Bicycle Sprocket Composite Design for Weight and Strength
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Solution Overview
Problem
Mountain bike sprockets face challenges in balancing strength, rigidity, and weight, particularly under strong pedaling forces and mud accumulation, while requiring agility and resistance to chain inclination stress.
Innovation Solution
A bicycle sprocket design featuring a sprocket body and tooth ring made of different materials, with non-threaded fasteners connecting them, and varying tooth sizes and shapes to enhance strength, reduce weight, and improve mud elimination, while maintaining chain engagement efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sprocket is made of strong and rigid material, then strength and rigidity are improved, but weight increases
Solution Approach 1:
The sprocket combines two different materials: a lightweight material (e.g., aluminum or plastic) for the sprocket body and a strong wear-resistant material (e.g., steel) for the tooth ring. This composite structure allows the main body to be lightweight while the tooth ring provides the necessary strength and wear resistance for chain engagement, thus resolving the contradiction between weight and strength.
Solution Approach 2:
The sprocket is divided into separate components: the sprocket body and the tooth ring, which are attached together. This segmentation allows each component to be optimized independently - the body for weight reduction and the tooth ring for strength - and then combined to achieve overall performance that balances both requirements.
2Reliability
If the tooth ring is made of different material than the sprocket body, then wear resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The tooth ring is designed as a separate component from the sprocket body, allowing it to be manufactured from a different material optimized for wear resistance. The separate tooth ring can be produced using processes suited for wear-resistant materials and then attached to the sprocket body, simplifying the overall manufacturing process compared to creating a monolithic component with varying material properties.
Solution Approach 2:
By using a composite structure with a tooth ring made of wear-resistant material (such as steel) and a body made of lighter material, the design achieves improved wear resistance at the chain engagement points while maintaining ease of manufacture through standardized attachment methods for the separate components.
3Power
If the chain line is inclined relative to the sprocket, then power transmission is improved, but bending stress on the sprocket increases
Solution Approach 1:
The tooth ring made of strong, rigid material (such as steel) is specifically designed to withstand the bending stresses generated by the inclined chain line. This material choice for the tooth ring provides the necessary structural strength to handle the increased stress while still allowing the chain line inclination to optimize power transmission.
Data Source
AI summary
A bicycle sprocket includes a sprocket body, a tooth ring, and at least one non-threaded fastener. The sprocket body is made of a first material and has a rotational center axis. A central portion of the sprocket body has a central opening through which the rotational center axis passes. The sprocket body further includes a plurality of arm portions that extend radially outward from the central portion with respect to the rotational center axis. Each arm portion includes a sprocket body attachment portion. The tooth ring is made of a second material different from the first material and includes an annular portion. The annular portion includes a plurality of tooth ring attachment portions and a plurality of chain-driving teeth extending radially outward from the annular portion. The non-threaded fastener fixedly connects a sprocket body attachment portion and to a corresponding tooth ring attachment portion.