Item 1574
DESIGN:
Electrotor-Simplex ~ Rotor - Hub - Overview of Gimbaled w/ Torque/Pitch Collective & Teetering Drive:
Drawing:
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The center of gravity of the above rotor will be below the aerodynamic center, which is at or near the teetering axis.
For an overview of this concern see the thread; Rotorhead: Vibration, Stability & Controllability on Rotary Wing Forum
Overview:
Cyclic control is by conventional gyrocopter pitch axial offset gimbaled rotorhead. The offset is good for forward flight as in a gyrocopter however it could be bad for any reverse flight in this helicopter. Perhaps it will be OK if the reverse velocity is severally restricted?
An interesting consideration is that of putting a small amount of roll axial offset on the two rotorheads. The object being to slightly lower the leading rotor and slightly rase the trailing rotor during sideward flight.
Collective control is by an electrical thumb control at the top of the cyclic grip. The torque driven collective is to have a hub-bar that will not bend inplane or out-of-plane but can twist about the it's longitudinal axis (blade's pitch axis). The torque that is imparted to the tops of the two stands from the mast should (may) twist the hub-bar slightly about it's longitudinal axis.
The torque-pitch collective eliminates the 3rd control rod, however, it has to be built, tested and proven.
For information on the torque-pitch collective see; Auto-Collective Rotor Hub.
For hub-bar see; Electrotor-Simplex ~ Rotor - Hub - Overview of Composite Hub-bar
The weight of the planetary reducer is ???
Notes:
Teetering Limits: Consider locating a fixed azimuth hub spring at approximately 45º azimuth to assure that the blades cannot hit the spars or pilot.
Blade Pitch Limits: Have stops in the rotor head that limits the blade pitch ranges to 0º to +9º. This way the default position is fixed for autorotation and a perturbation cannot put an excessively high pitch into the blades. Any torque beyond that which takes the pitch up to 9º will be applied directly to turning the rotor.
In addition, perhaps the offset on the offset-gimbal head will counteract an attempt by a perturbation to put an excessively high pitch into the blades.
Also see; DESIGN: Electrotor-Simplex ~ Rotor - Hub - Overview of Composite Hub-Bar
Design Notes:
Mast 1560; Extend out and curve to distribute the bending of the hub-bar when it flexes upward.
Reducer: It looks like the NEMA 42 frame Planetary reducer could be fitted in with reworking, if necessary.
Concerns:
See: Gimbaled Rotors and Gyroscopic Precession: This may not be a concern since the GP precession on the motor should be the same as the GP on the rotor.
Vibration - Rotor Induced:
The operation depends on varying the collective pitch by varying the rotor RPM. This varying rpm will very likely result in sympathetic (self-exciting) vibrations in the frame and long spars.
In addition, the changing difference in the rpm of the two rotors will probably add to this problem. Can encoders and a controller be used to keep the rpm of both rotors the same?
Perturbations and the Torque/Pitch Coupling:
Perturbations will result in short-term changes in the blade's angle of attack and this will cause short-term changes in the induced drag. This in turn will cause the torque/pitch coupling to change the blade's pitch. Unfortunately, this pitch change does not oppose the change in the angle of attack. It increases it. This may be OK since, with the craft's center of gravity ahead of the rotor, an upward gust will want to pitch the craft nose down and thereby counter the lift of the gust.
The following are three ways of overcoming this problem. Number 1 and 2 should work and number 2 may work.
- Mechanical Solution:
- Directly couple both pitch yoke to their respective pitch tube arm brackets. Any change to the pitch of one blade will cause an identical change in the pitch of the other blade, assuming that the pitch change linkages are sufficiently rigid.
- The torque producer is an electrical motor therefore an electronic accelerometer should be able to provide instant adjustment of the motor's power.
- A modified control circuitry should be able to detect a sharp non-pilot induced change in the torque and instantly adjust the motor's power.
Related Information:
Information on the Gimbaled Hub ~ Electrotor-Gimbaled ~ Rotor - Hub - Gyrobee Information
For a somewhat similar idea see; US 5,304,036 ~ Autogyro aircraft Groen.
Other Web Page at this Site on Auto-Collective ~ Torque Pitch
Note: The total weight, which varies according to the weight of the pilot, will probable effect the RRPM-Pitch-Torque balance. Can it be pre-flight adjustable to suit each flight?
OTHER: Miscellaneous - Thoughtless Ideas - Torque/Pitch Collective Rotor Hub
OTHER: Miscellaneous - Thoughtless Idea - Constant Speed Rotor
OTHER: Flight Dynamics - General - Cross-Coupling # Torque-Pitch
OTHER: Flight Dynamics - General - Lead-Flap Coupling, for Intermeshing Rotors & Pitch-Lag Coupling
OTHER: Flight Dynamics - General - Pitch-Lag Coupling
DESIGN: Single-Bladed All Electric Rotor- Rotor Hub - Pitch-Torque Coupling
DESIGN: Electrotor-Simplex ~ Rotor - Hub - Overview of Gimbaled w/ Torque Collective B
DESIGN: Electrotor-Simplex ~ Rotor - Hub - Overview of Gimbaled w/ Torque/Pitch Collective & Teetering Drive:
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Initially displayed: October 11, 2007~ Last Revised: May 2, 2009
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