Aerodynamic Bicycle Spoke Forging Without Strength Loss
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Solution Overview
Problem
Existing bicycle spokes face challenges in balancing weight reduction, aerodynamic efficiency, and strength, particularly in windy conditions, with existing manufacturing methods often compromising on strength properties during reworking for aerodynamic geometry.
Innovation Solution
A method involving cold forging and reshaping of a spoke blank to create a spoke body with specifically matched transition sections and end portions, using a shaping tool to achieve an aerodynamic cross-sectional geometry without compromising tensile and fracture strength, incorporating body and wings for stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If double-butted spokes are used to reduce weight, then weight is reduced, but manufacturing complexity increases
Solution Approach 1:
The spoke blank is pre-formed with accurately dimensioned transition sections during the initial forging process, so that the final shaping operation can directly produce the aerodynamic geometry without requiring complex multi-step manufacturing. This preliminary preparation of the blank with correct transition zone dimensions simplifies the overall manufacturing process while maintaining the weight benefits of double-butted construction.
2Shape
If reworking is performed to generate aerodynamic geometry, then aerodynamic properties are improved, but strength properties deteriorate
Solution Approach 1:
The transition sections are pre-formed with accurate dimensions and proper material flow characteristics during the initial forging, creating an optimized microstructure in these critical zones. This preliminary action ensures that when aerodynamic shaping is applied, the material can flow properly without creating weak points, thus maintaining strength while achieving the desired aerodynamic geometry.
Solution Approach 2:
The invention controls the dimensional parameters of the transition sections with high precision during forging, ensuring that the length and diameter variations are within tight tolerances. This parameter control allows the subsequent aerodynamic shaping to be performed without compromising the structural integrity, as the pre-established transition zones provide a buffer that accommodates the geometric changes while maintaining strength properties.
3Strength
If transition sections are made longer to maintain strength during reshaping, then strength is maintained, but weight increases
Solution Approach 1:
The invention optimizes the transition section parameters by precisely controlling the length, diameter reduction, and taper angle within specific ranges. This parameter optimization allows the transition sections to be sufficiently long to maintain strength during reshaping, yet short enough to minimize weight. The controlled dimensional changes ensure that the transition zones provide adequate material for plastic deformation while keeping the overall spoke weight low.
4Shape
If blade spoke geometry is used to reduce air drag, then aerodynamic drag is reduced, but control properties worsen in windy conditions
Solution Approach 1:
The invention applies aerodynamic shaping selectively to specific portions of the spoke rather than the entire length. The central section can be given an aerodynamic profile to reduce drag, while the end portions near the hub and rim maintain their traditional cylindrical geometry for strength and control. This local application of aerodynamic features allows drag reduction without compromising the spoke's ability to handle crosswinds and maintain control properties.
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 the spoke's strength and aerodynamic performance while maintaining or improving material properties, allowing for lightweight and durable bicycle wheels.
Implementation Method 1
reshaping and, in particular, cold forging by means of a forging device, of a wire material that is, in particular, cylindrical, obtaining a spoke blank
Data Source
AI summary
A method of manufacturing a spoke, including: reshaping a wire material to obtain a spoke blank by a forging device; wherein the spoke blank includes pre-stages of the central section and the end portions and the transition sections; and wherein the pre-stages of the central section and the end portions are forged cylindrically; the pre-stages of the transition sections are forged conically, so that they show a diameter decreasing in the direction of the central section; wherein the pre-stages of the transition sections are each manufactured in a length which differs by a maximum of one fourth from the pertaining length of the transition section; reshaping the spoke blank by a shaping tool, which reproduces a negative shape of the spoke body, so that the spoke body is generated; wherein at least the transition sections and the central section are each provided with a cross-sectional geometry different from their pre-stages.