Tapered Mounting Assembly for Torsional Load and Bolt Fatigue
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Solution Overview
Problem
Conventional mounting assemblies for nacelle sails on tiltrotor aircraft face challenges with producibility due to the need for manual sanding for close-tolerance fits, and they fail to effectively address torsional loads, leading to bolt fatigue.
Innovation Solution
A mounting assembly featuring a base with a tapered socket and a shaft with a tapered boss, along with a threaded surface and a conically shaped nut, provides a secure engagement that reacts to bending, torsional, and axial loads, using internal and external interlocking portions and a quick-release lock pin for easy installation and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a close tolerance, minimal clearance slip fit is used between the shaft and receiver, then the mounting assembly can react to bending loads, but manual sanding and smoothing is needed to accomplish the fit, making producibility difficult
Solution Approach 1:
The patent changes the geometric parameters of the shaft and receiver from straight cylindrical shapes to tapered shapes. The shaft has a tapered outer surface and the receiver has a tapered inner surface, allowing for a friction fit without requiring manual sanding or smoothing. The taper angle and dimensions are optimized to provide both easy assembly and adequate load reaction capability.
2Device complexity
If conventional mounting assemblies with straight cylindrical shafts and receivers are used, then assembly is simple, but the clearances increase and open up as the nacelle sail is loaded during flight
Solution Approach 1:
The patent applies curvature in the form of a taper to the shaft and receiver surfaces. The tapered geometry creates a wedge effect where the contact area increases under load, maintaining stable clearance and preventing the gap opening that occurs with straight cylindrical designs. The curved tapered surfaces distribute loads more effectively across the interface.
3Strength
If concentric holes with bolts are drilled through the shaft and receiver to react to torsional loads, then torsional load capacity is improved, but the bolts tend to fail due to fatigue after most flights
Solution Approach 1:
The patent extracts the fastening function from the load-bearing function. Instead of using bolts that simultaneously fasten and resist torsional loads (leading to fatigue), the design uses a tapered friction fit for fastening and a keyway for torsional load resistance. This separation of functions eliminates the fatigue problem in the fastening elements.
Solution Approach 2:
The patent introduces a keyway as an intermediary element between the shaft and receiver to handle torsional loads. The keyway fits into a corresponding groove and transfers torsional forces without requiring bolts, thereby protecting the fastening interface from fatigue while maintaining torsional load capacity.
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 solution enhances the durability and maintainability of the mounting assembly by providing 360-degree surface contact and reducing fatigue, allowing for cost and time savings in production and minimizing aircraft downtime.
Implementation Method 1
a tapered boss adjacent to first end, the tapered boss configured to engage the tapered socket
Implementation Method 2
the mounting assembly reacts to bending, torsional, and axial loads
Implementation Method 3
a second end opposite from the first end, the second end including a threaded surface; wherein when the shaft is in an engaged position, the shaft is static in the hollow portion of the base
Implementation Method 4
a conically shaped nut, and the base further includes an angled portion at the securing end to receive the conically shaped nut
Implementation Method 5
an external interlocking portion adjacent to the tapered boss configured to engage the internal interlocking portion
Data Source
AI summary
A mounting assembly for coupling an accessory to a frame including a base configured to be coupled to the frame; the base having a hollow portion; the hollow portion including a receiving end including a tapered socket; an internal interlocking portion adjacent to the tapered socket; and a securing end opposite from the receiving end; a shaft configured to be connected to an accessory at a first end and received in the hollow portion of the base in an engaged position, the shaft including a tapered boss adjacent to the first end, the tapered boss configured to engage the tapered socket; an external interlocking portion adjacent to the tapered boss configured to engage the internal interlocking portion; and a second end opposite from the first end, the second end including a threaded surface; wherein when the shaft is in an engaged position, the shaft is static in the hollow portion.