Motorcycle Rear Fork Diffusion Channel for Drag Reduction

Resolve Bottlenecks,
Find Innovative Solutions
Generate Solutions

Solution Overview

Problem

Current motorcycles, particularly racing motorcycles, experience negative aerodynamic phenomena such as turbulence between the rear driving wheel, rear fork, and frame, which affect their efficiency.

Innovation Solution

A motorcycle design featuring a fairing with a lower wall extending under the engine to the rear driving wheel, and a rear fork with a joining structure that forms a diffusion channel with the fairing, improving airflow around the rear wheel and fork.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a conventional rear fork structure is used, then the motorcycle structure is simple, but turbulence is generated between the rear driving wheel, rear fork, and frame, reducing aerodynamic efficiency

Engineering Contradiction:
Improverear fork structureVSAvoidturbulence
Core Design Contradiction:
Device complexityVSObject-affected harmful factors

Solution Approach 1:

The joining structure of the rear fork is designed with a curved rear surface that is substantially parallel to the profile of the rear driving wheel. This curvature allows the air flow to follow the contours of the wheel and fork structure, preventing flow separation and reducing turbulence generation in the gap between the rear fork and rear driving wheel.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

A diffusion channel is introduced as an intermediary flow path between the rear driving wheel and the rear fork. This channel, formed by the curved rear surface of the joining structure and the fairing, acts as a mediator that guides and smooths the air flow through the gap area, preventing direct turbulent interaction between the wheel and fork structures.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Volume of moving object

If the rear fork is positioned close to the rear driving wheel, then the motorcycle structure is compact, but negative aerodynamic phenomena are generated between the rear driving wheel, rear fork, and frame

Engineering Contradiction:
Improvemotorcycle structureVSAvoidaerodynamic drag
Core Design Contradiction:
Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The design extends the fairing in the longitudinal dimension to wrap around and cover the area between the rear driving wheel and the rear fork. This three-dimensional fairing structure creates a diffusion channel that spans multiple dimensions, effectively managing air flow in the gap area without increasing the overall footprint of the motorcycle.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Object-affected harmful factors

If a fairing extending under the engine is added, then aerodynamic efficiency is improved, but the device complexity increases

Engineering Contradiction:
Improveaerodynamic dragVSAvoidfairing structure
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The fairing structure is merged with the existing lower wall that extends under the engine from the front area toward the rear driving wheel. The rear portion of this integrated fairing structure forms the diffusion channel together with the rear fork joining structure, combining aesthetic coverage with aerodynamic function in a single integrated component.

Inventive Principle:
Principle #5Merging (Combining)

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 design enhances aerodynamic efficiency by smoothing airflow around the rear wheel and fork, reducing drag and improving handling and cooling of the motorcycle.

Implementation Method 1

a first portion of the rear surface of the joining structure and a rear portion of the fairing, which extends from the lower wall toward the rear fork, together form a diffusion channel for an air flow between the rear fork and the rear driving wheel

Methodology Applied
Scientific EffectDiffusion: Diffusion

Implementation Method 2

The diffusion channel improves the conditions of motion of the air in the area of the rear driving wheel and of the rear fork

Methodology Applied
Scientific EffectAerodynamic drag reduction: Drag

Data Source

PatentEP4284700B1Motorcycle with aerodynamically improved rear fork
Publication Date: 2025.04.02 PIAGGIO & C SPA
  • EP4284700B1 patent drawingFigure 1
  • EP4284700B1 patent drawingFigure 2
  • EP4284700B1 patent drawingFigure 3

AI summary

A motorcycle (1) with fairing is provided with a rear fork (17) that supports the rear driving wheel, which has two arms (51) connected by a joining structure (53). This structure has a rear surface (55) oriented toward the rear driving wheel (13) and forms, with a rear portion (59) of the fairing (21) a flow channel to guide the air around the rear driving wheel (13).