Disc Brake Rotor Coupling Arm Geometry for Strength-Weight Balance
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Solution Overview
Problem
Disc brake rotors for human-powered vehicles face challenges in achieving a balance between strength and weight, with existing designs often compromising on one aspect at the expense of the other.
Innovation Solution
The design incorporates a hub engagement member, an outer member, and a coupling arm with specific geometric configurations, including non-parallel axial and circumferential surfaces, varying axial and circumferential widths, and corner parts, to optimize the balance between strength and weight in the coupling arm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the coupling arm is made thicker or with larger cross-section to increase strength, then the strength is improved, but the weight increases
Solution Approach 1:
The coupling arm employs non-uniform cross-sectional dimensions along its length, with the intermediate part having a larger axial width than the inner and outer ends. This local quality variation concentrates material where bending moments are highest (at the intermediate section), providing enhanced strength precisely where needed while minimizing material usage in regions with lower stress demands, thus optimizing the strength-to-weight ratio.
Solution Approach 2:
The coupling arm features asymmetric geometric configuration with non-parallel axial surfaces and unequal diagonal distances between corner parts. This asymmetric design allows the structure to efficiently resist asymmetric loading conditions typical in disc brake rotors, distributing stresses more effectively throughout the arm while maintaining lower overall material consumption compared to a symmetric, uniformly thick design.
2Strength
If more material is used in the coupling arm to increase strength, then the strength is improved, but the material usage increases
Solution Approach 1:
The coupling arm employs non-uniform cross-sectional dimensions along its length, with the intermediate part having a larger axial width than the inner and outer ends. This local quality variation concentrates material where bending moments are highest (at the intermediate section), providing enhanced strength precisely where needed while minimizing material usage in regions with lower stress demands, thus optimizing the strength-to-weight ratio.
Solution Approach 2:
The axial width of the coupling arm varies along its radial length, with the intermediate part having a maximum axial width that is larger than at the inner and outer ends. This parameter change optimizes the distribution of material to match the stress distribution, placing more material where bending stresses are highest and less material where stresses are lower, thereby reducing overall material usage while maintaining required strength.
3Weight of moving object
If the coupling arm is made lighter by reducing material, then the weight is reduced, but the strength decreases
Solution Approach 1:
The coupling arm employs non-uniform cross-sectional dimensions along its length, with the intermediate part having a larger axial width than the inner and outer ends. This local quality variation concentrates material where bending moments are highest (at the intermediate section), providing enhanced strength precisely where needed while minimizing material usage in regions with lower stress demands, thus optimizing the strength-to-weight ratio.
Solution Approach 2:
The coupling arm utilizes three-dimensional geometric optimization with non-parallel axial surfaces and varying cross-sectional dimensions in multiple directions. By strategically shaping the arm in three dimensions with different axial and circumferential widths at different locations, the design achieves high strength-to-weight ratio through spatial distribution of material rather than simply increasing or decreasing overall size.
Data Source
AI summary
A disc brake rotor comprises a hub engagement member, an outer member, and a coupling arm. The hub engagement member is configured to engage with a hub assembly. The outer member is provided radially outwardly of the hub engagement member with respect to a rotational axis of the disc brake rotor. The coupling arm extends radially outwardly from the hub engagement member to the outer member. The coupling arm includes a first axial surface provided on a first axial side in an axial direction with respect to the rotational axis and a second axial surface provided on a second axial side reverse to the first axial side in the axial direction. At least one of the first axial surface and the second axial surface is non-parallel to a reference plane perpendicular to the rotational axis as viewed in a radial direction with respect to the rotational axis.