Dynamics ~ 2 Blade Rotor w/ Offset Flapping Hinges
Join Date: Jun 2001
Location: Australia
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lu
you > Now the observer is told to stand on the driven axis. Looking down on the rotating disc the observer will note that the blades are equally disposed at 90-degrees to each other.
i find this very hard to agree with lu, but thanks for the expenation.
i find this very hard to agree with lu, but thanks for the expenation.
Iconoclast
Join Date: Sep 2000
Location: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
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Don't shoot the messenger.
To: vorticey
These same descriptions can be found in several helicopter principles of flight text used in various US Universities. I am not saying they are true, just that this is how the subject was explained to the readers of the texts.
To: Dave Jackson
You are waging a war of words and their meaning. It is the same war I was involved in when I discussed Gy@#$%^&*c Pre^&**%#n. You will note that many of the corrective comments about your choice of words did not come from the US or Canada. They are coming from Oz, New Zealand and the UK. Accept the fact that neither of the participants in the discussion will ever change their views even though you are both discussing the same subject.
These same descriptions can be found in several helicopter principles of flight text used in various US Universities. I am not saying they are true, just that this is how the subject was explained to the readers of the texts.
To: Dave Jackson
You are waging a war of words and their meaning. It is the same war I was involved in when I discussed Gy@#$%^&*c Pre^&**%#n. You will note that many of the corrective comments about your choice of words did not come from the US or Canada. They are coming from Oz, New Zealand and the UK. Accept the fact that neither of the participants in the discussion will ever change their views even though you are both discussing the same subject.
Thread Starter
Join Date: Nov 2000
Location: Vancouver, BC, Canada
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It starts with a dream. (perhaps it ends as a nightmare. :)
The currently designed rotor (sketch D) will offer better control but it will also exhibit vibration at large displacements of the cyclic stick, when the tip path plane is not parallel to the rotor mast plane. This is due to the 2P change in the tipping moment on the mast, as the 2-blade rotor rotates. [described in blue above.]
It looks like the following is a solution to this vibration problem.
The hub in sketch D is now to be constructed as a 3-blade rotor, instead of the previous 2-blade rotor. The former tie-bar between elbows of the two yokes is now replaced by a triangular tie-bar, which connects the elbows of all three yokes. This means that the roots of the three blades teeter (flap) in an interlocked unison.
Temporary Coriolis (Hookes Joint Effect), will now input a lead-lag between the three blades as they flap. But, delta-3 by flap hinge geometry also inputs a lead lag into the blades as they flap. Therefor the angle of the delta-3 can be set so that the amount of lead at a specific angle of teeter (flap), due to the Hookes joint effect, can be absorbed by the same amount of lead input by the in-plane component of the delta-3 angle.
In other words, as the blade flaps up, the delta-3 will absorb the Hookes joint's lead and as the blade flaps down, the delta-3 will absorb the Hookes joint's lag. Sketch of rotor hub.
If anyone is still reading this thread and can find fault, please say so. Thanks.
Dave J.
It looks like the following is a solution to this vibration problem.
The hub in sketch D is now to be constructed as a 3-blade rotor, instead of the previous 2-blade rotor. The former tie-bar between elbows of the two yokes is now replaced by a triangular tie-bar, which connects the elbows of all three yokes. This means that the roots of the three blades teeter (flap) in an interlocked unison.
Temporary Coriolis (Hookes Joint Effect), will now input a lead-lag between the three blades as they flap. But, delta-3 by flap hinge geometry also inputs a lead lag into the blades as they flap. Therefor the angle of the delta-3 can be set so that the amount of lead at a specific angle of teeter (flap), due to the Hookes joint effect, can be absorbed by the same amount of lead input by the in-plane component of the delta-3 angle.
In other words, as the blade flaps up, the delta-3 will absorb the Hookes joint's lead and as the blade flaps down, the delta-3 will absorb the Hookes joint's lag. Sketch of rotor hub.
If anyone is still reading this thread and can find fault, please say so. Thanks.
Dave J.
