Four-bar flapping rotors for aircraft and associated methods

A flapping rotor hub comprising:

• a rotor hub having a first end and a second end, the first end opposite the second end along an axis of rotation of the rotor hub;
• a first link rotatably coupled to the rotor hub at the first end, the first link to rotate in a plane parallel to the axis of rotation;
• a second link rotatably coupled to the rotor hub at the second end, the second link to rotate in the plane;
• and
• a pitch housing rotatably coupled to the first link at a third end of the pitch housing, the pitch housing rotatably coupled to the second link at a fourth end of the pitch housing, the third end different than the fourth end, the pitch housing to rotate and translate in the plane, the pitch housing to receive a rotor blade, wherein a distance between the first end and the third end is larger than a distance between the second end and the fourth end.

A flapping rotor hub comprising:

• a rotor hub having a first end and a second end, the first end opposite the second end along an axis of rotation of the rotor hub;
• a first link rotatably coupled to the rotor hub at the first end, the first link to rotate in a plane parallel to the axis of rotation;
• a second link rotatably coupled to the rotor hub at the second end, the second link to rotate in the plane;
• and
• a pitch housing rotatably coupled to the first link at a third end of the pitch housing, the pitch housing rotatably coupled to the second link at a fourth end of the pitch housing, the third end different than the fourth end, the pitch housing to rotate and translate in the plane, the pitch housing to receive a rotor blade, wherein a distance between the first end and the third end is smaller than a distance between the second end and the fourth end.

A flapping rotor hub comprising:

• a rotor hub having a first end and a second end, the first end opposite the second end along an axis of rotation of the rotor hub;
• a first link rotatably coupled to the rotor hub at the first end, the first link to rotate in a plane parallel to the axis of rotation;
• a second link rotatably coupled to the rotor hub at the second end, the second link to rotate in the plane;
• and
• a pitch housing rotatably coupled to the first link at a third end of the pitch housing, the pitch housing rotatably coupled to the second link at a fourth end of the pitch housing, the third end different than the fourth end, the pitch housing to rotate and translate in the plane, the pitch housing to receive a rotor blade, wherein the rotor blade is rotatably coupled to the pitch housing, the rotor blade to rotate in a lead-lag direction.

A flapping rotor hub comprising:

• a rotor hub having a first end and a second end, the first end opposite the second end along an axis of rotation of the rotor hub;
• a first link rotatably coupled to the rotor hub at the first end, the first link to rotate in a plane parallel to the axis of rotation;
• a second link rotatably coupled to the rotor hub at the second end, the second link to rotate in the plane;
• and
• a pitch housing rotatably coupled to the first link at a third end of the pitch housing, the pitch housing rotatably coupled to the second link at a fourth end of the pitch housing, the third end different than the fourth end, the pitch housing to rotate and translate in the plane, the pitch housing to receive a rotor blade, wherein the first link and the second link are coupled to a first side of the pitch housing and the rotor hub further includes a third link and a fourth link, the third link and the fourth link rotationally coupled to a second side of the pitch housing and the rotor hub, the third link parallel to the first link, the third link sharing a first axis of rotation at the rotor hub and a second axis of rotation at the pitch housing with the first link, the fourth link parallel to the second link, the fourth link sharing a third axis of rotation at the rotor hub and a fourth axis of rotation at the pitch housing with the second link.

A flapping rotor hub comprising:

• a rotor hub having a first end and a second end, the first end opposite the second end along an axis of rotation of the rotor hub;
• a first link rotatably coupled to the rotor hub at the first end, the first link to rotate in a plane parallel to the axis of rotation;
• a second link rotatably coupled to the rotor hub at the second end, the second link to rotate in the plane;
• and
• a pitch housing rotatably coupled to the first link at a third end of the pitch housing, the pitch housing rotatably coupled to the second link at a fourth end of the pitch housing, the third end different than the fourth end, the pitch housing to rotate and translate in the plane, the pitch housing to receive a rotor blade, wherein the first link, the second link, the rotor hub, and the pitch housing form a four-bar linkage, the four-bar linkage dimensioned to cause a center of mass of the rotor blade to move in a substantially axial direction.