Bicycle Rear Axle Form-Locked Torque Transfer
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Solution Overview
Problem
Existing rear wheel axles for bicycles struggle to support large torques effectively due to friction-locked connections, which are insufficient for modern drivetrain systems, leading to longer wheel-changing times.
Innovation Solution
A rear wheel axle design featuring form-locked connections between the axle shaft and the bicycle frame, utilizing a combination of internal and external splines and a torque support mechanism that allows for high torque transfer, enabling secure engagement without requiring precise alignment of the wheel axle with the frame's dropouts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a friction-locked connection is used between the rear wheel axle and bicycle frame, then the wheel changing process is simple and rapid, but large torques cannot be supported on the bicycle frame
Solution Approach 1:
The connection between the axle shaft and bicycle frame is segmented into two distinct form-locked connections: a first form-locked connection between the first part of the axle shaft outside and the inside part of the wheel axle, and a second form-locked connection between the second part of the axle shaft outside and the bounding wall of the through hole in the drop outs. This segmentation allows each connection to be optimized for torque support while maintaining rapid wheel changing capability.
Solution Approach 2:
Instead of using a friction-locked connection that relies on friction forces, the invention inverts the approach by using form-locked connections that rely on geometric interlocking. The splines and corresponding recesses create a mechanical interlock that can support large torques, reversing the traditional friction-based approach.
2Strength
If a form-locked connection with splines is implemented to support large torques, then torque support capacity increases, but the device complexity and alignment requirements increase
Solution Approach 1:
The axle shaft design integrates multiple functions into a single component: it provides structural support, transmits torque through form-locked spline connections, and enables rapid wheel changing. The first and second parts of the axle shaft outside work together with the wheel axle and drop outs respectively, creating a multi-functional system that handles both torque support and quick release requirements.
Solution Approach 2:
The hollow wheel axle contains the axle shaft within it, creating a nested structure. The first part of the axle shaft outside is positioned within the hollow wheel axle, while the second part extends outward to engage with the drop outs. This nesting allows compact packaging of multiple functional elements.
3Strength
If the axle shaft is fixed to the bicycle frame with form-locked connections, then large torques can be supported, but the wheel changing time may increase due to additional connection points
Solution Approach 1:
The invention extracts the torque support function from the wheel changing process. The form-locked connections are designed to remain engaged during normal operation to support torques, but the entire wheel assembly can still be quickly removed by extracting the axle shaft from the hollow wheel axle and releasing from the drop outs, maintaining rapid wheel changing capability despite the robust torque support structure.
Data Source
AI summary
A rear wheel axle for a bicycle includes a hollow wheel axle and an axle shaft inserted therethrough and torque support elements for supporting torque exerted on the wheel axle on drop outs of a bicycle frame. The torque support elements are formed by a first part of an outside of the axle shaft and a part of an inside of the wheel axle, which parts jointly form a first form locked connection, and are also formed by a second part of the outside of the axle shaft, which together with a bounding wall of a through hole provided in an inserted piece which is fixed in the direction of rotation relative to one of the drop outs, forms a second form locked connection. The first and second parts of the outside of the axle shaft are fixed relative to each other in the direction of rotation of the axle shaft.