Question for Hugh Piggott [RE-wrenches]

[hugh piggott]

<x-flowed>>Hugh,
>     What can you tell me about field balancing a blade set on a Whisper
>3000?

I have never done it but it would be like any other.

>  I have the balancing sheet that Elliott Bayley sent me but that only
>balances them along the horizontal axis and center of gravity. I'd like to
>know if there's a better way to do this and if it's possible to do on site?

I have not seen Elliot's instructions.  I would aim to balance it in 
two dimensions.  I would remove the blade, place it flat, and find 
the exact centre.  Balance it on two different knife-edges through 
the centre, each at 45 degrees to the blade span direction.  I 
normally make a special jig from plywood or thin metal which bolts 
onto the blade centre, and I mark very exact lines or make punch 
marks (to fit wood-screw-tips) to set up a pivot on it.  Sit it dead 
level and it should sit happily. I then reverse the jig and do it 
again to double check.  I usually have to add pieces of lead to 
correct for imbalance.

A cruder way to do it on the machine shaft is to measure the amount 
of weight required to make it start turning, in a number of 
positions, and work to make this starting torque the same from 
anywhere.

There are other factors.  Once balanced, you have to check that the 
blades track each other precisely through space on the machine.  And 
finally that the blades angles are the same.  I had an experience 
with one wpt machine where a blade had warped, and was out of pitch. 
That rattled worse than a badly out of balance rotor, although 
perfectly balanced.

>My other alternative is to send the blades back to the factory....turn
>around is typically 3-6 weeks and means 2 trips to this remote site.

give it a go.  If I can make the above clearer, or help any further, just ask.
-- 
Hugh

Scoraig, Scotland
http://www.scoraigwind.co.uk

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