Bicycle Wheel Fairing Using Expanded Polypropylene Foam
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Solution Overview
Problem
Current bicycle wheels with aerodynamic rims made of carbon composite materials are expensive, non-recyclable, and heavy, limiting their use to high-end cycles and affecting cyclist performance due to their mass.
Innovation Solution
A bicycle wheel with a fairing made from expanded polypropylene foam, which is lightweight, recyclable, easy to manufacture, and resistant to shocks, attached to a structural ring that can be assembled elastically with the rim, providing improved aerodynamics and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon composite materials are used for aerodynamic rims, then aerodynamic performance is improved, but cost price increases and the material becomes non-recyclable
Solution Approach 1:
The invention changes the material parameters by using expanded polypropylene foam with density between 30-120 kg/m³ instead of carbon composite materials. This material substitution maintains aerodynamic functionality while dramatically reducing cost and enabling recyclability, directly resolving the contradiction between performance and manufacturing ease
Solution Approach 2:
The invention uses a composite structure combining expanded polypropylene foam with a structural ring (aluminum or steel). This composite approach provides the necessary mechanical strength and aerodynamic properties while using recyclable, low-cost materials, thereby achieving aerodynamic performance without the drawbacks of carbon composite materials
2Reliability
If carbon composite materials are used for rims, then aerodynamic performance is improved, but density increases and wheel mass increases
Solution Approach 1:
The invention changes the density parameter by using expanded polypropylene foam with density 30-120 kg/m³, which is significantly lower than carbon composite materials. This reduces wheel mass while maintaining aerodynamic performance through the foam's structural properties and the external aerodynamic shell
Solution Approach 2:
The invention uses a thin aerodynamic shell (5-10 mm thick) made of expanded polypropylene foam that provides aerodynamic benefits without significant weight penalty. The shell acts as a flexible aerodynamic surface that reduces drag while keeping the overall wheel mass low
3Reliability
If PVC fairing is used on the rim, then aerodynamic performance is improved, but the fairing becomes heavy considering PVC density
Solution Approach 1:
The invention changes the material parameter by substituting PVC (density ~1400 kg/m³) with expanded polypropylene foam (density 30-120 kg/m³). This represents a density reduction factor of 10-40 times, dramatically reducing fairing weight while maintaining aerodynamic functionality
Solution Approach 2:
The invention uses porous expanded polypropylene foam material for the fairing. The cellular structure of the foam provides sufficient mechanical strength and aerodynamic properties at very low density, resolving the contradiction between aerodynamic performance and weight
4Strength
If structural foam is trapped in composite shell, then rim structure is strengthened, but foam recovery for recycling is prevented
Solution Approach 1:
The invention segments the rim structure into two separate components: an external aerodynamic shell and an internal structural foam core. This segmentation allows the foam to be independently accessible and recyclable while still providing structural support when enclosed, resolving the contradiction between strength and recyclability
Solution Approach 2:
The invention enables recovery of the structural foam by designing the rim so the foam can be extracted from the shell. The foam can be discarded or recovered for recycling independently, while the shell can be separately processed, thereby enabling recyclability without compromising structural strength
5Reliability
If additional surface protection shell is added to withstand shocks, then shock resistance is improved, but excess weight is added
Solution Approach 1:
The invention changes the material parameter by using expanded polypropylene foam with density 30-120 kg/m³, which provides excellent shock absorption properties due to its cellular structure. This material absorbs shocks through cell collapse and deformation, providing protection without the weight penalty of traditional protective shells
Solution Approach 2:
The invention uses porous expanded polypropylene foam that provides inherent shock resistance through its cellular structure. The pores and cells compress and deform to absorb impact energy, providing shock protection without requiring additional solid protective layers that would add weight
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 solution results in a lightweight, recyclable, and cost-effective bicycle wheel that maintains aerodynamic performance while withstanding minor shocks and manipulations without additional weight, addressing the limitations of existing carbon composite rims.
Implementation Method 1
its assembly with the rim is easy, by elastic deformation
Implementation Method 2
having a very low plastic hysteresis after having undergone significant compression deformation
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The wheel (1) has a rim (3) including flanges (32.1, 33.1) designed to receive a tire (6). A fairing (5) is affixed to the rim, where the fairing is partially made from a material having a density less than 120 kilogram per cubic meter. The modulus of elasticity of the material is greater than 5 MPa, where the elongation of the material at breakage is greater than 10 percent. The material is an ARPRO (RTM: expanded polypropylene foam), where the polypropylene is of the polypropylene copolymer type. An independent claim is also included for a method for manufacturing a wheel.