Trunnion Assembly Stress Distribution via Nested Pivot Tube
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Solution Overview
Problem
Trunnion assemblies face significant stress failures due to the movement of pivoting points and relatively smaller pivots compared to the main body, which leads to structural weaknesses.
Innovation Solution
A trunnion assembly design featuring pivot-engagement components with attachment holes having threaded areas and counterbores, along with a fastener and pivot tube configuration that distributes stress effectively, allowing for enhanced strength and assembly flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional fasteners are used without pivot tubes, then the assembly is simpler, but the shear strength and bending strength are insufficient to withstand high stresses
Solution Approach 1:
The pivot assembly is segmented into distinct components: fastener, pivot tube, and retention feature. This segmentation allows each component to be optimized for its specific function - the fastener provides clamping force, the pivot tube resists shear and bending stresses, and the retention feature prevents disassembly. The segmentation enables the assembly to withstand high stresses while maintaining reasonable complexity through modular design.
Solution Approach 2:
The pivot tube is nested within the counterbore of the attachment hole, and the fastener is nested within the pivot tube. This nested configuration allows the stronger pivot tube to be positioned inside the counterbore where it can effectively resist bending and shear forces, while the fastener secures the entire assembly. The nesting maximizes strength within the available space without significantly increasing external dimensions or complexity.
2Strength
If the pivot tube outer diameter is increased to withstand higher stresses, then the strength increases, but the space required for assembly decreases
Solution Approach 1:
The pivot tube provides localized strength exactly where it is needed - within the counterbore area where bending and shear stresses are concentrated. The tube's outer diameter is optimized to provide sufficient strength while fitting within the counterbore dimensions. This local quality approach ensures high stress withstanding capacity in the critical region without requiring the entire assembly to be enlarged.
Solution Approach 2:
The solution moves from considering only the fastener diameter to utilizing the third dimension by inserting a pivot tube within the counterbore. This dimensional transition allows the pivot tube to provide additional strength through its wall thickness and length, effectively increasing the load-bearing capacity without increasing the external footprint of the assembly.
3Ease of operation
If the fastener head diameter is increased to provide better leverage for tightening, then the ease of operation improves, but the space required increases
Solution Approach 1:
The fastener head diameter is designed to provide sufficient leverage for tightening operations while maintaining a compact size. The dynamic aspect is reflected in the optimization of the head-to-shaft diameter ratio, which balances the need for operational leverage with the constraint of available space. The head diameter is sized to accommodate standard wrenches or tools while fitting within the overall assembly envelope.
Data Source
AI summary
A trunnion assembly, comprising at least two pivot-engagement sides located opposite each other, each of the at least two pivot-engagement sides including an attachment hole, each attachment hole including a threaded area and a counterbore, the at least two attachment holes being generally coaxially located relative to each other; and at least one through-hole perpendicular to and midway between the two attachment holes of the pivot-engagement sides; a fastener releasably attached to each of the at least two attachment holes, the fastener including a head and an at least partially-threaded shaft, and a pivot tube disposed around each of the fasteners between the head and the attachment hole, the pivot tube including an inner diameter larger than the diameter of the shaft and an outer diameter smaller than the diameter of a circumscribed circle of the head of the fastener and smaller than the diameter of the counterbore.