Adjustable Scissor Control Link for Dual Rotor Helicopter
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Solution Overview
Problem
Dual coaxial rotor helicopters face challenges in achieving a low-drag, low-weight solution that satisfies both pitching and tracking requirements for upper rotor blades, as primary pitch control links are often embedded within the rotor head and shaft, making tracking adjustments difficult.
Innovation Solution
The implementation of axially adjustable scissor control links that interface with the rotor bellcrank or walking beam and the rotating swashplate, allowing for both pitching and tracking of rotor blades while transmitting rotation to the rotating swashplate, thereby controlling the position of primary pitch control links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If primary pitch control links are embedded within the rotor head and shaft, then the structure is compact and integrated, but tracking adjustments become difficult
Solution Approach 1:
The control link is divided into multiple segments (first link, second link, third link) connected by bearings, allowing the structure to remain integrated while enabling adjustment of individual segments for tracking modifications
Solution Approach 2:
The control link incorporates adjustable elements that allow dynamic reconfiguration of the link geometry, enabling tracking adjustments without disassembling the integrated rotor head structure
2Ease of operation
If a separate mechanism is added for scissoring, then tracking control is improved, but weight and drag increase
Solution Approach 1:
The scissoring mechanism is merged with the secondary pitch control links, combining two functions (pitch control and scissoring for tracking) into a single integrated structure, thereby eliminating the need for a separate scissoring mechanism and reducing overall weight
Solution Approach 2:
The secondary pitch control links are designed to perform multiple functions: transmitting pitch control forces and providing scissoring motion for tracking adjustments, making the structure multi-functional and eliminating redundant components
3Device complexity
If bearing friction is present in the control links, then the structure is simple, but dragging formation occurs affecting rotor blade path
Solution Approach 1:
The friction effect is extracted and counteracted by introducing moment reactions through the scissor link geometry, separating the structural function from the friction problem and allowing the rotor blade path to remain smooth despite simple bearing structures
Data Source
Figure 1~2
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AI summary
A control link disposed to transfer rotor shaft rotation from an elongate element rotatable with a shaft to a rotatable element is provided and includes a structure terminating at a first end thereof as a mating element, which is securable to the elongate element such that the elongate element is rotatable about an axis defined through the mating element and such that a moment reaction in opposition to structure rotation about the elongate element is generated and a rod coupled to the rotatable element being and configured to be coupled to a second end of the structure at variable distances relative to the rotatable element.