Cycle Suspension Assembly Increasing Mechanical Trail
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Solution Overview
Problem
Telescopic front suspension forks in two-wheeled vehicles face issues with high stiction, reduced mechanical trail during compression, lack of leverage ratio, and undesirable braking reactions, leading to instability and reduced traction.
Innovation Solution
A wheel suspension assembly with a steering fork connected to a first arm and a shock link, featuring a shock absorber with adjustable pivots and a wheel carrier, which increases mechanical trail distance as the suspension compresses, providing a greater than 1:1 leverage ratio and improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If telescopic fork stantions are made larger to support fore/aft loads, then load-bearing capacity is improved, but stiction increases and compliance deteriorates
Solution Approach 1:
The suspension system is divided into separate functional components: a telescopic fork for steering and a swingarm suspension for shock absorption. This segmentation allows each component to be optimized for its specific function, eliminating the need for oversized stantions that generate high stiction while still providing adequate load support through the swingarm pivots.
Solution Approach 2:
The swingarm acts as an intermediary mechanism between the wheel and the frame. It transfers vertical loads from the wheel through the shock absorber to the frame, reducing the direct fore/aft loading on the telescopic fork stantions and thereby reducing stiction while maintaining load-bearing capacity.
2Strength
If telescopic fork stantions are made larger with larger bushings and sliding surfaces, then structural support is improved, but stiction increases and bump absorption effectiveness decreases
Solution Approach 1:
The suspension system separates steering functions (telescopic fork) from suspension functions (swingarm with shock absorber). The swingarm pivots are designed with appropriate bushing sizes for vertical load support, while the telescopic fork stantions can use smaller bushings since they primarily handle steering and reduced vertical loads.
Solution Approach 2:
The swingarm serves as a mediator that absorbs and isolates vertical impact forces from the telescopic fork. By positioning the shock absorber on the swingarm rather than in the telescopic fork, the system reduces stiction at the steering components while maintaining effective bump absorption through the swingarm suspension.
3Device complexity
If mechanical trail is constrained by steering axis angle and fork offset in telescopic forks, then steering geometry is simplified, but stability decreases as suspension compresses
Solution Approach 1:
The swingarm suspension creates a dynamic geometry system where the effective trail and steering characteristics change beneficially with suspension compression. As the swingarm rotates downward to absorb bumps, the wheel contact point moves relative to the steering axis in a way that maintains or increases mechanical trail, improving stability during compression while keeping the steering geometry relatively simple through the swingarm pivot arrangement.
Data Source
AI summary
A trailing link, multi-link, suspension assembly for a cycle having improved stability includes a first arm having a first arm fixed pivot and a first arm shock pivot. A shock link has a shock link fixed pivot and a shock link floating pivot. A shock absorber has a first shock mount and a second shock mount. A wheel carrier has a wheel carrier first pivot and a wheel carrier second pivot spaced apart from one another, and a wheel mount that is adapted to be connected to a wheel. A control link has a control link floating pivot and a control link fixed pivot, the control link floating pivot being pivotably connected to the wheel carrier second pivot, and the control link fixed pivot being pivotably connected to the first arm control pivot. A mechanical trail distance increases as the suspension assembly compresses relative to a fully extended state.