New Test Facility Mimics Rail Car "Humping"

Humping," in railroad jargon, means to couple railroad cars together by slamming them into one another at low speed. The technique works well, although the impact required to engage the couplers often damages shipping containers, racks, dunnage, and the products themselves. But a new humping impact simulator from Control Power-Reliance, Troy, Mich., can help engineers design packaging that better withstands the abuse.

The test equipment is nearly as massive as the rail cars it simulates. Over 400 ft ³ of reinforced concrete supports equipment used to absorb the impact from a 30,000-lb test car and up to a 12,000-lb payload. The car can accommodate packages (payloads) to 15-ft long, 9-ft wide, and 12-ft, 9-in. high. A 200-hp, variable-speed motor mounts on the head end of the rig. It powers the car at speeds to 15 mph down a 100-ft-long track through a high-strength, double-row chain and gearbox. A computer limits acceleration to 0.2 g which simulates real-world conditions.

At the tail (impact) end of the track is a host of purpose-built equipment including a large hydraulic cylinder and a series of directional valves and accumulators. The cylinder features a one-piece, forged rod and piston, set in a cast-steel body, also one piece. At impact, oil flows out of the blind end of the cylinder into a manifold. The manifold is fit with 16 computer-controlled directional valves, each piped to a nitrogen-charged accumulator. Deceleration time is controllable from 50 to 400 msec depending on the number of valves activated. The system allows the car to re-bound after impact or to be securely coupled.

"Data from these tests can help eliminate costly errors throughout the package design process," says Ed Myles, president of Control-Power Reliance. "Ultimately, this saves the customer time and money."