, 07:19   #2
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Re: Noisy generator

Is this vibration new or has it always been there? Also, how old is the unit? My 16 year old Onan recently started making lots of noise and transmitting vibration through my hull. I suspect that my motor mounts have reached the end of their useful life. In the parts manual they are called vibration isolators. Visually observing the engine with the cover open there is no more noticeable vibration than before this started. The isolators have a rubber core that can either break or get hard with age in which case normal diesel vibration will get transmitted to the hull. In my case this is a section of bridge deck that is quite flat and seems to act like a sound board in a musical instrument. So I have another boat project in my near future.
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Old 26-05-2018, 07:37   #3
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Re: Noisy generator

Sound Down makes great products. Get their decoupling mat and isolation mounts. Put the mat on the board under the genset and then use the isolation mounts to raise the genset up and isolate it from the boat.

http://www.soundown.com/Section%201%20PDFs/Brochure.pdf
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Old 26-05-2018, 07:56   #4
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Re: Noisy generator

Quote:
Originally Posted by Captain Bill View Post
Is this vibration new or has it always been there? Also, how old is the unit? My 16 year old Onan recently started making lots of noise and transmitting vibration through my hull. I suspect that my motor mounts have reached the end of their useful life. In the parts manual they are called vibration isolators. ...
The boat is new to us, so do not know how long it has been like this. The surveyor commented on how loud it was as well and thought it may be to do with how it was mounted but will look into the vibration isolators.

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Sound Down makes great products. Get their decoupling mat and isolation mounts. Put the mat on the board under the genset and then use the isolation mounts to raise the genset up and isolate it from the boat.
This looks great. I'll try the motor mounts first as per Captain Bill's post but like the idea of adding the mat and isolation mounts too.
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Old 26-05-2018, 09:12   #5
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Re: Noisy generator

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Originally Posted by captainjay View Post
Sound Down makes great products. Get their decoupling mat and isolation mounts. Put the mat on the board under the genset and then use the isolation mounts to raise the genset up and isolate it from the boat.

http://www.soundown.com/Section%201%20PDFs/Brochure.pdf

I second this recommendation. I installed new isolation mounts from Soundown plus put their lead mat product inside the gen box (replaced the ineffective mat). Also lined the floor with it. It’s way better now.

I also had the exhaust hose touching a bulkhead and enlarged the hole so it would not touch. Much of my noise was from vibration.
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Old 26-05-2018, 15:58   #6
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Re: Noisy generator

Hi Terah,

Our 10kw generator is quiet inside the boat- and outside... [Fischer-Panda; 3 cylinder Kubota engine; 3600 RPM.] You have to walk to that side of the deck and lean over to determine if the generator is running... From 25 ft away on the water you cannot hear it... [Neighbor friendly- although we rarely have any...]

The inside quiet was achieved by using a 1/2" thick steel plate as the generator platform. [Mass = quiet] The steel plate is mounted to the hull using vibration isolators. Vibration isolators are also used between the generator clam shell and that plate. [2nd set of vibration isolators.] Then the generator itself is on vibration isolators inside of its noise reducing factory clamshell. [3rd set of vibration isolators] All this yields a very quiet cabin when the gen is running, and no felt vibrations.

The outside quiet is accomplished using a stock water separator exhaust system.

Best wishes with your project.

Cheers! Bill
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Old 30-05-2018, 00:34   #7
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Re: Noisy generator

Good advice so far as the picture with the mounting looks like it could be improved. These generators are noisy normally.
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Old 30-05-2018, 17:08   #8
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Re: Noisy generator

Assuming there is no inherent problems with vibration from the Engine/ Gen itself, You may want to check the Engine Mounts (Vibration dampers) of the Mini40 unit. Over time, these will loose their resilience and allow more vibration to come through.
if these are Ok, perhaps some 'Waffle rubber' instead of the current board will help reduce the vibration?
Your photo also shows the Generator mounted close to a bulkhead and this could also be transmitting noise and vibration. You may want to look at acoustic deadening to help reduce this. I found quite by accident that some deadening will absorb fuel (if you have a leak) so may be worthwhile considering this if you decide to put the insulation in.
Cheers
PS. Make sure you keep electric cables away from any Sound insulation etc to allow adequate airflow around the cables
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Old 31-05-2018, 01:12   #9
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Re: Noisy generator

I understand the complaint. I got a diesel generator for house power. But I have even stopped using my generator at home. It's fine for an hour or so but during these long outages it is noisey, smelly, expensive and would soon wear out if used every day for hours.
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Old 10-06-2018, 09:50   #10
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Re: Noisy generator

Thanks all for the suggestions.

I asked the marina technicians to have a look and they say the internal vibration mounts need to be replaced. A week later I'm still waiting for a quote from them for doing it. Is this a tricky job?

I'd quite like to get it back to working as it was installed first, and then it should be fairly simple to add a mat and additional vibration mounts under the clam shell.
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Old 10-06-2018, 10:14   #11
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Re: Noisy generator

See if you can find hydraulic mounts (rubber filled with oil) . They are used in diesel cars and a mechanic friend adapted ones from VW to the Volvo on my ex-sailboat. That made a really great diference in the percieved sound/vibration inside when the engine was running
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Old 10-06-2018, 23:58   #12
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Re: Noisy generator

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Originally Posted by terah View Post
Thanks all for the suggestions.

