Rear Suspension Drivetrain With Free Stroke Against Pedal Kickback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bicycles with rear suspension experience pedal kickback and chain stress due to rear wheel travel, which destabilizes the rider and can lead to chain breakage, particularly in high-travel applications like downhill mountain biking.
Innovation Solution
A bicycle drivetrain system that includes a free stroke device allowing forward and backward angular strokes of the chain with respect to the crankset and hub assembly, featuring first and additional damper means to oppose the strokes and manage stress effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If rear suspension with large travel is used, then comfort and absorption of bumps are improved, but pedal kickback and chain stress increase causing instability and potential chain breakage
Solution Approach 1:
A free-stroke device is introduced as an intermediary mechanism between the chain and the crankset. This device includes a movable arm that can rotate independently, allowing the chain to move freely during suspension compression while maintaining torque transmission during pedaling. The movable arm acts as a mediator that decouples the harmful chain pull from the crankset while preserving the useful power transmission function.
Solution Approach 2:
The drivetrain system is segmented into independent functional components: the fixed crankset for power input, the movable arm with free-stroke capability for shock isolation, and the chain for power transmission. This segmentation allows each component to perform its specific function independently, with the movable arm absorbing suspension-induced chain movement while the crankset remains stable for efficient pedaling.
2Stability of the object's composition
If rear suspension with large travel is used, then comfort and absorption of bumps are improved, but chain stress increases causing potential chain breakage
Solution Approach 1:
The movable arm serves as a stress-isolating intermediary between the chain and crankset. During suspension compression, the movable arm rotates to accommodate chain length changes, preventing excessive stress from being transmitted to the chain and crankset. This mediator function protects the chain from breakage while maintaining system stability.
Solution Approach 2:
The free-stroke device provides beforehand cushioning by allowing controlled movement of the movable arm that absorbs chain tension spikes before they can propagate to the chain and crankset. The device is pre-configured to accommodate the maximum expected chain movement during full suspension travel, cushioning against extreme stress events.
3Object-affected harmful factors
If Spanish patent crankset with rotatable gear wheel and springs is used, then some damping is provided, but torque effectiveness is reduced and strong counter-blows persist
Solution Approach 1:
The movable arm is designed with dynamic freedom to rotate during suspension compression while maintaining a fixed relationship with the crankset during pedaling. This dynamic behavior allows the system to adapt its stiffness characteristics based on the operational phase: compliant during chain pull events and rigid during power transmission, unlike the always-compliant Spanish patent solution.
Solution Approach 2:
The free-stroke device exhibits asymmetric behavior: it allows free movement in the chain-pull direction (during suspension compression) while maintaining rigid torque transmission in the pedaling direction. This asymmetric design selectively dampens harmful vibrations while preserving useful power transmission, whereas the Spanish patent applies symmetric damping that reduces both harmful and useful forces.
4Object-affected harmful factors
If Japanese patent crankset with elastic gaskets is used, then some isolation is provided, but the gaskets are ineffective due to random and limited movement
Solution Approach 1:
The movable arm provides controlled dynamic movement that is specifically designed to match the chain's motion during suspension compression. Unlike the limited random movement of elastic gaskets, the movable arm rotates through a defined angular range that exactly accommodates the chain length变化, providing reliable and effective damping of chain stress.
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
The system effectively compensates for pedal kickback, increases stability and safety, and allows for easier resumption of pedaling, while also reducing chain stress and preventing breakage.
Implementation Method 1
first damper means that act for the entire forward angular stroke (A1), opposing it, and additional damper means that act only in a final stretch of forward angular stroke (A2), opposing it
Data Source
AI summary
A bicycle includes a frame, rear wheel, suspension system of the rear wheel with respect to the frame that allows a predetermined relative displacement between them, and drivetrain system for transmitting the motion from a crankset to the rear wheel. The drivetrain system includes a crankset fixed to the frame, a hub and pinion assembly fixed to the rear wheel that is rotatable about a common pivot axis thereof, and a drive chain placed to connect them directly to each other. The crankset and hub and pinion assembly are subjected to reciprocal displacement by the action of the suspension system, where at least one among the crankset and the hub and pinion assembly has a free stroke device placed to allow both a forward and backward free angular stroke of the chain with respect to the respective pivot axes of the crankset and/or of the hub and pinion assembly.