Pivoting Chain Guide Pulley for Suspension-Induced Chain Growth
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Solution Overview
Problem
Suspension-induced chain growth in off-road bicycles causes additional stress on derailleurs, leading to chain slap and potential derailment issues, as existing technologies fail to adequately address the lower portion of the drive chain length variation during suspension activation.
Innovation Solution
A pivoting mount for a common chain guide lower pulley is attached near the chain ring and bottom bracket, connected to the suspension, allowing it to take up and release chain length during suspension activation, thereby reducing or eliminating suspension-induced chain growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditionally sprung rear derailer is used, then the derailer can accommodate chain length variations, but the inertia of the chain pulls the derailer cage forward causing chain slap and potential derailment
Solution Approach 1:
A lower chain guide pulley is introduced as an intermediary component between the chain and the derailer cage. This pulley actively guides the chain and prevents it from slapping against the derailer cage during suspension activation, thereby eliminating chain slap while maintaining the derailer's ability to accommodate chain length variations
Solution Approach 2:
The lower chain guide pulley is made movable through a pivot mount that allows it to move in response to suspension activation. This dynamic movement enables the pulley to adapt to chain length changes and maintain proper chain alignment throughout the suspension range of motion, preventing both chain slap and derailment
2Length of moving object
If the lower portion of the drive chain is made flexible to accommodate suspension activation, then chain grow is reduced, but the derailer capacity requirements increase
Solution Approach 1:
The movable lower chain guide pulley serves as a mediator that actively manages chain length variations. By guiding the chain and allowing the pulley itself to move with suspension activation, it reduces the burden on the derailer to accommodate chain grow, thereby reducing derailer capacity requirements while maintaining chain length flexibility
3Device complexity
If a static chain guide pulley is used, then the structure is simple, but suspension induced chain grow cannot be accommodated
Solution Approach 1:
The chain guide pulley is transformed from a static component to a dynamic one through the pivot mount. This allows the pulley to move in response to suspension activation, enabling it to accommodate chain length variations while maintaining a relatively simple structure. The dynamic capability is achieved through a straightforward rotational joint rather than complex mechanisms
Data Source
AI summary
The present invention reduces or eliminates suspension induced lower portion chain grow for rear derailer equipped bicycle drive trains using a pivoting mount for the common chain guide pulley. Attached about or near concentric with the chain ring and bottom bracket this mounting plate has a pivotally connected link to the suspension. The chain guide pulley is positioned to “take-up” or store some lower portion of chain length around the chain ring. Suspension activation creates pivotal movement of the guide mounting plate to relieve suspension induced chain grow by releasing some or the entire taken-up length of the lower portion of the drive chain.