Piloted Nut Outer Diameter Radial Positioning
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Solution Overview
Problem
In turbomachinery, the lack of precision control between the threads of a nut and the face of a threaded component leads to inconsistent radial positioning of the nut, causing unrepeatable balance results and vibration issues due to radial expansion under axial load, which complicates the balancing process of rotating assemblies.
Innovation Solution
A rotating assembly design featuring a tie-shaft with an outer threaded portion, a rotor with an interior piloting surface, and a nut with a radial flange extending beyond its piloting feature, where the nut's piloting feature is on the exterior surface to maintain radial positioning without loosening under axial load, ensuring consistent axial compressive force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an inner diameter piloting surface is used on the nut, then radial positioning is provided, but under axial load the nut expands radially outward thus loosening the piloting fit
Solution Approach 1:
Instead of placing the piloting surface on the inner diameter of the nut (conventional approach), the invention inverts the approach by placing the piloting surface on the outer diameter of the nut. This inversion prevents the piloting fit from loosening under axial load because the outer diameter does not expand radially outward when the nut is tightened, thereby maintaining consistent radial positioning precision throughout operation.
2Force
If conventional nut designs are used, then axial compressive force is applied, but the radial position of the nut is driven off of the desired centerline position causing unrepeatable balance results
Solution Approach 1:
The invention introduces an intermediary piloting surface on the outer diameter of the nut that acts as a mediator between the nut and the rotor. This piloting surface maintains precise radial positioning of the nut relative to the rotor centerline while the axial compressive force is applied through the tie-shaft and nut assembly, thereby ensuring repeatable balance results without compromising the axial force application.
3Force
If the nut expands radially under axial load, then the axial clamp load is maintained, but the piloting fit is negated and radial positioning is lost
Solution Approach 1:
The invention inverts the conventional design by placing the piloting surface on the outer diameter rather than the inner diameter of the nut. This allows the axial clamp load to be maintained through normal nut tightening while preventing radial expansion from affecting the piloting fit, as the outer diameter surface remains stable under axial loading conditions.
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
This design maintains precise radial positioning of the nut relative to the rotor, reducing shaft bowing and achieving more repeatable balance results by preventing radial expansion of the nut, thus enhancing the reliability of turbomachinery balancing processes.
Implementation Method 1
the nut threaded portion is threadingly engaged with the tie-shaft threaded portion such that an axial compressive load is applied to the rotor between the tie-shaft shoulder and the radial flange
Implementation Method 2
a nut piloting feature disposed on an exterior surface of the nut and abutting the rotor interior piloting surface
Data Source
AI summary
The present application relates generally to a piloted nut. The piloted nut may be used on a tie-shaft to apply an axial load to a rotor. A piloting feature on an exterior surface of the nut provides radial piloting to the rotor. The piloted nut may be used in a gas turbine engine to apply an axial load to a rotor.