U-Shaped Flex Beam Clamp for Rotor Stiffness
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Solution Overview
Problem
Conventional flex-beam rotors for coaxial contra-rotating rotorcraft lack the necessary flat-wise stiffness and vibratory response, leading to potential blade collisions and increased drag, especially when trying to position rotor assemblies closer together for higher speeds.
Innovation Solution
A rotor assembly design featuring a rotor hub with U-shaped flexible structural members, a clamp member that ties deflection of the first and second arms, and a rotor blade pin for securing the rotor blade, along with a recessed channel lined with wear preventative material to reduce wear and prevent scissoring motion, enhancing stiffness and reducing internal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rotor assemblies are positioned closer together to increase rotor speeds and reduce drag, then speed and efficiency improve, but flat-wise stiffness decreases leading to potential blade collisions and poor vibratory response
Solution Approach 1:
The flex-beam arm is segmented into two separate arms (first arm and second arm) that are spaced apart radially. This segmentation allows each arm to independently support a rotor blade while maintaining structural integrity, thereby providing the necessary flat-wise stiffness even when rotor assemblies are positioned closer together.
Solution Approach 2:
The invention transitions from a conventional single-beam structure to a two-arm structure that utilizes radial spacing as an additional dimensional parameter. By distributing the arms radially outwardly from the rotor hub, the structure gains stiffness in the flat-wise direction without increasing the axial distance between rotor assemblies.
2Weight of moving object
If conventional flex-beam structure is used, then lightweight and cost-effective construction is achieved, but flat-wise stiffness and vibratory response are insufficient
Solution Approach 1:
The flex-beam is divided into two separate arms connected to the rotor hub, creating a U-shaped configuration. This segmentation distributes the structural loads more effectively while maintaining the lightweight advantage of the flex-beam design, achieving both weight efficiency and improved flat-wise stiffness.
Solution Approach 2:
The invention employs a composite structure combining the flexible structural member (flex-beam) with a clamp member that ties the deflection of both arms. This composite approach leverages the weight advantages of flexible materials while adding stiffness through the rigid clamp connection, resolving the contradiction between light weight and structural strength.
3Ease of manufacture
If flex-beam rotor design is used, then cost-effective construction is achieved, but blade collision risk increases due to insufficient stiffness
Solution Approach 1:
The two-arm configuration with radial spacing inherently prevents blade collisions by maintaining proper clearance between adjacent rotor blades. The segmented structure is relatively simple to manufacture using conventional processes, preserving cost-effectiveness while dramatically improving reliability.
Solution Approach 2:
The clamp member acts as an intermediary element that connects the two arms of the flex-beam structure. This intermediary component ensures synchronized deflection of both arms, preventing asymmetric motion that could lead to blade collisions, while being simple and cost-effective to manufacture.
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 design improves flat-wise stiffness and reduces vibratory response, preventing blade collisions and drag, while allowing for closer positioning of rotor assemblies for higher speeds and reduced wear, thereby enhancing the performance and efficiency of rotary wing aircraft.
Implementation Method 1
the channel includes a liner of a wear preventative material to reduce wear of the flexible structural member at the clamp member
Implementation Method 2
Each flexible structural member is substantially U-shaped and has a first arm extending from the rotor hub, a second arm extending from the rotor hub, and an end portion connecting the first arm to the second arm
Data Source
AI summary
A rotor assembly for a rotary wing aircraft includes a rotor hub having a central axis, the rotor hub rotatable about the central axis. A plurality of flexible structural members extend radially outwardly from the rotor hub, each flexible structural member substantially U-shaped and having a first arm extending from the hub, a second arm extending from the hub, and an end portion connecting the first arm to the second arm at a radially outboard end of the flexible structural member. A clamp member is positioned between the first arm and the second arm of each structural member and secured thereto to tie deflection of the first arm to deflection of the second arm. A rotor blade is secured to each flexible structural member of the plurality of flexible structural members via the clamp member.