RAILWAY AGE DECEMBER 2024 ISSUE: The Rail Dynamics Laboratory (RDL) at the Transportation Technology Center (TTC) has recently undergone significant transformation. As a full-scale testing laboratory for rail vehicles and other heavy equipment, the RDL plays a unique role in rail research and safety. Originally built in 1972, it was one of the first labs at the TTC. Today, the RDL’s modernization has made it cleaner, more efficient, and ready to support the latest demands in rail technology.
Revamping the RDL: A Modern Approach
Transforming the RDL involved extensive efforts to elevate its functionality and organization. Previously, the lab bore the marks of decades of rigorous testing, with oil-stained floors and grime. Recently, the TTC team took on the project of modernizing the space to create a clean, well-organized environment, enhancing both usability and accessibility. Additional RDL modernization efforts included refreshing power and control electronics. The revitalized RDL now matches the high standards of TTC’s testing capabilities, showcasing an upgraded space ready to meet the rigorous demands of modern rail testing.
Unpacking the Testing Systems
The RDL houses several specialized testing rigs, each offering crucial functions in vehicle safety and component durability testing: the Squeeze Test Fixture (STF) , Simuloader (SMU), Vibration Test Unit (VTU), and Mini-Shaker Unit (MSU).
The Squeeze Test Fixture (STF) supports compression testing with an impressive load capacity of up to 2,000 kips (8.9 MN). Designed for whole-vehicle testing, it evaluates crush compliance, structural stress, and impact resilience. Equipped with four longitudinal actuators, the fixture allows for both displacement and force control, providing the flexibility needed for precise testing. The STF used to be operated in a semi-automated fashion that required manual intervention. This previous mode of operation worked well for simple test, that does not require complex force-displacement scenarios. The new STF renovation involves a new hydraulics and controller that allows for the programming of complex loading scenarios without additional need for human intervention, adding reliability and safety to any test program.
With the capability to simulate decades of load environment within just a few months, the Simuloader (SMU) uses 11 hydraulic actuators to apply maximum loads of 750 kips (3.34 MN) longitudinally and 440 kips (1.96 MN) vertically. The SMU provides structural stress and deflection testing to railcar car bodies to evaluate long-term vehicle structural durability, helping assess service worthiness of new and reconditioned rolling stock. The SMU can simulate 50 years of operational stress, providing valuable insights into fatigue life and structural integrity within a condensed testing timeframe of 1-2 months. The SMU renovation efforts include new latest generation pumps and an upgrade to its state-of-the-art main controller. Additionally, a full set of new mechanical parts will be installed in gradual form to make sure that the machine will perform at the highest level for many years to come.
The Vibration Test Unit (VTU) provides critical data for ride quality and vibration testing ability to complete rail vehicles including their suspensions. It supports maximum loads of 50 kips (222 kN) longitudinally and 400 kips (1.8 MN) vertically, operating within a frequency range of 2 to 30 Hz. Essential for identifying flexible vibration modes, the VTU allows the TTC team to assess how rail vehicles respond to real-world vibrations, ensuring a comfortable and secure passenger experience, and the integrity of the commodities being transported in the case of freight service.
The Mini-Shaker Unit (MSU) is tailored for truck (bogie) components and truck assembly performance assessment, providing detailed testing for vehicle stability. With a maximum applied load of 150 kips (667 kN), it assesses suspension stiffness and damping across multiple axes, ensuring that truck components perform optimally under diverse conditions. Another important use of the SMU is in conducting modal tests to determine both rigid and flexible vibration modes of a car structure. Recent upgrades to the MSU include two 22.5-kip actuators to improve the accuracy of frequency determination during modal testing, along with a new set of pumps and a chiller. This addition (pumps and chiller) enables the MSU to operate as a fully independent machine; previously, the MSU and VTU shared hydraulic resources, making independent tests impossible. In addition to the MSU, the RDL also has air tables for determining friction coefficients between the car body and the trucks and/or span bolsters, as well as the turning moments at the same interfaces. Each air table is capable of handling 175,000 lbs.
2024 TTC Conference & Tour Highlights
On Oct.22-23, TTC held its 2nd Annual TTC Conference & Tour, drawing industry professionals from around the country to Pueblo, Colo.. Day two of the event, held at the TTC, offered attendees a unique opportunity to experience the TTC’s expansive testing capabilities through grouped tour stops across the facility. Among these tour stops was the Rail Dynamics Laboratory (RDL), where guests explored the RDL’s sophisticated equipment and observed real-world applications of rail safety and performance testing.
Inside the RDL, attendees were provided with hands-on insights into the lab’s core systems—the VTU, SMU and MSU—with dedicated monitors and posters detailing each machine’s function and purpose. Though a vehicle was installed in the SMU to showcase full-carbody testing, the highlight of the RDL tour was a live demonstration at the MSU led by TTC Director of Engineering Juan Carlos Valdes-Salazar. Using a hammer strike setup on a flat car, Valdes-Salazar engaged attendees in an interactive session where each strike generated a live strip chart, allowing participants to see the immediate impact of vibrations in real-time. This immersive experience brought the lab’s technology to life and demonstrated the TTC’s dedication to innovation, enabling attendees to engage directly with the RDL’s testing systems and to witness the rigorous evaluations that support rail safety advancements.
Future of the RDL
As the TTC continues to evolve, the Rail Dynamics Laboratory (RDL) remains a foundation of rail safety and innovation. By enhancing its facilities and capabilities, the TTC reaffirms its commitment to supporting the railway community with cutting-edge testing, evaluation, and research. Continued hands-on tour events are planned for the 2025 TTC Conference and Tour scheduled for Fall 2025. For more information and updates, visit ttc-conference.com.
