Gimbaled Tail Rotor Hub With Elastomeric Centrifugal Force Bearing
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Solution Overview
Problem
Existing tail rotor designs for helicopters face challenges in accommodating cyclic flapping and feathering requirements, leading to increased drag, noise, and maintenance issues due to blades lying in different planes, which can generate vortices and require more parts and heavier components.
Innovation Solution
A gimbaled tail rotor hub with elastomeric centrifugal force bearings allows the tail rotor blades to flap and feather in the same plane, reducing drag and noise, and incorporating a gimbal assembly that transfers rotational movement from the mast to the rotor hub, enabling pitch changes and reducing maintenance needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tail rotor blades are allowed to flap and feather to accommodate cyclic lift dissymmetry, then thrust balance and flapping control are improved, but device complexity and weight increase due to additional parts and heavier components
Solution Approach 1:
The patent combines the flapping hinge and feathering hinge into a single integrated hub structure, eliminating separate components for each function. The hub itself serves as both the flapping axis support and the feathering axis support, merging two previously distinct mechanisms into one unified structure that reduces part count while maintaining both thrust balance and flapping control functions
Solution Approach 2:
The hub structure is designed to perform multiple functions simultaneously: it serves as the flapping hinge, the feathering hinge, and the structural connection between the mast and blades. This multi-functional design eliminates the need for separate dedicated components for each function, reducing overall device complexity while maintaining reliability for both thrust balance and flapping accommodation
2Reliability
If tail rotor blades lie in different planes to accommodate flapping motion, then cyclic lift dissymmetry is compensated, but drag and noise increase due to vortex generation
Solution Approach 1:
The patent transitions from out-of-plane flapping motion to in-plane flapping motion by reorienting the flapping hinge axis. Instead of blades moving in different vertical planes, the blades now flap within the same horizontal plane by rotating around a horizontally oriented hinge axis in the hub, eliminating vortex generation from planar displacement while maintaining flapping compensation capability
Solution Approach 2:
The hub incorporates a movable flapping hinge that allows dynamic adjustment of the flapping axis orientation. This dynamic mechanism enables the blades to flap in-plane while maintaining optimal aerodynamic alignment, compensating for cyclic lift dissymmetry without generating harmful vortices that would increase drag and noise
3Adaptability or versatility
If traditional tail rotor designs are used with separate flapping and feathering mechanisms, then blade articulation is achieved, but maintenance requirements increase
Solution Approach 1:
The patent merges the flapping hinge and feathering hinge into a single integrated hub structure, reducing the number of moving parts that require maintenance. By combining two separate articulation mechanisms into one unified hub, the design maintains full blade articulation capability while reducing maintenance frequency and complexity
Solution Approach 2:
The elastomeric centrifugal force bearing automatically adjusts to centrifugal loads during rotation, providing self-lubrication and self-adjustment properties that reduce maintenance requirements. The bearing material itself provides the necessary friction and wear characteristics without requiring external lubrication systems or frequent manual adjustment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables efficient flapping and feathering of tail rotor blades in an in-plane configuration, reducing drag, noise, and maintenance, while providing a lighter and more efficient design with fewer parts, improving the overall performance and lifespan of the tail rotor assembly.
Implementation Method 1
The elastomeric centrifugal force bearing is configured to withstand centrifugal force of a rotor blade when the mast is rotated
Implementation Method 2
a gimbaled tail rotor hub with elastomeric centrifugal force bearings
Data Source
AI summary
A rotor hub comprises a gimbal assembly and an elastomeric centrifugal force bearing. The gimbal assembly is configured to transfer rotational movement of a mast to the rotor hub and to enable the rotor hub to flap relative to the mast. The elastomeric centrifugal force bearing is configured to withstand centrifugal force of a rotor blade when the mast is rotated and is configured to accommodate pitch changes of the rotor blade. A method comprises designing a gimbal assembly that enables a tail rotor hub to flap relative to a tail rotor mast. A centrifugal force bearing is selected that enables tail rotor blades to withstand centrifugal force and that allows for tail rotor blade pitch change articulation. Then, instructions are provided to use the gimbal assembly and the centrifugal force bearing in an in-plane tail rotor assembly.