Segmented Bicycle Gearbox Shifting Without Belt Displacement
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Solution Overview
Problem
Existing bicycle gearbox technologies face challenges in efficiently shifting gears without displacing the belt out of its plane, leading to potential mechanical stress and reduced durability, especially under load conditions.
Innovation Solution
The implementation of segmented sprocket clusters with a shifting system that includes a wedge mechanism to pivot gear segments in and out of the belt plane, allowing for gear ratio changes without displacing the belt, thereby maintaining belt alignment and reducing mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional gear shifting mechanisms are used, then gear ratio changes can be achieved, but the belt is displaced out of its plane causing mechanical stress and reduced durability
Solution Approach 1:
The inboard gear is divided into multiple segments that can independently pivot relative to the gear body. This segmentation allows individual segments to be moved into or out of the belt plane without displacing the entire gear or the belt, enabling gear ratio changes while maintaining belt alignment and reducing mechanical stress on the belt.
Solution Approach 2:
The gear segments are designed to pivot in a dimension perpendicular to the belt plane, allowing them to move into or out of the belt's operational plane. This dimensional movement enables gear ratio changes without lateral displacement of the belt, resolving the contradiction between gear shifting capability and belt durability.
2Adaptability or versatility
If gear segments are moved into and out of the belt plane, then gear ratio changes are achieved, but the shifting mechanism complexity increases
Solution Approach 1:
The gear segments are designed with pivotability, transforming them from static components to dynamic elements that can change position. This dynamic capability allows the segments to pivot into or out of the belt plane as needed for gear ratio changes, providing adaptability without requiring entirely separate mechanisms for each gear position.
Solution Approach 2:
The shifting mechanism is designed to be actuated by the rider through the existing drivetrain components, with the gear segments automatically pivoting into or out of engagement based on the belt's position and tension. This self-service approach reduces the need for additional complex actuation systems while maintaining gear ratio change capability.
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
This solution enables smooth and efficient gear shifting under load, improves durability by reducing mechanical stress, and maintains belt alignment, enhancing the overall performance and reliability of the gearbox.
Implementation Method 1
a shifting system including a wedge mechanism to pivot gear segments in and out of the belt plane
Data Source
AI summary
A gearbox may include a drive spindle and several interconnected gear clusters arranged in a housing. A first of the gear clusters is coaxially fastened to the spindle, and has an outboard gear and an inboard gear. The first gear cluster drives a belt to operate one or more of the other gear clusters, and the inboard gear is physically divided into a plurality of segments. A shifting system for the gearbox includes an actuator configured to urge the segments of the inboard gear of the first gear cluster into and out of the plane of the belt, such that a gear ratio of the gearbox is changeable without displacing the belt out of the plane.