Bicycle Rim Assembly With Low-Density Inserts for Wider Tire Aerodynamics
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Solution Overview
Problem
Wider bicycle tires, which offer lower rolling resistance and improved comfort, cause aerodynamic and handling issues due to their 'bulging' shape when mounted on traditional rims, leading to increased aerodynamic drag and lateral movement during cornering, and increasing the weight of the rim to address these issues results in heavier wheels with sluggish acceleration.
Innovation Solution
A rim assembly with a rim component of lower density than the rim itself, integrated into the external surface to increase the external width while maintaining minimal weight, using materials like foam or epoxy resin to form the rim component, which can be bonded or inserted into recesses on the rim, allowing for wider rims with improved aerodynamics and handling without significant weight penalty.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the external width of the rim is increased to accommodate wider tyres, then aerodynamic drag is reduced and handling is improved, but the weight of the rim increases leading to heavier wheels with sluggish acceleration
Solution Approach 1:
The rim is constructed using composite materials, specifically carbon fibre reinforced plastic (CFRP), which provides high strength and stiffness while maintaining low weight. This allows the rim to achieve the required structural integrity for wider dimensions without proportionally increasing weight, thus reducing aerodynamic drag without suffering from excessive weight penalty
Solution Approach 2:
The rim profile is optimized with varying wall thicknesses at different locations - thicker sections where structural strength is needed and thinner sections where weight reduction is prioritized. This local quality variation allows the rim to achieve optimal balance between aerodynamic performance, structural integrity, and weight, enabling wider rims without linear weight increase
2Object-affected harmful factors
If the wall sections of the rim are thickened to reduce tyre bulging, then aerodynamic efficiency is improved, but the weight of the rim increases
Solution Approach 1:
Carbon fibre reinforced plastic provides exceptional strength-to-weight ratio, allowing the rim to achieve the necessary stiffness to control tyre bulging without requiring thick wall sections. The composite material's high modulus of elasticity enables thin-walled construction that still resists tyre expansion forces, thereby maintaining aerodynamic efficiency without weight penalty
Solution Approach 2:
The rim design utilizes advanced material properties and optimized geometric parameters including wall thickness distribution, cross-sectional shape, and reinforcement patterns. These parameter changes allow the rim to achieve adequate tyre support function with minimized material usage, reducing weight while maintaining control over tyre bulging characteristics
3Object-affected harmful factors
If wider rims are manufactured to accommodate wider tyres, then aerodynamic performance is improved, but the amount of material required increases leading to heavier rims
Solution Approach 1:
The use of carbon fibre reinforced plastic enables wider rim construction with reduced material quantity compared to traditional materials. The high specific strength and stiffness of CFRP allow the rim to achieve required structural performance with thinner sections and optimized material distribution, thereby reducing total material consumption while maintaining aerodynamic benefits of wider design
Solution Approach 2:
The rim structure is segmented into different zones with varying material density and thickness - denser sections where structural support is critical and sparser sections where aerodynamic shaping is prioritized. This segmentation allows optimal material distribution that reduces overall material quantity while maintaining both structural integrity and aerodynamic performance of the wider rim design
Data Source
AI summary
A rim assembly for a bicycle wheel, comprising a rim having generally opposing first and second wall sections configured for mounting a bicycle tire, each of said first and second wall sections comprising an outwardly facing recess and; a rim component located in each recess, wherein each rim component has a lower density than the rim, wherein the rim components do not form part of a braking section of the bicycle wheel.