Elastomeric Main Rotor Rod End Structure for Lower Cocking Stiffness

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Solution Overview

Problem

State-of-the-art main rotor damper elastomeric rod ends exhibit undesirable stiffness, known as cocking stiffness, which causes spiral motion and premature wear of damper internal components.

Innovation Solution

The design replaces traditional circular steel-elastomeric rod ends with two steel-elastomeric core cartridges separated by voids, reducing cocking and torsional stiffness through a tapered shape aligned with the axial load axis, thereby minimizing damper wear and extending its lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional steel-elastomeric rod ends are used, then structural strength is maintained, but cocking stiffness increases causing spiral motion and premature wear

Engineering Contradiction:

Improvedamper lifespanVSAvoidcocking stiffness

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The rod end is divided into multiple segments: a central void region and multiple elastomeric cartridges arranged around it. This segmentation creates void space that reduces cocking stiffness while the distributed elastomeric cartridges maintain structural strength and load-bearing capability, preventing spiral motion and reducing wear

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the rod end are given different properties: the central void region provides flexibility and reduced stiffness, while the elastomeric cartridges provide localized strength and damping. This local differentiation allows the structure to have both low cocking stiffness and adequate strength simultaneously

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If elastomeric core cartridges with voids are used, then cocking stiffness is reduced minimizing spiral motion, but structural complexity increases

Engineering Contradiction:

Improvespiral motionVSAvoidrod end structure

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

Multiple elastomeric cartridges are merged into a single integrated rod end structure that surrounds a central void. This combination achieves the desired reduction in cocking stiffness and elimination of spiral motion while maintaining a compact, unified structure rather than separate components

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The rod end uses composite construction with elastomeric materials combined with void space. This composite approach reduces cocking stiffness through the elastomeric properties and void configuration, while the overall structure remains structurally sound through the distributed elastomeric cartridges

Inventive Principle:

Principle #40Composite materials

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

This configuration effectively reduces unwanted stiffness and wear, enhancing the durability and performance of the damper assembly by using elastomeric core cartridges in place of steel spherical bearings.

Implementation Method 1

the rod end comprising at least two elastomeric core cartridges separated by a void

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS11505312B2Main rotor damper elastomeric rod end

Publication Date: 2022.11.22 LOCKHEED MARTIN CORP

AI summary

A damper assembly includes a housing defining at least one or more cavities. A piston is in operable communication with the housing. A rod end is operatively coupled to the piston, the rod end having at least two cartridges.