Propeller Hub Bushing Limits Axial Noise
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Solution Overview
Problem
Existing marine propeller assemblies require specific designs for different motor brands, leading to inventory challenges and increased costs, and they often generate noise during operation due to unnecessary movement, which affects efficiency and engine safety.
Innovation Solution
A propeller assembly design featuring a housing structure with a spindle and bushing assembly that includes a frangible key system and a resilient bushing, allowing for limited rotation before disengagement and reduced noise through axial movement limitation, enabling compatibility with various propeller shafts and minimizing noise during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a removable propeller housing design is used to reduce inventory requirements and costs, then adaptability across different motor brands is improved, but unnecessary movement of the propeller assembly occurs which generates noise and reduces efficiency
Solution Approach 1:
A resilient bushing made of elastomeric material is used as a flexible element between the propeller hub assembly and the propeller shaft. This bushing allows for limited axial movement to accommodate different shaft specifications while dampening vibrations and reducing noise generation during operation.
Solution Approach 2:
The resilient bushing acts as an intermediary element between the rigid propeller hub assembly and the propeller shaft. It mediates the connection by providing both mechanical coupling and isolation, allowing the removable housing design to adapt to different shafts while preventing excessive movement that would cause noise.
2Object-generated harmful factors
If a resilient bushing is used to reduce noise through limited axial movement, then noise generation is reduced, but the complexity of the hub assembly increases
Solution Approach 1:
The resilient bushing is molded directly over the frangible keys and spindle, integrating multiple functions into a single component. This merging of the bushing with the key system simplifies the overall hub assembly structure while maintaining noise reduction capabilities.
Solution Approach 2:
The bushing is formed from elastomeric material that combines flexibility for noise damping with sufficient structural integrity to maintain proper alignment and transmit torque effectively.
3Reliability
If a frangible key system is implemented to allow limited rotation before disengagement, then engine damage is prevented, but the manufacturing complexity increases
Solution Approach 1:
The frangible keys are designed as sacrificial components that can be easily replaced. They are made from material that allows them to break under excessive load, protecting the expensive engine and drive system. The keys are molded as integral parts of the bushing assembly, simplifying their manufacture despite their specialized function.
Solution Approach 2:
The frangible keys are pre-positioned within the bushing structure during manufacturing. This preliminary placement ensures proper alignment and functionality while reducing assembly complexity during installation, as the keys are already in their correct positions before the assembly reaches the customer.
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 reduces noise generation, allows for easy mounting and removal, and prevents engine damage by limiting axial movement, thus enhancing operational efficiency and adaptability across different motor brands.
Implementation Method 1
A bushing formed from a rubber or elastomeric material is provided between the inner surface of the inner housing and the outer surface of the drive member. The elastomeric bushing provides shock absorbency between the propeller hub assembly and the drive shaft.
Implementation Method 2
A plurality of spaced, longitudinally extending keys extend along the outer surface of the spindle. In the event that the propeller blades become fixed during operation of the watercraft, the keys fragment from the outer surface of spindle so as to disengage the spindle from the housing structure.
Data Source
AI summary
A propeller assembly is provided for mounting on a rotatable propeller shaft having a terminal end. The propeller assembly includes a housing structure extending along a longitudinal axis and having first and second ends. The housing structure includes an inner surface defining a cavity and an opening in the second end in communication with the cavity. A bushing assembly has first and second ends and includes an outer surface engageablc with the inner surface of the housing structure. An adaptor has first and second sides and is adapted for receipt on the propeller shaft. The adaptor has an enlarged portion having a diameter greater than a diameter of the opening in the second end of the housing structure. A nut is receivable on the terminal end of the propeller shaft. The nut is threadable on the propeller shaft to a tightened configuration wherein the nut engages the adaptor and maintains the propeller assembly on the propeller shaft. The nut, in the tightened configuration, the first side of the adaptor engages the second end of the bushing assembly and the enlarged portion of the adaptor is spaced from the second end of the housing structure.