Angled Steering Axis Outboard Motor Handling
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Solution Overview
Problem
Conventional outboard motor designs face handling and stability issues due to the distance of the center of gravity from the steering axis being too high, which is exacerbated by four-stroke engines having a center of gravity further back than two-stroke engines, leading to potential oversteering and increased steering forces.
Innovation Solution
The steering axis of the outboard motor is tilted at an angle of less than 45 degrees relative to the driveshaft axis, increasing the distance to the center of pressure and reducing the distance to the center of gravity, thereby improving handling and stability without increasing the engine's size or weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the steering axis is positioned vertically (parallel to driveshaft axis), then the structure is simple and compact, but the center of gravity is too far from the steering axis causing handling issues and oversteering
Solution Approach 1:
The patent changes the orientation parameter of the steering axis from vertical (parallel to driveshaft axis) to an angled configuration (less than 45 degrees from vertical). This parameter change moves the center of gravity closer to the steering axis, improving handling and stability while preventing oversteering. The angled steering axis configuration is achieved through the swivel bracket design that allows rotation about the angled axis.
2Power
If four-stroke engines are used, then power and efficiency are improved, but the center of gravity moves further back exacerbating handling issues
Solution Approach 1:
The patent compensates for the rearward center of gravity of four-stroke engines by changing the steering axis orientation parameter. The angled steering axis (less than 45 degrees from vertical) creates a more favorable geometric relationship between the center of gravity and steering axis, maintaining proper handling characteristics despite the engine type change.
3Ease of operation
If the steering axis is angled less than 45 degrees from vertical, then handling and stability are improved, but the structural complexity increases
Solution Approach 1:
The swivel bracket is designed to perform multiple functions: it supports the outboard motor, enables steering rotation about the angled axis, and accommodates the driveshaft connection. This multi-functional design achieves the angled steering axis configuration without proportionally increasing overall structural complexity.
Solution Approach 2:
The swivel bracket provides dynamic rotation capability about the angled steering axis, allowing the outboard motor to steer effectively. The dynamic rotational joint accommodates the angled configuration while maintaining steering functionality, resolving the complexity issue through appropriate mechanical design of the rotation mechanism.
Data Source
AI summary
An outboard motor has a drive unit including an engine rotating output shaft and a driveshaft extending along a driveshaft axis and having an upper end coupled in torque-transmitting relationship with the output shaft. A propulsor shaft extends along a propulsor shaft axis and has a first end coupled in torque-transmitting relationship to a lower end of the driveshaft and a second end coupled to a propulsor. The propulsor shaft axis defines a direction of thrust generated by the propulsor. A transom bracket couples the drive unit to the marine vessel. A steering support couples the drive unit to the transom bracket and rotates the drive unit about a steering axis to change a direction of the thrust generated by the propulsor. The steering axis is substantially non-parallel to the driveshaft axis, and is oriented with respect to the driveshaft axis at a given angle of less than 45 degrees.