Forged Bicycle Spoke Geometry for Low Weight and High Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bicycle wheel spokes face a trade-off between weight reduction and maintaining high tensile and breaking strength, which affects handling and aerodynamics, with previous methods either compromising strength or increasing sensitivity to crosswinds.
Innovation Solution
A method involving cold forging of cylindrical wire material into a spoke blank with specifically shaped transition sections, where the preliminary stages are adapted to form a new cross-sectional geometry that balances strength and aerodynamics without compromising material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the diameter of the central section is reduced to save weight, then the weight of the spoke is reduced, but the tensile strength and breaking strength are compromised
Solution Approach 1:
The spoke is designed with varying cross-sectional properties along its length. The central section has a reduced diameter for weight reduction, while the end sections maintain larger diameters for strength. The transition sections feature optimized geometry that gradually changes the cross-section, ensuring that each part has the quality needed for its specific function - lightweight in the center, strong at the ends.
2Object-affected harmful factors
If bladed spokes with flat cross-section are used to reduce aerodynamic drag, then wind resistance is reduced, but crosswind sensitivity increases making the bicycle less steerable
Solution Approach 1:
The spoke cross-section is designed with an airfoil geometry that changes parameters along its length. The radially outer area features an airfoil cross-section optimized for reducing aerodynamic drag, while other sections maintain geometries that provide structural strength and stability. This parameter variation allows the spoke to achieve low drag without sacrificing steerability.
3Object-affected harmful factors
If a second forming process is applied to create aerodynamic geometry, then aerodynamic properties are improved, but the overall strength properties deteriorate
Solution Approach 1:
The transition sections are pre-formed during the initial forging process with optimized geometry that prepares the material structure for subsequent aerodynamic shaping. This preliminary action ensures that when the second forming process creates the airfoil geometry, the material is already positioned and structured to minimize strength deterioration, as the transition sections are designed to accommodate the forming process while maintaining structural integrity.
4Weight of moving object
If the precursor of the central section is reduced in diameter more than the end sections, then weight is reduced, but the transition sections require precise length control to maintain strength
Solution Approach 1:
The transition sections are designed with optimized geometric parameters including specific length, diameter variation, and cone angles that accommodate normal manufacturing tolerances. By optimizing these parameters, the design becomes less sensitive to small variations in transition section length, allowing weight reduction through central section thinning while maintaining strength without requiring extremely precise manufacturing control.
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 method enhances tensile and breaking strength while improving aerodynamics, ensuring the spoke's reliability and reducing weight, without adverse effects on strength or increasing sensitivity to crosswinds.
Implementation Method 1
forming and in particular cold forging of a particularly cylindrical wire material into a spoke blank using a forging device
Implementation Method 2
The precursors of the transition sections are forged conically (or tapered) so that they each have a diameter that decreases towards the central section
Implementation Method 3
Inserting the spoke blank into a forming tool. The forming tool at least partially forms a negative form of the spoke body
Data Source
Figure 1~3
Figure 3a~4a
Figure 5
AI summary
A method for manufacturing a spoke, comprising the following process steps: forming a wire material (18) into a spoke blank (8) using a forging device (28), wherein the spoke blank (8) has preforms (30, 40, 50) of the central section (3) and the end sections (4) and the transition sections (5), and wherein the preforms (30, 40) of the central section (3) and the end sections (4) are forged cylindrically; wherein the preforms (50) of the transition sections (5) are forged conically, such that they have a diameter (150) decreasing in the direction of the central section (3); wherein the preforms (50) of the transition sections (5) are each manufactured with a length (151) which differs by a maximum of one quarter from a respective length (25) of the transition sections (5);Forming the spoke blank (8) with a forming tool (9) which creates a negative mold of the spoke body (2), such that the spoke body (2) is formed, wherein at least the transition sections (5) and the central section (3) each have a different cross-sectional geometry than their predecessors (30, 50). The invention also relates to a spoke.