Here is a short article from SRI International (formerly the Stanford Research Institute) about the development of the Hydra-Cushion underframe. The last sentance makes me wonder how long ago it was written.
Really interesting web site.
It is hard to imagine that that technology goes back more or less, 50 plus years and is still used today. I suspect it was the use of that Hydro-Cushion technology, with its increases in coupler length [as the coupler hardware stuck out farther than with standard coupler installations on boxcars].
The licensing and wide spread use of the H-C/DF cars that may have contributed to the decline and departure of ladders to reach the tops of cars, the gangways on those car tops as well. The distance between cars with the cushioned technology made that jump across from car to car, in particular while moving, a pretty dicey move.
Remember, into the fifties, brakemen and switchmen still had to "decorate’ the car tops; and they did so while working on moving trains. Southern Pacific eventually had many cars with the HydroCushion underframe technology, their fleets of auto parts cars, 50 footers and the big jumbo autoracks as well as the parts cars, utilized the DF concept as well. DF iincluded moveable bulkheads, rack and bars sysems that could be used to construct internal decks was also used in these cars as well. Cars equipped with the H-C/DF were highly sought after by shippers all over for their ability to control cargo meovement without having to use extensive cribbing and dunnage construction within the cars.
The Hydra-Cushion underframe was - and still is - far superior to the end-of-car systems now in wide-spread use. As mentioned, the customers just loved them, and the train crews - espicially the engine crews - liked them as well because they handled just like a car without cushioning. Not the way the e-o-c types handle.