Got vibrations from your wind generator? - SailNet Community
 
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post #1 of 8 Old 10-23-2012 Thread Starter
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Got vibrations from your wind generator?

I recently installed a wind generator on my radar arch and whilst it is really quiet on deck it is decidedly not when down below in our aft cabin. So I decided to make a vibration absorber to reduce the noise. Thought I would share that with the forum.

The raw materials look like this:



Two stainless tubes, the little one fits the insert of the wind gen, a piece of "soft" polyurethane (red) and a piece of hard acetyl plastic (grey). The polyurethane is to absorb the vibration, the acetyl is to provide anti-crush properties to the piece where the bolts hold the assembly onto the arch.

The two inserts are machined to a press fit into the outer sleeve. This is the soft part pressed in on a hydraulic press and then bored, the hard part is the same on the other end with a 20mm gap between.



Then the two inserts are machined, the red sleeve to the same press fit for the inner tube and the grey to a snug slide fit for easier installation to the arch. The inner tube is pressed into the red sleeve on the press (sorry I couldn't get the image to stay "rotated").



The lower part is drilled to take three bolts into the arch pipe (not shown here) and nuts are glued into the arch pipe to take the bolts.

For those interested, this is the machine I have to do this stuff.



For those who have the same vibration problem, if you can't do this yourself, get a mate to help or something - it's worth the effort.


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post #2 of 8 Old 10-24-2012
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Re: Got vibrations from your wind generator?

Thanks
a great solution


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post #3 of 8 Old 10-24-2012
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Re: Got vibrations from your wind generator?

Looks like a fine piece of work. StAnna, do you have a similar problem ?

Not being aft cabin this is probably not a hastle for the likes of us but Andre, did this mod have any effect at all on the above deck noise level ?

p s- what wind gen do you have ? either of you .

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post #4 of 8 Old 10-25-2012
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I used to have an aerogen wind generator on the previous yacht. now I have no wind generator I am very aware of the vibrations.

The mounting of a wind generator will of course control and determine the level of vibration.

Andre has it right I think.


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post #5 of 8 Old 10-25-2012 Thread Starter
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Re: Got vibrations from your wind generator?

I have a Rutland 904 which is a 6-blade unit so the above deck noise is low anyway - nothing more than wind in a pine tree so haven't noticed any appreciable difference to the noise levels on deck.

But I have also modified the boat with solid rails around the aft deck and the vibration was noticeable in the railings when you put your hand on them - that is now also much better as is the noise down below.

Before, from the cabin below, it sounded like I had a outboard dingy circling my boat and had to stop the gen at night to get decent sleep - now just a very low level buzz.


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post #6 of 8 Old 10-25-2012
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Re: Got vibrations from your wind generator?

Noise from the wind gen (Air X) is bad enough that at anchor, I never leave the thing running at night. Then again I do enjoy sitting outside in the middle of a pleasant night and find any mechanical noise irritating.

I think most of the noise from ours is blade generated not vibration. I do wish they were somewhat more effective though.

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post #7 of 8 Old 10-25-2012
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Re: Got vibrations from your wind generator?

Nice 'vibration absorber' ...

There are several ways to lessen /dampen vibrations:
1. absorbing ... as you did construct
2. Balancing the blades .... find a specialty shop that does dynamic balancing, usually servicing the 'racing' portion of the automotive industry
3. Change the ('natural') frequency .... frequency can be altered by changing the mass of object that is generating the vibration; or, changing the mass of the portion of your boat that is 'sympathetically' being induced to vibrate. You can also change the natural frequency of the 'pole' that the vibration source is attached either by 'stressing' it (bowing, etc.) or changing the mass.

Vibrational frequency response (induced vibrations) is changed by altering mass and the natural frequency of the object being vibrated.
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Re: Got vibrations from your wind generator?

Quote:
Originally Posted by RichH View Post
Vibrational frequency response (induced vibrations) is changed by altering mass and the natural frequency of the object being vibrated.
The noise I had was more of a rumble I guess than a vibration - kind of like the bearings were rough but they're brand new. I'm reasonably sure it's not an out-of-balance issue.

But your'e absolutely right about mass and frequency - for many years motor car manufacturers have been attaching what seem to be random blocks of metal onto strange places in automobiles just to reduce what they call NVH (Noise Vibration Harshness)


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