Bicycle Crank Assembly Axial Offset for Wider Tires
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Solution Overview
Problem
Conventional bicycle crank assemblies pose a challenge when trying to install wider tires at the rear end of a bicycle frame, as the chain may come into contact with the chain stay due to inadequate configuration, limiting the width of the tire that can be installed.
Innovation Solution
A bicycle crank assembly design that includes specific axial and transverse center plane configurations, with the first and second axial distances set between 90 mm and 170 mm, and the second axial distance set between 57 mm and 85 mm, to prevent chain contact with the chain stay, allowing for the installation of wider tires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the width of the rear end is increased to install a wider tire, then the tire width is improved, but the chain may come into contact with the chain stay
Solution Approach 1:
The patent applies dimensionality change by positioning the sprocket in a transverse direction relative to the crank axle, creating a spatial offset that separates the chain path from the chain stay. The first transverse center plane of the sprocket is positioned at a specific distance from the second transverse center plane of the crank axle, establishing a three-dimensional configuration that prevents chain contact while allowing wider tire installation.
Solution Approach 2:
The patent employs parameter changes by specifying precise axial distance parameters: the first axial distance between pedal attachment surfaces is set to 170 mm or less, and the second axial distance between transverse center planes is set to 55 mm or more. These parameter adjustments optimize the spatial arrangement to prevent chain contact while accommodating wider tires.
2Object-affected harmful factors
If the first axial distance is reduced to prevent chain contact, then chain contact is prevented, but the crank assembly size is reduced
Solution Approach 1:
The patent applies parameter changes by optimizing the first axial distance to be 170 mm or less, which prevents chain contact while maintaining a compact crank assembly. This parameter optimization balances the conflicting requirements of chain contact prevention and size reduction.
Solution Approach 2:
The patent uses dimensionality change by arranging the sprocket and crank components in specific transverse and axial positions, creating a compact three-dimensional configuration that prevents chain contact without requiring excessive axial length.
3Object-affected harmful factors
If the second axial distance is increased to position the sprocket properly, then chain contact is prevented, but the overall crank assembly length increases
Solution Approach 1:
The patent applies parameter changes by setting the second axial distance to 55 mm or more, which positions the sprocket to prevent chain contact while controlling the overall axial length. This parameter optimization resolves the contradiction between chain contact prevention and size control.
Solution Approach 2:
The patent employs dimensionality change by positioning the sprocket's first transverse center plane at a specific distance from the crank axle's second transverse center plane, creating an optimized spatial arrangement that prevents chain contact without excessive axial length.
Data Source
AI summary
A bicycle crank assembly has a sprocket, a first crank arm, a second crank arm and a crank axle, A first axial distance is defined between the first pedal attachment surface and the second pedal attachment surface in an axial direction. A second axial distance is defined between the first transverse center plane of the sprocket and the second axial center plane of the crank axle in the axial direction. The first axial distance is smaller than or equal to 170 mm. The second axial distance is larger than or equal to 55 mm.