Bicycle Crank Arm Segmented Composite Design
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Solution Overview
Problem
Traditional bicycle crank arms made of single metal pieces are heavy, and while recent advancements have used lighter metal alloys and composite materials, there is a need for a design that achieves both weight savings and reliable support for crank and pedal axles.
Innovation Solution
A bicycle crank arm design featuring a first structural member made of a non-metallic material and a second structural member made of a different material, with optional reinforcement members, configured to support crank and pedal axles while optimizing weight and rigidity through material selection and attachment methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single piece of metal is used to construct the crank arm, then the crank arm has sufficient strength and rigidity, but the crank arm becomes heavy
Solution Approach 1:
The crank arm is divided into multiple separate members (first structural member, second structural member, and optionally third structural member) instead of being a single piece. These members are attached together to form the complete crank arm, allowing weight reduction while maintaining structural integrity through the distributed architecture.
Solution Approach 2:
The patent uses different materials for different structural members - typically combining metal materials (for strength) with non-metallic composite materials (for weight reduction). This composite approach allows each member to be optimized for its specific functional requirements, achieving overall weight reduction while maintaining sufficient strength and rigidity.
2Weight of moving object
If multiple separate members are used to reduce weight, then the crank arm becomes lighter, but the reliability of supporting crank and pedal axles may be compromised
Solution Approach 1:
Multiple structural members are attached together to form an integrated crank arm assembly that reliably supports both the crank axle and pedal axle. The attachment mechanisms (such as adhesives, mechanical fasteners, or integral bonding) ensure that the combined structure achieves the necessary reliability and load-bearing capacity despite being composed of separate members.
Solution Approach 2:
Different regions of the crank arm are made from different materials optimized for their specific functions - metal members provide strength at critical load-bearing points (such as where axles are supported), while non-metallic composite members provide weight reduction in less critical areas. This local optimization maintains reliability while achieving weight reduction.
3Weight of moving object
If different materials are used for different structural members, then weight is reduced and rigidity is optimized, but the manufacturing complexity increases
Solution Approach 1:
The crank arm is segmented into separate members that can be manufactured independently using material-optimized processes, then assembled together. This segmentation allows each member to be produced using the most suitable manufacturing technique for its material type, potentially simplifying overall manufacturing despite the multi-material approach.
Solution Approach 2:
Attachment mechanisms serve as intermediaries between different material members, providing standardized interfaces that simplify the assembly process. These intermediaries (adhesives, fasteners, or bonding structures) enable easy joining of different materials without requiring complex integrated manufacturing processes.
Data Source
AI summary
A bicycle crank arm is basically provided that includes a first structural member and a second structural member attached to the first structural member. The first structural member is made of a first material including a non-metallic material. The second structural member is made of a second material that is different from the first material.