Railroad Hydracushion

In the 1950s, damage to rail freight shipments amounted to more than $100 million per year in the United States alone. In 1954, Southern Pacific asked SRI to investigate ways of reducing this loss by mitigating shocks to loaded railroad box cars. A joint development program was undertaken that has greatly reduced cargo damage, extended railcar service life, and reduced maintenance costs.

The problems of freight-car impacts were analyzed and a new type of underframe was designed to hydraulically absorb and dissipate the shocks from coupling, starting, and stopping. The new system was required to be low cost, simple in construction, reliable in operation, and maintenance-free.

An existing freight car was modified in 1955 to prove the soundness of the design. Following encouraging tests, a new car was built incorporating an improved Hydra-Cushion element and placed into normal service for fragile loads. The performance of this car was so promising that 350 additional cars were built and placed in regular service during the summer of 1957. The cars were reserved for the more damage-susceptible items such as canned goods, furniture, household appliances, paint, wine, tin-plate, and glass.

During the first year of service, these cars make 1,745 loaded trips. On 1,425 (82%) of these trips, no damage to any goods was reported. Of the 445 shipments of canned goods in Hydra-Cushion cars, 70% were without damage. By comparison, of 53,000 shipments of canned goods made during 1957 in standard cars, only 48% were undamaged. Furthermore, the average dollar value of the damage loss was reduced by more than a factor of 25 in the Hydra-Cushion cars.

Southern Pacific licensed the Hydra-Cushion technology for use throughout the railroad industry. It remains the standard to this day.