Just an afterthought: You CAN'T balance the blades on the generator itself.
The bearing friction and just the nature of a PM generator do not allow
the blades to freewheel.

Doug

"GeoffSchultz" wrote in message
oups.com...

Doug Dotson wrote:
"GeoffSchultz" wrote in message
oups.com...
I recently had to replace 2 of the blades on my KISS wind generator
due
to small cracks which I found near the mounting holes. The blades
were
replaced with spares purchased at the same time that the generator
was
purchased. One of the replacement blades weighs a lot more than
the
other blades and none of the blades weighs the same, even in the
complete spare set. This is causing a lot of vibration.

KISS supplies a lead tape to place along the back side of the
blades to
balance them. I made a scale to balance the blades such that they
all
weighed the same. One blade ended up with 4" of tape, another with
12"
and one with 18". Even though they weighed the same, it was even
worse
than before.

So, does anyone have any ideas how to determine who to determine
where
the tape needs to be placed?

-- Geoff

P.S. I'll be out of Internet access for a few days.

You can't balance them by statically weighing them. My KISS
was able to be balanced by trimming maybe less than an inch of the
tape
from 1 or 2 of the blades. Did you try and balancing them according
to the
procedure in the manual? I had no trouble doing it that way. The
balance of
the blades depends not only upon the weight but the distribution of
the
weight
along the length of the blade. ie a bit of weight further out on the
blade
has
more affect than the same amount of weight close to the root. Also,
replacing only 2 out of three blades may not be a good idea. My KISS
blades
after 3 years of service have clearly eroded. I do have a spare set
and I
suspect
that the new blades probably weigh more than the original ones.

My suggestion is to use a complete set of new blades and use the
original
balancing technique.

Doug
s/v Callista

The problem with replacing all 3 blades is that the 3rd blade of the
replacement set has a very large front to back warp to it which causes
a lot of vibration on it's own. To explain further, when the blades
spin the tips of the blades should rotate on the same "X" plane and
have little "Y" plane variation. However, the 3rd replacement blade
has about 5/8" of Y plane variation.

All of the blades were stored together and wrapped in foam. The
original set had some variation, but I was able to correct that by
placing tape shims on the hub where the blades attach. The 5/8"
variation is too much to correct that way, so I'm only using 2 of the
spare blades.

I suspect that this is due to differences in the manufacturing/curing
process. They're made in Trinidad and I suspect that the process may
have a lot of variables in it, and this has lead to the differences in
the blades.

In the past I've tried to use their prescribed method of balancing the
blades, which requires turning the blades in a windless environment and
determining which blade is heavier. That's great if you're somewhere
where the wind isn't blowing, but in the Caribbean that's almost never.
Moving the generator to a sheltered location would be a major project,
so forget that.

I thought that this would be similar to balancing a tire or a ceiling
fan and I hoped that someone would have a good method to achieve this
given my environment.

-- Geoff