Variable Radius Bicycle Sprocket Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bicycle transmission systems face challenges in smoothly and continuously shifting gear ratios due to issues like chain slipping, jumping, or falling off, particularly when trying to vary the radius of gear sprockets without increasing the distance between the teeth, which disrupts power transfer.
Innovation Solution
The system employs sliding gear segments on a base plate with spring-biased locking pins that are adjusted by non-rotating control plates, allowing the gear segments to change their effective radius without increasing the distance between the teeth, enabling smooth transitions between gear ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gear segments are used to increase the radius of the sprocket, then the gear ratio can be varied, but complex mechanisms are required to change the positions of these segments
Solution Approach 1:
The gear segments are made movable along radial slots in the base plate, allowing dynamic adjustment of the effective sprocket radius. The segments can slide to different positions along the slots and be locked in place, enabling continuous variation of gear ratio without complex mechanisms. This transforms a static gear system into a dynamic one where the effective radius can be adjusted on-the-fly.
Solution Approach 2:
The sprocket is divided into multiple independent gear segments that can be positioned separately along radial slots. Each segment can be independently adjusted to change the effective radius, allowing flexible gear ratio variation. The segmentation enables simple positional adjustment rather than requiring complex continuous mechanisms.
2Adaptability or versatility
If the radius of the gear sprocket is increased, then the gear ratio changes, but the distance between the teeth of the sprocket increases while the distance between chain links remains constant
Solution Approach 1:
The gear segments slide along radial slots to adjust the effective radius dynamically. When segments move to a larger radius position, they maintain their original tooth spacing relative to each other, ensuring proper chain engagement. The dynamic positioning allows the sprocket to adapt its radius without compromising tooth-to-chain link alignment.
Solution Approach 2:
The gear segments are pre-positioned along the radial slots at appropriate intervals. This preliminary arrangement ensures that when the segments are engaged to form the effective sprocket, their teeth are properly spaced to match the chain link pitch, regardless of the chosen radius. The segments are prepared in advance at correct positions rather than requiring continuous adjustment during operation.
3Adaptability or versatility
If traditional circular chain rings are used to achieve varying power transfer, then gear ratios can be changed, but the use of a gear derailleur creates friction and interrupts power transfer
Solution Approach 1:
Instead of using a derailleur to shift the chain between fixed chain rings, this invention dynamically adjusts the effective radius of a single sprocket by sliding gear segments along radial slots. This eliminates the need for chain disengagement and derailleur mechanisms, maintaining continuous power transfer without friction losses associated with traditional derailleurs.
Solution Approach 2:
The derailleur mechanism and multiple chain rings are completely removed from the system. The function of varying gear ratios is extracted and achieved through a different mechanism - sliding gear segments along radial slots on a single base plate. This extraction eliminates the harmful friction and power transfer interruptions caused by derailleur operation.
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 allows for seamless shifting between gear ratios without interrupting power transfer, reducing weight and complexity compared to existing mechanisms, and enabling easy installation on bicycles without complicated adjustments.
Implementation Method 1
spring-biased locking pins are released by movable control plates to adjust the effective radius of the gear segments
Data Source
AI summary
A bicycle transmission allows a bicycle operator to change the radius of a pedal crank's transmission gear as sliding gear segments, radially arranged on a base ring assembly, vary their relative radial position from the center of the base plate. These gear segments slide in and out to change the effective radius of the gear. Spring biased locking pins engage adjustable control plates as the crank rotates. The locking pins release to make further adjustments to increase or decrease the effective radius. The transmission may also be used as a variable-ratio prime mover for other motive power applications, to transfer power from the wheel to another rotating component. The transfer of power may be via a chain or a belt.