Two-Part Ring Nut Assembly for Small-Diameter Bicycle Cogsets
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Solution Overview
Problem
The challenge is to securely fix a monolithic set of sprockets with a small inner diameter to a sprocket-carrying body without increasing the weight of the bicycle rear wheel assembly, as conventional ring nuts with small diameters struggle to engage due to the limited axial opening.
Innovation Solution
A sub-assembly featuring a sprocket-carrying body with a radially inner threaded portion and a ring nut that is free to rotate, where the ring nut has a larger threaded diameter than the monolithic set's opening, allowing it to screw directly onto the sprocket-carrying body without needing to pass through the set's axial opening, and is composed of two parts for easier assembly and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional ring nut is used to fix the monolithic set, then the fixation is secure, but the ring nut cannot engage due to the limited axial opening of the small-diameter monolithic set
Solution Approach 1:
The ring nut is divided into two separate parts: a first part with an axial opening for passing through the monolithic set, and a second part with the threaded portion for engagement with the sprocket-carrying body. This segmentation allows each part to perform its specific function independently, solving the problem of unable to engage both the small-diameter monolithic set and the sprocket-carrying body simultaneously.
Solution Approach 2:
The first part of the ring nut is inserted through the axial opening of the monolithic set from the outer side, while the second part is inserted from the inner side. The two parts are then assembled together to form the complete ring nut structure. This nested assembly approach enables the ring nut to adapt to small-diameter monolithic sets while maintaining secure fixation capability.
2Adaptability or versatility
If the number of sprockets is increased to 11, 12 or more, then the gear ratio availability is improved, but the inner diameter of the smallest sprocket becomes too small to mount on normal sprocket-carrying bodies
Solution Approach 1:
The fixing mechanism is segmented into two parts that can be assembled separately, allowing the first part to pass through the small-diameter monolithic set while the second part provides the engagement threads. This enables mounting of monolithic sets with very small inner diameters that would otherwise be impossible to fix securely.
Solution Approach 2:
Instead of requiring the entire ring nut to pass through the axial opening, the solution uses a two-part assembly where the threaded portion engages radially with the sprocket-carrying body while the first part passes axially through the monolithic set. This dimensional approach allows fixation despite the limited axial opening.
Data Source
AI summary
A bicycle rear wheel sub-assembly having a sprocket-carrying body, a cogset including a plurality of axially adjacent sprockets with at least three of the plurality of sprockets formed into a monolithic set and a ring nut securing the cogset to the sprocket-carrying body. The ring nut is formed as two parts assembled together—an axially outer first part on which a tubular body and a flange are formed, and an axially inner second part on which a threaded portion is formed. This structure provides a simple and effective coupling of the ring nut with the monolithic sub-set of the cogset and the sprocket-carrying body.