Rotatable Bicycle Stem Assembly for Parallel Storage
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Solution Overview
Problem
The storage and transportation of bicycles with rotatable handlebars are challenging due to their perpendicular orientation, which makes them difficult to align parallel with the frame, a desirable configuration for space-saving purposes.
Innovation Solution
A rotatable stem assembly for bicycles featuring a tubular sleeve with first and second splines and channels that allow for rotational adjustment between a riding and storage configuration, enabling handlebars to be perpendicular or parallel to the frame, utilizing a combination of splines, channels, collars, and threaded connections for secure engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If handlebars are kept in perpendicular orientation to the frame, then riding functionality is maintained, but storage and transportation space efficiency deteriorates
Solution Approach 1:
The handlebar stem is designed with rotational capability allowing it to dynamically change orientation between perpendicular (riding) and parallel (storage) positions. The stem includes a bore that can rotate 90 degrees relative to the steerer tube, enabling the handlebars to transition between two fixed orientations based on operational needs.
Solution Approach 2:
The stem is divided into functional segments: a steerer tube portion, a bore portion for handlebar insertion, and locking mechanisms. This segmentation allows independent rotation of the bore relative to the steerer tube while maintaining secure connection, enabling orientation change without compromising structural integrity.
2Adaptability or versatility
If a rotatable stem mechanism is added to enable handlebar rotation, then storage efficiency is improved, but device complexity increases
Solution Approach 1:
The rotational mechanism is merged into the stem structure itself rather than being a separate add-on. The bore is integrated into the stem body with internal splines that mate with external splines on the steerer tube, combining the rotation function with the existing stem support function to minimize additional complexity.
Solution Approach 2:
Splines act as an intermediary mechanism between the steerer tube and the bore, providing a simple mechanical interface for rotation and locking. The spline engagement allows controlled rotational movement while preventing unintended rotation, serving as a mediator that simplifies the overall rotation mechanism.
3Reliability
If splines and channels are used for mating engagement, then rotational security is improved, but manufacturing precision requirements increase
Solution Approach 1:
The spline profile is designed with asymmetric geometry where the engagement surfaces are optimized for both strength and tolerance compensation. The spline teeth have varying thickness and spacing that provide inherent alignment features, reducing the need for extremely tight manufacturing tolerances while maintaining reliable engagement.
Solution Approach 2:
The spline dimensions are optimized to provide a balance between engagement reliability and manufacturing feasibility. By adjusting parameters such as spline tooth height, thickness, and spacing, the design achieves sufficient mechanical interlocking without requiring ultra-precise manufacturing, accommodating typical manufacturing variations.
Data Source
AI summary
A rotatable stem assembly for a bicycle is provided. The assembly includes: a tubular sleeve configured to fit over a steerer tube of the bicycle, an outer surface of the sleeve having a plurality of first splines and first channels; and a stem including a first bore for receiving the sleeve, the first bore having an inner surface with a plurality of second splines and second channels configured for mating engagement with the plurality of first splines and first channels; wherein the first and second splines and channels are matingly engageable in a riding configuration and in a storage configuration, wherein in the riding configuration the stem relative to the sleeve is rotationally perpendicular with the stem relative to the sleeve in the storage configuration.