Hinge mechanism for a weight-shifting coaxial helicopter

1. An unmanned helicopter comprising:

a propulsion system comprising:

a first rotor assembly comprising a first motor coupled to a first rotor, the first rotor comprising a plurality of first fixed-pitch blades; and

a second rotor assembly comprising a second motor coupled to a second rotor, the second rotor comprising a plurality of second fixed-pitch blades, the second rotor being coaxial to the first rotor, the second rotor configured to be counter-rotating to the first rotor;

a fuselage comprising:

a power source; and

a controller; and

a gimbal assembly coupling the fuselage to the propulsion system, the gimbal assembly comprising:

a first gimbal motor configured to control pitch of the unmanned helicopter; and

a second gimbal motor configured to control roll of the unmanned helicopter;

wherein:

each of the plurality of first and second fixed-pitch blades is coupled to a hub of its respective rotor via a hinge mechanism that is configured to allow each of the fixed-pitch blades to pivot from a first position to a second position, the first position being substantially parallel to the fuselage and the second position being substantially perpendicular to the fuselage;

each hinge mechanism comprising a hinge axle extending through one or more apertures of a respective hub; and

each hub comprising a locking bar configured to lock a respective fixed-pitch blade in the second position.

2. The unmanned helicopter of claim 1 , wherein the hinge mechanism further comprises a torsion spring positioned about the hinge axle and configured to swing the fixed-pitch blades from the first position into the second position.

3. The unmanned helicopter of claim 2 , wherein the hinge mechanism further comprises one or more protrusions, each protrusion having at least a first surface and a second surface, wherein the first surface is substantially curved and the second surface is substantially flat.

4. The unmanned helicopter of claim 2 , wherein the hinge mechanism couples to each of the plurality of fixed-pitch blades using one or more fasteners.

5. The unmanned helicopter of claim 2 , wherein the hinge axle couples the hinge mechanism to the hub.

6. The unmanned helicopter of claim 1 , wherein:

the locking bar is operable to move along first and second surfaces of one or more protrusions of the hinge mechanism; and

each hub further comprises:

one or more apertures through which the locking bar extends; and

one or more spring pistons operable to apply force to the locking bar.

7. The unmanned helicopter of claim 6 , wherein the fixed-pitch blades are locked in the second position when the locking bar is in contact with the second surface.

8. The unmanned helicopter of claim 6 , wherein:

the one or more apertures of the hub comprise a first side and a second side; and

the locking bar is locked in the second position when one or more spring pistons force the locking bar against the second side of the one or more apertures.

9. The unmanned helicopter of claim 1 , wherein the fixed-pitch blades, once locked, remain in the second position until manually pivoted back to the first position.

10. The unmanned helicopter of claim 1 , wherein locking the fixed-pitch blades in the second position prevents the plurality of first fixed-pitch blades from contacting the plurality of second fixed-pitch blades.

11. A helicopter comprising:

a gimbal assembly;

a first rotor assembly mechanically coupled to the gimbal assembly, the first rotor assembly comprising a first rotor, the first rotor comprising a plurality of first fixed-pitch blades; and

a second rotor assembly mechanically coupled to the gimbal assembly, the second rotor assembly comprising a second rotor, the second rotor comprising a plurality of second fixed-pitch blades, the second rotor configured to be counter-rotating to the first rotor;

a fuselage mechanically coupled to the gimbal assembly;

a controller;

wherein:

each of the plurality of first and second fixed-pitch blades is coupled to a hub of its respective rotor via a hinge mechanism that is configured to allow each of the fixed-pitch blades to pivot from a first position to a second position, the first position being substantially parallel to the fuselage and the second position being substantially perpendicular to the fuselage;

each hinge mechanism comprising a hinge axle extending through one or more apertures of a respective hub; and

each hub comprising a locking bar configured to lock a respective fixed-pitch blade in the second position.

12. The helicopter of claim 11 , wherein the hinge mechanism further comprises a torsion spring positioned about the hinge axle and configured to swing the fixed-pitch blades from the first position into the second position.

13. The helicopter of claim 12 , wherein the hinge mechanism further comprises one or more protrusions, each protrusion having at least a first surface and a second surface, wherein the first surface is substantially curved and the second surface is substantially flat.

14. The helicopter of claim 12 , wherein the hinge mechanism couples to each of the plurality of fixed-pitch blades using one or more fasteners.

15. The helicopter of claim 12 , wherein the hinge axle couples the hinge mechanism to the hub.

16. The helicopter of claim 11 , wherein:

the locking bar operable to move along a first and second surface of the one or more protrusions; and

each hub further comprises:

one or more apertures through which the locking bar extends; and

one or more spring pistons operable to apply force to the locking bar.

17. The helicopter of claim 16 , wherein the fixed-pitch blades are locked in the second position when the locking bar is in contact with the second surface.

18. The helicopter of claim 16 , wherein:

the one or more apertures of the hub comprise a first side and a second side; and

the locking bar is locked in the second position when one or more spring pistons force the locking bar against the second side of the one or more apertures.

19. The helicopter of claim 11 , wherein the fixed-pitch blades, once locked, remain in the second position until manually pivoted back to the first position.

20. The helicopter of claim 11 , wherein locking the fixed-pitch blades in the second position prevents the plurality of first fixed-pitch blades from contacting the plurality of second fixed-pitch blades.