1647

Item 1647

DESIGN: SynchroLite ~ Rotor - Hub - 2-blade Teetering w/ Control Power - Vibration Suppressor

Overview:

To minimize any transmission to the fuselage of the 2P vibration that is created by Rotor - Hub - 2-blade Teetering w/ Control Power- Offset Bi-hinged.

Option A ~ Cam and Cam Follower between Mast and Fuselage:

Drawing:

Objective:

Assume that the objective is to tilt the craft forward. (180º azimuth)

The blades will be highest at 0º, have greatest velocity downward at 90º, lowest at 180º, and have greatest velocity upward at 270º.

There will be a forward tilting moment of the mast when a blade is located at 180º, and this results in a 2/rev vibration.

The objective of this vibration suppressor is to provide comperable moments when the blades are at 90º and 270º azimuth, thereby providing a relatively constant moment.

Method:

When the blades are near 180º azimuth their tilting moment is directly transferred to the fuselage.

When the blades are near 90º and 270º azimuths they are experiencing their greatest rate of teetering (flapping). This results in transferring a forward teetering moment to the fuselage due to the cam's upward motion on the ramp.

Expected Result:

The mast and attached power-train will experience a 2P moment.

The fuselage will experience a constant moment.

Option B ~ Chordwise Side-shifting of Rotorhead:

Calculations: re Chordwise Sideshifting of Rotorhead on Splined Teetering Axle:

Based upon forward cyclic. I.e. the disk is tipped down at 180º azimuth.

Motion of Rotor: Arc of rotor rotation = 180º

Time: 600 RRPM = 180º of revolution in 0.05 seconds

Mass: For rotorhead, hub-springs and a pair of blades use 25 lbs for now.

Acceleration: is related to the sine of the azimuth angle of the rotor [sin(Ψ)]. Note that 180º to 360º is negative.

Lateral Displacement:

Force:

Vertical Arm Length (CG to rotorhead):

Moment

From the above graph it appears that this vibration suppressor will change a 2P vibration into a 4P vibration with half the amplitude.

Utilizing delta3 may negate any centrifugal force caused by the off-center rotor.

Consider a ball spline for the spline on the teetering axle.

Centripetal Force and Centrifugal Effect:

To consider the effect of an off-center rotorhub at the top of the mast; at it's most extreme position.

For blade element method, the centripetal force: F acting on a body of mass M is given by the equation F = (Mv²)/r, where v is its velocity and r is the radius of its path. [F is in pounds], [M is in slugs (1 slug = 32.175 lbs)], [v² is in ft/sec.], [r is in feet].

Initial assumptions: Mass: For rotorhead, hub-springs and a pair of blades use 25 lbs for now. Offset: 0.5" (1" of total side-shifting)

Force: F = (Mv²)/r = [25 / 32.175] * [(600 / 60) * (0.5 / 12) * 2 * (22/7) ]² / [0.5 / 12] = 0.777 [slugs] * 6.86 [ft/sec] / 0.042 [ft] = 127 lbs.

Oscillating Force:

To consider the effect of rotorhub sideshifting.

Acceleration - Linear: [a] (m/s²) | a = F * m The time-rate change of velocity and is expressed as velocity divided by time or as distance divided by time squared, that is, in feet per second per second or feet per second squared. The metric SI unit is the meter per second squared, where force is in Newtons and mass is in kilograms.

Initial assumptions: Mass: For rotorhead, hub-springs and a pair of blades use 25 lbs for now. Offset: 0.5" (1" is total side-shifting). One-half revolution is 600 RPM / (60 seconds = 10 revolutions per second = 0.05 seconds for a half revolution.

Acceleration - Linear: as distance divided by time squared, that is, in feet per second per second or feet per second squared.

a = d / t² = (1.0 /12) / 0.05² = 33.33 feet per second per second

Force: F = a / m = assuming that mass is in pounds 33.33 / 25 = 1.33

Another answer is 24 lb force

Option C ~ Three (or four) Springs and Dampers between Mast and Fuselage:

Three springs and dampers in fixed positions at 120º spacing around the top of the mast. Interfacing with the mast through a common bearing about the mast. Do little sketch?

Operation is by giving a pushback from the action of the hub spring approximately 90º [0.025 seconds] later.

An optional idea; The damper may work by connecting the rear ports of all 3 cylinders and/or the front (with rods) port of all 3 cylinders. Then put 2-way flow controls on all 3 or 6 lines. An accumulation cylinder will probly be required in the middle to handle the unequal volume flows of the 3 cylinders.

The oil might have to be very light due to the high frequency of oscillation.

The hub spring moments will probably be twice that of the 'cylinder & spring' moments.

Eventually come up with a simpler 360º azimuth spring and damper device.

Initially displayed: May 12, 2008 ~ Last Revised: May 31, 2008

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.