Snowmobile Ski Suspension Adaptive Trail Geometry
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Solution Overview
Problem
Conventional snowmobiles face difficulties in counter-steering, particularly in situations like side-hilling or boon-docking, where the current design's positive trail enhances directional stability but hinders easy maneuverability.
Innovation Solution
The snowmobile's ski design is engineered to have a negative trail when tilted during turns and a positive trail when traveling straight, altering the relationship between the steering axis and load axis to facilitate counter-steering by decreasing directional stability and increasing the tendency to turn.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the snowmobile is designed with positive trail (steering axis forward of load axis), then directional stability is improved, but counter-steering maneuverability deteriorates
Solution Approach 1:
The patent applies the dynamics principle by making the trail characteristic of the ski changeable based on operating conditions. The ski suspension system is designed so that the relative position between the steering axis and load axis changes dynamically: when the snowmobile is tilted during turns, the ski geometry causes the load axis to shift rearward relative to the steering axis, creating negative trail that facilitates counter-steering. This dynamic adjustment resolves the contradiction by providing positive trail for stability during straight travel and negative trail for maneuverability during tilted turning operations.
Solution Approach 2:
The patent employs parameter changes by altering the geometric parameters of the ski-suspension system. Specifically, the design modifies the trail parameter (the horizontal distance between steering axis and load axis) based on the tilt angle of the snowmobile. When tilted, the ski's contact point and load distribution change, transforming the trail from positive to negative. This parameter change enables the system to switch between stability-oriented and maneuverability-oriented modes, resolving the technical contradiction between these two opposing requirements.
2Stability of the object's composition
If the steering axis is positioned forward of the load axis (positive caster), then the snowmobile self-centers and maintains straight travel, but the tendency to turn naturally is reduced
Solution Approach 1:
The patent makes the self-centering characteristic dynamic rather than static. The positive trail that provides self-centering force is present only when the snowmobile travels straight. When the snowmobile tilts during turning operations, the geometry changes cause the trail to become negative, which eliminates the self-centering effect and allows the ski to turn naturally in the direction of the tilt. This dynamic behavior resolves the contradiction by providing self-centering when needed for straight travel and turnability when needed for maneuvering.
Solution Approach 2:
The patent applies preliminary anti-action by designing the ski geometry to counteract the self-centering effect when turning is desired. The negative trail configuration that develops during tilt creates a natural turning moment that opposes the self-centering tendency. This preliminary design feature ensures that when the operator tilts the snowmobile for turning, the system automatically generates the opposite effect (negative trail) to facilitate the turn, resolving the contradiction between self-centering and turnability.
Data Source
AI summary
Snowmobile having a suspension assembly comprising an upper A-arm, a lower A-arm, and a ski leg. The ski leg is pivotably connected to the upper A-arm via an upper A-arm connector and to the lower A-arm via a lower A-arm connector and is pivotable about a kingpin axis. A ski is connected to the ski leg via a ski connector. The upper A-arm connector, the lower A-arm connector and the ski connector are positioned one with respect to the others such that the kingpin axis is behind the ski connector at a level of the ski connector when the ski is viewed from the side.