1501

Item 1501

OTHER: Helicopter - Inside - Single-Bladed All Electric Rotor - Coaxial Cyclical RRPM

An Ultralight helicopter that has the theoretical advantage of a significantly higher Lift/Drag ratio then existing helicopters. This is due to the use of only two blades and no tail rotor, plus the advantage of utilizing an optimized angle of attack at all azimuths during forward flight and hover.

Overview:

During the forward flight of a conventional helicopter the mean airflow velocity on the advancing blade is greater than the mean airflow velocity on the retreating blade. This would result in a dissymmetry of lift if it were not for the increased pitch on the retreating side and the decreased pitch on the advancing side. However, if it is possible to have the mean airflow velocity on the retreating side equal the mean airflow velocity on the advancing side, then the pitch can remain constant around the disk, just as it does during hover. This constant pitch will allow the rotor to fly with a significantly improved lift/drag ratio.

A means of achieving this is to give the blade a faster rotational speed on the retreating side and a slower rotational speed on the advancing side.

Concern:

It should be noted that this 1/rev acceleration and deceleration does not exist during hover and vertical climb. The problem only starts, and increases, as the horizontal velocity increases. Will the large 1/rev cyclical acceleration and deceleration forces be excessive?

The mean lift of the blade must be equal at all azimuths about the disk.

Therefore, the mean drag must be fairly equal at all azimuths about the disk also.
Therefore, the mean airspeed across the blade must be fairly equal at all azimuths about the disk.
Therefore, the rotational speed differences between the retreating side and that of the advancing side must increase as the forward velocity of the craft increases.

Potential Solution: Perhaps the only way to operate at higher forward speeds is to significantly reduce the rotational inertia of the blade; by reducing its weight, and in addition, reducing the length of the movement arm.

Blade weight: The weight can be reduced, by using all composite carbon construction, by eliminating the leading edge weight, and eliminating the tip weight. Anyone got a few thousand black widow spiders that are willing to give up their thread for the creation of super strong and light composite tow ?Low mass (rotor inertia) may not be a problem for autorotation since the collective immediately drops upon loss of power.

Loss mass will be a problem for using centrifugal force to offset flapping (teetering). Perhaps, replace the teetering rotor with a rigid rotor. Lightening the blade doubles the advantage because it results in an equal weight reduction in the counterweight of a single bladed rotor.

Reducing the length of the moment arm: A large taper and large twist will reduce this length somewhat.

Also, the root of the blade should start outboard of the maximum circle of reverse velocity. This will also reduce vibration due to acceleration and deceleration.

Centrifugal Force: When one blade is travelling faster than the other it will be producing a greater centrifugal effect than the slower blade, which is on the other side. However, its CW will also be producing a greater centrifugal effect than the slower CW.

Sketch:

Features:

Two single-bladed rotors, which are coaxial and counter-rotating.

The blades experience a constant mean aerodynamic velocity (at approximately 75% of blade radius), irrespective of whether the craft is hovering or in forward flight. In other words, the rotational velocity (RRPM) of the blade varies as it rotates about the mast during forward flight.

Rotor thrust is varied by changing the mean aerodynamic velocity of the blade. This differs from the conventional method of changing the pitch of the blade.

The collective is a 2-position device. Up for flight and down for autorotation.

Cyclic control is the same as that of a gyrocopter. The two single-bladed rotors are mounted on a common non-rotating mast, which is gimbaled at the bottom.

Vibration due the thrust of the blade as it rotates around the mast is virtually eliminated by the method on; DESIGN: Single-Bladed All Electric Rotor- Rotor Hub - Hub #1.

Vibration due to the drag of the blade is virtually eliminated because Drag and Lift (Perhaps only Induced lift - CHECK INTO) are in a close ratio and on the rotors on this craft have a constant lift around the disk. (WHAT MAKES THS DIFFERENT FROM THE TEETERING ROTORS ON THE Single-Bladed All Electric Rotor?)

