Composite Bicycle Front Sprocket for Higher Lateral Stiffness
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Solution Overview
Problem
Traditional bicycle front sprockets made from metals like aluminum have low lateral stiffness, leading to inefficiencies and mechanical issues due to significant lateral pull during cross-chaining, especially in bicycles with multiple gears.
Innovation Solution
A composite front sprocket assembly is created using a combination of materials, such as aluminum for the outer assembly and carbon fiber reinforced nylon for the center, with a ceramic or metal crank drive ring, integrated through injection molding or composite layering to enhance stiffness and reduce material waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional metal front sprockets are used, then manufacturing is straightforward through subtractive processes, but lateral stiffness is low leading to drive efficiency loss and mechanical issues
Solution Approach 1:
The patent applies composite materials by combining aluminum outer assembly with carbon fiber reinforced nylon center assembly, creating a front sprocket with significantly enhanced lateral stiffness. The composite structure allows the carbon fiber reinforced nylon to provide high stiffness in the lateral direction while the aluminum provides structural support and tooth engagement, resolving the contradiction between ease of manufacture and lateral stiffness.
Solution Approach 2:
The front sprocket is segmented into multiple components: aluminum outer assembly, carbon fiber reinforced nylon center assembly, and ceramic or metal crank drive ring. This segmentation allows each component to be manufactured using optimal processes for its material properties, then assembled together to achieve the desired lateral stiffness without requiring complex subtractive manufacturing of the entire structure.
2Loss of substance
If traditional subtractive manufacturing processes are used, then material waste is high, but production costs increase
Solution Approach 1:
The patent applies preliminary action by pre-forming the aluminum outer assembly and carbon fiber reinforced nylon center assembly using molding processes before final assembly. The aluminum outer assembly is formed with recesses that receive the center assembly, and the teeth are formed during molding rather than through subtractive processes. This preliminary forming action significantly reduces material waste compared to traditional machining and punching operations.
3Strength
If flat-structure front sprockets are used, then manufacturing is simple, but lateral stiffness is insufficient under cross-chaining conditions
Solution Approach 1:
The patent uses composite materials with the carbon fiber reinforced nylon center assembly providing high lateral stiffness through the carbon fiber reinforcement orientation. The aluminum outer assembly complements this with its own structural properties. This composite approach achieves the required lateral stiffness without requiring complex geometric features or thickening of the overall structure, thus managing device complexity while improving strength.
Data Source
AI summary
Methods and apparatus for a composite bicycle front sprocket are disclosed herein. One embodiment discloses a composite bicycle front sprocket assembly having an outer assembly of a first material. The bicycle front sprocket assembly also has a center assembly of a second material. The center assembly is disposed at least partially within the outer assembly. The center assembly is irremovably coupled with the outer assembly. The center assembly is irremovably coupled with the outer assembly without an external fastening device to irremovably couple the center assembly with the outer assembly.