Thanks Adriaan. the pendulam safety system outlined in kd485 is really interesting, chapter 7 in kd35 makes me wish I had done alot better in school!
Such a great resource, thank you.
Im trying to envisage what you describe and I have tried drawing it out and using cut pieces of card to understand, and im afraid im failing. In this design, you mention the blades are hinged in the middle, so are the hard fixed or hinged at the hub to to allow them to move forward?
I am quite aware that im revisiting obviously flawed and long proven to be hopeless concepts. The problem is that straight away its not obvious to me, (or guys I know) why they wont work and obviously flawed designs arent easy to find examples of! So i do apologize if it seems Im insulting the long established work of the likes of Jacobs, Piggott, Bergley, Proven etc by submitting these.
But they stick in my head and sometimes keep me from sleeping until I can see why they wont work.
Im currently reinventing the wheel (cutting wheel on one of my stump grinders) but thats a much simpler thing than a wind turbine.
When you talked about the centrifugal forces countering the blades pitching backwards and how little they had to pitch backwards to loose power, it got me to thinking.
Again not to any real scale or sense of mechanical reality.
Under high wind speed, centrifugal force forces the blade from its "rested" between the "elbow" and hub plate to a pitched position
1) Where the blade elbows, there would be alot of stress as centrifugal forces try to straighten it (the elbow could be much longer or different angle or braced of course)
2) There would be bending stress on the blade as the centrifugal force trys to counter the pitch angle forced on it by the elbow. dependant on the stiffness, weight and rotational speed, the force could well win.
Both of these would possibly be a cause of metal fatigue over time.
Third issue would be that the blades would not pitch far enough back as required to control RPMs or wind force on the blades to prevent damage.
The more I look at this the more variable pitch systems such at found on the windspot seems simpler to build!