Conical Bicycle Cassette Support Structure for Stress Distribution
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Solution Overview
Problem
Unitary sprocket assemblies with a conical shape face premature failure due to highly localized stress in unsupported areas, which can be mitigated by either increasing thickness for strength or reducing weight, but neither solution effectively addresses the issue of stress distribution.
Innovation Solution
A conical shaped bicycle cassette with a unitary sprocket assembly that alternates axial and radial support zones around its circumference, ensuring that each sprocket is mechanically supported either axially or radially, thereby distributing chain driving loads and reducing localized stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If holes and windows are machined into the sprocket assembly to reduce weight, then the overall weight of the sprocket assembly is reduced, but the annular size and cross section of the individual sprockets decrease and unsupported sections create areas of highly localized stress
Solution Approach 1:
The sprocket assembly is segmented into multiple individual sprockets connected by connecting portions, with each sprocket being a separate annular element. This segmentation allows weight reduction through strategic material removal while maintaining structural integrity through the distributed support architecture.
Solution Approach 2:
The patent introduces radial support zones that extend in the radial direction from the hub outward, creating a three-dimensional support structure. This radial dimension provides additional load paths and support for the sprocket teeth, preventing localized stress concentrations while allowing weight reduction through axial and radial windows.
2Strength
If the thickness of unsupported areas is increased to support localized stress, then the strength of the sprocket assembly is improved, but the overall weight of the sprocket assembly becomes objectionably high
Solution Approach 1:
The sprocket assembly features non-uniform thickness distribution with strategically placed thick sections at the connecting portions and thin sections in the unsupported areas. The connecting portions have increased thickness to provide structural support, while the sprocket bodies maintain reduced thickness for weight savings. This local variation in quality optimizes the strength-to-weight ratio.
Solution Approach 2:
The patent employs a composite structure combining different material densities and thicknesses within a single sprocket assembly. The connecting portions use thicker, more robust material to provide structural support, while the sprocket bodies use thinner material for weight reduction. This composite approach allows the assembly to achieve both strength and weight reduction goals simultaneously.
3Ease of manufacture
If a flat shape of the sprocket is used to transmit driving forces, then the driving force transmission is simplified, but areas of highly localized stress are created in the unsupported regions
Solution Approach 1:
The sprocket assembly features a conical shape with curved surfaces transitioning from the hub outward to the sprocket bodies. This curvature distributes stress more evenly across the connecting portions and prevents stress concentration at sharp edges or flat interfaces. The tapered, curved geometry provides gradual load transitions while maintaining the essential flat driving surfaces for chain engagement.
Data Source
AI summary
A conical shaped bicycle cassette has a unitary sprocket assembly. Each annular portion of an individual sprocket is mechanically supported either from a back of the sprocket, in an axial direction toward a bicycle hub or from an inner radial direction toward a centerline axis of the bicycle cassette and hub. The axial support zones and radial support zones are alternated around a circumference of the sprocket so that an entirety of the sprocket is supported in either the axial direction or the radial direction. In this way, the chain driving loads on the cassette are spread throughout the entire cassette and the areas of highly localized stress from the cassette are removed.