Two-Piece Backing Ring Assembly for Railcar Axle Fretting Wear
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Solution Overview
Problem
Tapered roller bearings on railcar axles experience fretting wear due to shaft deflections, leading to loose backing rings and increased axial play, which accelerates wear and potentially causes shaft or bearing failure, especially in prior generation railcar axles with non-fitted backing rings that lack rigidity.
Innovation Solution
A novel backing ring assembly composed of an annular body affixed to the journal and a locking ring that connects with the annular body and the dust guard, reducing axial movement caused by shaft and journal deflections, which can be retrofitted or used in both current and prior generation railcar axles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a non-fitted backing ring is used, then the device complexity is reduced, but the stability and wear resistance deteriorate due to lack of rigidity and increased fretting wear
Solution Approach 1:
The backing ring is divided into two separate components: an annular body that fits onto the journal and a locking ring that secures the annular body. This segmentation allows each component to perform its specific function optimally - the annular body provides the bearing surface while the locking ring prevents axial movement, thereby solving the contradiction between structural simplicity and wear resistance.
Solution Approach 2:
The locking ring is positioned over the annular body and engages with it through interlocking features. This nested arrangement allows the locking ring to secure the annular body without adding significant external complexity, while effectively preventing the fretting wear that plagued the non-fitted design.
2Reliability
If a fitted backing ring with interference fit is used, then the stability and rigidity are improved, but the manufacturing precision requirements increase due to closely toleranced dust guard diameter
Solution Approach 1:
By separating the fitting function (annular body on journal) from the locking function (locking ring on dust guard), the design allows the annular body to provide stable support while the locking ring handles the connection to the dust guard. This reduces the criticality of dust guard tolerances compared to the integrated fitted design where the entire backing ring depended on dust guard fit.
Solution Approach 2:
The annular body acts as an intermediary component between the journal and the locking ring. It receives the locking ring which in turn connects to the dust guard, thereby decoupling the precision requirements. The annular body can be fitted to the journal with standard tolerances while the locking ring provides the secure connection.
3Reliability
If the backing ring rigidity is increased to reduce fretting wear, then the wear resistance improves, but the device complexity increases due to additional locking mechanisms
Solution Approach 1:
The segmentation into annular body and locking ring creates a modular assembly where the locking ring is a simple, straightforward component rather than a complex integrated feature. This modular approach actually reduces overall complexity by making each component simpler and more standardized.
Solution Approach 2:
The locking ring can be independently installed, removed, and replaced without affecting the annular body or the journal. This recoverability simplifies maintenance and installation procedures, offsetting the slight increase in assembly complexity by enabling easy servicing and component replacement.
Data Source
AI summary
A novel two-piece backing ring assembly for a railcar axle is presented. The backing ring assembly has an annular body affixed to the fillet of the journal and a locking ring for further affixing the annular body into position on the journal. The locking ring has an inboard end affixed to the dust guard of the shaft and an outboard end for engaging a slot in the annular body. The locking ring assembly may be retrofitted to older generation railcar axles to increase the structural rigidity of the bearing assembly and minimize fretting wear caused by railcar axle deflection.