Bicycle Frame Rear Suspension with Flexible Segment
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Solution Overview
Problem
Rear suspension systems in bicycles often suffer from 'pedal bob,' which wastes rider energy and can cause loss of traction, due to shifting weight and chain force variations, and are complicated by additional pivots and links that increase weight, cost, and maintenance issues.
Innovation Solution
A bicycle frame design featuring a substantially rigid front and rear frame portion with a flexible frame segment that acts as a leaf spring, connected by pivots to reduce pedal bob while maintaining pedaling efficiency, and incorporating a shock absorber to oppose or promote pivoting based on suspension travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If additional pivots and links are incorporated into the rear suspension to minimize pedal bob, then pedal bob is reduced, but device complexity and weight increase
Solution Approach 1:
The frame is divided into rigid and flexible segments, with the flexible segment acting as a spring element. This segmentation allows the suspension function to be distributed between the rigid frame portions and the flexible segment, reducing the need for additional pivots and links while still minimizing pedal bob.
Solution Approach 2:
The flexible frame segment's stiffness is varied along its length, with the greatest flexibility at the pivot connection and decreasing flexibility toward the rear frame portion. This parameter change allows the single flexible segment to provide progressive suspension action, replacing multiple pivots and links.
2Loss of energy
If additional pivots and links are incorporated into the rear suspension to minimize pedal bob, then pedal bob is reduced, but weight increases
Solution Approach 1:
The suspension function is merged into the frame structure itself through the flexible segment, eliminating the need for separate suspension components like additional pivots, links, and shock absorbers. This integration reduces overall weight while maintaining pedal bob minimization.
Solution Approach 2:
By varying the stiffness parameter along the flexible segment's length, the design achieves progressive suspension action that effectively minimizes pedal bob without requiring multiple heavy mechanical components, thus reducing overall frame weight.
3Loss of energy
If additional pivots and links are incorporated into the rear suspension to minimize pedal bob, then pedal bob is reduced, but maintenance issues increase
Solution Approach 1:
The flexible segment extracts the suspension function from the traditional multi-pivot linkage system, eliminating numerous moving parts that require maintenance. The single flexible segment has no internal moving parts, drastically reducing maintenance complexity.
Solution Approach 2:
The flexible segment provides self-contained suspension action through its inherent flexibility, requiring no external lubrication, adjustment, or maintenance. The structure serves itself by using material elasticity rather than mechanical friction-based pivots.
4Device complexity
If a flexible frame segment is used to reduce the number of pivots and links, then device complexity is reduced, but the ability to control suspension characteristics may be limited
Solution Approach 1:
The stiffness parameter is varied continuously along the flexible segment's length, allowing progressive suspension action that adapts to different loading conditions. This parameter gradient enables the single flexible segment to provide multiple suspension characteristics that would traditionally require multiple adjustable components.
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 design effectively reduces pedal bob by varying spring force to resist or promote pivoting, enhancing pedaling efficiency and reducing maintenance complexities by minimizing the number of links and pivots, thus improving ride quality and reducing energy loss.
Implementation Method 1
The frame segment is flexible parallel to an axis of the third pivot... The frame segment is configured to flex to enable the first pivot to move in the arc about the second pivot as the frame segment pivots about the third pivot between a rest position and a fully pivoted position.
Implementation Method 2
The frame segment behaving as a leaf spring as it flexes, with the frame segment being configured to provide a spring force that varies between opposing and promoting pivoting of the rear fame portion about the third pivot as the rear frame portion is pivoted about the third pivot from a rest position to a fully pivoted position.
Implementation Method 3
a shock absorber pivotably connected between the rear frame portion and the front frame portion to oppose pivoting of the rear frame portion relative to the front frame portion in a clockwise direction about the third pivot
Data Source
AI summary
A bicycle frame includes a substantially rigid front frame portion and a substantially rigid rear frame portion. A link is connected to the rear frame portion by a first pivot and to the front frame portion by a second pivot. A frame segment is rigidly connected at a first end to one of the rear frame portion and the front frame portion and pivotably connected at a second end to other of the rear frame portion or the front frame portion by a third pivot. The frame segment is flexible parallel to an axis of the third pivot.