Canted Steering Stem for Double Wishbone Motorcycle Rake Adjustment

Solution Overview

Problem

Traditional methods for modifying the rake angle in motorcycles with double wishbone front suspension systems are ineffective in reducing trail and altering ride quality, as they change the steering axis and leverage of the suspension, unlike traditional triple tree designs.

Innovation Solution

A canted body steering stem with a primary section aligned with the steering axis and a secondary section having a cant axis varying between 1° and 16° degrees, attached to a tubular steering housing and non-telescoping fork assembly, allows for adjustable trail length by altering the position of the front wheel's contact patch relative to the steering axis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the length of upper and lower control arms is changed to modify rake angle, then the steering axis position changes, but the trail reduction is ineffective and ride quality deteriorates

Engineering Contradiction:

Improvesteering effortVSAvoidride quality

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The steering stem is divided into two separate sections: a primary section that defines the steering axis and a secondary section that attaches to the fork assembly. This segmentation allows the secondary section to be positioned at a different angle (cant angle of 1°-16°) relative to the primary section, enabling independent adjustment of the steering axis position without altering the suspension leverage or control arm geometry.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The canted secondary section of the steering stem acts as an intermediary element between the primary steering axis and the fork assembly. By introducing this intermediate canted section, the patent achieves trail reduction and steering axis repositioning without directly modifying the control arms or suspension leverage, thus maintaining ride quality while improving steering characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If control arm length is modified to change rake, then steering axis moves, but suspension leverage changes adversely affecting ride quality

Engineering Contradiction:

Improverake angle adjustmentVSAvoidsuspension leverage

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The steering stem is divided into two separate sections: a primary section that defines the steering axis and a secondary section that attaches to the fork assembly. This segmentation allows the secondary section to be positioned at a different angle (cant angle of 1°-16°) relative to the primary section, enabling independent adjustment of the steering axis position without altering the suspension leverage or control arm geometry.

Inventive Principle:

Principle #1Segmentation

3Ease of operation

If traditional triple tree design is used to modify rake by changing down tube angle, then trail is reduced and steering effort decreases, but the design is not applicable to double wishbone suspension

Engineering Contradiction:

Improvesteering effortVSAvoidsuspension type compatibility

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The canted secondary section of the steering stem acts as an intermediary element between the primary steering axis and the fork assembly. By introducing this intermediate canted section, the patent achieves trail reduction and steering axis repositioning without directly modifying the control arms or suspension leverage, thus maintaining ride quality while improving steering characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The canted steering stem design provides a universal solution that can be applied to double wishbone suspension systems, achieving the same steering effort reduction as traditional triple tree designs but without requiring telescoping forks or internal spring/shock assemblies. The solution adapts the rake modification concept to a different suspension architecture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11560196B2Rake device for a three wheel motorcycle

Publication Date: 2023.01.24 MOTOR TRIKE INC

AI summary

A method of modifying the rake angle on a motorcycle having a double wishbone front suspension. The motorcycle has a tubular steering housing connected to a non-telescoping fork assembly by a straight body steering stem. The method includes the step of replacing the straight body steering stem with a canted body steering stem. The canted body steering stem includes (i) a primary section having a steering axis corresponding to a steering axis of the motorcycle; and (ii) a secondary section having a cant axis which varies from the steering axis by between 1° and 16°.