Freewheel Assembly Switching Fixed-Gear and Freewheel Modes

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Solution Overview

Problem

Current bicycle hubs that switch between freewheel and fixed-gear modes are inconvenient, often requiring disassembly, alteration of chain length, and re-alignment of brakes, and existing solutions are either mechanically complex or heavy, lacking a simple and efficient method for riders to switch between modes on existing wheels.

Innovation Solution

A freewheel assembly with a non-frictional positive locking mechanism that allows for reversible conversion between freewheel and fixed-gear operation, using set screws, pins, or solenoids to mechanically lock the sprocket to the drive ring, enabling easy switching between modes without slippage or frictional coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a flip-flop hub design is used to switch between freewheel and fixed-gear modes, then mode switching capability is achieved, but the process requires removing the rear wheel and altering chain length, making it inconvenient and complex

Engineering Contradiction:

Improvemode switching capabilityVSAvoidconvenience of switching

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The hub is divided into two separate sides: a fixed-gear side with a fixed cog rigidly attached to the hub, and a freewheel side with a conventional freewheel mechanism. This segmentation allows each side to be optimized for its specific function while enabling mode switching through simple wheel removal and reversal, eliminating the need for complex internal switching mechanisms

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of attempting to switch modes within a single hub structure, the invention inverts the approach by using two separate hub sides that are mirror images of each other. The rider switches modes by removing the wheel and flipping it to the opposite side, transforming a complex internal switching problem into a simple external reversal operation

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If frictional coupling mechanisms are used to lock the sprocket to the drive ring, then fixed-gear mode is achieved, but slippage occurs under high torque conditions, reducing reliability

Engineering Contradiction:

Improvefixed-gear mode capabilityVSAvoidlinkage reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The invention replaces frictional coupling mechanisms with a positive locking mechanism using a set screw that directly engages with a threaded hole in the drive ring. This mechanical substitution eliminates slippage by creating a rigid, non-frictional connection between the sprocket and drive ring, ensuring reliable power transmission under all torque conditions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The set screw locking mechanism discards the unreliable frictional coupling approach and recovers reliability through a simple, robust mechanical engagement. The set screw can be easily installed or adjusted by riders to ensure positive locking, providing a fail-safe connection that maintains reliability throughout the component's service life

Inventive Principle:

Principle #34Discarding and recovering

3Adaptability or versatility

If complex internal locking mechanisms are incorporated into the hub, then fixed-gear mode is achieved, but the device complexity and weight increase, defeating the simplicity advantage of fixed-gear bikes

Engineering Contradiction:

Improvemode switching capabilityVSAvoidmechanism complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The invention extracts the locking mechanism from the complex internal hub structure and places it on the simpler external sprocket assembly. The set screw and threaded hole are installed on the sprocket itself, allowing the hub to remain simple and lightweight while still achieving reliable fixed-gear locking through this external, minimalistic approach

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The set screw mechanism uses simple, inexpensive components that can be easily replaced or adjusted if needed. Rather than investing in complex, expensive internal locking mechanisms, the invention adopts a simple, disposable-style solution that maintains reliability without adding complexity or weight to the hub assembly

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

4Reliability

If a non-frictional positive locking mechanism is used to rigidly connect the sprocket to the drive ring, then reliability is improved, but the ease of installation and adjustment may be reduced

Engineering Contradiction:

Improvelinkage reliabilityVSAvoidinstallation ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The positive locking mechanism is applied locally at the critical connection point between the sprocket and drive ring, rather than requiring complex mechanisms throughout the entire hub assembly. The set screw is positioned to engage a single threaded hole in the drive ring, providing reliable locking with minimal intervention, making installation straightforward for riders or mechanics

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11590797B2Freewheel assembly switchable between fixed-gear and freewheel modes

Publication Date: 2023.02.28 ENGEL NICHOLAS REDMOND

AI summary

A bicycle freewheel assembly is provided which is capable of being readily and reversibly switched from fixed-gear to freewheel operation, without the necessity of removing the wheel from the bicycle. The freewheel assembly is mountable on pre-existing freewheel hubs.