1490

Item 1490

DESIGN: Single-Bladed All Electric Rotor- Rotor Hub - Hub #1

Proposed Means of Achieving the Objective:
PROBLEM: See the end of this section.
Pictures of Hub #1:


Top view, showing the universal joint. A conventional yoke is attached to the mast. The other yoke has a larger diameter and goes downward outside of the conventional yoke.	Bottom view with lower hub ring removed. Shows the crown gear, which is attached to large diameter yoke (black) of universal joint.

A radial bearing on the mast is located between the two parallel guide bars. The guide bars dictate the direction of teetering. In this picture the teetering is conventional. I.e. there is no delta3.

Drawing of Hub #1:

See; DESIGN: Single-Bladed All Electric Rotor- Power Train - Crown & Pinion

Drawing Related to Hub #1 & #7: and perhaps the others:

Place the teetering hinge 2.79" ABOVE the line between to two centroids.

This method appears to achieve the same result as #4 except it will be simpler and the unwanted vertical motion is less. A universal joint is mounted on the top of the mast. The conventional upper yoke of the universal joint is replaced with a large diameter yoke which goes downward outside of the other yoke. The crown is attached to this large diameter joint, so that it can tip longitudinally and laterally but it cannot rotate. The gearbox is mounted on the large diameter yoke by a pair of bearings, so that this box and the pinion can rotate about the crown.

A needle bearing or cam follower is mounted on the mast, probably within the gearbox. There is a guide rail on both sides of this bearing and their job is to allow the gearbox (and blade and motor etc.) to teeter but not tilt to the sides.

Description of Hub #1:

A stationary mast.
A universal joint yoke is affixed vertically to the top of the stationary mast.
The universal joint is used instead of a teetering hinge because the mast does not rotate with the blade & counterweight.
A larger diameter stub mast extends approximately 5" downward from the upper yoke of the universal joint.
This stub mast can tilt longitudinally and laterally but it cannot rotate about the vertical axis.
At the top and at the bottom of the stub mast are mounted bearings bearings.
Affixed to the outer race of these two bearing is housing of the rotor hub.
This housing can tilt with the stub mast and it can rotate about the stub mast.
Firmly attached to the stub mast between the two bearings is a crown gear, which has its teeth facing downward.
The housing has two extensions [A & B] that are located at 180º to each other about the azimuth.
Extension [A] contains two bearing that support the pinion shaft and the pinion.
The pinion gear interfaces with the crown gear.
This pinion shaft extends outward approximately 18" to a planetary gearbox.
Outboard of this gearbox is the motor for this rotor.
The pinion gear, the pinion shaft, the planetary gearbox components, and the motor's armature all rotate in the same direction.
These arms are aerodynamic to reduce parasitic drag.
Extension [B] extend out from the hub in the direction of the blade.
Extensions [A & B] both support pitch bearing that in turn support the blade assembly.
The axis of the power-train components and the pitch axis of the blade are coaxial.

PROBLEM:

This method appears to be ideal for removing the 1P vibration caused by the pull change of teetering on the thrust vector. However; It does not remove the 1P vibration caused by the effect of variable drag. This is because the change of drag is related to the change in pitch, not the change in teetering. In fact, it appears that the change in drag is most closely associated with the change in the angle of attack; i.e. induced drag.

Delta3 could be incorporated for its normal function of removing some of the pitch as the flap increases, however it's action has a detrimental effect in that it shifts the blade-CW centroid in the opposite direction to the desired direction. This compounds the problem of 1P vibration due to drag.

Potential Solutions to Drag:

Option A:

The two mast guide bars are aligned along the pitch axis. They have the capability of being shifted to either side in unison, however they will always remain parallel with the pitch axis. The guide bars will move in the direction of the leading edge (i.e. in a direction 90º azimuth ahead of the azimuth of the blade). This will give a slight delta3 to the blade, which is good. Linked to this guide bar assembly is a small counterweight and this counterweight moves to the same side as the guide bars are moving. The movement and the mass of this small counterweight will exceed that created by the side movement of the blade-CW in the other direction. This will therefore provide the offset centrifugal force to counter the increase in the induced drag of the blade and the opposing offset centroid of the blade-CW.
An example of the above paragraph. The view is from the counterweight looking toward the tip of the blade and the blade is advancing to the left. When the blade pitches up, the guide bar assemble will slide to the left. This forces the centroid of the rotor-CW to move to the right of the mast. It will also remove some of the pitch in the blade. Lastly, it will also swing a small mass to the left of the blade with a moment arm, which is considerably greater than that of the blade-CW, which is in the opposite direction. The offset centrifugal force of this small counterweight will balance the increased drag and the offset mass of the blade-CW.
Note that the arm of the small counterweight will probably require and additional device to locate its offset from the mast. This device will be actuated by the angle of attack. In other words the pitch input to the small counterweight will be modified by the angle of attack input.

Hold It: Revise the above. Make delta3 a separate item that can be utilized or not and the angle can be anything desired. For drag just link the small counterweight to the pitch change, and adjust the amount of movement by the angle of attack.

Option B:

An increase in induced drag is the result of greater airflow velocity and/or an increase in the angle of attack. However, there is a symmetry of lift, therefore the induced drag will be fairly constant around the disk irrespective of whether the cause is climb or forward flight. I think. The forgoing applies to rotors with two blades, but the single blade and counter-weight may be different because of the difference in the drag arm lengths during forward flight.

An increase in the pitch is the result of an increase in motor torque.

The requirement is to shift the weight, which counters drag, at the same time and rate as the pitch changes. (This may not be exactly true due to the overcoming the inertia of the weight.) Therefore can the shaft to the pinion have a constant velocity joint and as the motor twists the bplade pitch the motor (and planetary reducer) could move about the rotor's azimuth in a negative direction. I.e. moving the weight in the direction of the blades leading edge. This eliminates the need for a separate counter weight.

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Initially displayed: January 9, 2006 ~ Posted on PPRuNe; January 11, 2006; on Rotary Wing Forum; January 9, 2006~ Last Revised: February 21, 2006

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.