Does the blade retreat from the hub radially...and ... at the same time do something else.
The black cylinder appears to move out of the white pipe whilst the blade moves up and rotates around ... is that it?

Are two systems working in tandem, or is one system(blade outwards movement) controlling the twist, as well as the black cylinder with the "ball joints" (which appear slightly adumberate at this stage.)

Before I was just ignorant, now I am confounded as well.

Can the black cylinder moving out of the white pipe do away with the radial movement, and so get rid of one more variable (dynamic blade length and tip to tip balance) - radius change of the blade.

Please keep up the good work as it will help me design a variable system for over here one day.

You'll never get it to work ya know....your bench is too tidy....a messy bench yeilds the best results.... ask Joe's brother.

It is a really nice and simple design.
I see no reason, the same design couldn't be done such a way that it would start in a course pitch to help low wind start up and finally would go too flat to prevent too high speeds.

http://www.eoltec.com/English/Main_en.htm

if i get it properly, on every blade there is spring and small metal plate with weight at the end of it.

when turbine is turning on desired speeds, all is in balance. but, when stronger wind cause faster and faster turning, weight on the blade becomes stronger than spring and starts to "pull" out blade from basic attack angle to reduce rotation speed.

You have had an excellent idea that has opened your mind to understand such principles.

In the Pitch control environment, there are two common RPM controllers that do not require electrical setting means -- this for the small wind mills

One is the Centrifugal Pitch control
Another is the Torque Pitch control

And an improvement, for some, is the marriage of both

Torque Pitch control is the most logical with present available technologies and one that is quite appealing when set with negative feedback.

This negative pitch control sets the blades to an angle that requires certain air velocity to start the rotation to produce a minimum energy for the load to start acting to set the blades angle for the RPM defined by the generator load and torque that may be higher than normal.

Centrifugal pitch control sets the blades to "flat" angle to allow the turbine to start at low wind velocities and the Centrifugal elements sets the Maximum RPM that the mill may operate even when fully loaded.

The Torque controlled blades are set by the load, so if the load goes away the negative feedback forces the RPM to lower is number that may be just enough to rotate and initiate power generation if the load requires power to reset the turbine to the LOAD RPM needed to fulfill the load requirements ( this is assumed that the wind has enough energy to supply such power).

The Marriage of Centrifugal and Torque control is the ideal case, specially in low wind regimes areas.

The centrifugal part sets the blade for the best angle to start at low wind velocities and once rotating (set to an RPM just enough for the load to set the LOAD RPM) for the Torque pitch to enter in action, and centrifugal elements are not longer active.