Direct Fixation Track Mounting Assembly with Dual Stiffness
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Solution Overview
Problem
Existing rail mounting assemblies lack the ability to provide dual stiffness for tracks subjected to mixed axle traffic, which can include transit vehicles, high-speed passenger trains, and freight, as they are typically locked into a single stiffness dictated by the heaviest axle, failing to accommodate varying loads effectively.
Innovation Solution
A direct-fixation mount with an elastomeric pad for vertical stiffness and separate end restraints for horizontal stiffness, allowing for customizable stiffness levels by varying the elastomer properties and design of the pad and restraints, which are interchangeable to suit different load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single stiffness mounting assembly is used for tracks, then the structure is simple and easy to manufacture, but it cannot accommodate varying loads from different axle types (transit, passenger, freight)
Solution Approach 1:
The mounting assembly is divided into two independent stiffness control mechanisms: (1) vertical stiffness controlled by the elastomeric pad thickness and material properties, and (2) horizontal stiffness controlled by the end restraints with adjustable spacing. This segmentation allows each component to be optimized independently for different load conditions without increasing overall complexity
Solution Approach 2:
The mounting assembly transitions from a fixed single-stiffness design to a dynamic dual-stiffness system where the elastomeric pad provides vertical compliance and the end restraints provide adjustable horizontal restraint. The spacing between end restraints can be modified to adapt to different axle types, making the system dynamically adaptable rather than static
2Ease of manufacture
If the elastomeric sheet is bonded only at angled end faces, then the bonding process is simple, but the sheet lacks support underneath except at the angled end faces
Solution Approach 1:
The base frame is designed with upwardly extending surfaces that preliminarily support the elastomeric sheet in its uncompressed state before any load is applied. This preliminary support ensures the sheet is properly positioned and supported throughout the assembly process, eliminating the need for complex bonding patterns while maintaining reliability
Solution Approach 2:
The base frame acts as an intermediary structure between the substrate and the elastomeric sheet, providing distributed support through its upwardly extending surfaces. This intermediary support system distributes the load and support function across multiple contact points rather than relying solely on bonded regions
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
Enables tailored stiffness settings for tracks, accommodating light and heavy axles by providing adjustable vertical and horizontal resistance, enhancing the system's ability to handle diverse traffic loads without being locked into a single stiffness, thus improving vibration isolation and stability.
Implementation Method 1
the sole function of the sheet in this region is to undergo vertical compression
Implementation Method 2
an elastomeric pad of predetermined stiffness underneath the plate and atop the surface so that the track and plate bears downward via the pad on the surface
Implementation Method 3
The elastomeric masses are each of L-section and engaged between the respective inner leg and an outer and upper face of the respective inner part
Data Source
AI summary
A direction-fixation mount secures a track assembly to a flat upper surface of a fixed substrate. The track assembly includes a flat plate having a pair of opposite end edges, a track sitting on the plate, and fasteners securing the track to the plate. The direct-fixation mounting assembly has an elastomeric pad of predetermined stiffness underneath the plate and atop the surface so that the track and plate bears downward via the pad on the surface, and a pair of end restraints each having a rigid outer part fixed to the substrate offset outward from a respective one of the end edges of the plate, a rigid inner part spaced inward from the outer part and fixed to the respective outer end edge of the plate, and an elastomeric mass separate from the pad and fixed to and between the respective inner and outer parts.