1350

Item 1350

DESIGN: SynchroLite ~ Rotor - Hub - 3-blade - CVJ & HS - Layout

(Concentric Double Universal Joint & Hub Spring)

Objective:

A low cost rotorhub that embodies the advantageous features of both the teetering rotor and the articulated rotor

Overview of Hub Concept:

See; Concentric Double Universal Joint with Hub Spring

Mockup Picture:

Drawing:

1350.dc.

This was the primary drawing.

1350 - Alt A.dc.

Crown on outer races.

1350 - Alt B.dc.

Crown on inner races.

1350 - Alt C.dc.

Crown on outer races.

1350 - Alt D.dc.

Crown on outer races. This was the one.

If the pitch bearings should be stronger, use pair of angular NTN 7206and one deep groove NTN BL305.

1350 - Alt H.dc.

1350 - Alt J.dc.

This is currently the one.

If the pitch bearings should be stronger, increase the gap between them and/or use one deep groove NTN BL305.

Design Notes: To eventually be moved to separate pages.

Number of Blades: There will be 3 blades per rotor. 2-blade rotors with a hub spring will have a 2/rev vibration.

Lateral Spring: See; DESIGN: SynchroLite ~ Rotor - Hub - 3-blade CVJ & HS - Bearing - Mast - Azimuth Teeter

Two pair of hub springs aligned with the bisectors rocking axis may be the only ones needed to align the bisector but three or more pair of hub springs will be needed to provide the actual function of hub springs.

Mast: Dimensions from SynchroLite MAKE: SynchroLite ~ Power Train (2 engine) - Mast - Machining; 1.3780 OD., 0.9780 ID.

Teeter: 8º maximum at present This will consist of 4º on the inner elastomer and 4º on the outer elastomer. With a 3:1 ration between fully expanded and fully compressed, the width must be 12º.

Pitch bearing Seal: This may leak. See 1409 Lubrication.

HS Retainer: Consider having the cap come up the outside of the Crown to help strengthen the Crown during large thrust loads on the blade, so that the Crown can be weakened (lightened).

Pitch Horn: Assuming that the UniCopter/Dragonfly style of hub and blade grip is used then there is the opportunity, with some modifications, to locate the pitch horns inside the hub.

Blade Chord: The blade cord should be small at the radius where it passes over the other hub.

Bisector:

By using Trunnion - Inner [1427] this Bisector can be installed as one part. In addition, the Bisector does not need the large cutout below it for installing the lower X-outer.

Make the main part of the bisector by spinning thin wall steel tubing. The steel tubing will weigh more than aluminum but it will be thinner and this will result in the two sides of the hub spring opposing each other more and it will put less upward thrust on the head

Composite Hub:

It might be possible for the hub to accept some in-plane bending while resisting out-of-plane bending. This might be done by producing the hub out of composite construction with specific directions to the threads. In addition, the hub could have an increased depth and a decreased width at the lobes. The construction might be wound thread or specially shaped clot patterns.

Pitch Horn & Drag Brace:

The intent is to locate the pitch horns on the trailing edge side of the blades. This is to maximize the vertical clearance between the rotor hub components and the blades on the other rotor. The pitch horn and drag brace are to be a common unit, which clamps to the outside of the blade grip. The drag brace, which attaches to the trailing edge of the blade, must be removable so that the blades can swing back for transportation.

October 14, 2001 ~ D.K. has suggested that the drag brace be replaced by a Bell 206 style of latch, so that the blades are easly removable for a more compact form of transportation.

Undersling:.

For calculated undersling see; DESIGN: SynchroLite ~ Rotor - Disk - Undersling

The following is copied from my PPRuNe posting

A pre-cone angle is included to reduce the loads on the feathering bearings and the blades etc. Of course, this cause the rotor's center of mass being further above the intersection point of the feathering axes and the mast's centerline.

The undersling was included on this 3-blade teetering rotor for basically the same reasons it is included on the 2-blade teetering rotor. It helps in keeping the rotor's centers of mass, inertia, lift and drag etc. as close to the centerline of the mast as possible during all flight maneuvers. With the CVJ causing the 'virtual mast to be normal to the tip-path-plane these justifications for undersling may be marginalised, then again, because the hub spring is resisting the teetering and the blade will cone, some undersling may be beneficial.

More thinking and prototype testing will be required to determine if undersling is needed, and if so, how much it should be. However, there does not appear a downside or difficulty to including it, at this point in time.

A further thought; ~ November 4, 2004. The only basis for determining the amount of undersling might be that of clearance with the blades on the other rotor.

The hub (bearings etc) must have a benign failure mode.

The hinge spring force must not vary with the rotation of this rotor hub. For proof see .....

Transportability:

The greater strength of the CVJ rotor & blades, over that of the offset teetering hinge & blades, means that they will stand up better to ground transportation.
Have the rear legs removable, just like the SynchroLite.
Have the blades swing forward or back, just like

Material:

Consider titanium from Tubesales (UK) Limited.

General:

Look at the thoughts and concerns on Eng-Tips, New Rotorhub Invention thread.

See drawing 0472-CJV+HS.dc for complete proposed helicopter.

Inside Relevant Information:

DESIGN: SynchroLite ~ Rotor - Disk - Hub Spring Induced Lead/Lag Mitigation

OTHER: Mechanical Joint ~ Universal Joint

OTHER: Mechanical Joint ~ Constant Velocity Joint

OTHER: Flight Dynamics - Rotor Hub - Hub Spring

OTHER: Flight Dynamics - Rotor - Hub - Teetering w/ Hinge Spring (Hub Spring)

OTHER: Flight Dynamic - General - Phase Lag

OTHER: Flight Dynamic - General - Lead/Lag

Perhaps Outside Relevant Information:

Thompson Coupling ~ It looks like this coupling is a concentric double universal coupling which has linkage to cause the two angles between the input shafts and the center of the coupling to always be equal.

Cornay Universal Joint

http://www.eng-tips.com/viewthread.cfm?qid=99412~ A discussion about Cornay Joints and others on Eng-Tip - Transmission and Driveline engineering Forum

Related patent: Rotor head for a rotary-wing aircraft, 7,037,072, May 2, 2006 , Filed: March 3, 2004

Revision Required:

The pitch bearing package must accept an inward axial load

Current Development Concerns:

Can a steel retaining ring be screwed into an aluminum housing? Expansion rates? Holding power?

Will the blades will flap (bow) too much and will this result in a desire to lead/lag.

Will the Spindle - Crown connection be strong enough?

What is being done to stop lead/lag motion about the single grip pin?

Could the 3º precone in conjunction with rotor upwash result in too little forward cyclic control?

Could the transverse flow result in an excessive decrease in the clearance between the advancing blade and the other hub? [See ~ RWP3 p.28]

The mast and the rotor hub will be turning at a constant velocity however the bisector, which represents the intermediate shaft, may likely be accelerating & decelerating. Its mass is insignificant however it's accelerating & decelerating may interact with the inner and outer elastomeric bearing unless a pair of radial bushings can be located between the bisector and the elastomeric bearings.

Initially displayed: October 6, 2004 ~ Last Revised; September 23, 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.