|
One way to balance
your windmill turbine.
String Method, by forum members
Gill with a little help from Klaus.
"I have found this method most
satisfactory. It gives a high degree of accuracy for
the static balancing of a prop.
Here is an action shot with no movement
evident.
With this method the prop is a beam
balance and the string entry to the plug is the fulcrum.
A little balance theory now:
There are 3 basic actions (movements)
of the beam about the fulcrum. These are influenced
by the centre of gravity in relation to the fulcrum.
The first action is Accelerating.
This is bought on by the centre of gravity being above
the fulcrum. When balanced, if the beam is deflected
from balance, it will continue to move at an accelerating
rate to the limit of it's travel.
The second action is Neutral. This
is bought on by the centre of gravity being on the
fulcrum. If deflected from balance, the beam will
remain in that position.
The third and the one we use is Vibrating.
This is where the centre of gravity is below the fulcrum.
If deflected from balance the beam will return to
the balance state.
As the centre of gravity is moved
from just under the fulcrum to a much lower point,
the beam goes from being Sensitive to Dead. This means
that more weight is required to bring about the same
change in balance.
Here is the stub off an F&P shaft
I made to plug the hole and provide a fulcrum with a
centre of gravity adjustment.
The main thing to note if you make your
own, is that for consistency, the thread must be firm
and the string must be tight through the string hole.
Method:
- Pick a dead calm day or go indoors
where no draughts.
- Fit the plug to the prop.
- Lower the C of G (centre of gravity)
for a dead action.
- Add weight for a horizontal balance.
- Raise the C of G and adjust with
weight as required.
- Repeat this step until a very sensitive
action is achieved.
Never fear, most will go to far to a
neutral or accelerating action and get odd and confusing
readings. Just go back a little.
Well that's how I do mine. Hope you
have fun.
Gill"
"Hi Gill,
Let me see if I got that
- what you call the 'fulcrum' is the
top end of the threaded rod, where the string exits?
- the balancing 'action' positions
are adjusted by screwing the threaded rod in and out
(up or down actually) on the splined stub?
- your propellor hangs backside up
and the washers (or lack of them) are your balancing
weights?
Did I get it? Very clever, your method
that is.
Klaus"
"Your spot on working out what
I didn't say. It's a YES to each question though the
backside facing upward is because the CofG is closer
to that face on this prop.
If the blades protruded forward and
the C of G was to be near or even further forward than
the front of the hub, then that face would need to be
uppermost. In such cases the threaded rod can protrude
past the splined stub to position the fulcrum in correct
relation to the C of G even if the C of G appears to
be in no-mans-land.
Gill"
|
