OTHER:Rotor Concept - Independent Root & Tip - Torque Tube Method
~ A proposed means of achievingActive Blade Twist ~
Proposed Method of ProvidingIndependent Root and Tip Pitch Control:
The skin of the blade is firmly attached to the spar at all locations along the span. The spar consists of unidirectional pultruded carbon thread running spanwise. The skin and the spar twist in unison. The root of the blade is controlled by the root pitch horn. The tip of blade is controlled by the tip pitch horn. The tip and the tip pitch horn are connected by a torque tube, which is located in the middle of the spar. The torque tube consists. Of filament wound carbon thread at a bias.
The torque tube is bonded to the inner surface of the spar by an elastomeric material along much of the span. This elastomeric assists in transmitting a progressive twist to the tip of the blade
This method is currently being developed for the UniCopter.
The intent is that the tip control be the main or sole provider of pitch and roll. Therefore, it must be noted that on the retreating side, as the tip speed ratio approaches 1 the effectiveness on the retreating side will diminish.
More importantly, at speeds greater than mu = 1 the pitch at the tip when near azimuth 270º will be in reverse velocity. This will result in the blade tip pitch generating a force that is the opposite of what is desired.
Will the torque tube c/w the elastomeric bearing resistblade flutter, particularly when the blade is subjected to reverse airflow?
If this method ends up not looking feasible then the next option isOTHER: Rotor Concept - Independent Root & Tip - Floating Root Method.
Note that if the Torque Tube Method is unable to provide sufficient torque to twist theAbsolutely Rigid Rotors blade then the Aerodynamic Tip Method will probably be unable to do it. Perhaps, the Aerodynamic Tip Method may work well for conventional flexible rotors.
US patent 5730581, March 24,1998 is similar to the above except that it uses tension in the spar to effect torsion in the skin.Have hard copy.
US Patent 6,382,556 ~ VTOL airplane with only one tiltable prop-rotor ~ Filed December 18,2000. It describes a blade twist method similar to the one on this page. Have hard copy.
US patent 7,695,249, April 13, 2010, Bearingless rotor blade assembly for a high speed rotary-wing aircraft
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Initially displayed: April 17, 2003 ~ Last Revised: April 24, 2010
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