It should significantly reduce advancing tip compression and retreating blade stall ~ if it will work. This will allow the blades to be optimized for lift.

Requirements:

The rotor blade and its counterweight must have the lowest possible mass, so that it offers the least resistance to rotational acceleration and deceleration about the mast.

The driving torque of each rotor is opposed by the driving torque of the other rotor, which is counterrotating.

Both rotors might require an individual small armature located near the mast. These two armatures would react against a common stator, which is rigidly affixed to the mast.

Related Web Pages:

This Site:

OTHER: Helicopter - Inside - Single-Bladed All Electric Rotor

OTHER: Helicopter - Inside - Coaxial - Electric Motor Located between Rotors

Alternative - Mechanical engine & drive train; ~ DESIGN: Misc. - Thoughtless Idea - Coaxial Transmission w/ Yaw Control

Outside Sites:

VTOL Gyrocopter

This is somewhat similar to the Bolkow Bo 46.

Efficiency:

Only Two Blades: The fewer blades the better power-to-lift ratio, therefore two single-bladed rotors and no tail rotor may improve efficiency.

Optimized Angle of Attack: The ability to maintain an optimized pitch and optimized mean airflow across the blade should improve efficiency.

The outer portion of the blades will perform similar to the wings of an airplane during cruise.
The inner portion of the blades will perform similar to the wing of airplane with its slats extended during takeoff and landing.

1 and 2 are possible due to the large twist and taper of the blades

Providing of Maximal Acceleration/Deceleration and Minimal Torsional Vibration:

The counterweight for each blade is located on the opposite side of the mast for its blade, however the counterweight and the blade are independently mounted on the static mast. This allows them to accelerate and decelerate at different rates. Two extremely strong and opposing springs attempt to hold a 180º alignment between the blade and its spring.

During hover and vertical flight this 180º alignment is maintained by the springs and by a relatively small electrical linear actuator. As the forward velocity of the craft increases, the electrical linear actuator causes the counterweight to become out of phase with the blade. The 'spring' of this unbalanced phasing is the major contributor to the acceleration and deceleration of the blade. The unbalanced phasing is increased as the forward velocity of the craft is increased.

Another major advantage for the acceleration and deceleration concern is that only the rotational inertia of the blade must be considered, not the counterweight. This is because the counterweight is on the other side of the springs from the blade.

Applications:

Ultralight:

Complying with the 254# empty weight limitation should not be a problem. This is because there is no transmission, the electric motor.
The speed limitation is a slow 65 mph. This will also serve as a limitation on the vibration inducing forces.

Unmanned Air Vehicle (UAV):

The incorporation of only two blades should give a good loiter time; except for the fact that it is electrical. The battery weigh is the negative. Would solar cells help a little?
A UAV craft provides a safe way to develop and test the craft.
Absolutely quiet.
For special long range or long loiter flights, cheap one-charge electrical storage devices (batteries etc.) could be progressively dropped when there energy has been consumed. This will reduce the total weight and extend the duration of the flight.

Additional Notes:

The very high frequency at which the power of the motor can be changed should allow for Higher Harmonic Control. This should reduce the rotor -rotor (blade - blade) induced vibration. The pulse widths on the motor may be varied at 25,000 per second therefor if the RRPM is 560 there are 7.4 pulses per degree of rotor azimuth. Of course, inertia will significantly reduce this rate of HHC.

During forward flight the blade accelerates from 90º to 270º azimuth and decelerates from 270º to 90º azimuth. Approximately ???

During forward flight the blade will cross at 0º azimuth and 180º azimuth. Approximately ???

