AeroVantage ~ PropRotor - Adjustable Pitch (Adjustable Thrust?)

2x4

• The craft must have adjustable collective blade pitch. This is required so that the Angle of Attack can be optimized for fast forward velocities during cruise, AND for hover, where the velocity of the free stream is zero and the drag (gravity) is greater.
• I think that the optimum will be for the pilot and gyros (controllers) to have direct and fast control over the pitches of the four PropRotors. The torque is then adjusted by the system to maintain a constant rpm.
• The rotational speed of all motors is to be identical, however there may be an advantage in having a relatively small adjustment for the optimizing of the Figure of Merit during hover.

• The current idea October 3, 2008 is to have the blade pitch set by the sum of two functions;
• The act of transitioning between hover and cruise will change the pitch or the blades. The pitch will increase as the PropRotor changes from providing lift to providing forward propulsion.
• There will be a self-adjusting torque-pitch coupling between the motor and the blades.
• A further thought October 6, 2008. Perhaps this can be developed in 3 stages;

• The electrical power is controllable remotely and the transmission of this power to the motors is not an option. Is there a means of controlling pitch and maintaining rpm from within the PropRotor-Motor assemble?
• It must be noted that the flight characteristics of cruise and that of hover are very different. In cruise the resistance to axial thrust (drag and gravity) is much less than during hover, whereas the velocity (free stream & induced) during cruise will be much higher than it will be during hover.
• The Aeromatic [RPM-Pitch Coupling] must be ground set to the unique characteristics of each different airplane. The cruise/hover differences will be too great for this.
• The Torque-Pitch Coupling does not appear to have the ability to adjust the radical pitch change between cruise and hover.
• Two conditions that could be sensed at the PropRotor-Motor assembly are; free air speed (see http://www.v-prop.com/index.html) and inclination of the PropRotor.
• A crazy idea might be to mechanically tie a potentiometer to the inclination of the PropRotor and then electrically contribute to the setting of the pitch.
• Alternatively, simply have the inclination of the PropRotor mechanically contribute to the stetting of the pitch. In other words, use the RPM-Pitch Coupling or the Torque-Pitch Coupling with an additional input from the angle of the PropRotor-Motor axis.
• The angle of the PropRotor-Motor axis is the primary input then the RPM-Pitch Coupling or the Torque-Pitch Coupling does its thing on to of this.
• This may tend to feather the blades during cruise and put them into autorotation during hover.

Notes: To eventually be moved down to Item level.

• There is no need for a hollow shaft motor if the pitch adjustment mechanism and power for it are located in the hub. This will allow for power and control to be transmitted to the hub by brushed and rings.
• Might a damper be required to eliminate oscillations.
• Possible Methods of Providing Variable Pitch:
• Automatic Pitch-Changing Propeller (alternate; Pitch-Change) [Source ~ AP p.41]
• http://www.notplanejane.com/images/AeroMatic/AeroMatic%20Propeller%20Info%205-05.doc. This is by RPM-Pitch Coupling. Have hard copy.
• Jeppesen; page 41, page 42.
• http://www.v-prop.com/index.html, Silent R 1,61m V2 Automatic-variable-pitch propeller

• Patent US 2,491,862, Airplane Propeller, Dec, 20,1949. Have hard copy. Of no Value.
• Patent US 2,547,037, Automatic Pitch Change Propeller, April 3, 1951.
• Patent US 2,566,884, Preloaded Pivot Mount for Variable Pitch Propeller Blades, Sept. 4, 1951. Have hard copy. Of little or no Value.
• Patent US 2,685,933, Variable Pitch Propeller. Aug. 10, 1954. Have hard copy.
• Patent US 4,928,241, Aircraft Propeller Control, May 22, 1990
• Patent US 5,286,166, February 15, 1994, Automatic centrifugal force variable pitch propeller
• Patent US 5,931,637, Propeller with variable rate of pitch change, Little to no interest.
• Patent US 6,158,960, December 12, 2000, Propeller hub with self-adjusting pitch mechanism. This is by Torque-Pitch Coupling. Have hard copy.
• Controllable Pitch Propeller [Source ~ AP p.45]
• Above + "airplane" on Google 10,700 hits.
• Ivoprop Check that the blades can be small enough for a 1/2-scale craft (Front = 25" dia. Aft = 20" dia.). Check that the range of pitch change is great enough. Probably too slow in changing the blade pitch.
• Two-Position Propeller System [Source ~ AP p.47]
• (aerospace engineering) An airplane propeller whose blades are limited to two angles, one for take off [hover] and climb and the other for cruising.
• ["Two-Position Propeller" airplane] Google 222 hits.
• mini-imp No info on their two-position propeller.
• Constant Speed Propeller [Source ~ AP p.55]
• Perhaps a constant speed is desired to maintain an optimum tip speed. Then just vary the power. Will this work during hover when quick and frequent changing of the pitch is required?
• Airmaster Constant Speed Propeller.
• Thoughts:
• Re: Automatic Pitch-Changing Propeller:
• It appears that this method [Source ~ AP p.41] may be excellent for the transitioning between hover and cruise. However, it may not have a fast enough reaction time for flight-control during hover.
• It also appears that the Pitch-Torque Coupling method may not work for transition. I think that when transitioning from hover to cruise the free-air speed will increase -> the angle-of-attack will decrease -> the rpm will increase and the torque will reduce -> the pitch will decrease (whereas it is required to increase).
• It is looking like there must be control over the pitch.

• OTHER: Miscellaneous - Thoughtless Idea - Constant Speed Rotor
• OTHER: Miscellaneous - Thoughtless Ideas - Torque/Pitch Collective Rotor Hub

• http://www.woodcomp.cz/en/stavitelne_za_letu.htm

Scale Model:

• Have the pitch changed by only the inclination of the PropRotor-Motor assemblies; on a graduating basis.
• Thrust change will be done by varying the power and thereby the rpm.

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