Rotor assembly
A rotor assembly includes a first rotor, a second rotor and a damper system. The first and second rotors are arranged to be rotated about a common axis for thrust generation by a drive system. The first rotor is rotatable about the common axis relative to the second rotor between a stowed configuration of the rotor assembly in which a rotor blade of the first rotor and a rotor blade of the second rotor are substantially angularly aligned and a deployed configuration in which the rotor blade of the first rotor and the rotor blade of the second rotor are angularly misaligned. The damper system is arranged to generate a damper force opposing the relative rotation between the first and second rotors in at least one of the direction towards the stowed configuration and the direction towards the deployed configuration.
1 . A rotor assembly comprising a first rotor, a second rotor and a damper system, the first and second rotors being arranged to be rotated about a common axis for thrust generation by a drive system and where the first rotor is rotatable about the common axis relative to the second rotor between a stowed configuration of the rotor assembly in which a rotor blade of the first rotor and a rotor blade of the second rotor are angularly aligned and a deployed configuration in which the rotor blade of the first rotor and the rotor blade of the second rotor are angularly misaligned and where the damper system is arranged to generate a damper force opposing the relative rotation between the first and second rotors in at least one of the direction towards the stowed configuration and the direction towards the deployed configuration, and where the damper system comprises a rotary fluid viscous damper.
2 . A rotor assembly according to claim 1 where torque from the drive system is delivered to the first rotor through the damper system.
3 . A rotor assembly according to claim 1 where the damper system is arranged such that the damper force increases proportionally with increasing relative rotation rate between the first and second rotors.
4 . A rotor assembly according to claim 1 arranged such that the relative rotation occurring towards the deployed configuration is at least in part passively driven.
5 . A rotor assembly according to claim 1 arranged such that the relative rotation occurring towards the stowed configuration is at least in part passively driven.
6 . A rotor assembly according to claim 1 , wherein the first rotor is biased with a force to rotate it towards the stowed configuration of the rotor assembly.
7 . A rotor assembly according to claim 6 comprising a biasing means that biases the first rotor with the force, and wherein the biasing means is combined in a unit with the damper system.
8 . A rotor assembly according to claim 1 where to the extent that the rotor assembly remains in the deployed configuration whilst the first rotor is being driven by the drive system, the deployed configuration is maintained at least in part passively.
9 . A rotor assembly according to claim 1 where to the extent that the rotor assembly remains in the stowed configuration, the stowed configuration is maintained at least in part passively.
10 . A rotor assembly according to claim 1 where the second rotor is rigidly mounted to a drive shaft of the drive system, thereby rotating with the drive shaft.
11 . A rotor assembly according to claim 1 where the first rotor is mounted to the drive shaft via a bearing.
12 . A rotor assembly according to claim 1 where a separation between the blades of the first and second rotors is less than 100% of a mean aerodynamic blade chord length of each of the blades of the first and second rotor assemblies.
13 . A rotor assembly according to claim 1 where each of the first and second rotors has exactly two blades.
14 . A rotor assembly according to claim 1 where the rotor assembly is arranged for use in generating thrust to power a flying vehicle.
15 . A rotor assembly according to claim 1 where the rotor assembly is a non-tilting vertical thrust rotor assembly.
16 . A rotor assembly according to claim 1 where when in the stowed configuration the rotor blade of the first rotor and the rotor blade of the second rotor are arranged such that their longitudinal axes are aligned with an incoming air flow direction during forward flight.
17 . A flying vehicle comprising the rotor assembly according to claim 1 .
18 . A method of controlling reconfiguration of a rotor assembly, the rotor assembly comprising a first rotor and a second rotor, the first and second rotors being arranged to be rotated about a common axis for thrust generation by a drive system and where the first rotor is rotatable about the common axis relative to the second rotor between a stowed configuration of the rotor assembly in which a rotor blade of the first rotor and a rotor blade of the second rotor are angularly aligned and a deployed configuration in which the rotor blade of the first rotor and the rotor blade of the second rotor are angularly misaligned, the method comprising a damper system comprising a rotary fluid viscous damper generating a damper force opposing the relative rotation between the first and second rotors in at least one of the direction towards the stowed configuration and the direction towards the deployed configuration.