That game of darts...

[Learjet]

With all due respect....a well known aeronautical engineer, 25year rotorcraft president of the EAA America, well known gyro manufacturer.............all agreed with me. I am no expert and do not hold there qualifications.....so it is difficult to not believe them......is it not???????

I will pick there brains a little more and get back to us non experts.........

Regards

Hi Ebie,
If he can substantiate his thinking - just about every helicopter / rotor wing principles of flight reference manual and text book will have to be re-written!

I'm not an aeronautical engineer and I'm very, very open to having my understanding corrected!
Rotor aerodynamics is a hugely complex subject and not one that I even begin to feel I have even the slightest grasp and understanding of beyond the basic and general principles of precession and what is visibly determinable on the rotor pitch change demonstration I referred to earlier.
I don't have a dogmatic view on the topic - and I simply seek to share what my current understanding and limited knowledge allows - which currently is that gyros are not weight shift controlled aircraft by definition.
If you can provide the links to any literature to support the theory of gyros being weight shift I promise to read it with a very open mind.

In the meantime - hopefully we are all in agreement that the rotor blade pitch can and does actually change with cyclic input?

P.S. I'm really finding this discussion most interesting - please don't see this as a disagreement, but rather me challenging the weight shift theory as an opportunity to learn more about rotor behaviour - even if It turns out I am completely wrong in my understanding - well I will have learned a lot more which is a good thing!

[John Boucher]

Use it lose it .....

http://www.asra.org.au/Control.htm

[saraf]

http://youtu.be/RfGDzgyeZPc

[crazydoc]

Yes Learjet, to me you have a big point there (your second last post). The physics pointed out to us by John Bouchers reference is just to difficult for me to understand ,so i have to see it from a different angle. thus: If i look at a microlight and how the guy hanging on his harnass , is throwing his weight all over the show with quite big inputs( far away from his original hanging position) just to make this light fuselage(basically just a wing) go left or right or up and down. I can just imagine how far my gyro fuselage must move to the side to shift the cpg to make my much heavier gyro move to the left right or where ever and that doesnt look like it is happening. My rotordisc plane vs fuselage angle only changes slightly when i initiate movement in any direction through the stick. And imagine even much heavier gyros. I know this is put very simplistic but sometimes that is all, uneducated people (in physics off course) like me,can go on.
So whatever other physics ( which i will try and figure out reading Johns reference article probably a hundred times ) make the gyro turn, to me Learjets visual anology changes my mindset back away from weightshift again and im probably back on the GSP theory (plus others??) . Sorry Eben

[Learjet]

Thanks crazydoc, but you know, the more I try to learn about rotor aerodynamics - the more I realise what an immensely complicated subject it is - so much so that I certainly don't see this as a "who is right who is wrong" situation - all of us may be at slightly different points along the road to rotor enlightenment - but the path is long and our knowledge is little.
My understanding is still taking baby-steps!

[Gyronaut]

Personally, in an open and frank discussion about aerodynamics, I take exception to clicking on a link that says "Never Argue With Stupid People"

http://youtu.be/RfGDzgyeZPc

What is Eben Mocke Jnr saying to us??
That a Gyro is a weight shift and we're all stupid? I think not….

ffs

[saraf]

Hi Len,

Most def NOT..

it was the only laughable, animated thing i could find to put some humur to this situation and discussion.

Nobody on this forum is stupid.

Regards
Eben Mocke Jnr.

[saraf]

http://www.rcgroups.com/forums/showthread.php?t=1358183

Interesting.........

[crazydoc]

Interresting? .....is an understatement Eben. .. I ll have to go and sit and think about this one. Very long and hard.

[Learjet]

http://www.rcgroups.com/forums/showthread.php?t=1358183

Interesting.........

The drone is using servos to change the CoG relative to the "wing" (which in this instance is a series of ducted fans) - so I concur that this is weight-shift.
But as a stupid person (and not wishing to argue) I can't see how this is relevant to a gimbled / teetering rotor?
The drone's static / fixed thrust arrangement is such that it wouldn't make any difference if the source of lift was ducted fan, turbine jet or rocket propulsion?
With one little exception - because it is using ducted fans with spinning "discs' - these must create torque and precession (precession being the dominant force I still believe we leverage to effect disc AoA change in a gyro), however because this drone is relying on weight-shift the builder has had to include gyro-stabilization to counter the generated torque and precession forces or it would be uncontrollable. If the torque & precession forces were not present (as per in the gyro = a weight shift claim) - then surely this drone wouldn't need to be gyro-stabilized?


P.S. Ha! I see the drone's builder has confirmed by stability suspicion in a later post

The gyro stabilization is essential for stability. Without it I doubt anyone could fly it RC

[PTKay]

Use it lose it .....

http://www.asra.org.au/Control.htm

Thanks for the link, John.

"You can bring the horse to the water, but you cannot make it drink."

You can link and quote as many scientific evidence as you wish,
the "flat earth society" will always find their arguments to contradict it.

Yes, Eben, you are right.
There is no reason to argue wit stupid people.

There is a saying:

"Don't argue with stupid people, they will pull you down
to their own level and beat you with their experience there."

[Magnifan]

Here is a thought experiment which may help to visualise the situation. If you put the rotor blade in the fore and aft position, in line with the flight path, and move the cyclic fore and aft whilst holding the blade fixed you have no effect on the airframe. The blade simply teeters. There is thus no way that weight shift can cause the aircraft to climb or descend when the rotor is in that plane. If you set the rotor blade 90 degrees to the line of flight and do the same thing, all that happens is that the rotor's angle of attack changes, there is no way that weight shift can cause the aircraft to climb or descend when the rotor is in that plane either.

So why does a forward and aft movement of the cyclic cause the aircraft to climb or descend? When you pull the cyclic back, the change in angle of attack when the blade is at 90 degrees to the flight path causes an upward force on the advancing blade and a downward force on the receding blade. This causes the advancing blade to precess upwards reaching its maximum at 90 degrees to the position where the force was applied, i.e. in front of the aircraft, tilting the disc upward and causing the aircraft to climb. The jury is still out on how much of the precession is due to purely gyroscopic forces and how much is caused by the forward moving blade "flying" upwards through the air as a result of its angle of attack change, which also results in the blade moving upwards and reaching a maximum 90 degrees from where the angle of attack change occurred. This is called aerodynamic precession.

Note that the cyclic can have no effect on the rotor in the fore and aft plane and can only change the angle of attack between 90 degrees and 180 degrees. The amount of angle of attack change caused by moving the cyclic is at a maximum at 90 degrees and falls to zero at 180 degrees, reaches a negative minimum at 270 degrees and returns to zero at 0 degrees. O degrees being at the rear of the aircraft.

[Gyronaut]

Magnifan
+1