Bicycle Rear Suspension Linkage for Vertical Axle Path Control
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Solution Overview
Problem
Existing rear suspension systems in off-road bicycles face issues such as increased weight, undesirable performance near the end of suspension travel, and a high center of gravity due to the placement of the shock absorber, which affects handling and pedal and braking forces.
Innovation Solution
A rear suspension system with a multiple linkage assembly that includes a lower arm, upper frame link, upper arm, upper shock link, and lower shock link, with the shock absorber positioned to bias the articulating frame portion to a relaxed configuration, allowing the rear axle to follow a more vertical path and reducing the center of gravity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single lever rear suspension design is used, then the system is simple and reliable, but pedal forces and braking forces are transmitted into the rear suspension assembly
Solution Approach 1:
The single lever suspension is divided into multiple independent lever members (first lever member and second lever member) that are pivotally connected to the frame at different locations. This segmentation allows each lever to independently manage specific force vectors, isolating pedal and braking forces from the main suspension assembly while maintaining structural simplicity.
2Object-generated harmful factors
If multiple lever members are used to isolate pedaling forces, then force isolation improves, but the shock absorber must be positioned at a high location raising the center of gravity
Solution Approach 1:
The shock absorber is repositioned from a high vertical location to a lower position by utilizing the horizontal spacing between the first and second lever members. The shock absorber connects between these laterally spaced pivot points, allowing force isolation to be achieved without raising the center of gravity, thus maintaining good handling qualities.
3Adaptability or versatility
If large suspension travel is designed, then bump absorption capability increases, but the rear wheel follows a forward arc path causing harsh bottoming out
Solution Approach 1:
The first and second lever members are designed with asymmetric geometry and different pivot point locations relative to the frame. This asymmetric configuration creates a progressive leverage ratio where the mechanical advantage changes throughout the suspension travel, allowing large suspension travel while preventing harsh bottoming out through controlled force distribution.
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 achieves a lower center of gravity, improved handling, a more progressive leverage ratio, and better absorption of bumps by maintaining a vertical rear axle path, reducing weight, and enhancing manufacturability.
Implementation Method 1
a shock absorber having a first end and a second end, the first end pivotally supported at a fourth axis by the main frame portion, the second end pivotally supported at a fifth axis by the upper shock link and the lower shock link, the shock absorber configured to bias the articulating frame portion to the relaxed configuration
Implementation Method 2
the shock absorber configured to bias the articulating frame portion to the relaxed configuration
Data Source
AI summary
A bicycle comprises a front wheel; a rear wheel; a frame comprising a main frame portion and an articulating frame portion, the articulating frame portion comprising: a lower arm pivotally supported at a first axis by the main frame portion; an upper frame link pivotally supported at a second axis by the main frame portion; an upper arm pivotally coupled to the upper frame link at a third axis; an upper shock link pivotally coupled to the upper frame link and the upper arm at the third axis; and a lower shock link pivotally coupled to the main frame portion and the lower arm at the first axis; and a shock absorber having a first end pivotally supported at a fourth axis by the main frame portion, and a second end pivotally supported at a fifth axis by the upper shock link and the lower shock link.