Motorcycle Swing Arm with Inclined Inner Surfaces for Stress Reduction
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Solution Overview
Problem
The existing swing arm designs for motorcycles suffer from stress concentration issues at the connection points between the base section and the rear arm sections, leading to reduced lateral bending rigidity and increased weight, especially when trying to maintain a deep banking angle during turns.
Innovation Solution
The design incorporates inclined inner surfaces on the rear arm sections and bracket sections, allowing for a larger circular arc dimension and reduced stress concentration, along with recessed parts to absorb lateral forces, thereby improving torsional rigidity and reducing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the arm sections are made thin in the width direction to reduce lateral bending rigidity, then the lateral bending rigidity is reduced, but stress concentration occurs at the connection parts between the base section and the arm sections
Solution Approach 1:
The invention applies curvature by forming the inner corner parts bridging between the arm sections and base section into circular arc shapes as viewed from the top. This curved geometry distributes stress more evenly compared to sharp corners, reducing stress concentration at the connection parts while maintaining the thin arm section design for reduced lateral bending rigidity.
Solution Approach 2:
The invention implements local quality by creating a non-uniform width profile along the arm sections. The arm sections have different widths at different locations: thinner at the rear end for reduced lateral bending rigidity, and wider at the connection parts with circular arc corners for stress distribution. This localized variation in geometry optimizes both requirements simultaneously.
2Stress or pressure
If the connection parts between the base section and arm sections are reinforced to reduce stress concentration, then the stress concentration is reduced, but the weight of the chassis framework increases
Solution Approach 1:
The circular arc shaped inner corner parts provide structural reinforcement through geometry alone, distributing stress without adding material. This curved design achieves stress concentration reduction while maintaining the lightweight characteristic of the thin arm sections, avoiding the need for additional reinforcement that would increase weight.
Solution Approach 2:
The invention changes the geometric parameters of the connection parts by forming circular arc shapes with specific radius dimensions. This parameter optimization allows the thin arm sections to connect to the base section in a way that naturally distributes stress, achieving reinforcement效果 without increasing the overall mass of the swing arm assembly.
3Length of moving object
If the radius of the circular arc at the corner parts is made small to secure clearance between the rear wheel and arm sections, then the clearance is secured, but the corner parts are subjected to large stress concentration
Solution Approach 1:
The invention applies circular arc shaping to the inner corner parts, creating a smooth curved transition between the arm sections and base section. This curved geometry inherently reduces stress concentration compared to sharp corners, while the radius can be optimized to maintain both adequate clearance and stress distribution.
Solution Approach 2:
The invention implements local quality by varying the corner radius specifically at the connection parts between arm sections and base section. This localized geometric feature provides stress distribution exactly where needed (at the connection parts) without affecting the overall clearance dimensions between the rear wheel and arm sections elsewhere.
Data Source
AI summary
There is provided a swing arm for a motorcycle. A base section is connected to a chassis framework via a pivot member. A pair of rear-arm sections extend rearwards from the base section. A pair of bracket sections are respectively provided at rear end portions of the rear-arm sections to rotatably support a rear wheel. Each of the bracket sections is formed into a shape including a hole through which an axle of the rear wheel passes, an engaging plane formed at a region surrounding the hole, and a peripheral formation plane positioned to connect with the outer periphery of the rear-arm sections. An inner surface of the peripheral formation plane in the width direction is formed so as to be inclined outwards in the width direction from a side of formation region of the hole towards a front side as viewed from the top.