B455

OTHER: ~ Rotor Concept - Intermeshing w/ Precone/Decone

Overview:

An intermeshing helicopter where the obliquity of the masts is much closer to the vertical than on previous intermeshing helicopters.

Advantages for the Intermeshing Helicopter:

The blade to ground clearance at all azimuths will be equal to or greater than that of a comparable single-rotor craft.

The lateral distance between the rotorhubs is significantly decreased, which will reduce parisitic drag.

A significant reduction of the pitch~torque cross-coupling.

The lift of both rotors is very close to vertical.

The stability of the craft should be enhanced.

Conceptual Sketch & Parameters:

In the above sketch, the obliquity of each mast is 3º.

The precone at the hub is 9º between the hubs. The decone is -6º, giving 3º for the remainder of the span.

The center of the blade clears the hub of the other rotor by 2".

The advancing blade (outside forward) is horizontal at 90º-azimuth.

FORM ~ Rotor - Disk - Interaction:

Port Azimuth:	Port Intersection Radius:	Starboard Azimuth:	Starboard Intersection Radius:	Vertical Center to Center Distance
90º	21.0"	270º	0.0"	4.39"
95º
100º	20.0"	160º	3.7"	3.52"
105º
110º	21.0" ⁽¹⁾	170º	7.3"	3.11"
115º
120º	24.2"	180º	12.13"	2.66"
125º
130º	32.2"	190º	21" ⁽²⁾	2.06" ⁽⁴⁾
135º
140º	57.7"	200º	47"	3.34"
145.2º	114.0" ⁽³⁾	205º	103"	6.25"

(1) The Port blade's decone location is directly over the Starboard rotorhub's arm.

(2) The Port's blade is directly over the Starboard's decone location.

(3) At the tip of the Port rotor.

(4) This is the closest location. It is too close.

See the bottom drawing on 0854.dc for drawing check of the above calculation.

Working Notes:

Considerations:

The portion of the span out to just past the other hub is part of the hub.

The radial bearings are located at the outer end of the rotorhub's arms and are small diameter (needle bearings) which do not cause much drag.

The axial load might be handled by a tension-torsion strap, which is attached at the center of the hub.

The strap might be located in the center of the pitch-control tube and 'universal-joint'.

Superficially consider four blades per rotor.

A test model could be made with conventional straight bevel gears, due to the small angle.

It may be possible to bury the rotor hubs down a little into the fuselage; for less drag.

There may have to be a universal joint on the pitch control, at the location of the -6º decone. This may be similar to DESIGN: Dragonfly ~ Rotor - Hub - Layout.

May want to modify the Form ~ Rotor - Disk - Interaction to include the precone and the decone ~ or ~ modify the mockup, so as to determine blade-blade clearances. Review stagger. <- Am doing

May want to quickly re-look at 4-blade rotor.

Flight-Control for This Rotor:

The root of the blade provides little lift during hover. During fast forward flight, the advancing root provides lift but the retreating root will be providing some negative lift. Due to the arrangement of the intermeshing configuration, it may be advantageous to extend the blade spar so that it is equal to or greater than the stagger. Then provide only a 1P or less independent root control, which will be set by the forward velocity. The preferred method of control is probably ~ OTHER: Rotor Concept - Independent Root & Tip - ARR w/ Floating Root Method

It should be noted that this does not necessarily entail separate root and tip pitch links (i.e. 1P control over the root and the tip). It only requires a means of (slowly) changing the twist of the blade (much less than 1P).

Concerns:

Have not yet calculated blade to blade clearance at crossing. For initial reference see; Rotor - Disk - Blade to Blade Clearance - 3-blade rotors 0854

Will it be possible to incorporate Independent Root & Tip Control with the concept on this page?

OTHER: Rotor Concept - One-Piece Hub and Spars

DESIGN: UniCopter ~ Rotor - Disk - Pre-cone

DESIGN: UniCopter ~ Rotor - Disk - Blade to Blade Clearance - 3-blade Rotors

Initially displayed: February 23, 2005 ~ Last Revised: March 3, 2005

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.