1566

Item 1566

DESIGN: Electrotor-Simplex ~ Rotor - Hub - Overview of Gimbaled w/ Torque Collective A

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.

Drawing:

The two modifications from the basic gyro rotorhead are;

The pitch hinge will become two separate hinges, on a common axis, except that there will be a space between these hinges where the motor-reducer will be located. The roll hinge will be split in the same manner as the pitch hinge, for the same reason. Using the above picture as an example, the whole assembly from the rotor bearing down to the lower plates will be opened up to accommodate a 4" diameter motor and planetary reducer, which will both move with the rotorhead.
The thinking is to make the hub-bar of composite material. It will act as a tension-torsion strap and thereby allow the torque between the gearbox and the rotor to set a 2-position blade pitch mechanism.

Cyclic control is by conventional gyrocopter offset gimbaled rotorhead plus torque driven collective.

The idea for the torque driven collective is to have a hub-bar that will on 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 problems.

The idea is to have both stands rotate independently about the teetering axis. The teetering bearing in each stand will handle rotation about the teetering axis and a smaller amount of rotation about its vertical axis. Torque from the mast to the hub-bar, via the two stands, will cause the hub-bar to twist about the blades, with the diametrical corners climbing or lowerinng together. This twist as generated and allowed by the two stands.

For information on the torque-pitch collective see; OTHER: Miscellaneous - Thoughtless Ideas - 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:

Consider locating a fixed azimuth hub spring at approximately 235º azimuth to assure that the blades cannot hit the spars or pilot.

Have a stop between the two teeter stands so that their opposed rocking motion is limited to say a blade pitch range of 0º to +9º. This way the default position is fixed for autorotation and a perturbation cannot put an excessively high pitch into the blades.

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

Calculations:

For Putting the Torque into the Teeter Stands:

The page DESIGN: SynchroLite ~ Rotor - Disk - Blade Lag Angle (2-blade rotor) shows a centrifugal force on a blade of 3,548 lb.

The page Electrotor-Simplex ~ Power Train shows an output torque for 20 hp of 5252 * 20 / (6000/12) = 210 lb-ft, For a hover HP of 12 the torque will be 210 * 12/20 = 126 lb-ft.

The page DESIGN: SynchroLite ~ Rotor - Disk - Undersling shows an undersling is 1.1692".

The CF on each end of each half of the hub-bar is 1,774 lb

Assuming that the distance between the centers of the teetering posts is 4", then the force at each teetering post is (126 lb-ft * 12"/2" )/2 = 378 lb.

If the Hub bar is 24" long then the moment arm of the teetering is half way out each half of the arm, which is 6" there for the force of the moment is (378 / 6 )/2) = 31.5 lbs.

Opp/adj = tan A; 31.5/1774 = 0.0177 = 1º. Way too small. Think through the idea again.

For 8º the rotational force must be increased from 31.5 lb to 247 lb

For Putting the Torque into the Vertical Pitch Links:

The current drawing is of this.

Concerns:

See: Gimbaled Rotors and Gyroscopic Precession:

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?

In addition, see the concerns on the linked page; OTHER: Miscellaneous - Thoughtless Ideas - Auto-Collective Rotor Hub

Cyclical Coriolis:

Teetering of the blades will cause the rotor to want to accelerate. Will this reduce the torque applied by the powertrain to the rotor and thereby result in a lower pitch when the blades are in a teetered (flapped) position?

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Initially displayed: September 29, 2007 ~ Last Revised: October 4, 2007

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