Prompted by a plea for having no wind
generators in another thread:
KISS Balancing and wind generator noise
noises aren't entirely the fault of blade design.
Sometimes it's also a matter of balance.
I have one of the large-fan versions, a KISS, with which we are well
pleased, despite its having been very abused in our 14 years of use
(which included a 12-hour salt water
immersion and an extended fresh
immersion, both of which responded to a spraydown with fresh
, an air-dry, and spray with Corrosion
Block before reassembly).
However, a balancing axle is available. A static balance may match by
weight, but does not include rotational forces. If you have a
different model wind generator
, you may have to fabricate a balancing
axle; it will be well worth the effort.
KISS is no longer made, but new blades and hub are available from the
prior manufacturer (now retired). The blades are gram-matched,
ostensibly meaning that when you mount them, all is good.
Not so fast, Bucko. Dynamic balance that rig!
I used lead tape. In order to balance (see below on my modus), it
took over a foot on two of the blades. It has to be done in a
, of course. And, natch, I attach at the back
side of the blade so as to not muck with the aerodynamics.
Here's how I measure whether I'm truly balanced or not:
My not-perfectly straight-flat workbench in the walkthrough has a
fiddle. I find a level spot (how full the tanks
are, and davits
so on affects that) for one end of the axle, and use an aluminum
torpedo level for the other. If both ends are level, it should not
rotate if it's balanced. When it IS balanced, a slight tilt of the
level (max bubble-touch, not way off) will cause the blade to rotate
with the axle heading downhill. As my axle ends are about 1/4 inch,
you can imagine that it takes a fair amount of torque to move a 30"
blade - but, while slow, it WILL rotate, but not do so when level.
I put on the tape in amounts I estimate will work
(it comes with a
plastic sheet backing, like you'd find on double-stick tape rolls),
sticking the ends lightly, initially. I start with one end relatively
close to the hub. Some fiddling with how far out the tape is, and I'm
close. When I have it reasonably close, with tape on two of the three
blades, I get down to fine tuning.
By "close" I mean that the blades will rotate, but only slowly, with
the bare blade light. By that I mean that regardless of whether I
start the blade at 8 or 4 in clock position, it wants to rise to the
top from there. I then remove all the protective tape and fully
attach the lead.
I then start, with a utility knife, removing segments of the tape from
the ends to balance (slice gently so as to not damage the blade).
Keep your pieces; you likely will have to fiddle with matching up the
two weighted blades; mine are as small, as I get close, as 1/8" - but
if handled carefully, will re-adhere. I start relatively large and
get smaller as I approach nirvana
In the end, my metric is that the unweighted (now "heavy") blade, from
either 10 or 2 clock positions, takes a minute or more to reach
bottom - and that I can make the smallest adjustment to 'level' and
also have it turn.
The difference, at least in our KISS, is stark. A mere
Whiiiiissssshhhh, instead of a moan or groan or roar.
I suspect that any blade set could be similarly balanced, whether KISS
or not. If you can put your hand on however it's mounted, and can
feel vibration in the pole, likely your blades are not really
balanced, even if your blade weights are within micrograms of each