MxV RAIL R&D, RAILWAY AGE JULY 2025 ISSUE: Under the Association of American Railroads (AAR) Strategic Research Initiatives Program, MxV Rail and its Damage Prevention & Loading Services (DP&LS) group conducted a series of impact tests using boxcars loaded with paper rolls. The impact tests were conducted to 1) support the evaluation of current damage prevention standards; 2) characterize the current impact environment experienced by cars; and 3) evaluate the effects that new draft system types might have on-car and lading responses.
The tests were conducted using a 60-foot boxcar with double-plug doors. The boxcar was fully loaded with 58-inch diameter rolls of paper, a typical but challenging closed carload approved for use with both cushioned underframe cars and standard draft gear cars. This type of paper roll load is common because it is used to make cardboard shipping boxes. For each set of impacts, the boxcar was equipped with one of three draft systems: hydraulic 15-inch end-of-car-cushioning (EOCC) units, dual draft gear “hybrid” systems, or standard draft gears.
The measurements recorded during the tests included speed, coupler force, displacement and carbody accelerations for both the hammer and the struck anvil car. Both paper roll accelerations and end wall void displacements were also measured to evaluate the response of the lading. The boxcar was impacted into four different anvil string configurations (see Figure 1, below) intended to evaluate various impact scenarios.
Test 1 is a scenario similar to the Standard Impact Test from the Closed Car Loading Standards. The Test 2 scenario resembles the AAR Manual of Standards and Recommended Practices (MSRP) Section B, Specification M-921B2 Impact Performance Test used for evaluating 15-inch EOCC units. Test 3 represents a flat switching event, which is the most common type of impact scenario encountered in revenue service. Test 4 is a scenario similar to the Impact Test Setup for evaluating hybrid draft systems found in MSRP Section B, Specification M-902.3 Depending on the specific test scenario, the hammer car was impacted into the stationary anvil car in both the forward and reverse directions at various speeds from 1 to 8 mph.
The test results showed that the maximum coupler forces, carbody accelerations, and paper roll accelerations were the lowest for the boxcar with EOCC units and the highest for the boxcar with draft gears, due to the larger energy absorption and displacement stroke of the EOCC units compared to the draft gear. The boxcar with hybrid systems had lower coupler forces, carbody accelerations, and paper roll accelerations than the boxcar with draft gears, as well as a lower displacement stroke than the EOCC units, which may have performance benefits in terms of controlling slack in over-the-road operations.
The results indicated that the Test 1 scenario of impacts into the empty anvil string was the least severe scenario evaluated. The Test 1 scenario was modeled after the Standard Impact Test from the Closed Car Loading Standards, which is intended to evaluate loading and securement methods without pushing the car to its mechanical limits. The results also showed that the Test 2 scenario of impacts into the loaded anvil string was the most severe scenario evaluated. The Test 2 scenario was modeled after the Impact Performance Test in Specification M-921B, a mechanical specification intended to evaluate whether a car with EOCC units can manage loads from a demanding service environment. The results from the Test 3 impacts with the three-car hammer string showed that low speed, low acceleration impacts can still generate high forces as the mass of the moving cars increases. Further research in this project will continue to review the mechanical and freight related aspects of draft system performance.
References
- AAR. 2023. Closed Car Loading Standards. General Information Bulletin No. 2: “Rules and Procedures for Testing of New Loading and Bracing Methods or Materials.”
- AAR. 2024. Manual of Standards and Recommended Practices (MSRP). Section B: Couplers and Freight Car Draft Components. Specification M-921B: Cushioning Devices, End-of-Car.
- AAR. 2024. Manual of Standards and Recommended Practices (MSRP). Section B: Couplers and Freight Car Draft Components. Specification M-902: End-of-Car Energy Management Systems.
Further Reading, MxV Rail R&D: Wheel/Rail Vertical Impact Force Measurement Validation
