Blades / was tower vibration [RE-wrenches]

[Hugh Piggott]

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At 5:47 pm -0400 30/4/06, Kirk Herander wrote:
>
>Blade 1: 430 grams (15.3 oz)
>Blade 2: 450 grams (16.1 oz)
>Blade 3: 545 grams (19.5 oz)
>
>Blade 3 is 20% heavier than the other two.

Blade weight is a crude measure of balance.  To balance the blades 
you will need to measure the moment of weight.  this is simpler than 
it sounds.

Set each blade up so that it rests on a pivot at or near to the 
centre of rotation.  I use a blade clamping device with a pivot at 
the correct place just inboard of the blade root.  Then measure the 
weight at the tip.   measure this at the same place on each blade as 
near to the tip as convenient.

For each blade, this tip weight should be the same.  This may mean 
adding several pounds of lead to a suitable location near to the root 
of the blade in this case.

Of course if the imbalance is caused by moisture then a period of 
very dry weather will make it shake again :-)

Replacement blades would be a good way to go, along with careful 
drying out and re-sealing of the original set to keep as spares.
-- 
Hugh

Scoraig Wind Electric
http://www.scoraigwind.co.uk/

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