Free-Coaster Hub Clutch and Epicyclic Gear Slack Control
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Solution Overview
Problem
Existing bicycle free-coaster hubs face challenges in maintaining a consistent gap or slack between the driving system and the driven element when coasting backward or freewheeling forward, leading to accidental engagement of the drive, which can be dangerous and disrupt the rider's balance.
Innovation Solution
The driving mechanism of the bicycle free-coaster hub includes a driving assembly, clutch assembly, epicyclic gear assembly, resisting member, forward drag member, and reverse drag member, which work together to maintain a constant gap or slack between the driving system and the driven element, preventing accidental engagement of the drive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large degree of backlash or slack is introduced to prevent accidental engagement, then rider safety is improved, but acceleration performance and pedaling smoothness deteriorate
Solution Approach 1:
The patent employs dynamic drag members (spring-loaded) that automatically adjust the gap between drive elements based on wheel rotation direction. During backward coasting, the drag members maintain a larger gap to prevent accidental engagement. During forward acceleration, the drag members reduce the gap for smoother, faster engagement. This dynamic adjustment resolves the contradiction by making the gap variable rather than fixed.
Solution Approach 2:
The patent changes the parameter of gap size between drive elements based on operational conditions. Through the drag members, the gap is enlarged during backward motion to prevent accidental engagement, and reduced during forward motion to improve acceleration. This parameter change approach allows the system to optimize both safety and performance for different riding scenarios.
2Reliability
If the hub is designed with maximum slack to ensure safety, then accidental engagement is prevented, but the rider must pedal more to engage drive which can throw off balance
Solution Approach 1:
The drag members dynamically adjust the gap based on wheel rotation direction, making the system adaptive rather than static. During backward coasting, the gap is naturally maintained at a safe distance. During forward acceleration, the gap automatically reduces, providing predictable and consistent engagement characteristics regardless of the safety-oriented design.
Solution Approach 2:
The drag members provide mechanical feedback that responds to wheel rotation direction and force applied. This feedback mechanism ensures that the gap between drive elements is automatically adjusted based on actual operating conditions, making the engagement behavior predictable and consistent while maintaining safety margins during backward coasting.
3Productivity
If the wheel is constantly biasing drive elements into engagement during forward spinning, then forward drive is improved, but accidental engagement on landing from jumps increases
Solution Approach 1:
The patent introduces asymmetric drag members that respond differently to forward and backward wheel rotation. The drag members are positioned and biased to allow easy engagement during forward motion (improving forward drive efficiency) while automatically maintaining a protective gap during backward motion (preventing accidental engagement on landing). This asymmetric design resolves the contradiction by treating forward and backward directions differently.
Solution Approach 2:
The drag members provide preliminary protective action by maintaining a gap during backward rotation before any engagement can occur. This preliminary anti-action prevents the harmful effect of accidental engagement on landing from jumps, while not interfering with normal forward drive operation where the gap naturally closes under applied force.
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 effectively prevents accidental engagement of the drive during coasting or freewheeling, enhancing rider safety and balance by maintaining a consistent gap or slack, thereby reducing the risk of sudden forceful backward movement of the cranks.
Implementation Method 1
a coil-spring having one end inserted into the retaining device and a coil body encircled on the outer surface of each of the cams and the retaining piece respectively so that each of the cams can be moved stably along the first or second ramps of each of the receiving rooms
Implementation Method 2
Each of the cams has a first portion, a second portion, an inner surface and a roughened outer surface
Data Source
AI summary
A driving mechanism of a bicycle free-coaster hub includes a driving assembly, a clutch assembly, an epicyclic gear assembly, a resisting member, and forward drag and reverse drag members. The clutch assembly includes an output clutch unit disposed inner the hub and an input clutch unit disposed with the driving assembly to form a clutching or engaging state with the output clutch unit. The epicyclic gear assembly includes a sun gear coupled with the input clutch unit, a ring gear mounted on the hub, a planet gear carrier having a plurality of planet gears engaged with the ring gear and the gear portion of the sun gear. The resisting member is disposed between the sun gear and the hub axle. The forward drag member is disposed between the ring gear and the sun gear. The reverse drag member is disposed between the planet gear carrier and the hub axel.