Bicycle Sprocket Assembly Weight Reduction via Composite Materials
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Solution Overview
Problem
Conventional multiple sprocket assemblies for bicycles are heavy due to thick and heavy driver and sprocket profiles, and lighter materials used to reduce weight compromise on hardness, deformation, and wear resistance.
Innovation Solution
A multiple sprocket assembly featuring a hollow conical body with annular support elements and different-sized sprockets, where the annular support elements are configured in a stepped arrangement with openings and connectors to maximize strength, reduce weight, and channel dirt away from the assembly, while ensuring torque transmission and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If sprockets are made of lighter materials with openings to reduce weight, then weight is reduced, but hardness, deformation resistance and wear resistance deteriorate
Solution Approach 1:
The sprocket assembly uses a composite structure combining aluminum alloy (lightweight material) for the sprocket body with steel inserts (high strength material) at critical stress points. This composite approach allows the majority of the structure to be lightweight while maintaining strength and wear resistance at load-bearing locations, directly resolving the contradiction between weight reduction and strength maintenance.
Solution Approach 2:
The design implements local quality by applying different material properties to different regions of the sprocket. The sprocket body uses lightweight aluminum alloy, while critical areas such as tooth roots and mounting interfaces use high-strength steel. This localized material differentiation allows weight reduction in non-critical areas while preserving strength where needed, solving the contradiction between overall weight reduction and local strength requirements.
2Force
If profile areas of driver and sprocket are made thick and heavy to transmit torque, then torque transmission capability is improved, but weight increases
Solution Approach 1:
The driver and sprocket profiles use a composite construction with aluminum alloy providing the bulk structure for weight reduction, while steel reinforcement elements provide the necessary torque transmission capability. This allows the profiles to be thinner and lighter than solid steel constructions while maintaining adequate torque transmission through the high-strength steel components at critical locations.
Solution Approach 2:
The profile structure is segmented into multiple functional zones: lightweight aluminum alloy sections for general structure, steel inserts for high-stress torque transmission areas, and optimized geometric features. This segmentation allows each zone to be optimized for its specific function, reducing overall weight while maintaining torque transmission capability where required.
3Weight of moving object
If openings are added to sprockets to reduce weight, then weight is reduced, but structural strength may deteriorate
Solution Approach 1:
The openings are strategically positioned in non-critical areas of the sprocket where material removal does not significantly compromise structural strength. The distribution, size, and location of openings are optimized to maintain structural integrity while maximizing weight reduction. Critical load-bearing areas retain full material density, while non-critical areas feature openings for weight reduction.
Solution Approach 2:
The opened structure is compensated by steel reinforcement elements that are strategically placed to restore structural strength. The combination of opened aluminum alloy sections with steel reinforcement creates a composite structure that achieves both weight reduction from the openings and strength restoration from the reinforcement, resolving the contradiction between weight reduction and structural strength maintenance.
Data Source
AI summary
A multiple sprocket assembly receives a chain and transfers torque therefrom to a rear wheel hub of a bicycle. The multiple sprocket assembly includes a plurality of different-sized multiple-toothed sprockets arranged coaxially about the rear wheel hub. A plurality of annular support elements extend between the sprockets and have a plurality of openings disposed circumferentially on the annular support element. The openings are aligned with tooth gaps of an adjoining smaller sprocket. The sprockets and the annular support elements are configured to transmit torque from the smaller sprocket to a larger sprocket.