Bicycle Bottom Bracket Shell with Bosses for Tube Connection
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Solution Overview
Problem
The existing bottom bracket shell assemblies in alloy bicycle frames have a limited strength-to-weight ratio due to the reliance on welding, which is operator-dependent and results in inconsistent weld quality, and the structural limitations imposed by the small circumference of the bottom bracket shell, leading to increased sidewall thickness and multiple welds, compromising the frame's strength.
Innovation Solution
The design features a bottom bracket shell assembly with left and right sidewalls that include lateral surfaces and peripheral rims joined by techniques like lap joints, flanged joints, or butt joints, with bosses projecting from the periphery to connect with the down tube, seat tube, and chainstays, moving the connection away from the crowded junction, allowing for increased diameters without sacrificing strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the down tube and seat tube are welded to the bottom bracket shell, then the frame structure is formed, but the weld quality varies and structural strength is compromised
Solution Approach 1:
The bottom bracket shell is divided into left and right halves that are joined together, allowing each half to be separately manufactured and assembled. This segmentation enables more controlled welding processes and facilitates quality consistency while maintaining overall structural strength through the joined configuration.
Solution Approach 2:
The bottom bracket shell acts as an intermediary component between the down tube, seat tube, and chainstays. By providing a dedicated intermediate structure with integrated bosses, the design reduces the need for direct welding between tubes and the bottom bracket shell, thereby improving weld quality consistency while preserving structural integrity.
2Ease of manufacture
If the tube diameters are limited to fit on the bottom bracket shell, then welding is feasible, but the strength-to-weight ratio is reduced
Solution Approach 1:
The design extends the connection interface in the radial dimension by providing bosses that protrude from the bottom bracket shell surface. This dimensional extension allows tubes to connect at optimal locations without being constrained by the limited circumference of the bottom bracket shell, enabling larger tube diameters that improve strength-to-weight ratio while maintaining welding feasibility.
Solution Approach 2:
The bosses on the bottom bracket shell serve as intermediary connection points that facilitate optimal tube connections. These protruding features allow tubes to be positioned at ideal locations for both structural performance and manufacturing, resolving the conflict between welding feasibility and strength requirements.
3Ease of manufacture
If multiple welds are placed on top of each other to accommodate limited tube diameter, then tubes can be connected, but the risk of material loss increases
Solution Approach 1:
By dividing the bottom bracket shell into separate left and right halves with integrated bosses, the design distributes welding operations across different locations and surfaces. This segmentation reduces the concentration of multiple welds in a single area, thereby minimizing the risk of material loss while maintaining tube connection capability.
Solution Approach 2:
The protruding bosses extend the connection interface radially outward, spreading weld locations across different spatial zones. This dimensional distribution prevents the stacking of multiple welds in the same area, reducing the cumulative risk of material loss during welding operations.
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
This configuration enhances the strength-to-weight ratio by reducing the need for multiple welds, allowing for thicker tubes and improved material distribution, thereby increasing the structural integrity of the bottom bracket shell while minimizing the risk of material loss during welding.
Implementation Method 1
The peripheral rims may be joined by a lap joint, a flanged joint, a butt joint, or a number of other joining techniques known in the art
Data Source
AI summary
A bottom bracket shell assembly includes left and right sidewalls. The left and right sidewalls each include a peripheral rim and a lateral surface. The lateral surfaces define a generally circular void. A bearing support is disposed at the voids of the left and right sidewalls. Left and right first bosses project away from the left and right sidewalls at a periphery of the lateral surface. The first bosses include boss ends configured to connect to a first tubular member. The left and right sidewalls are joined at the peripheral rim to form contiguous front and rear surfaces. The present disclosure maximizes the strength to weight ratio for low modulus frame materials.