The concept for the test rig consists of two railroad axle-boxes, which are subjected to repeated loading cycles that accurately reflect the service conditions of the intended high-speed application.
The design of test rig permits axial and radial loads, either separately or in combination, onto two hub assemblies. These loads are applied on the bearing centreline and through two mounting points on the axle-box casing. i.e. the axle-box assemblies are connected to a rigid steel support structure and also connected to the main shaft. The main shaft is then driven by an electric motor via pulleys and a timing belt.
Several design considerations needed to be addressed whilst the designing the assemblies of the test rig. However our main challenges were on the design of the Shaft Assembly as this would be subjected to the Radial & Axial load conditions.
Within this challenge was to select the size and type of bearings that would be used to replicate the axle of a rail bogie that would withstand the test conditions and enable a continuous drive to be provided to the shaft assembly through a pulley and timing belt arrangement.
Other challenges presented in this assembly, would be to find a solution to ensure the bearings within the shaft assembly could be lubricated efficiently throughout the test cycle.
Our shaft assembly design incorporated bespoke split bearing housings that would contain both fixed and floating bearing arrangements. Whilst designing the assembly we took into account many of the critical features of the shafts detail design.
– Material selection of components.
– Stress & Dynamic Analysis of components.
– Properties of bearings that are used in railroad applications.
– Thermodynamic / fluid properties of components within the assemblies.
Designed onto this assembly was a custom labyrinth sealing solution that allowed the bearings to be lubricated throughout the test cycle as part of the bearing cooling solution. External fans were also added to ensure the temperatures were not exceed.
The final design of the shaft assembly allowed the test rig to withstand the test criteria with the shafts fatigue life capable of lasting over 15 years.