Telescopic Assembly With Non-Uniform Bushing for Sideload Binding

Solution Overview

Problem

Telescopic assemblies in vehicles, such as dropper seat posts, experience issues with loose or tight fits leading to sideload forces that cause binding, rattling, and increased friction, affecting performance and potentially damaging internal components.

Innovation Solution

A non-uniform thickness bushing is used in telescopic assemblies, featuring a first portion with a greater thickness than a second portion, which biases the second post out of coaxial alignment with the first post under no load, allowing for improved axial alignment and reduced friction when sideloads are applied.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the bushing fit is made tight to prevent sideload binding, then the inner post binding issue is reduced, but the running friction increases causing high friction ride feel

Engineering Contradiction:

Improveprevention of inner post bindingVSAvoidrunning friction

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The bushing is designed with non-uniform thickness, having a first portion with greater thickness and a second portion with lesser thickness. This local variation in geometry allows different regions of the bushing to serve different functions: the thicker portion provides stability and prevents binding under sideload, while the thinner portion reduces contact area and minimizes running friction during axial movement.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The bushing employs asymmetric thickness distribution around its circumference, with the first portion (greater thickness) positioned to face the direction of potential sideload and the second portion (lesser thickness) positioned to minimize friction during axial compression. This asymmetric design allows the bushing to handle multidirectional forces effectively while maintaining smooth axial operation.

Inventive Principle:

Principle #4Asymmetry

2Ease of operation

If the bushing fit is made loose to reduce running friction, then the friction ride feel improves, but the inner post binds under sideload force

Engineering Contradiction:

Improverunning frictionVSAvoidprevention of inner post binding

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The bushing is designed with non-uniform thickness, having a first portion with greater thickness and a second portion with lesser thickness. This local variation in geometry allows different regions of the bushing to serve different functions: the thicker portion provides stability and prevents binding under sideload, while the thinner portion reduces contact area and minimizes running friction during axial movement.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The bushing design allows dynamic adjustment of the effective fit based on loading conditions. Under axial load, the thinner portion reduces friction. Under sideload, the thicker portion engages to prevent binding. This dynamic response to different force directions resolves the contradiction between low friction and binding prevention.

Inventive Principle:

Principle #15Dynamics

3Ease of manufacture

If a uniform thickness bushing is used, then the manufacturing is simple, but the bushing cannot simultaneously reduce binding and friction under varying loads

Engineering Contradiction:

Improvebushing manufacturing simplicityVSAvoidperformance under varying loads

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The bushing is designed with non-uniform thickness, having a first portion with greater thickness and a second portion with lesser thickness. This local variation in geometry allows different regions of the bushing to serve different functions: the thicker portion provides stability and prevents binding under sideload, while the thinner portion reduces contact area and minimizes running friction during axial movement.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The bushing employs asymmetric thickness distribution around its circumference, with the first portion (greater thickness) positioned to face the direction of potential sideload and the second portion (lesser thickness) positioned to minimize friction during axial compression. This asymmetric design allows the bushing to handle multidirectional forces effectively while maintaining smooth axial operation.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS20250304200A1Telescopic assembly with a non-uniform bushing

Publication Date: 2025.10.02 FOX FACTORY INC

AI summary

A telescopic assembly with a non-uniform thickness bushing is provided. The telescopic assembly includes a second telescopic member slidably coupled within a first telescopic member. The non-uniform thickness bushing is coupled to an end of the second telescopic member and located between the second telescopic member and the first telescopic member. The non-uniform thickness bushing includes a bushing body forming a ring with an aperture extending therethrough; a first portion extending from the bushing body on one side of the ring, the first portion having a first thickness; and a second portion extending from the bushing body on a side of the ring opposite the side of the first portion, the second portion having a second thickness. The first thickness is greater than the second thickness placing an axis of the second telescopic member in a position out of coaxial alignment with an axis of the first telescopic.