The crossing azimuths of the blades will be a constant at a constant forward speed. The two azimuths will be different for different forward speeds. The X-ing azimuths for hover will be 0º and 180º. During forward flight it will be near 10º and 170º. This last statement may not be true ~ they may always cross at 0º and 180º

The slowing blade might act as a generator. Probably not since the blade is reacting with its counterweight. A pair of large coil spring between the blade and its counterweight might assist with the rotational forces that are required to provide this oscillatory 'lead & lag' during forward flight. This assistance would allow for higher forward speeds. independent

The rotors must have very low inertia, if there is the desire to have any reasonable forward velocity.

The rotational inertia of the blade and its counterweight must be equal. The linear actuator(s) used to excite and control the oscillation between each blade and it counterweight will be located in the counterweight to keep the blade weight as low as possible.

Safety:

Idea: A large lightweight capacitor might be included to provide a small amount of short duration power for flare during an autorotation landing.

Acceleration and Deceleration: (Crude values taken from Single-Bladed All Electric Rotor - Disk - Forces & Moments)

A crude and initial start at looking at oscillatory rotational inertia.

This may allow for a rigid rotor - I.e. no teetering - LOOK INTO

Forward velocity (maximum)	65 mph	95.3 fps
Radius of rotor disk: R	10 ft.
Radius of mean lift: R_MEAN	7.5 ft.
Rotor speed: RRPM_MEAN \| Ω_MEAN	560 rpm	58.6 rad/sec
Forward velocity of craft: V	65 mph	95 ft/sec
Tangential velocity at 75% R at 0º azimuth: V_MEAN	440 ft/sec

Tangential velocity at 75% R, at 90º azimuth, at V_MEAN:	535 ft/sec
Tangential velocity at 75% R, at 270º azimuth, at V_MEAN:	345 ft/sec

Rotor speed at at 75% R at 90º azimuth to equal mean speed ( V_MEAN): ω_o	439 rpm	46.0 rad/sec
Rotor speed at 75% R at 270º azimuth to equal mean speed ( V_MEAN): ω_f	682 rpm	71.4 rad/sec
One half revolution (180º): θ	3.142 radians
Time for one half revolution (θ) at RRPM_MEAN: t \| t = 60 / (560 * 2 ) =	0.0536 sec
Time for one half revolution \| t = 2θ / (ω_f + ω_o ) = 2 * 3.142 / (71.4 + 46.0) =	0.0535 sec

Angular acceleration: α \| α = (ω_f - ω_o² ) / 2θ = (71.4 - 46.0²) / (2 * 3.142) =	-325.4 rad/sec/sec	Why the difference?
Angular acceleration: α \| α = (ω_f - ω_o ) / t = (71.4 - 46.0) / 0.0535 =	474.8 rad/sec/sec	Why the difference?

Moment of inertia: J_M\| J_M= m r²= (10 5 * 5) + ( 10 * 2.5 * 2.5) =	312.5 ft-lbs-sec²	Is algorithm correct?
Unbalanced torque: T₀\| T₀= J_M α* = 312.5 * 474.8	148,375 lb-ft	Is algorithm correct?
The above value is probably crazy? Should Slug be considered? The spring will reduce the required torque considerably. Will the spring function properly at various frequencies???	Leave this page for a rainy day.

Blade mass:	10 lbs. @ 5 ft.

Counterweight mass:	20 lbs. @ 2.5 ft.


Acceleration a	x
Angular velocity of the body at the time acceleration a is to be determined: w	x
Radius from the axis to the point P: r	x

[Source ~ MH p.151+]

Note that a change of the mean RRPM makes no difference to the amount of acceleration and deceleration.

J_{M =}m * r²Units are ft-lbs-sec²(slug-ft²) or in-lbs-sec²

a = √ (rw²)² + (rα)²

Control and UAV:

This small (25 employee) Canadian company interesting. http://www.micropilot.com/. There is an article on it in the business section May 30, 2006 Globe and Mail.

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Initially posted: Early this Millenium ~ Last Revised: January 13, 2007

The above utility invention is openly and publicly disclosed on the Internet to negate an entity from patenting it, to the exclusion of all others whom may wish to use it. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.