Bicycle Fork Steer Tube Composite Design
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Solution Overview
Problem
Existing bicycle fork designs lack sufficient strength and durability, particularly at the steer tube and crown intersection, where high loads are concentrated, leading to potential failure under impact.
Innovation Solution
A bicycle fork design featuring a metallic steer tube bonded to a carbon-reinforced plastic crown, with a tapered steer tube and thickened walls for impact absorption, utilizing a combination of materials to distribute loads and provide redundancy through the brake bolt reinforcement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic steer tube is used, then strength and toughness are improved, but weight increases
Solution Approach 1:
The patent applies composite materials by bonding a metallic steer tube to a carbon-reinforced plastic crown. This combination allows the metallic portion to provide strength and toughness where needed (at the steer tube and crown intersection), while the carbon fiber portion maintains lightweight properties. The composite structure resolves the contradiction by strategically placing different materials based on their respective advantages.
Solution Approach 2:
The patent applies local quality by using a tapered steer tube design with varying wall thickness. The wall is thickest at the crown intersection where loads are concentrated, and tapers toward the top. This localized material distribution provides maximum strength where needed while minimizing weight elsewhere, resolving the strength-weight contradiction.
2Reliability
If the steer tube wall is thickened for impact absorption, then durability is improved, but weight increases
Solution Approach 1:
The tapered steer tube design applies local quality by concentrating thick wall sections at the crown intersection where impact loads are most severe, while reducing wall thickness toward the top. This localized reinforcement improves durability at critical areas without unnecessarily increasing overall weight.
Solution Approach 2:
The composite construction allows the metallic steer tube to provide impact resistance and durability where needed, while the carbon fiber crown maintains lightweight properties. The material combination resolves the contradiction between durability and weight by placing each material where it provides the most benefit.
3Strength
If continuous carbon fibers are used to reinforce the crown, then strength is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the carbon fiber-reinforced crown portion with embedded continuous fibers before bonding the metallic steer tube to it. This preliminary construction of the crown with integrated fiber reinforcement simplifies the overall manufacturing process compared to attempting to install fibers after assembly, reducing manufacturing complexity while maintaining strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enhances strength and toughness by allowing the steer tube to deform under impact while maintaining fork integrity, offering improved durability and resistance to damage, while maintaining a lightweight structure.
Implementation Method 1
the ductile material of the steer tube deforms but holds the fork together
Implementation Method 2
a carbon reinforced plastic portion comprising a steer tube stub and fork crown
Implementation Method 3
the brake bolt passes through the fork body and the aluminum steer tube
Data Source
AI summary
A fiber reinforced plastic bicycle fork uses a reinforced crown steer tube junction extending the steer tube through a tapered socket to the brake bolt such that the metal steer tube coacts with the fiber reinforced plastic fork to preserve structural integrity in the event of application of high stress to the fork.