Integrally Molded Wheel Spokes for Heavy E-Bikes
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Solution Overview
Problem
Existing bicycle wheels, especially those for electrically powered bicycles and cargo bikes, face challenges in balancing low weight, high stability, and cost-effectiveness, particularly in withstanding increased mechanical stresses and lateral impact loads.
Innovation Solution
A wheel design featuring a hub and at least three solid-body spokes arranged rotationally symmetrically, made in one piece by injection molding of glass-fiber reinforced thermoplastic, with an S-shaped cross-section and tapering spokes, eliminating the need for metallic reinforcement and allowing for efficient mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If carbon construction is used to achieve low weight and high stability, then the wheel stability and weight requirements are met, but the manufacturing cost and complexity increase significantly
Solution Approach 1:
The patent uses glass-fiber reinforced plastic material to create an integrally molded wheel that combines the stability of composite materials with the simplicity of injection molding. The glass fibers provide structural strength and stability while the thermoplastic matrix allows for complex geometries to be formed in a single manufacturing process, eliminating the need for costly carbon construction methods.
Solution Approach 2:
The hub, spokes, and rim are merged into a single integrally molded component. This consolidation eliminates the need for separate parts and assembly steps, reducing manufacturing complexity while maintaining structural integrity through the S-shaped spoke design that provides both strength and flexibility.
2Weight of moving object
If the number of spokes is reduced to decrease weight, then the wheel weight decreases, but the stability and load-bearing capacity deteriorate
Solution Approach 1:
The spokes feature an S-shaped cross-section with varying wall thickness distribution, where the material is concentrated in regions experiencing higher stresses. This local optimization allows each spoke to bear maximum load with minimum material, enabling reduced spoke count while maintaining stability.
Solution Approach 2:
The S-shaped curved cross-section of the spokes provides structural efficiency by distributing stresses more effectively than straight spokes. The curvature allows the spoke to flex and absorb lateral impact loads while maintaining overall wheel stability, compensating for the reduced number of spokes.
3Ease of manufacture
If glass-fiber reinforced plastic is used instead of metal or carbon, then the manufacturing cost decreases, but the stability under lateral impact loads may be insufficient
Solution Approach 1:
The glass-fiber reinforced thermoplastic combines the high strength-to-weight ratio of glass fibers with the toughness and impact resistance of thermoplastic materials. The glass fibers provide stiffness and strength while the thermoplastic matrix absorbs impact energy, creating a composite that resists lateral impact loads effectively.
Solution Approach 2:
The S-shaped cross-section of the spokes provides structural efficiency by distributing stresses more effectively than straight spokes. The curvature allows the spoke to flex and absorb lateral impact loads while maintaining overall wheel stability, compensating for the reduced number of spokes.
Data Source
AI summary
A stable, low-weight wheel which is particularly suitable for high system-weight bicycles, such as electrically powered bicycles and cargo bikes, includes a hub, at least three solid-body spokes disposed rotationally symmetrical to the wheel axis, and a rim. The body of the hub, spokes and rim is made in one piece by injection molding of a glass-fiber reinforced thermoplastic. The spokes have an S-shaped cross-section with an opening angle which increases in the direction of the rim, taper from the rim towards the hub in a central cross-section of the wheel, and taper from the hub towards the rim in a wheel cross-section running through the center of least one spoke. A method for producing the wheel is also provided.