Variable Radius Strut Assembly for Non-Linear Tension Control
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Solution Overview
Problem
Current wing strut designs face challenges in managing non-linear tension member length changes, leading to buckling, increased weight, and aerodynamic drag, particularly during varying flight conditions and ground conditions, where they must carry compression without buckling and avoid the 'scissor jack phenomenon while minimizing weight and drag.
Innovation Solution
A variable radius assembly comprising a spindle, variable radius guide members, and a tension member that wraps around a spiral body, allowing for non-linear tension member length changes for constant spindle rotation, enabling the strut to brace at an inclination angle and transition between contracted and extended positions efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a full-span wing strut is used to span between fuselage and wing underside, then the strut provides continuous support and reduces bending moment, but the strut becomes thick and heavy due to increased buckling length
Solution Approach 1:
The wing strut is divided into multiple segments: a primary strut attached to the fuselage, and multiple jury struts (auxiliary struts) fastened along the length of the primary strut. These segments work together to provide continuous support while reducing the effective buckling length of each individual strut segment, thereby reducing weight while maintaining strength.
2Weight of moving object
If jury struts are added to break up buckling length, then the primary strut can be thinner and weight is reduced, but aerodynamic drag increases
Solution Approach 1:
The jury struts are designed to be movable relative to the primary strut, allowing them to adjust their position and orientation. This dynamic configuration enables the struts to be repositioned to minimize aerodynamic drag during flight while maintaining their structural function for buckling resistance.
3Object-affected harmful factors
If cable struts are used to reduce aerodynamic drag, then drag is minimized, but the wing must be sized for cantilever conditions and becomes heavier
Solution Approach 1:
Instead of using a single heavy cable strut system, the support function is segmented across multiple lighter jury struts distributed along the primary strut. This segmentation provides distributed support that reduces the loading on the wing root, allowing the wing to be lighter while still maintaining aerodynamic efficiency.
4Stability of the object's composition
If pre-stressing is applied to eliminate cable droop, then droop under -1g condition is reduced, but connection hardware size, bending, and compression increase causing unwanted weight
Solution Approach 1:
The jury struts are designed with movable connections that allow them to dynamically adjust their position and orientation in response to loading conditions. This dynamic adaptability provides stability and prevents droop without requiring heavy pre-stressing hardware, as the movable joints can passively accommodate and correct for position changes.
Data Source
AI summary
There is provided a variable radius assembly having a spindle, at least one variable radius guide member coupled to, and driven by, the spindle, and a tension member attached to the variable radius guide member. The tension member is configured to attach to at least one variable length structural member. The variable radius assembly further has at least one gear coupled to, and driven by, the spindle, and has at least one rotational power source coupled to the spindle, and configured to rotate the spindle. The variable radius guide member enables a tension member length change at a non-linear rate for a constant rate of rotation of the spindle, allowing the at least one variable length structural member to be braced by the tension member at an inclination angle to the at least one variable length structural member throughout a range of motion.