Cassette-Based Power Meter Torque Sensing
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Solution Overview
Problem
Conventional hub-based power meters are difficult and time-consuming to transfer between bicycles, making them impractical for users who ride multiple bikes, and are often cost-prohibitive to outfit each bike with a power meter.
Innovation Solution
A torque sensing device is integrated within a hollow rear cassette, using strain gauges or bending beams to measure torque, with electronics and a transmitter housed within the cassette for real-time data processing and transmission, allowing for easy interchangeability between bikes and wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque sensing components are mounted to the rear hub, then torque measurement is achieved, but the device becomes difficult and time-consuming to transfer between bicycles
Solution Approach 1:
The power meter system is divided into two separate modules: a torque sensor module that mounts to the rear hub for torque measurement, and a separate processing unit with electronics and battery that mounts to the bicycle frame. This segmentation allows the torque sensor to be quickly removed and transferred between bicycles without transferring the entire hub assembly, significantly reducing transfer time while maintaining measurement capability.
Solution Approach 2:
The processing electronics, battery, and data transmission components are extracted from the rear hub assembly and placed in a separate processing unit that mounts to the bicycle frame. This extraction allows the torque sensing components to be independently transferred between bicycles, eliminating the time-consuming process of disassembling the entire wheel structure while preserving all measurement and processing functions.
2Adaptability or versatility
If the entire wheel structure is disassembled to transfer the hub assembly, then the power meter can be used with another bicycle, but the process becomes cost-prohibitive and time-consuming
Solution Approach 1:
The system is segmented into a portable torque sensor module and a stationary processing unit. The torque sensor module with strain gauges and basic electronics mounts to the rear hub and can be independently removed and installed on different bicycles, enabling versatile bike compatibility without requiring complete wheel disassembly or transfer of the entire hub assembly.
Solution Approach 2:
The torque sensor module is designed as a universal component that can interface with multiple rear hub configurations through standardized mounting mechanisms. The separate processing unit handles all bicycle-specific integrations, allowing the same torque sensor module to serve multiple bicycles with different wheel and hub configurations, thereby achieving universality without complex disassembly procedures.
3Measurement precision
If strain gauges are mounted on the rear hub, then torque detection is achieved, but the device complexity increases
Solution Approach 1:
The system complexity is managed by segmenting functions: the rear hub contains only the simple torque sensing elements (strain gauges or bending beams) that detect torque, while all complex electronics, data processing, power management, and transmission components are located in a separate processing unit. This segmentation keeps the hub modification simple and the complex elements separate and modular.
Solution Approach 2:
A separate processing unit acts as an intermediary between the simple torque sensor on the hub and the bicycle's data system. This intermediary handles all complex functions including signal amplification, analog-to-digital conversion, power management via battery, wireless data transmission, and integration with bicycle computers, thereby isolating the torque measurement function from system complexity.
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 provides a lightweight, cost-effective, and easily transferable power measurement system that can be used with various rear wheel configurations, reducing the time and expense associated with switching between bicycles.
Implementation Method 1
Strain gauges or other torque sensing devices are mounted to the rear hub and in communication with the torque coupling member such that any torque experienced by the torque coupling member is detected by the strain gauges
Implementation Method 2
The torque sensing element may include a bending beam configured to detect the torque applied to the freehub of the bicycle
Data Source
AI summary
A cassette-based power measuring apparatus includes a power sensing arrangement mounted within a cavity defined by a hollow bicycle cassette. The power sensing arrangement includes a torque sensing assembly including torque sensing elements configured to measure a user applied torque. The torque sensing elements are in communication with an electronics assembly configured to process the measured data and transmit it to a receiver. The torque sensing assembly may comprise a torque tube or a series of bending beams secured between a rear plate of the cassette and a freehub. The torque tube or bending beams may include strain gauges bonded thereto for measuring strain induced by application of forces in response to user-applied power.