I asked the marina technicians to have a look and they say the internal vibration mounts need to be replaced. A week later I'm still waiting for a quote from them for doing it. Is this a tricky job?

I'd quite like to get it back to working as it was installed first, and then it should be fairly simple to add a mat and additional vibration mounts under the clam shell.
The Dynamics Mini 40 manual under “Detecting Alternator Anomalies” for Noise as : “Loosening of some clamping” and the solution as “ Check the clamping of all nuts and bolts” It additionally shows Generator elastic support as 6mm diameter, with Alternator and Engine supports at 10mm. Plus torque tension values . If you take the top and side covers off the generator you will see the mounts in the corners of the unit. As per the other writers, look at the condition of these and replace with new isolators. The trickiness of the job will be depend on how much relative room you have to access the unit once the covers are off.

You’ll probably have to disconnect the exhaust and move the generator away from the bulkhead to reach the rear mounts. The manual shows threaded entries into the base plate. This may be problematic as to remove the isolation mount , may require all mount nuts to be loose and jacking the whole unit up 30mm to change the mount. The illustration I can see on line shows a 10mm stud with a 20mm spacer mount, rather than a more normal separated mount. Your own inspection will confirm what you have. Your local chandler or auto shop may offer an alternative mount. Suggest this is a good job you should be able to do with a friend over a day, with basic hand tools. As other suggest, if that does not cure it, additional isolators between the plate and vessel structure will help.

Note before working on the unit, disconnect the alternator starting battery so you don’t get an unexpected start. Also maintain the 240V electrical integrity by ensuring those electrical covers stay on. Since the unit is new to you, good time to download the Dynamics Mini 40 manual and change the oil and oil filter and perform 3& 6 monthly checks, so you have a base line condition of the unit.
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Old 12-06-2018, 08:04   #13
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Re: Noisy generator

@OldGreyB - thanks! that helps a lot.

A few more pics at:

https://farm2.staticflickr.com/1735/...751b541b_h.jpg
https://farm2.staticflickr.com/1754/...ec1094cf_h.jpg
https://farm1.staticflickr.com/899/4...e01b3b86_h.jpg

I've just taken the covers off and the mounts seem in OK condition, though if I pull the generator forward a little the noise improves. Aside from access issues it doesn't seem too bad a job. Is it a case of removing current ones and taking them to a shop or is there a specific part? I've grabbed the Mini 40 manual but can't see it listed in there.

What I can't quite work out is, if I do decide to put additional mounts in, how do I remove the board the generator is sitting on? - it seems to be through-bolted to the floor of the lazerette.
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Old 12-06-2018, 17:59   #14
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Re: Noisy generator

Your photos, don’t show mounts that are dried out looking or cracked – a sign of hardening – so yours may be fine. However they do all harden over time, and are easy and cheap (£5.00) to obtain from any machinery supplier. Mounts are generic in nature for standard applications such as this. Pull one out and get on line or to your local machinery trade shop for replacements. Since you are in the UK: Male-Male Anti-Vibration Bobbins with M10 thread

But before you do that, since your observation of moving the unit away from the bulkhead drops noise and in photo 1754, the mount looks OK, I suggest first see if just more isolation from the boat works:
From your photos is appears to be a 10mm hex bolt top holding the generator base pad to the generator enclosure base, and then the allen key hex head and washer looks like they are holding the enclosure to the vessel floor board. I suggest that loosening the allen key hex headed bolt and confirm they are holding the generator enclosure to the vessel floor. If you confirm this to be the correct observation, undo all, raise the unit up as a temporary measure, put two pool noddles (or similar) underneath and run the unit, ensuring it is away from the bulkhead too. If that immediately reduces the noise – then you are on the right track and you can follow others suggestions re additional vibration isolators or mats.

To your question on “how do I remove the board the generator is sitting on?” the potential answer is you don’t. You separate the floor of the generator enclosure from the vessel support board with vibration dampers, either with additional mounts or mat.

Since the allen key hex head bolts (if confirmed as above) are already into threading into the large floor board, then all you have to so is install additional machinery vibration mounts between the two using the same mounting locations and existing thread size: Anti-Vibration Machine Mountings with 2 holes

An alternative is to install a vibration mat under the enclosure area, and over drill clearance holes say 4mm through the enclosure base plate, (so no physical / vibration noise path) install rubber washer under the large washer and tighten the hex head down again.

Also check you exhaust area – make sure there is no metal to bulkhead contact. Note: All the above are suggestions based on your writings and photos, and any final solution is your call. Have a try and let us all know how you get on and the final solution.
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Old 13-06-2018, 05:08   #15
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Re: Noisy generator

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Originally Posted by terah View Post
I've just taken the covers off and the mounts seem in OK condition, though if I pull the generator forward a little the noise improves.

If you can move the generator, maybe it's not as tightly mounted as it should be.

-Chris
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