Is anyone aware of a windmill using vanes for an elliptical surface?

[MattM]

I was looking at hydraulic pumps and when I saw a vane pump it got me thinking of windmills.  Basic principle of a vane pump is an offset rotor using sliding vanes to elongate/shorten as the rotor rotates.  It is not a perfect hydraulic solution, but it is very efficient.  I can see how the basic vane length control could be applied to a windmill.  The vanes are pressurized or spring loaded so that they expand out to the outer circle.

I'm not sure if this would add anything to windmills, but it is an interesting pump method.  Perpetual motion machines always do quirky ideas like this so it probably has no merit.  On the other hand Google pops up a patent application for windmill blades that have variable length.  Could this be what they expect to make?

[Frank S]

MattM; the patents for the windmill vanes are much like many (do to do) patents  some have Merritt while others are nothing more than the ability to get one's name in publication.
 However that being said several windmill makers of yester year tried many things to extract as much energy from the wind at a given moment while at the same time trying to limit the run-away speed.
 there were variable pitch variable length variable width vanes even counter rotating.
 for variable length the problem of countering centrifugal force is the big issue the faster something tries to spin the higher the 'G' forces are on the vanes, these forces had to be mechanically controlled one way to do this was   by an elliptical tract and center pivot for each vane the faster the rotational speed and the harder the wind sheared off the leading face to the vane caused it to pivot slightly left or right this reduced the outer diameter of the total fan area. it also reduced the flow through volume capacity Try ti visualize an iris set up in a camera lenz only instead of reducing the center opening area it would be reducing the outer circumference Very difficult to control.
  Another example of reducing the vane length or outer diameter area and total surface would be to tilt the vanes inward from the outer to the center . A company in California did this quite successfully for a while by making the fan a split vane set up whereby the inner set of vanes were of a fixed size and pattern. The outer vanes had a pivotal axis at some percentile above 50% of their total swept area. while at rest or low RPM the total fan would be a huge diameter but the harder the wind blew the vanes would be forced to open from the center causing the outer diameter to reduce. think of how a flower closes at night drawing its petals inward.
 one other type of area reduction was to reduce the vane width by sliding one van into another Think of the slats on an large airliner they extend outward on take off and landing to increase the wing swept area at low speeds and retract at flight speeds to reduce drag and overall lift. also think of a geisha fan she expands it to cover her face while preforming and to add a certain provocative entertainment. (One note of trivia though most of the performing Japanese Geisha's were male).
 One last method of fan area reduction was the bent vane umbrella the tip or point faced into the wind and the harder the force on the surface the tighter it tried to close reducing the swept diameter.
 I hope this completely confuses you or addresses part of your question.
 Windmill fan/ sail / vane design & technology was a passion of mine back in the mid to late 60's ,
 Oh yes I almost forgot 400 years ago the Dutch developed a way to retract the fabric on their windmills by the use of ropes  in  High winds they would catch the end of a rope as the vane swung past and untie a slip knot or pull  the knotted end of the rope to another notch in the frame. think of slightly lowering the sail on a square rigger boat in high winds this was very dangerous and until all sail areas of every vane frame were matched the whole fan was out of balance Lots of FUN Yum!!

[MattM]

You made sense and grabbed the meaning to my question.  Thank you.  I wish there were YouTube videos if for nothing else to see the novelty of it.

[tanner0441]

Hi

There have bee a few designs shown on here with something similar from hinged blades , to things like venetian blinds.
The thing with an eccentric vane pump is it is a positive displacement pump which is OK on hydraulics but not very good when you don't want to stop the air dead.

Also they are drag devices and are therefore lower than a lift blade for efficiency.

Brian.

[Frank S]

Now that is the scariest thing I've been told all day

[tanner0441]

Hi Frank

Yes and if you want a good hydraulic pump that will run cool and deliver real pressure you would go for Berman Gear or Concentric.....

Brian

[MattM]

The only thing I could see a vane approach do was add complexity.  The iris idea might BD simpler to use than trying to balance furl devices.  You are just reducing the blade efficiency as you shrink said radius as wind blows harder rather than hoping it furls.  I can think of at least two ways to do it.