What do you think of this rotor?

Aviator168

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I don't know what the design is. Looks like as long as it is loaded, it will keep spinning doesn't matter up or down.

 

Jean Claude

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If the pitch setting is 0 degrees, then the rotor turns as well whatever the direction of the air flow.
But 0° gives a lot of profile losses
 

XXavier

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The 'Wells turbine' is an example:



 
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C. Beaty

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A model rotor with blades made from flat sheet metal will autorotate in either direction and also with airflow from either direction. It will also flutter when its critical speed is reached.

2 or 3 small machine screws (nose weights) mounted near the leading edge at ~ 70% radius will prevent flutter.

A strip of 0.020” aluminum 1¼” wide, 16” long with teeter hinge in center illustrates this perfectly.
 
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XXavier

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I think it is just an articulated rotor but on flapping. No blade advance and pitch compensation.
It doesn't seem to be articulated, and indeed It doesn't need to be. A rigid zero-pitch rotor blown by a mass of air moving parallel to its axis will turn around that axis, the torque being due to the projection of the aerodynamic force on the plane of rotation... Of course, in order to get the needed amount of projection, you'll need also some amount of pre-rotation...
 

C. Beaty

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Watch the “Magic Rotor” on Youtube. Each blade is on a torsion bar with effective hinge near the leading edge. With load, each blade twists nose down.

The person presenting the video doesn’t understand autorotation and thinks he’s invented something.
 

XXavier

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Watch the “Magic Rotor” on Youtube. Each blade is on a torsion bar with effective hinge near the leading edge. With load, each blade twists nose down.

The person presenting the video doesn’t understand autorotation and thinks he’s invented something.

Perhaps, in the case of that toy, the blades do flex and twist nose down, but that's not necessary for autorotation, that would take place even if those blades were completely rigid and non-deformable...
 

Aviator168

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If you the blades are link in pitch, when the advancing blade pitches down, the retreating blade pitches up, the blades don't need to be flapping any more. Mast bumping won't be an issue, right?
 

XXavier

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If you the blades are link in pitch, when the advancing blade pitches down, the retreating blade pitches up, the blades don't need to be flapping any more. Mast bumping won't be an issue, right?
I'm not sure if a rotorhead with such a linkage does actually exist. Something like that was invented in the 1930s, I think... A 4-bladed rotor with each pair of opposed blades linked in pitch... A variation of the 'floating hub'...
But I'm not sure. It's just a fuzzy memory...
 

Vance

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If you the blades are link in pitch, when the advancing blade pitches down, the retreating blade pitches up, the blades don't need to be flapping any more. Mast bumping won't be an issue, right?
What do you feel would cause the advancing blade to pitch down and the retreating blade to pitch up?

It appears to me with a two blade semi rigid rotor the advancing blade pitches up and the retreating blade pitches down.
 

Doug Riley

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I wonder about the magnitude of this rotor's thrust (if any!) at various reasonable disk angles of attack.

Unlike windmillers, we rotorcrafters are interested in the rotor's thrust, not its torque as such.
 

Aviator168

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I'm not sure if a rotorhead with such a linkage does actually exist. Something like that was invented in the 1930s, I think... A 4-bladed rotor with each pair of opposed blades linked in pitch... A variation of the 'floating hub'...
But I'm not sure. It's just a fuzzy memory...
The linkage is simple. Just allow the pitch to freely float and the two blades are hard linked together so if the pitch of goes up, the other much go down. I have not figured out how to set the pitch during flight; but a preset pitch is possible.
 

Jean Claude

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Doug,
Calculated comparison with usual pitch setting of 3 degrees and with 0 degrees (Rotor 7 m x 0.18 m, NACA0012, Forward speed 90 km/h, Lift 2500N)
With the pitch setting of 3 degrees: Rotor drag 473N and 400 rpm
With the pitch setting of 0 degree : Rotor drag 786N and 521 rpm
 

Aviator168

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Doug,
Calculated comparison with usual pitch setting of 3 degrees and with 0 degrees (Rotor 7 m x 0.18 m, NACA0012, Forward speed 90 km/h, Lift 2500N)
With the pitch setting of 3 degrees: Rotor drag 473N and 400 rpm
With the pitch setting of 0 degree : Rotor drag 786N and 521 rpm
Wow. I was not expecting that drag is a lot higher at 0 AoA.
 
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